Graphene‑based nanomaterials for drug delivery: Design strategies, mechanisms and clinical perspectives (Review)

Introduction

Cancer remains a major global health challenge, with conventional chemotherapy still limited by poor selectivity, systemic toxicity and unpredictable therapeutic outcomes (1–4). These limitations have driven the development of advanced drug delivery systems (DDSs) that increase intratumoural drug accumulation while reducing off-target toxicity (5,6). Nanotechnology has played a key role in improving DDSs by enabling controlled drug release and improved pharmacokinetics. Various nanocarriers, including liposomes (7,8), polymeric nanoparticles (9–11) and inorganic nanomaterials (12,13), have been explored for cancer therapy. However, these systems frequently suffer from limited drug loading, instability in biological environments or complex manufacturing processes. An effective DDS should integrate favourable pharmacokinetic properties, efficient tumour targeting and the capability to achieve spatiotemporally controlled and site-specific drug release within pathological microenvironments (14–18). Such coordinated regulation is crucial for enhancing therapeutic efficacy, minimising systemic side effects and supporting precision cancer therapy (19).

Graphene, a representative two-dimensional sp2-hybridised carbon nanomaterial, has attracted extensive attention owing to its unique crystal structure and exceptional physicochemical properties (20–24). Besides its established applications in nanoelectronics, energy storage and catalysis, graphene and its derivatives are being increasingly investigated for biomedical applications (25–34), including biosensing (27–29), bioimaging (30,31), drug and gene delivery (32), cancer therapy (33) and tissue engineering (34). For drug delivery applications, graphene-based nanomaterials exhibit distinct advantages, making them promising nanocarrier candidates. In particular, their ultrahigh specific surface area (up to ~2,630 m2/g) endows a high loading capacity for various therapeutic agents, including small-molecule drugs, nucleic acids and proteins. For instance, Qian et al (35) developed a hyaluronic acid (HA)-functionalised graphene oxide (GO) nanocarrier via nano-functionalisation and nucleic acid co-assembly, leading to MDR1 gene silencing and microRNA (miRNA/miR)-489-mediated epithelial-mesenchymal transition inhibition, which considerably reduced the half-maximal inhibitory concentration of doxorubicin (DOX) to 5.61 µg/ml and markedly increased its cytotoxicity against drug-resistant MCF-7/ADM breast cancer cells. The extended π-conjugated framework of graphene-based nanomaterials facilitates efficient non-covalent loading of therapeutic compounds while preserving their structural and functional integrity. Furthermore, the abundant surface functional groups of these nanomaterials enable precise chemical modification through the attachment of targeting ligands and stimuli-responsive moieties, thereby improving specificity and control in drug delivery. Beyond GO, other graphene-derived nanostructures, such as graphene nanoribbons (36,37) and graphene quantum dots (38,39), exhibit size-dependent properties and greater functional tunability, expanding the material basis for graphene-based delivery systems.

Although graphene and its derivatives offer major advantages in drug delivery, notable challenges hinder their practical use in biomedical settings (40–42). First, graphene-based nanomaterials tend to aggregate in physiological microenvironments, reducing their dispersion stability and thereby limiting their in vivo circulation and tumour accumulation efficiency. Second, questions regarding their biotoxicity and long-term biosafety persist. High doses or prolonged exposure may result in oxidative stress, cell membrane damage and adverse immune responses. Additionally, the poor biodegradability of graphene-based nanomaterials raises concerns about long-term accumulation in the body, which could limit their clinical applicability (43–45).

To address the aforementioned challenges, substantial efforts have recently been devoted to optimising graphene--based delivery systems through surface functionalisation, composite development, stimuli-responsive design and biocompatibility improvement. Salimi and Mohammadi-Manesh (46) prepared Fe3O4/TiO2/GO nanocomposites via thermal treatment for curcumin delivery. Compared with the GO-free nanocomposite, the GO-containing nanocomposite exhibited superior pH-dependent drug adsorption and release, increased cancer cell cytotoxicity and negligible haemolytic toxicity, demonstrating that GO surface chemistry and composite architecture directly influence drug release kinetics and biological performance. Dilpreet and Mandavi (47) introduced hybrid nanophotonic graphene systems as externally controllable transdermal drug delivery platforms. In these systems, the photothermal effects of graphene, combined with its electrical and thermal conductivity, enhance skin permeability and enable controlled drug transport. These advancements indicate that graphene-based systems are shifting from passive drug reservoirs to interface-driven, stimuli-responsive and spatiotemporally controlled delivery platforms. However, this progress is also associated with unresolved issues related to reproducible fabrication, controlled release, long-term biocompatibility and clinical applicability (48,49).

Furthermore, the aforementioned challenges become more pronounced when graphene-based materials are incorporated into complex biological systems. Grecca et al (50) reviewed GO-integrated three-dimensional printed systems combined with mesenchymal stem cells for drug delivery and tissue regeneration, showing that GO can improve cell adhesion, proliferation and osteogenic differentiation. However, substantial uncertainties remain regarding the mechanisms and safety of GO-based therapies. These findings indicate that current research is limited by an incomplete understanding of the structure-surface chemistry-drug release relationship, the behaviour of graphene-based nanomaterials in complex in vivo microenvironments, and the connections among physicochemical design, biological outcomes, biosafety and clinical translation. Furthermore, the mechanisms through which various surface functionalisation strategies influence drug loading efficiency (51,52), spatiotemporally controlled release and biocompatibility remain inadequately understood. Concurrently, approaches that enable synergistic responses to multiple tumour microenvironmental signals (such as pH gradients, intracellular redox states and tumour-specific enzymatic activity) are still in early development and require further research to realise their full potential in cancer therapy.

For the present review, a literature search was conducted to identify representative studies on graphene-based nanocarriers for tumour drug delivery. Relevant publications were retrieved from major scientific databases, including Web of Science (https://www.webofscience.com/, Web of Science Core Collection, continuously updated online. Literature search was performed in September 2026.) and Scopus (URL: https://www.scopus.com/, Scopus continuously updated online. Literature search was performed in September 2026.), using combinations of key words such as ‘graphene oxide’, ‘functionalisation’, ‘nanocarrier’, ‘drug delivery’, ‘nanocarriers’ and ‘stimuli-responsive release’. Studies published between 2015 and 2026 were considered.

Building on this background, the present review provides a mechanism-focused analysis of graphene-based nanocarriers for tumour drug delivery. Unlike numerous reviews that predominantly summarise material synthesis, surface functionalisation or biomedical applications (53–55), the present review emphasises how structural features and interfacial chemistry influence drug-carrier interactions, loading and release behaviour, biological responses and translational performance. Graphene, GO and reduced GO (rGO) are discussed by linking their physicochemical properties and functionalisation abilities with tumour-targeting efficiency, stimuli-responsive delivery, biosafety, biodegradation and in vivo fate. Particular attention is devoted to unresolved translational challenges, including long-term safety, limited biodegradability, uncertain clearance pathways and the absence of standardised evaluation frameworks. By integrating insights regarding material design, delivery mechanisms, biological effects and clinical constraints, the present review aims to establish a rational framework for developing safer, more predictable and clinically viable graphene-based nanomedicine platforms for precision cancer therapy.

Synthesis of graphene and its derivatives

Synthesis of graphene

Graphene can be synthesised using various approaches, broadly categorised as top-down (56,57) and bottom-up (58,59) strategies. These methods considerably differ in terms of structural quality, defect density, scalability and surface chemistry, all of which influence the physicochemical properties and biomedical performance of graphene-based nanomaterials.

Top-down approaches

Top-down approaches involve exfoliating graphite into graphene layers by overcoming the weak van der Waals interactions between stacked sheets. This is a key method for synthesising graphene, offering advantages of simplicity and low cost (56,60). It mainly includes liquid-phase exfoliation, mechanical exfoliation, solid-phase exfoliation, electrochemical exfoliation, chemical oxidation-reduction, the arc-discharge method and unzipping of carbon nanotubes, which produce thin-layer nanomaterials by exfoliating or etching bulk layered precursors. Among these approaches, mechanical exfoliation is the earliest and most fundamental technique for isolating graphene; it uses physical forces to exfoliate graphite layers, producing single- or few-layer graphene sheets from bulk graphite. This method typically yields graphene with near-perfect crystallinity, minimal defect density and well-preserved intrinsic properties, making it highly suitable for fundamental investigations of the physicochemical and electronic characteristics of graphene. However, its practical application is constrained by extremely low yield, limited scalability and poor control over layer count (61). Consequently, it is mainly used in laboratory research and is not suitable for large-scale production or biomedical applications.

Liquid-phase exfoliation has become a more scalable alternative. In this approach, graphite is dispersed in organic solvents, surfactant solutions or ionic liquids and then exfoliated through ultrasonication or shear mixing. The choice of solvent is vital for stabilising exfoliated graphene sheets by matching their surface energy. Although this technique allows for large-scale production, the resulting graphene often shows a broad range in lateral size and thickness and contains structural defects caused by sonication (62). Another effective top-down technique is electrochemical exfoliation, wherein graphite electrodes are subjected to an applied voltage in an electrolyte solution, leading to intercalation and exfoliation. This method provides benefits such as higher yield, faster processing and tuneable surface functionalisation. However, it can also introduce defects and oxygen-containing groups that may modify the intrinsic properties of graphene (63).

Bottom-up approaches

Bottom-up synthesis constructs graphene from molecular precursors (64–66), with chemical vapour deposition (CVD) being the most common technique used for high-quality graphene film production (67–69). In CVD, carbon-containing gases, including methane, are decomposed at high temperatures on catalytic metal substrates, such as copper or nickel, resulting in graphene layer formation. CVD-produced graphene offers robust crystallinity, uniform thickness and low defect levels, making it suitable for electronic and optical applications. For example, Niu et al (70) fabricated transferred CVD-grown graphene islands on copper foils using atmospheric-pressure CVD, followed by polymethyl methacrylate-assisted wet transfer onto SiO2/Si and post-annealing in H2/Ar, resulting in more uniform strain and carrier density on copper single crystals. However, the high temperatures, complex transfer process and high production costs hinder its scalability for biomedical purposes. Other bottom-up approaches include epitaxial growth on silicon carbide (SiC) substrates and molecular self-assembly, where high-temperature decomposition of SiC forms graphene layers on its surface. Although this method yields high-quality graphene, it requires stringent conditions and expensive substrates (71).

Synthesis of graphene derivatives

GO and rGO are essential functionalised graphene derivatives that have garnered intensive research interest in drug delivery. Compared with pristine graphene, these nanomaterials offer superior dispersibility and abundant surface functional moieties. Their inherent structural and compositional advantages support their use in efficient DDSs, allowing for adjustable biocompatibility, controlled release and high drug payloads, all aimed at targeted therapy in complex biological microenvironments.

Synthesis of GO

GO is mainly synthesised by oxidising graphite chemically, most extensively via Hummers' method and its variants (72), as shown in Fig. 1. Al-Gaashani et al (72) prepared high-quality GO and rGO via modified Hummers' methods with mixed acids and low-temperature control, achieving tuneable C/O ratios and abundant oxygen-rich functional groups that enhance hydrophilicity. In this process, strong oxidisers oxidise graphite, enabling intercalation of oxygen-containing functional groups between the graphitic layers. This weakens the interlayer interactions, allowing the material to be exfoliated into single- or few-layer GO sheets. The oxidation creates numerous oxygen-containing groups, including hydroxyl and epoxy moieties on the basal plane, as well as carboxyl groups predominantly at the sheet edges. These functionalities disrupt the extended sp2-conjugated network, increasing the hydrophilicity of GO and thereby improving its dispersibility in aqueous media. Additionally, the negatively charged surface of GO provides electrostatic stabilisation, important for maintaining stability under physiological conditions.

Figure 1. Processes used in graphene oxide synthesis.

Synthesis of rGO

The formation of rGO occurs when oxygen-containing groups are partially removed from GO via chemical, thermal or electrochemical reduction strategies (73–76). Among these approaches, chemical reduction is the most extensively employed method, typically using reductants, such as hydrazine, sodium borohydride or ascorbic acid. For example, Zhuang et al (76) produced high-performance rGO-cellulose nanocrystal composite films through mild oxidation, confined evaporation, and hydroiodic acid (HI) reduction which improved their mechanical strength, electrical conductivity and electromagnetic-interference shielding performance in the X-band. During conventional evaporation, a large evaporation height can generate a concentration gradient and promote the formation of a skin layer, which may lead to disordered stacking and wrinkles in the resulting film. Spatially confined evaporation reduces the effective evaporation height and enables repeated confined evaporation, thereby facilitating the gradual accumulation and more orderly arrangement of graphene-based nanosheets (76). Thermal reduction can further decrease oxygen levels and promote the reconstruction of graphitic domains at higher temperatures. The extent of reduction markedly affects the balance among electrical conductivity, hydrophilicity and surface reactivity. Highly reduced graphene offers superior electronic properties but reduced dispersibility in aqueous environments, whereas partially reduced graphene maintains a sufficient density of functional groups for subsequent chemical functionalisation, which is beneficial for biomedical applications (77).

Overall, different synthesis methods for graphene and its derivatives produce materials with unique structural and surface chemical properties. These features influence their effectiveness in drug delivery applications. In such systems, graphene derivatives with controlled defect structures and surface functionalities are preferred since they show improved dispersibility and modifiability. Therefore, defect-engineered or partially oxidised graphene materials are more commonly used than pristine graphene.

Graphene and its derivatives in drug delivery

Characteristics of graphene-based materials and their relevance in drug delivery

Graphene and its derivatives have become highly versatile nanoplatforms for drug delivery owing to their unique two-dimensional structure, extensive specific surface area, tuneable surface chemistry and capacity for multimodal functionalisation (78,79). Unlike conventional nanocarriers, graphene-based materials offer multiple interaction sites for therapeutic agents and can incorporate targeting, imaging and stimuli-responsive features in a single delivery platform. These characteristics make them attractive candidates for cancer treatment, where efficient drug loading, prolonged circulation, tumour-specific accumulation, controlled drug release and reduced systemic toxicity are critical.

Drug loading strategies

Drug loading onto graphene-based nanocarriers can be achieved through non-covalent adsorption (80–83) or covalent conjugation; these commonly used drug-loading strategies are illustrated in Fig. 2. Non-covalent methods are the most common as they preserve the structure of therapeutic molecules and enable reversible drug release under specific physiological conditions. Among them, π-π stacking and hydrogen bonding are among the most commonly exploited mechanisms for loading drugs onto graphene-based nanocarriers (35). In addition, electrostatic interactions are also important, particularly for charged therapeutics. The negatively charged GO surface interacts with positively charged drugs, peptides or nucleic acids, and surface modification with cationic polymers further enhances the loading of anionic biomolecules, including small interfering RNA, miRNA and plasmid DNA. For example, Garwal et al (80) fabricated polyvinyl alcohol (PVA)-grafted magnetic GO (GO-PVA-Fe3O4) nanocomposites via chemical co-precipitation and carbodiimide-activated esterification, which enhanced 5-fluorouracil (5-FU) loading capacity, lowered systemic haemolysis risk and enabled tumour acidic microenvironment-triggered controlled drug release. GO-PVA-Fe3O4 possesses a 5-FU loading capacity of 14.17 weight percent (wt%) and the cumulative 5-FU release of GO-PVA-Fe3O4−5FU reaches 30.40% at pH 4.0, which is ~2.5-fold higher than the release (15.4%) under physiological conditions (pH 7.4). Afzal et al (81) developed ZnO-GO nanocomposites via facile chemical deposition; hydrogen bonds between GO functional groups and DOX considerably increased drug loading efficiency to 89% [higher than that of pure ZnO (82%)], and the composites showed pH-responsive release behaviour.

Figure 2. Drug loading strategies for graphene-based nanocarriers. DOX, doxorubicin.

Covalent conjugation enhances drug stability and minimises leakage during systemic circulation using cleavable linkers, such as hydrazone, disulphide, ester or peptide bonds. These linkers remain stable under normal conditions but cleave under tumour-associated stimuli, including acidic pH, elevated glutathione (GSH) levels or specific enzymatic activity. For instance, Rabchinskii et al (82) synthesised carboxylated rGO via wet-chemical modification and covalently anchored an hepatitis B virus (HBV)aptamer via amide bonds for stable bioconjugation, supported by theoretical conformation analysis. Specifically, a unit mass of carboxylated rGO carrier can bind 4.1×10−12 mmol/g of HBV aptamer. Although this rGO-based system was initially designed for chemiresistive biosensing rather than drug delivery, it serves as a valuable example of covalent biomolecule immobilisation on functionalised graphene surfaces, which can be adapted for ligand conjugation and molecular modification of graphene-based nanocarriers.

Each loading strategy has advantages and disadvantages. For instance, non-covalent methods, employing π-π stacking, electrostatic interactions, hydrogen bonding or hydrophobic interactions, are simple and versatile, enabling the loading of diverse therapeutic cargos while preserving their biological activity; however, these reversible interactions may result in premature drug leakage under physiological conditions due to competitive interactions with proteins and ions. In particular, ionic-driven displacement has been experimentally demonstrated in buffered media (83). By contrast, covalent modification strategies can be exemplified by the work of Matiyani et al (84), who fabricated polyamidoamine (PAMAM)-functionalised GO via EDC/NHS-mediated amide coupling and achieved enhanced quercetin (QSR) loading with pH-responsive release behaviour and improved anticancer activity against breast cancer cells. The covalent conjugation methods provided improved stability, reducing premature release through cleavable linkers. Compared with the QSR loading capacity of 30.79±1.53% in pure GO, the QSR loading capacity in GO-PAMAM reached as high as 37.42±1.72%. At the same time, under physiological conditions (pH 7.4), the cumulative QSR release rate from GO-PAMAM-QSR over 72 h is 20–21%. However, it involves more complex synthesis and may affect drug accessibility. Therefore, the choice of loading strategy depends on the chemical properties of the therapeutic cargo and the target biological application.

Surface functionalisation for improved stability and biocompatibility

Graphene-based nanomaterials hold considerable potential as drug carriers. However, their direct biomedical application is limited by aggregation, non-specific protein adsorption, rapid clearance and potential toxicity. To address these issues, surface functionalisation is crucial for boosting colloidal stability, biocompatibility and in vivo delivery performance (85–87), as shown in Fig. 3. Polyethylene glycol (PEG) functionalisation (PEGylation) is one of the most widely used modification approaches. PEGylation enhances aqueous stability, reduces opsonisation by serum proteins, prolongs blood circulation time and decreases uptake by the mononuclear phagocyte system (88). For example, Karimi and Namazi (88) developed PEGylated triazine dendrimer (TD)-grafted GO/Fe3O4 nanocomposites (GO-TD-Fe3O4@PEG), where Fe3O4 nanoparticles were pre-coated with PEG. With the PEG coating enhancing hydrophilicity and colloidal stability to achieve high-efficiency pH-responsive DOX delivery. The DOX loading capacity of GO-TD-Fe3O4@PEG is 9.26 wt% and the encapsulation efficiency of GO-TD-Fe3O4@PEG reaches 92.6%. At pH 7.4 (normal blood environment), the cumulative DOX release percentage can be up to 66.1%. Besides PEG (89), polymers such as chitosan (90–92), polyethyleneimine (93), HA (94), dextran (95) and polydopamine (96) have been used to modify graphene-based nanocarriers. These polymers improve dispersion stability while providing additional functional groups for drug conjugation or ligand attachment.

Figure 3. Surface functionalisation of graphene-based nanocarriers for improved biocompatibility. GO, graphene oxide.

Tumour-targeted delivery strategies

Efficient tumour targeting is key in DDS design. Tumour-targeted delivery strategies are broadly classified into passive and active targeting, as shown in Fig. 4. Passive targeting relies on the enhanced permeability and retention effect, where nanoscale carriers accumulate in tumour tissues due to leaky vasculature and impaired lymphatic drainage. However, tumour vasculature heterogeneity and variability among tumour types can reduce passive targeting reliability. To improve specificity, active targeting is often used and involves the conjugation of tumour-recognition ligands (97–100). For example, Rostami et al (97) prepared ZnFe2O4@L-cysteine-N/RGO nanocarriers for chemo-sonodynamic therapy, featuring pH/ultrasound dual-responsive curcumin release. The curcumin loading efficiency of ZnFe2O4@L-cysteine-N/RGO was 71.65%, which was higher than the 63.17% of ZnFe2O4@L-cysteine. For ZnFe2O4@L-cysteine-N/RGO, only 33.03% of curcumin leaked at pH 7.4 within 96 h. Liu et al (98) fabricated light-driven tubular rGO/Cu2+1O nanomotors for active targeted DOX delivery and combined melanoma therapy via π-π stacking interaction. The DOX loading capacity of rGO/Cu2+1O nanomotors reached 11.7±1.2 wt% after a 120-min incubation. In addition, Sridharan et al (92) fabricated folic acid-modified rGO/Co3O4/chitosan (GCC) ternary nanocomposites for folate-targeted pH-sensitive DOX delivery against lung and breast cancer cells. The maximum DOX loading percentage of GCC reached 95.25%. Only 10–11% of DOX leaked at pH 7.4 within 10 h. Moreover, Gupta et al (99) constructed a biotin-adorned poly-(ethylene oxide) bis-(amine) conjugate (BPBA) for targeted gallic acid (GA) therapy using a rGO nanocarrier (rGONC), forming BPBA@GA-rGONC, for treating A549 lung tumour cells. The GA loading capacity of BPBA@GA-rGONC was 12.8 wt% and the corresponding entrapment efficiency was 25.6%. At physiological pH 7.4, 52.5% of GA was cumulatively released within 48 h, whereas the total GA release percentage reached 67% at tumour-mimicking acidic pH 5.0 with strengthened anticancer activity (99).

Figure 4. Tumour-targeted delivery strategies of graphene-based nanocarriers.

However, graphene tumour-targeted nanocarriers face translational barriers: Passive targeting lacks consistency across tumour subtypes, single-ligand active targeting is restrained by variable tumour receptor expression and excessive ligand-induced off-target interactions, while serum protein corona blocks ligand recognition and poor intracellular transport weakens therapy (100). Next-generation graphene carriers should combine optimised ligand layout, biocompatible anti-protein adsorption coating and stimulus-triggered release for reliable tumour-specific delivery.

Stimuli-responsive drug release mechanisms

Stimuli-responsive release is a key advantage of graphene-based DDSs. Tumour tissues possess distinctive microenvironmental features, including acidic extracellular pH, elevated intracellular GSH concentrations, upregulated enzymes, hypoxia and abnormal reactive oxygen species levels. Graphene-based nanocarriers can be designed to respond to these endogenous stimuli, enabling site-specific and controlled drug release.

Drug release responsive to pH

The release of drugs in response to pH has been extensively studied in graphene-based nanocarriers (101–104), primarily owing to the acidic tumour microenvironment (pH 6.5–6.8) and even lower pH in endo/lysosomal compartments (pH 4.5–5.5). GO is enriched with oxygen-containing functional groups, including carboxyl, hydroxyl and epoxide moieties, enabling facile modification with pH-sensitive linkers or polymers and allowing controlled drug release under acidic conditions. Drugs are typically loaded onto GO via π-π stacking and hydrophobic interactions, which are destabilised in acidic environments, thereby accelerating drug desorption. Sultana et al (101) developed gelatin-chitosan composite films incorporating PEG-functionalised few-layer graphene as pH-responsive mesna delivery systems, with the materials exhibiting marked pH-dependent release kinetics and accelerated drug release under acidic conditions (pH 4.5). Zainab et al (102) reported tetraethyl orthosilicate (TEOS)-crosslinked, GO-reinforced chitosan/sodium alginate hydrogels as pH-responsive oral insulin carriers, which suppressed premature release at gastric pH (pH 1.2) and achieved near-complete sustained release at intestinal pH (pH 6.8), with 94% encapsulation efficiency and Fickian diffusion kinetics.

Redox-responsive drug release

Redox-responsive drug release is a widely studied approach in nanomedicine, leveraging the differences in redox conditions between extracellular and intracellular environments to achieve selective drug release (105,106). In graphene-based DDSs, redox-responsive release is most commonly achieved through the cleavage of disulphide bonds (−S-S-). For instance, Liu et al (106) developed a redox-responsive NGO-SS-HA-Gef nanocarrier for targeted gefitinib delivery. HA was conjugated to nano-GO through a cystamine disulphide linker, while gefitinib was loaded through π-π stacking and hydrophobic interactions. The HA coating improved colloidal stability and biocompatibility and promoted CD44 receptor-mediated uptake by CD44-upregulated tumour cells. Intracellular GSH cleaved the disulphide linkage, thereby removing the HA barrier and accelerating gefitinib release. The system achieved a maximum gefitinib loading of ~13.8%. At pH 5.5, cumulative gefitinib release over 72 h increased from 30.8% without GSH to 60.1% in the presence of 10 mM GSH, whereas 10 µM GSH caused little additional release, indicating limited premature release under circulation-like conditions (106). Overall, disulphide-based redox response improves extracellular stability and enables rapid, on-demand intracellular drug release, thereby improving therapeutic selectivity and reducing off-target toxicity. This strategy is highly suitable for graphene-based platforms as their large surface area and facile functionalisation enable the integration of redox triggering with other modalities (such as photothermal effects) for synergistic therapy.

Externally triggered physical stimuli-responsive release

Graphene-based nanocarriers can be engineered to respond to external physical stimuli, including near-infrared (NIR) light, temperature, magnetic fields and ultrasound. Compared with endogenous stimuli, these externally triggered systems provide more precise spatiotemporal control, as release can be achieved at selected tumour sites and defined times. Among these strategies, NIR-responsive drug release is particularly well-studied (107–109). GO, rGO and other graphene derivatives absorb NIR light efficiently and convert it into heat (110). When graphene-based nanocarriers are irradiated with NIR light, the resulting photothermal effect raises the temperature around the nanosheets, weakening non-covalent interactions, such as π-π stacking, hydrogen bonding and hydrophobic interactions, thereby accelerating drug desorption. Local heating can also disrupt thermosensitive polymer coatings or damage tumour cell membranes, further enhancing intracellular drug release. Beyond light- and temperature-responsive modalities, magnetic field-triggered systems are gaining attention as exogenous platforms for spatiotemporally precise cargo transport and on-demand release, featuring deep tissue penetration, non-invasive remote manipulation and favourable biocompatibility (111,112). These systems commonly incorporate magnetic nanoparticles, such as Fe3O4, onto GO or rGO surfaces, providing magnetic targeting and the ability to generate heat under an alternating magnetic field. In such systems, the external magnetic field directs the nanocarriers to the tumour, while magnetothermal heating weakens drug-carrier bonds or alters surface coatings, leading to controlled drug release. Overall, such physical stimuli-responsive graphene-based systems achieve drug release through externally controlled photothermal conversion (113), polymer phase transitions (114) or magnetic heating-induced effect (115). These mechanisms enable on-demand drug release, offering promising strategies to enhance therapeutic accuracy and minimise systemic toxicity.

Compared with passive release systems, stimuli-responsive graphene-based nanocarriers provide improved spatial and temporal control over therapeutic delivery. Notably, pH-responsive systems exploit acidic tumour microenvironments, whereas GSH-responsive systems use intracellular reduction conditions for selective drug release. Enzyme-responsive approaches add further specificity by responding to biological signals associated with tumours. Externally triggered systems, such as NIR-responsive platforms, enable on-demand release through graphene-mediated photothermal conversion. Nonetheless, the practical performance of these systems depends on tumour heterogeneity, stimulus accessibility, release reproducibility and clinical applicability. Moreover, despite the development of numerous graphene-based loading and release strategies, direct quantitative comparison of systems remains challenging as performance is strongly influenced by graphene derivatives, cargo properties, functionalisation methods, experimental conditions and test protocols. Therefore, performance data should be interpreted in the context of specific experimental setups, not generalised across different systems.

Table I systematically evaluates and compares various graphene-based DDSs; it includes parameters such as loading performance, stimulus-triggered release modes, in vitro and in vivo verification results, therapeutic effectiveness and biosafety profiles. The multi-stimulus responsive, covalently modified graphene composite platforms show superior overall therapeutic performance. By contrast, simple non-covalent GO formulations face major challenges, including protein corona interference, limited biodegradability and the lack of in vivo validation, highlighting areas for future focus and improvement.

Table I. Comparison of modified graphene oxide nanocarriers for drug delivery.

Table I.

Comparison of modified graphene oxide nanocarriers for drug delivery.

Samples	Surface functionalisation strategies	Drug delivery	Release mechanism	In vitro/in vivo model	Therapeutic effect	Toxicity assessment	Major limitations	(Refs.)
GO/zinc oxide	Hydrogen bonds	Doxorubicin	pH response	In vitro tumour cell models	Increased apoptosis rate	Low cytotoxicity	Lack of animal validation	(78)
GO/chitosan/dextran	Electrostatic attraction	Doxorubicin hydrochloride	pH response	Multiple in vitro tumour cell lines	Reducing non-specific protein adsorption	No acute cytotoxicity	Forming protein capsids	(79)
GO/Fe2O3	PEG grafting	Doxorubicin	pH response	In vitro tumour cell models	Improved colloidal stability	Low haemolytic toxicity	Reduced endocytosis efficiency	(85)
GO/Fe3O4	Covalent modification	Doxorubicin	pH/NIR response	In vivo breast cancer tumour-bearing mouse models	A three-fold increase in drug accumulation	Low systemic toxicity	Incomplete biodegradability	(91)
GN quantum dots	Peptide covalent linkage	Doxorubicin	Tissue protease response	In vitro tumour cell fluorescence tracing model	Real-time monitoring of drug release	Controllable cytotoxicity	Short duration of action	(98)
GN/gelatin-chitosan	PEG grafting	Mesna	pH response	In vitro mucosal biofilm models	Triples the sustained-release period of the drug	Excellent local biocompatibility	Topical mucosal administration	(92)

[i] PEG, polyethylene glycol; NIR, near-infrared; GN, graphene.

Toxicity and biosafety of graphene-based nanomaterials for drug delivery

The toxicity of graphene-based nanomaterials depends on physicochemical parameters such as size, lateral dimensions, thickness, morphology, surface charge, oxidation and reduction levels, functionalisation and aggregation (116,117). Smaller graphene derivatives generally exhibit enhanced cellular uptake and tissue penetration but may increase oxidative stress, whereas larger nanosheets show reduced uptake but prolonged retention. Thickness, morphology and aggregation affect membrane interactions and inflammation (118). Surface charge regulates cellular internalisation and biological compatibility; positively charged materials improve uptake but may increase protein adsorption, haemolysis and immune response (119). GO is more dispersible and susceptible to functionalisation owing to abundant oxygen-containing groups, whereas rGO has enhanced photothermal properties but shows increased aggregation. Surface functionalisation improves colloidal stability and biocompatibility, but excessive modification alters protein corona formation and cellular responses.

The in vivo behaviour of graphene-based nanomaterials remains a major translational challenge. Owing to their stable carbon structure, graphene derivatives can persist in organs of the mononuclear phagocyte system, including the liver, spleen and lungs. Their biodegradation and clearance are heavily influenced by size, oxidation level, surface chemistry, aggregation and administration route (120). Thus, understanding how their structure affects biodistribution, degradation and clearance is crucial for designing safer nanocarriers. Currently, a key limitation in graphene-based nanomedicine is the absence of standardised biosafety protocols. Variability in graphene types, sizes, oxidation states, surface modifications, doses, administration routes, exposure durations and biological models often produces inconsistent toxicity results. For example, at comparable concentrations, extensively sonicated small-flaked GO exhibits markedly higher genotoxic and oxidative-stress effects compared with untreated larger GO sheets under identical test systems (121). Future safety evaluations should integrate systematic physicochemical characterisation with biological assessments, covering hemocompatibility, immune compatibility, cytotoxicity, genotoxicity, biodistribution, pharmacokinetics and biodegradation, as well as acute and chronic toxicity. Developing standardised and physiologically relevant evaluation methods is vital for establishing reliable structure-property-biological outcome relationships and advancing the clinical use of graphene-based DDSs.

Biological and methodological implications

Graphene-based nanomaterials are promising platforms for drug delivery owing to their two-dimensional structure, large surface area, π-conjugated network and adjustable surface chemistry, which facilitate enhanced drug loading, versatile functionalisation and stimuli-triggered release. Compared with conventional nanocarriers such as soluble polymers, inorganic nanoparticles and magnetic nanoparticles (122), graphene-based systems provide a larger interface for drug adsorption and greater adaptability for incorporating targeting, imaging and therapy functions. However, these features can also cause issues such as non-specific protein adsorption, aggregation in physiological environments, oxidative stress, membrane damage, immune activation and long-term tissue retention (123,124). Therefore, evaluating their biological performance should include not only drug loading and release efficiency but also how material structure, surface chemistry, biological interactions and in vivo fate interrelate. Prior research indicates that the effectiveness of graphene-based drug delivery depends on material design and testing conditions. GO and partially rGO tend to disperse more optimally (125) and show higher functionalisation potential relative to pristine graphene, making them more suitable for biomedical uses. Non-covalent drug loading maintains activity and enables reversible release, whereas covalent conjugation enhances stability but complicates synthesis and affects drug activity (126). Surface modifications, including PEGylation, improve colloidal stability and biocompatibility, but their impact on release, cellular uptake and immune response varies with polymer density, molecular weight, linkage chemistry and surface coverage (127). Responsive systems triggered by pH, redox conditions, enzymes, NIR, temperature or magnetic fields can improve spatiotemporal control over drug release, but their performance depends on tumour heterogeneity and trigger condition reproducibility (106). These aspects may account for differences observed in drug loading, release kinetics, cytotoxicity, targeting efficiency and treatment outcomes across studies.

Clinical translation of graphene-based DDSs

Despite the promising therapeutic potential of graphene-based nanocarriers demonstrated in numerous in vitro and animal studies (128,129), their clinical translation remains limited. Graphene-based DDSs are still at the preclinical phase and clinically validated platforms for cancer therapy remain scarce. The major challenges include concerns over long-term biosafety, uncertain in vivo fate, material heterogeneity and a lack of standardised evaluation criteria (130,131). Beyond safety, reliable manufacturing processes are essential for clinical application. Good manufacturing practice-compatible, large-scale batches with consistent properties are challenging since the features of graphene, such as lateral size, thickness, oxidation level, surface chemistry and aggregation, strongly influence biological performance. Sterilisation, endotoxin removal, impurity control and quality assurance must be developed carefully to ensure product consistency and meet regulatory standards. Before clinical trials, comprehensive preclinical testing is necessary, covering pharmacokinetics, biodistribution, biodegradation, clearance pathways, hemocompatibility, immune response and genotoxicity, as well as acute and chronic toxicity. Establishing standardised characterisation methods and physiologically relevant evaluation models is crucial to ensure safety profiles and gain regulatory approval.

Conclusion and prospects

Graphene-based nanomaterials have emerged as highly adaptable platforms for tumour-targeted drug delivery owing to their two-dimensional structure, large surface area and chemically tuneable interfaces. These features enable high-capacity drug loading, modular functionalisation, tumour-targeted delivery and stimuli-responsive behaviour. Notably, graphene-based nanocarriers hold practical value for precision cancer therapy as they enhance local drug accumulation, reduce systemic toxicity, overcome multidrug resistance and support combined therapies, such as chemo-photothermal therapy, immunomodulation and image-guided treatment. The field is evolving from passive carriers towards stimuli-responsive and increasingly sophisticated cascade-activated systems that utilise tumour-associated signals and external physical triggers to improve selectivity and therapeutic efficacy. However, clinical translation is limited by gaps in understanding structure-property-biological outcome relationships, heterogeneity in material fabrication, unclear long-term biodistribution and clearance, potential immunotoxicity and the absence of standardised evaluation frameworks. Future research should focus on mechanism-based, clinically relevant designs, scalable preparation, biodegradable or transformable graphene systems with predictable in vivo fate, and integrated platforms for targeting, imaging and therapy. Using physiologically relevant models for evaluating graphene-based nanomedicines will be vital for improving reproducibility, safety assessment and clinical translation. These developments can lead to safer, more predictable and clinically applicable graphene-based nanomedicines for precision cancer therapy.

Acknowledgements

Not applicable.

Funding

The present review was supported by the Henan Provincial Engineering Research Center for Biomedical Materials in Respiratory Diseases Open Research Projects (grant no. SWCLGCJS KF02) and the Henan Province Engineering Research Center for Advanced Materials and Applications of 3D Printing in Personalized Respiratory Diseases (Henan Provincial Development and Reform Commission, September 2023; grant no. 3DDYXJCLKF02).

Availability of data and materials

Not applicable.

Authors' contributions

HL conceptualised the review framework and wrote the original manuscript. HY was responsible for reviewing the manuscript. SLiu performed literature searching and revised the manuscript. YX was responsible for manuscript polishing. JH was responsible for writing, reviewing and editing the manuscript and supervision. SLi was responsible for writing, review and editing the manuscript, supervision and funding acquisition. All authors have read and approved the final version of the manuscript. Data authentication is not applicable.

Ethics approval and consent to participate

Not applicable.

Patient consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

References