Promises, facts and challenges for graphene in biomedical applications

Preparation of poly(lactic acid)/graphene oxide nanofiber membranes with different structures by electrospinning for drug delivery

Nanofiber membranes display promising potential in biomedical fields, especially as scaffolds for drug delivery and tissue engineering. The structures and components of nanofibers play crucial roles in improving the mechanical properties and drug-releasing performance of nanofiber membranes. In this work, poly(lactic acid) (PLA)/graphene oxide (GO) nanofiber membranes with different structures (single-axial and co-axial structure) were prepared by electrospinning. The morphologies, structures, and mechanical properties of the as-prepared nanofiber membranes were characterized and compared. Furthermore, the drug-releasing performance of the as-prepared nanofiber membranes with different structures was evaluated by using an organic dye (Rhodamine B, RhB) as a drug model. Results show that the addition of GO not only significantly improved the thermal stability and mechanical properties of the PLA nanofiber membranes, but also promoted the cumulative release and release rate of RhB from nanofiber membranes. At the same GO concentration, the nanofiber membrane with the co-axial structure displayed a higher tensile strength and Young's modulus, but exhibited a lower cumulative release and release rate. The formation of the co-axial structure is beneficial in suppressing the initial burst release of RhB from nanofiber membranes.

PLA/GO nanofiber membrane with the co-axial structure exhibited the improved mechanical properties, which is also beneficial to separately loading different drugs in core-/sheath-structure and suppressing the initial burst release of drugs.

Anisotropic architecture and electrical stimulation enhance neuron cell behaviour on a tough graphene embedded PVA: alginate fibrous scaffold

Tough scaffolds comprised of aligned and conductive fibers are promising for peripheral nerve regeneration due to their unique mechanical and electrical properties. Several studies have confirmed that electrical stimulation can control the axonal extension in vitro. However, the stimulatory effects of scaffold architecture and electrical stimulation have not yet been investigated in detail. Here, we assessed a comparison between aligned and random fibers made of graphene (Gr) embedded sodium alginate (SA) polyvinyl alcohol (PVA) (Gr-AP scaffolds) for peripheral nerve engineering. The effects of applied electrical stimulation and orientation of the fabricated fibers on the in vitro attachment, alignment, and proliferation of PC12 cells (a rat neuronal cell line) were investigated. The results revealed that the aligned fibrous Gr-AP scaffolds closely mimicked the anisotropic structure of the native sciatic nerve. Aligned fibrous Gr-AP scaffolds significantly improved mechanical properties as well as cell-scaffold integration compared to random fibrous scaffolds. In addition, electrical stimulation significantly improved PC12 cell proliferation. In summary, our findings revealed that aligned fibrous Gr-AP scaffolds offered superior mechanical characteristics and structural properties that enhanced neural cell–substrate interactions, resulting in a promising construct for nerve tissue regeneration.

Tough scaffolds comprised of aligned and conductive fibers are promising for peripheral nerve regeneration due to their unique mechanical and electrical properties.

Bioaccumulation and Toxicity of Carbon Nanoparticles Suspension Injection in Intravenously Exposed Mice

Carbon nanoparticles suspension injection (CNSI) has been widely used in tumor drainage lymph node mapping, and its new applications in drug delivery, photothermal therapy, and so on have been extensively investigated. To develop new clinical applications, the toxicity of CNSI after intravenous exposure should be thoroughly investigated to ensure its safe use. Herein, we studied the bioaccumulation of CNSI in reticuloendothelial system (RES) organs and the corresponding toxicity to mice. After the intravenous injection of CNSI, no abnormal behavior of mice was observed during the 28-day observation period. The body weight increases were similar among the exposed groups and the control group. The parameters of hematology and serum biochemistry remained nearly unchanged, with very few of them showing significant changes. The low toxicity of CNSI was also reflected by the unchanged histopathological characteristics of these organs. The injection of CNSI did not induce higher apoptosis levels either. The slight oxidative stress was observed in RES organs at high dosages at day 7 post-exposure. The implication to the clinical applications and toxicological evaluations of carbon nanomaterials is discussed.

Graphene Improves the Biocompatibility of Polyacrylamide Hydrogels: 3D Polymeric Scaffolds for Neuronal Growth

In tissue engineering strategies, the design of scaffolds based on nanostructures is a subject undergoing intense research: nanomaterials may affect the scaffolds properties, including their ability to interact with cells favouring cell growth and improving tissue performance. Hydrogels are synthetic materials widely used to obtain realistic tissue constructs, as they resemble living tissues. Here, different hydrogels with varying content of graphene, are synthesised by in situ radical polymerization of acrylamide in aqueous graphene dispersions. Hydrogels are characterised focusing on the contribution of the nanomaterial to the polymer network. Our results suggest that graphene is not a mere embedded nanomaterial within the hydrogels, rather it represents an intrinsic component of these networks, with a specific role in the emergence of these structures. Moreover, a hybrid hydrogel with a graphene concentration of only 0.2 mg mL-1 is used to support the growth of cultured brain cells and the development of synaptic activity, in view of exploiting these novel materials to engineer the neural interface of brain devices of the future. The main conclusion of this work is that graphene plays an important role in improving the biocompatibility of polyacrylamide hydrogels, allowing neuronal adhesion.