No abstract

As an emerging applied material, graphene has shown tremendous application potential in many fields, including biomedicine. However, the biological behavior of these nanosheets, especially their interactions with cells, is not well understood. Here, we report our findings about the cell surface adhesion, subcellular locations, and size-dependent uptake mechanisms of protein-coated graphene oxide nanosheets (PCGO). Small nanosheets enter cells mainly through clathrin-mediated endocytosis, and the increase of graphene size enhances phagocytotic uptake of the nanosheets. These findings will facilitate biomedical and toxicologic studies of graphenes and provide fundamental understanding of interactions at the interface of two-dimensional nanostructures and biological systems.

Soluble carbon nanotubes are promising materials for in vivo delivery and imaging applications. Several reports have described the in vivo toxicity of carbon nanotubes, however, their effects on male reproduction have not been examined. Here we show that repeated intravenous injections of water-soluble multi-walled carbon nanotubes into male mice can cause reversible testis damage without affecting fertility. Nanotubes accumulated in the testes, generated oxidative stress, and decreased the thickness of the seminiferous epithelium in the testis at day 15, but the damage was repaired after 60 and 90 days. The quantity, quality, and integrity of the sperm and the levels of three major sex hormones were not significantly affected throughout the 90-day period. The fertility of treated male mice was unaffected; the pregnancy rate and delivery success of female mice that mated with the treated male mice did not differ from those that mated with untreated male mice.

We have discovered functionalized multiwalled carbon nanotubes with reduced protein-binding, cytotoxicity, and immune response and the associated structure-activity relationships using in silico surface molecular diversity design, combinatorial library synthesis, and multiple biological screenings. Our results demonstrated the general utility of the nanocombinatorial library approach in nanomedicine and nanotoxicity research.

We report our findings on cellular membrane penetration, endocytosis, endosomal leakage and nuclear translocation of multiwalled carbon nanotubes (MWCNTs). Our data is consistent with a working model for MWCNTs' cell uptake and cellular translocations.

The protein binding propensity of nanoparticles determines their in vivo toxicity and their fate to be opsonized and cleared by human defense systems. In this work, protein-binding mechanisms of pristine and functionalized multiwalled carbon nanotubes (f-MWNTs) were investigated by varying f-MWNTs' diameters, nanotube surface chemistry, and proteins using steady-state and time-resolved fluorescence, and circular dichroism (CD) spectroscopies. The f-MWNTs with a larger diameter (∼40 nm) generally exhibited stronger protein binding compared to those with a smaller diameter (∼10 nm), demonstrating that the curvature of nanoparticles plays a key role in determining the protein binding affinity. Negative charges or steric properties on f-MWNTs enhanced binding for some proteins but not others, indicating that the electrostatic and stereochemical nature of both nanotubes and proteins govern nanotube/protein binding. Protein fluorescence lifetime was not altered by the binding while the intensity was quenched indicating a static quenching through complex formation. The binding-induced conformational changes were further confirmed by CD studies.

Fluorescence imaging of biological systems in the second near-infrared window (NIR-II) has recently drawn much attention because of its negligible background noise of autofluorescence and low tissue scattering. Here we present a new NIR-II fluorescent agent, graphene quantum dots dual-doped with both nitrogen and boron (N-B-GQDs). N-B-GQDs have an ultra-small size (~ 5 nm), are highly stable in serum, and demonstrate a peak fluorescent emission at 1000 nm and high photostability. In addition to the NIR-II imaging capability, N-B-GQDs efficiently absorb and convert NIR light into heat when irradiated by an external NIR source, demonstrating a photothermal therapeutic effect that kills cancer cells in vitro and completely suppresses tumor growth in a glioma xenograft mouse model. N-B-GQDs demonstrate a safe profile, prolonged blood half-life, and rapid excretion in mice, which are the characteristics favorable for in vivo biomedical applications.

Glioblastoma (GBM) is a deadly and debilitating brain tumor with an abysmal prognosis. The standard therapy for GBM is surgery followed by radiation and chemotherapy with temozolomide (TMZ). Treatment of GBMs remains a challenge, largely due to the fast degradation of TMZ, inability to deliver an effective dose of TMZ to tumors, and lack of target specificity which may cause systemic toxicity. Here, we present a simple method to synthesize a nanoparticle-based carrier that can protect TMZ from rapid degradation in physiological solutions and can specifically deliver them to GBM cells through the mediation of a tumor targeting peptide chlorotoxin (CTX). Our nanoparticle, namely NP-TMZ-CTX, had a hydrodynamic size of less than 100 nm, exhibited sustained stability in cell culture media for up to two weeks, and could accommodate stable drug loading. TMZ bound to nanoparticles showed much higher stability at physiological pH, with a half-life 7-fold greater than free TMZ. NP-TMZ-CTX was able to target GBM cells and achieved 2–6-fold higher uptake and 50–90% reduction of IC50 at 72 h post-treatment as compared to non-targeted NP-TMZ. NP-TMZ-CTX showed great promise in its ability to deliver a high therapeutic dose of TMZ to GBM cells, and could serve as a template for targeted delivery of other therapeutics.