Green synthesis of Pluronic stabilized reduced graphene oxide: Chemical and biological characterization

New graphene-containing pharmaceutical formulations for infrared lamps-based phototherapy of skin cancer: In vitro validation and ex-vivo human skin permeation

Basal cell carcinoma (BCC) is the most common form of human cancer, and treatment usually involves surgery, with alternative strategies being needed. We propose the use of carbopol hydrogels (HG) for topical administration of nanographene oxide (GOn) and partially-reduced nanographene oxide (p-rGOn) for photothermal therapy (PTT) of BCC. GOn and p-rGOn incorporated into the HG present lateral sizes ∼200 nm, being stable for 8 months. After 20 min irradiation with an infrared (IR) photothermal therapy lamp (15.70 mW cm-2), GOn-HG increased temperature to 44.7 °C, while p-rGOn-HG reached 47.0 °C. Human skin fibroblasts (HFF-1) cultured with both hydrogels (250 μg mL-1) maintained their morphology and viability. After 20 min IR irradiation, p-rGOn HG (250 μg mL-1) completely eradicated skin cancer cells (A-431). Ex vivo human skin permeability tests showed that the materials can successfully achieve therapeutic concentrations (250 μg mL-1) inside the skin, in 2.0 h for GO HG or 0.5 h for p-rGOn HG.

The Green Synthesis of Reduced Graphene Oxide Using Ellagic Acid: Improving the Contrast-Enhancing Effect of Microbubbles in Ultrasound

There is an urgent need to realize precise clinical ultrasound with ultrasound contrast agents that provide high echo intensity and mechanical index tolerance. Graphene derivatives possess exceptional characteristics, exhibiting great potential in fabricating ideal ultrasound contrast agents. Herein, we reported a facile and green approach to synthesizing reduced graphene oxide with ellagic acid (rGO-EA). To investigate the application of a graphene derivative in ultrasound contrast agents, rGO-EA was dispersed in saline solution and mixed with SonoVue (SV) to fabricate SV@rGO-EA microbubbles. To determine the properties of the product, analyses were performed, including ultraviolet-visible spectroscopy (UV-vis), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectrum (XPS), X-ray diffraction analysis (XRD) and zeta potential analysis. Additionally, cell viability measurements and a hemolysis assay were conducted for a biosafety evaluation. SV@rGO-EA microbubbles were scanned at various mechanical index values to obtain the B-mode and contrast-enhanced ultrasound (CEUS) mode images in vitro. SV@rGO-EA microbubbles were administered to SD rats, and their livers and kidneys were imaged in CEUS and B-mode. The absorption of rGO-EA resulted in an enhanced echo intensity and mechanical index tolerance of SV@rGO-EA, surpassing the performance of SV microbubbles both in vitro and in vivo. This work exhibited the application potential of graphene derivatives in the field of ultrasound precision medicine.

A 3D-Printed Graphene BioFuse Implant for Postsurgical Adjuvant Therapy of Cancer: Proof of Concept in 2D- and 3D-Spheroid Tumor Models

Three-dimensional printing is an emerging technology that is finding its niche applications in diverse fields owing to its flexibility concerning personalization and design. Surgery followed by adjuvant therapy is the standard treatment plan in most cancers from stage I to stage III. Most of the available adjuvant therapies, like chemotherapy, radiation therapy, immunotherapy, hormonal therapy, etc., are associated with severe side effects that considerably reduce the quality of life of patients. In addition, there is always the chance of tumor recurrence or metastasis development followed by surgery. This investigation reports the development of a 3D-printed, biodegradable, laser-responsive implant with a chemo-combined thermal ablating potential for adjuvant therapy of cancer. The 3D-printable ink was developed using poly(l-lactide) and hydroxypropyl methylcellulose as the base polymer, doxorubicin as the chemotherapeutic agent, and reduced graphene oxide as the photothermal ablating agent. The personalized implant released the drug pH-dependently (p value < 0.0001) for an extended period (93.55 ± 1.80% → 28 days). The 3D-printed implant exhibited acceptable biophysical properties (tensile strength: 3.85 ± 0.15 MPa; modulus: 92.37 ± 11.50 MPa; thickness: 110 μm) with laser-responsive hyperthermia (ΔT: 37 ± 0.9 °C → 48.5 ± 1.07 °C; 5 min; 1.5 W/cm²) and inherent biodegradable property (SEM analysis). The 3D-printed implant was evaluated for its therapeutic potential in 2D- and 3D-spheroid tumor models (MDA-MB 231 and SCC 084 2D cells) employing MTT cytotoxicity assay, apoptosis assay, cell cycle analysis, and gene expression analysis. The biomolecular aspects and biomechanics of the 3D-printed BioFuse implant were also evaluated by determining the effect of treatment on the expression levels of HSP1A, Hsp70, BAX, and PTEN. It is advocated that the knowledge developed in this project will significantly assist and advance the science aiming to develop a clinically translatable postsurgical adjuvant therapy for cancer.

Mosquito-Borne Diseases and Their Control Strategies: An Overview Focused on Green Synthesized Plant-Based Metallic Nanoparticles

Mosquitoes act as vectors of pathogens that cause most life-threatening diseases, such as malaria, Dengue, Chikungunya, Yellow fever, Zika, West Nile, Lymphatic filariasis, etc. To reduce the transmission of these mosquito-borne diseases in humans, several chemical, biological, mechanical, and pharmaceutical methods of control are used. However, these different strategies are facing important and timely challenges that include the rapid spread of highly invasive mosquitoes worldwide, the development of resistance in several mosquito species, and the recent outbreaks of novel arthropod-borne viruses (e.g., Dengue, Rift Valley fever, tick-borne encephalitis, West Nile, yellow fever, etc.). Therefore, the development of novel and effective methods of control is urgently needed to manage mosquito vectors. Adapting the principles of nanobiotechnology to mosquito vector control is one of the current approaches. As a single-step, eco-friendly, and biodegradable method that does not require the use of toxic chemicals, the green synthesis of nanoparticles using active toxic agents from plant extracts available since ancient times exhibits antagonistic responses and broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on the different mosquito control strategies in general, and on repellent and mosquitocidal plant-mediated synthesis of nanoparticles in particular, has been reviewed. By doing so, this review may open new doors for research on mosquito-borne diseases.

Development and assessment of phospholipid-based luteolin-loaded lipid nanocapsules for skin delivery

Luteolin is an excellent flavone possessing several beneficial properties such as antioxidant and anti-inflammatory effects which are interesting for skin delivery. Development of an appropriate skin delivery system could be a promising strategy to improve luteolin cutaneous performance.So, the main aim of this work was to fabricate, characterize and evaluate phospholipid-based luteolin-loaded lipid nanocapsules for skin delivery. The influence of phospholipid/oil ratio, surfactant type and chitosan coating were investigated. The prepared formulations underwent in vitro assessment and the selected formulations were evaluated ex vivo and in vivo. The mean diameters of investigated formulations varied between 174 nm and 628 nm while zeta potential varied between -25.7 ± 4.8 mV and 6.8 ± 1.7 mV. Increasing in phospholipid/oil ratios resulted in decrease in particles size with little effect on zeta potential and drug encapsulation. Cremophor EL showed the lowest particle sizes and the highest drug encapsulation. Chitosan coating shifted zeta potential towards positive values. Structural analyses showed that luteolin is incorporated into lipid core of nanocapsules. Selected formulations (LNC4 and LNC13) exhibited sustained in vitro release and antioxidant activity. LNC13 (chitosan coated) showed higher flux (0.457 ± 0.113 µg/cm²/h), permeability (45.70 ± 11.66 *10^-5 cm²/h) and skin retention (121.66 ± 7.6 µg/cm² after 24 h) when compared to LNC4 and suspension. It also showed disordered the integrity of the stratum corneum, increased epidermal thickness and relieving most of inflammatory features in animal model. In conclusion, this study proves that lipid nanocapsules could effectively deliver luteolin into skin and then can be established as a potential system in the pharmaceutical and cosmeceutical horizons.

Remediation of pharmaceutical pollutants using graphene-based materials - A review on operating conditions, mechanism and toxicology

Graphene is a high surface area special carbon compound with exceptional biological, electronic and mechanical properties. Graphene-based materials are potential components used in water treatment on different modes and processes. Ibuprofen and ciprofloxacin are two commonly found pharmaceutical contaminants discharged into water bodies from industrial, domestic and hospital sources. Their concentration levels in water bodies are reported in the range of 1 μg/L to 6.5 mg/L and 0.050-100 μg/L respectively. Their toxic effects pose very high risk to the inhabiting organisms. Their ability to resist biodegradation and capacity to bioaccumulate makes the conventional methods less effective in removal. In the present article, treatment of these compounds via three methods, adsorption, photocatalytic degradation and electro-fenton reactions using graphene-based materials along with the methods adopted for synthesis and treatment are reviewed. The uptakes obtained by graphene-derived adsorbents are presented along with the optimal operating conditions. Studies reported complete removal of ibuprofen from wastewater was achieved at 7 pH for 60 min using graphene membrane as adsorbent and uptake of 99% of ciprofloxacin was exhibited for graphene nanoplates/boron nitrate aerogel at a pH of 7 and 60 min. The reduced graphene oxide surface exhibits higher affinity to light adsorption which leads to the formation of photo generated electrons. The future perspectives for improved applications of graphene-based materials and the research gap currently existing are highlighted.

Graphene-Based Nanomaterials for Dental Applications: Principles, Current Advances, and Future Outlook

With the development of nanotechnology, nanomaterials have been used in dental fields over the past years. Among them, graphene and its derivatives have attracted great attentions, owing to their excellent physicochemical property, morphology, biocompatibility, multi-differentiation activity, and antimicrobial activity. In our review, we summarized the recent progress about their applications on the dentistry. The synthesis methods, structures, and properties of graphene-based materials are discussed. Then, the dental applications of graphene-based materials are emphatically collected and described. Finally, the challenges and outlooks of graphene-based nanomaterials on the dental applications are discussed in this paper, aiming at inspiring more excellent studies.

Development of Graphene-Based Materials in Bone Tissue Engineaering

Bone regeneration-related graphene-based materials (bGBMs) are increasingly attracting attention in tissue engineering due to their special physical and chemical properties. The purpose of this review is to quantitatively analyze mass academic literature in the field of bGBMs through scientometrics software CiteSpace, to demonstrate the rules and trends of bGBMs, thus to analyze and summarize the mechanisms behind the rules, and to provide clues for future research. First, the research status, hotspots, and frontiers of bGBMs are analyzed in an intuitively and vividly visualized way. Next, the extracted important subjects such as fabrication techniques, cytotoxicity, biodegradability, and osteoinductivity of bGBMs are presented, and the different mechanisms, in turn, are also discussed. Finally, photothermal therapy, which is considered an emerging area of application of bGBMs, is also presented. Based on this approach, this work finds that different studies report differing opinions on the biological properties of bGBMS due to the lack of consistency of GBMs preparation. Therefore, it is necessary to establish more standards in fabrication, characterization, and testing for bGBMs to further promote scientific progress and clinical translation.

In vitro and in vivo evaluation of cyclosporine-graphene oxide laden hydrogel contact lenses

Drug-eluting contact lens can substitute the multiple eye drop therapy. However, loading hydrophobic drug like cyclosporine in the contact lens is very challenging, due to low drug uptake (via soaking method); and alteration in the swelling and optical properties which restricts its clinical application. To address the above issues, graphene oxide (GO, large surface area with oxygen containing functional groups) was incorporated in the contact lenses during fabrication. These GO-laden contact lenses (SM-GO-Cys) as well as blank contact lenses (SM-Cys) were soaked in the solution of cyclosporine. Alternatively, cyclosporine-laden contact lenses (DL-Cys-20) and cyclosporine-GO-laden contact lenses (DL-Cys-20-GO) were fabricated by adding drug and drug-GO (at various level of GO) during fabrication, respectively. Contact angle and swelling data showed increase in water holding capacity of GO laden contact lenses. Optical property was significantly improved due to molecular dispersion of drug on the surface of GO sheets. The drug uptake and in vitro release profile was improved with GO-laden contact lenses by soaking method (SM-GO-Cys-400n) due to hydrophobic interactions between GO and drug. Adding cyclosporine-GO (DL-Cys-20-GO-800n) during fabrication significantly improved drug release kinetics with higher drug leaching (during extraction and sterilization) due to increased swelling, improved dissolution and molecular dispersion of drug on GO sheets. Ocular irritation and histopathological studies demonstrated the safety of GO-contact lens. The in vivo drug release studies in the rabbit eye showed significant improvement in mean residence time (MRT) and area under the curve (AUC) using DL-Cys-20-GO-800n contact lens compared to eye drop solution with reduction in protein adherence value. The study demonstrated that the incorporation of GO into the contact lens can control the release of cyclosporine as well as improved the lens swelling and transmittance properties.

Green Synthesis of Metal and Metal Oxide Nanoparticles: Principles of Green Chemistry and Raw Materials

Increased request for metal and metal oxide nanoparticles nanoparticles has led to their large-scale production using high-energy methods with various toxic solvents. This cause environmental contamination, thus eco-friendly “green” synthesis methods has become necessary. An alternative way to synthesize metal nanoparticles includes using bioresources, such as plants and plant products, bacteria, fungi, yeast, algae, etc. “Green” synthesis has low toxicity, is safe for human health and environment compared to other methods, meaning it is the best approach for obtaining metal and metal oxide nanoparticles. This review reveals 12 principles of “green” chemistry and examples of biological components suitable for “green” synthesis, as well as modern scientific research of eco-friendly synthesis methods of magnetic and metal nanoparticles. Particularly, using extracts of green tea, fruits, roots, leaves, etc., to obtain Fe3O4 NPs. The various precursors as egg white (albumen), leaf and fruit extracts, etc., can be used for the „green” synthesis of spinel magnetic NPs. “Green” nanoparticles are being widely used as antimicrobials, photocatalysts and adsorbents. “Green” magnetic nanoparticles demonstrate low toxicity and high biocompatibility, which allows for their biomedical application, especially for targeted drug delivery, contrast imaging and magnetic hyperthermia applications. The synthesis of silver, gold, platinum and palladium nanoparticles using extracts from fungi, red algae, fruits, etc., has been described.

Controlled bimatoprost release from graphene oxide laden contact lenses: In vitro and in vivo studies

Ocular drug delivery using contact lenses may be able to substitute for eye drop therapy. However, issues with hydrophobic drugs (like bimatoprost that is used to treat glaucoma) such as low drug uptake using a simple soaking method into preformed contact lenses and alteration in the swelling and transmittance of lenses restricts the application for drug delivery. This research uses graphene oxide (GO) to control the release of bimatoprost from contact lenses along with improvements in the drug uptake, and lens swelling and transmittance. GO was loaded into silicone hydrogel contact lenses by adding the GO at the same time as lenses were polymerized. These lenses were soaked in bimatoprost. Alternatively contact lenses, either with or without GO, were produced by adding bimatoprost during lens polymerization. GO improved contact lens swelling due to its water binding capacity and lens transmittance due to the molecular dispersion of bimatoprost on the surface of the GO which prevented the local precipitation of the drug. The bimatoprost uptake was not improved in the presence of GO. However, its in vitro release profile was improved. Adding bimatoprost and GO at the same time as lenses were polymerized (DL-GO-BMT) significantly decreased the loss of drug during extraction and sterilization in comparison to contact lenses (DL-BMT) without GO. As the amount of GO was increased, the DL-GO-BMT lenses showed a significant decrease in the burst and cumulative release of bimatoprost. Ocular irritation and histopathology reports demonstrated the safety of GO contact lens. The in vivo pharmacokinetic studies in the rabbit tear fluid showed significant improvement in mean residence time (MRT) and area under the curve (AUC) with DL-GO-0.2 μg-BMT-100 contact lens in comparison to eye drop solution. The study demonstrated that the addition of GO to contact lenses can control the release of bimatoprost as well as improved the lens swelling and transmittance. However, further optimization is needed to modulate the release of drug within the therapeutic level to manage glaucoma.

Factors affecting the biological response of Graphene

Nanotechnology has gained significant importance in different fields of medical, electronic, and environmental science. This technology is founded on the use of materials at the nanoscale scale (1-100 nanometers) for various purposes, particularly in the biomedical area, where its application is growing daily due to the need of materials with advanced properties. Over the past few years, there has been a growing use for graphene and its derivative composite materials. However, different physico-chemical properties influence its biological response; therefore, further studies to explain the interactions of these nanomaterials with biological systems are critical. This review presents the current advances in the applications of graphene in biomedicine with a focus on the physico-chemical characteristics of the graphene family and their influences on biological interactions.

Green Approaches to Carbon Nanostructure-Based Biomaterials

The family of carbon nanostructures comprises several members, such as fullerenes, nano-onions, nanodots, nanodiamonds, nanohorns, nanotubes, and graphene-based materials. Their unique electronic properties have attracted great interest for their highly innovative potential in nanomedicine. However, their hydrophobic nature often requires organic solvents for their dispersibility and processing. In this review, we describe the green approaches that have been developed to produce and functionalize carbon nanomaterials for biomedical applications, with a special focus on the very latest reports.

Transdermal delivery of buprenorphine from reduced graphene oxide laden hydrogel to treat osteoarthritis

The patients with chronic pain in osteoarthritis often have insufficient pain relief from non-opioids analgesics. Buprenorphine is a promising molecule for symptomatic relief of chronic pain. The marketed parenteral injections and sublingual tablets have short duration of action (half-life = 2.7 h), which is not suitable to manage chronic pain. The purpose of this research was to design buprenorphine-loaded Pluronic F127-reduced graphene oxide transdermal (noninvasive) hydrogel to achieve sustained release of buprenorphine to manage chronic pain in osteoarthritis. Pluronic F127 was used to stabilize the reduced graphene oxide in hydrogel system. The characterization studies including Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy confirmed the synthesis of Pluronic F127-reduced graphene oxide from graphite. The transmission electron microscopy image showed flat nanosheets of reduced graphene oxide (rGO). The developed hydrogel showed desirable pH, viscosity, adhesiveness, hardness, and cohesiveness for transdermal application. The ex vivo release study demonstrated the ability of the Pluronic F127-reduced graphene oxide (P-rGO) hydrogel to prolong release up to 14 days, owing to the strong π-π interactions between the graphene oxide (GO) and the buprenorphine. In cold ethanol tail flick model, the GO hydrogel showed sustained analgesic effect in comparison with hydrogel without rGO. Thus, this study demonstrated the potential of using Pluronic F127-reduced graphene oxide nanocarriers to prolong local analgesia for effective management for chronic pain.

Lidocaine-loaded reduced graphene oxide hydrogel for prolongation of effects of local anesthesia: In vitro and in vivo analyses

Lidocaine is widely used as a local anesthetic for alleviation of post-operative pain and for management of acute and chronic painful conditions. Although several approaches are currently used to prolong the duration of action, an effective strategy to achieve neural blockage for several hours remains to be identified. In this study, a lidocaine-loaded Pluronic® F68-reduced graphene oxide hydrogel was developed to achieve sustained release of lidocaine. Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy confirmed the synthesis of Pluronic® F68-reduced graphene oxide. Transmission electron microscopy showed wrinkled, flat nanosheets with micelles attached. The developed hydrogel showed desirable pH, viscosity, adhesiveness, hardness, and cohesiveness for topical application. The ex vivo release study demonstrated the ability of the Pluronic® F68-reduced graphene oxide hydrogel to prolong release up to 10 h, owing to the strong π-π interactions between the graphene oxide and the lidocaine. In comparison with a commercial lidocaine ointment, the developed graphene oxide hydrogel showed sustained anesthetic effect in the radiant heat tail flick test and sciatic nerve block model. Thus, this study demonstrates the potential of using Pluronic® F68-reduced graphene oxide nanocarriers to realize prolonged effects of local anesthesia for effective pain management.

Sustained release of tulobuterol from graphene oxide laden hydrogel to manage asthma

Bronchial asthma is a chronic disease which is currently treated using various inhalants. However, the medication adherence with the inhalants is poor due to complex procedure to use them along with frequent dosing. In this paper, we have developed tulobuterol loaded Pluronic® F127-reduced graphene oxide transdermal hydrogel to sustain the release of tulobuterol to manage asthma for days. The synthesis of Pluronic^® F127-reduced graphene oxide was confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. The transmission electron microscope showed wrinkled flat nano sheets. The hydrogel showed sufficient mechanical properties for topical application and was safe in the skin irritation study (rabbit model). The ex vivo release data demonstrated the ability of reduced graphene oxide to sustain the release of tulobuterol for 72 h, due to strong π-π interaction between drug and graphene oxide. The pharmacokinetic profile in Sprague-Dawley rat model confirmed the potential of tulobuterol-Pluronic^® F127-reduced graphene oxide hydrogel to sustain the release of tulobuterol for effective management of asthma.

RETRACTED: Pluronic® F127 stabilized reduced graphene oxide hydrogel for the treatment of psoriasis: In vitro and in vivo studies

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors. Significant similarities were noticed post-publication between this article and an article submitted to the journal on the same day, by an apparently unrelated research group: Hui Li, Yanlu Jia and Chunling Liu, Colloids and Surfaces B: Biointerfaces 195 (2020) 111259 https://doi.org/10.1016/j.colsurfb.2020.111259. Moreover, the authors did not respond to the journal request to comment on these similarities and to provide the raw data, and the Editors decided to retract the article. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and genuine. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process. Although this article was published earlier than the article from Colloids and Surfaces B: Biointerfaces 195 (2020) 111259, the Editors decided to retract this article given the concerns on the reliability of the data.

RETRACTED: Pluronic® F127 stabilized reduced graphene oxide hydrogel for transdermal delivery of ondansetron: Ex vivo and animal studies

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors. Significant similarities were noticed post-publication between this article and an article submitted to the journal on the same day, by an apparently unrelated research group: Qiang Li, Fangmei Li, Xixi Qi, Fuqiao Wei, Hongxiao Chen and Ting Wang, Colloids and Surfaces B: Biointerfaces 195 (2020) 111246 https://doi.org/10.1016/j.colsurfb.2020.111246. Moreover, the authors did not respond to the journal request to comment on these similarities and to provide the raw data, and the Editors decided to retract the article. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and genuine. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Hyaluronic acid and graphene oxide loaded silicon contact lens for corneal epithelial healing

Hyaluronic acid (HA) eye drop solution is widely used to treat and manage various corneal diseases like keratoconus (after corneal cross-linking) and dry eye syndrome. However, ocular dosage forms like eye drop solution affect the routine life style of patients due to frequent dosing schedule. In this study, HA and reduced graphene oxide (rGO) was directly loaded in the silicon contact lenses (HA-GO-DL) and compared with the conventional soaking method (HA-GO-SM). The contact lenses at lower level of rGO showed permissible swelling and transmittance properties. The water retention property of HA-GO-DL contact lenses was confirmed by water evaporation studies. The flux data of HA-GO-SM contact lenses showed high burst release with 24 h release duration. While, HA-GO-DL lenses confirmed low burst with sustained release up to 96 h. In ocular irritation study, the HA-GO-DL-2 lenses was found to be safe. The HA-GO-DL-2 batch showed high HA-tear fluid concentration (rabbit model) and improvement in the rabbit tear fluid volume (Schirmer strip studies) in comparison to the soaking method (HA-GO-SM-2) and eye drop solution. The study successfully demonstrate the potential of HA-GO loaded contact lenses to improve tear fluid volume to manage various ocular diseases like dry eye syndrome.

Synthesis, Characterization, and Toxicity Assessment of Pluronic F127-Functionalized Graphene Oxide on the Embryonic Development of Zebrafish (Danio rerio)

BACKGROUND

In the current literature, there are ongoing debates on the toxicity of graphene oxide (GO) that demonstrate contradictory findings regarding its toxicity profile. As a potential drug carrier, these findings are very concerning due to the safety concerns in humans, as well as the dramatic rise of GO being excreted into the environment. Therefore, there is an imperative need to mitigate the potential toxicity of GO to allow for a safer application in the future.

PURPOSE

The present study aims to address this issue by functionalizing GO with Pluronic F127 (PF) as a means to mitigate toxicity and resolve the biocompatibility of GO. Although results from previous studies generally indicated that Pluronic functionalized GO exhibits relatively low toxicity to living organisms, reports that emphasize on its toxicity, particularly during embryonic developmental stage, are still scarce.

METHODS

In the present study, two different sizes of native GO samples, GO and NanoGO, as well as PF-functionalized GO, GO-PF and NanoGO-PF, were prepared and characterized using DLS, UV-Vis, Raman spectroscopy, FTIR, and FESEM analyses. Toxicological assessment of all GO samples (0-100 µg/mL) on zebrafish embryonic developmental stages (survival, hatching and heart rates, and morphological changes) was recorded daily for up to 96 hours post-fertilization (hpf).

RESULTS

The toxicity effects of each GO sample were observed to be higher at increasing concentrations and upon prolonged exposure. NanoGO demonstrated lower toxicity effects compared to GO. GO-PF and NanoGO-PF were also found to have lower toxicity effects compared to native GO samples. GO-PF showed the lowest toxicity response on zebrafish embryo.

CONCLUSION

These findings highlight that toxicity is dependent on the concentration, size, and exposure period of GO. Functionalization of GO with PF through surface coating could potentially mitigate the toxicity effects of GO in embryonic developmental stages, but further investigation is warranted for broader future applications.

Organ distribution and biological compatibility of surface-functionalized reduced graphene oxide

Graphene is an sp² hybridized allotrope of carbon with a honeycomb lattice structure that has many applications in biomedicine owing to its unique physico-chemical properties. Graphene has attracted much interest from scientists for its biomedical potential, including in drug/gene delivery, fluorescent labeling of target analytes, tissue engineering, regenerative medicine and MRI contrast enhancement. However, there are very limited data available concerning the toxicity of graphene, and efforts have been made to study the bio-nano interactions of Pluronic functionalized reduced graphene oxide (rGO-P) in animal models. The present study aimed to evaluate the systemic toxicity of rGO-P and its ability to cross the blood-brain barrier in Swiss Albino mice subject to acute exposure to 10 mg kg^-1 body weight of rGO-P. Prolonged exposure was evaluated in female Wistar rats by analyzing feto-placental transmission and any associated developmental neurotoxicity after intravenous administration of 5 mg kg^-1 and 10 mg kg^-1 body weight of rGO-P. Biodistribution analysis using confocal Raman mapping indicated that tiny amounts of rGO-P accumulated in major organs of both dams and pups, with no evident toxic response. The accumulation of rGO-P in various tissues of rat pups born to treated dams is ample evidence of feto-placental transmission. The present study clearly suggests that rGO-P is not toxic under any of the experimental conditions. These findings can therefore be carried forward for application of rGO-P in drug/gene delivery, early diagnosis and treatment of various diseases in neonates and adults. The results of the study show that rGO-P is an auspicious and promising material for future healthcare applications.

Graphenic Materials for Biomedical Applications

Graphene-based nanomaterials have been intensively studied for their properties, modifications, and application potential. Biomedical applications are one of the main directions of research in this field. This review summarizes the research results which were obtained in the last two years (2017-2019), especially those related to drug/gene/protein delivery systems and materials with antimicrobial properties. Due to the large number of studies in the area of carbon nanomaterials, attention here is focused only on 2D structures, i.e. graphene, graphene oxide, and reduced graphene oxide.

Biofabrication of Lysinibacillus sphaericus-reduced graphene oxide in three-dimensional polyacrylamide/carbon nanocomposite hydrogels for skin tissue engineering

The biological synthesis of reduced graphene oxide (rGO) from graphene oxide (GO) is an emerging phenomenon for developing biocompatible nanomaterials for its potential applications in nanomedicine. In this study, we demonstrated a simple, green, and non-toxic method for graphene synthesis using the live biomass of Lysinibacillus sphaericus as the reducing and stabilizing agent under ambient conditions. Ultraviolet-visible spectroscopic analysis confirmed the formation of graphene from GO suspension. X-ray diffraction studies showed the disappearance of the GO peak and the appearance of characteristic graphene broad peak at 2θ = 22.8°. Infrared analysis showed the decrease/disappearance of peaks corresponding to the oxygen-containing functionalities, and appearance of a peak at 1620 cm^-1 from unoxidized graphitic domains. Scanning electron microscopic images showed that L. sphaericus-reduced graphene oxide (L-rGO) contains aggregated graphene nanoflakes. Evaluation of the in vitro cytotoxicity of L-rGO nanosheets on human skin fibroblasts using the WST-1 assay did not show any significant effects after 24 h of exposure, which is indicative of biocompatibility. Polyacrylamide hydrogels with L-rGO were synthesized and used as scaffolds to support the growth and proliferation of skin fibroblasts. Cell viability assays and DAPI staining showed proliferation of fibroblasts and exhibited 83% of cell viability even after 28 days. Biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus was enhanced in nanocomposite hydrogels in the presence of 0.25 mg/mL GO and L-rGO in 48 h. Overall, this study showed that microbially-synthesized L-rGO can be used as a dopant in polymeric scaffolds for tissue engineering and highlighted their role in biofilm formation.