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Polyurethanes (PU) make up a large portion of commodity plastics appearing in applications including insulation, footwear, and memory foam mattresses. 

Abstract Bioactive degradable scaffolds that facilitate bone healing while fighting off initial bacterial infection have the potential to change established strategies of dealing with traumatic bone injuries. To achieve this a composite material made from calcium phosphate graphene (CaPG), and MXene was synthesized. CaPG was created by functionalizing graphene oxide with phosphate groups in the presence of CaBr with a Lewis acid catalyst. Through this transformation, Ca²⁺and PO₄³⁻inducerons are released as the material degrades thereby aiding in the process of osteogenesis. The 2D MXene sheets, which have shown to have antibacterial properties, were made by etching the Al from a layered Ti₃AlC₂(MAX phase) using HF. The hot‐pressed scaffolds made of these materials were designed to combat the possibility of infection during initial surgery and failure of osteogenesis to occur. These two failure modes account for a large percentage of issues that can arise during the treatment of traumatic bone injuries. These scaffolds were able to retain induceron‐eluting properties in various weight percentages and bring about osteogenesis with CaPG alone and 2 wt% MXene scaffolds demonstrating increased osteogenic activity as compared to no treatment. Additionally, added MXene provided antibacterial properties that could be seen at as little as 2 wt%. This CaPG and MXene composite provides a possible avenue for developing osteogenic, antibacterial materials for treating bone injuries. 

Plastic upcycling, which involves making plastic-derived products with unique or improved properties from discarded plastic materials, is a promising alternative to recycling and disposal to help reduce the overall production of waste. However, recycled and reused materials typically have inferior mechanical, thermal, optical, and barrier properties compared with virgin plastics. Upcycled plastic materials could improve these properties while addressing future waste accumulation. In this study, we use waste poly(ethylene terephthalate) (PET) collected from disposable food packaging to create a repurposed plastic graphene oxide (GO) composite with a goal of upcycling. We developed a one-pot “dynamic depolymerization” to break down PET in the presence of GO and successfully enabled transesterification of the polymer onto GO. Covalent attachment of PET onto GO and tailorable plastic content was confirmed by thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. These covalent composites (PET-GO) were found to be relatively impermeable to water vapor, showing promise for applications in packaging materials. Aqueous degradation experiments on the composite materials demonstrated that, in bulk conditions, PET-GOs remain mechanically robust while in contact with water over appropriate time scales for packaging applications, while beginning to break down in accelerated conditions. The use of depolymerization methods to promote polymer grafting concurrently with polymer deconstruction could provide a more general method for grafting waste polymers onto oxidized carbonaceous substrates with further study. 

Wound dressings based on natural materials, such as fish skin, represent an important strategy for the treatment of burns. Despite their utility, contamination of these natural materials with bacteria (planktonic and biofilm forms) introduces significant risks to patients under treatment. This disadvantage can be overcome by modifying the material’s surface to prevent bacterial deposition through chemical or physical interactions. In this work, functional graphenic materials (FGM) with tunable surface charges were incorporated into tilapia (Oreochromis niloticus) fish skin as a part of a strategy to control the biofilm adhesion on surfaces. The antibiofilm activity was evaluated against S. aureus and K. pneumoniae due to the biofilm-forming properties of these bacterial strains. FGM-modified tilapia skin samples possess a strong capacity to reduce biofilm formation on the tilapia fish skin with a higher antibiofilm activity against Gram-positive bacteria, compared to Gram-negative bacteria. Negatively charged FGMs were more effective than positively charged FGMs in preventing biofilm formation on the impregnated tilapia skin xenografts: negatively charged Claisen graphene achieved an 88.8% reduction in biofilm formation on the tilapia skin. Overall, this study demonstrates the utility of FGM-impregnated tilapia skins as a treatment for burn wounds due to their ability to modulate bacterial adhesion. 

The balance of bacterial populations in the human body is critical for human health. Researchers have aimed to control bacterial populations using antibiotic substrates. However, antibiotic materials that non-selectively kill bacteria can compromise health by eliminating beneficial bacteria, which leaves the body vulnerable to colonization by harmful pathogens. Due to their chemical tunablity and unique surface properties, graphene oxide (GO)-based materials – termed “functional graphenic materials” (FGMs) – have been previously designed to be antibacterial but have the capacity to actively adhere and instruct probiotics to maintain human health. Numerous studies have demonstrated that negatively and positively charged surfaces influence bacterial adhesion through electrostatic interactions with the negatively charged bacterial surface. We found that tuning the surface charge of FGMs provides an avenue to control bacterial attachment without compromising vitality. Using E. coli as a model organism for Gram-negative bacteria, we demonstrate that negatively charged Claisen graphene (CG), a reduced and carboxylated FGM, is bacterio-repellent through electrostatic repulsion with the bacterial surface. Though positively charged poly- l -lysine (PLL) is antibacterial when free in solution by inserting into the bacterial cell wall, here, we found that covalent conjugation of PLL to CG (giving PLL n -G) masks the antimicrobial activity of PLL by restricting polypeptide mobility. This allows the immobilized positive charge of the PLL n -Gs to be leveraged for E. coli adhesion through electrostatic attraction. We identified the magnitude of positive charge of the PLL n -G conjugates, which is modulated by the length of the PLL peptide, as an important parameter to tune the balance between the opposing forces of bacterial adhesion and proliferation. We also tested adhesion of Gram-positive B. subtilis to these FGMs and found that the effect of FGM charge is less pronounced. B. subtilis adheres nondiscriminatory to all FGMs, regardless of charge, but adhesion is scarce and localized. Overall, this work demonstrates that FGMs can be tuned to selectively control bacterial response, paving the way for future development of FGM-based biomaterials as bacterio-instructive scaffolds through careful design of FGM surface chemistry. 

Traditional metal implants such as titanium, cobalt, and chromium have found wide utility in medicine; however, these come with a risk of toxicity. To overcome metal-related toxicity and enable degradability, polyesters including polycaprolactone (PCL), polylactic acid (PLA), and polyglycolic acid (PGA) show promise for the replacement of various biomedical applications of metals due to their accepted biocompatibility and FDA approval. However, polyesters are less stiff than their metallic counterparts, limiting their application to non-load bearing injury sites, such as fixation hardware for fingers. To improve mechanical properties, graphene oxide (GO)-polyester composites are a promising class of biodegradable scaffolds. Initial reports of these composites are encouraging, but mechanical properties still fall short. Traditional composites rely on non-covalent association between GO and the polyesters, which often leads to failure at the interface and weakens the overall strength of the material. Herein, we present a strategy for attachment of these FDA-approved polyesters onto a derivative of GO using a robust covalent bond. By covalently functionalizing the graphenic backbone with polyesters and without metal catalysts, we create functional graphenic materials (FGMs) to not only simultaneously retain biodegradability and compatibility, but also mechanically strengthen PCL, PLA, and PGA; we observed an average increase in the Young's modulus of over 140% compared to the graphenic backbone. These polyester-functionalized FGMs are a promising platform technology for tissue implants. 

Graphene is a valuable material in biomedical implant applications due to its mechanical integrity, long-range order, and conductivity; but graphene must be chemically modified to increase biocompatibility and maximize functionality in the body. Here, we developed a foundational synthetic method for covalently functionalizing a reduced GO with bioactive molecules, focusing on synthetic peptides that have shown osteogenic or neurogenic capability as a prototypical example. X-ray photoelectron spectroscopy provides evidence that the peptide is covalently linked to the graphenic backbone. These peptide–graphene (Pep–G) conjugate materials can be processed into mechanically robust, three-dimensional constructs. Differences in their electrostatic charges allow the Pep–G conjugates to form self-assembled, layer-by-layer coatings. Further, the Pep–G conjugates are cytocompatible and electrically conductive, leading us to investigate their potential as regenerative scaffolds, as conductive surfaces can stimulate bone and nerve regeneration. Notably, PC12 cells grown on an electrically stimulated Pep–G scaffold demonstrated enhanced adhesion and neurite outgrowth compared to the control. The functionalization strategy developed here can be used to conjugate a wide variety of bioactive molecules to graphene oxide to create cell-instructive surfaces for biomedical scaffold materials.