Broad-Spectrum Antimicrobial Polycarbonate Hydrogels with Fast Degradability

Quaternary ammonium-based biomedical materials: State-of-the-art, toxicological aspects and antimicrobial resistance

Microbial infections affect humans worldwide. Many quaternary ammonium compounds have been synthesized that are not only antibacterial, but also possess antifungal, antiviral and anti-matrix metalloproteinase capabilities. Incorporation of quaternary ammonium moieties into polymers represents one of the most promising strategies for preparation of antimicrobial biomaterials. Various polymerization techniques have been employed to prepare antimicrobial surfaces with quaternary ammonium functionalities; in particular, syntheses involving controlled radical polymerization techniques enable precise control over macromolecular structure, order and functionality. Although recent publications report exciting advances in the biomedical field, some of these technological developments have also been accompanied by potential toxicological and antimicrobial resistance challenges. Recent evidenced-based data on the biomedical applications of antimicrobial quaternary ammonium-containing biomaterials that are based on randomized human clinical trials, the golden standard in contemporary medicinal science, are included in the present review. This should help increase visibility, stimulate debates and spur conversations within a wider scientific community on the implications and plausibility for future developments of quaternary ammonium-based antimicrobial biomaterials.

An overview of the therapeutic potential of regenerative medicine in cutaneous wound healing

The global burden of disease associated with wounds is an increasingly significant public health concern. Current treatments are often expensive, time-consuming and limited in their efficacy in chronic wounds. The challenge of overcoming current barriers associated with wound care requires innovative management techniques. Regenerative medicine is an emerging field of research that focuses on the repair, replacement or regeneration of cells, tissues or organs to restore impaired function. This article provides an overview of the pathophysiology of wound healing and reviews the latest evidence on the application of the principal components of regenerative medicine (growth factors, stem cell transplantation, biomaterials and tissue engineering) as therapeutic targets. Improved knowledge and understanding of the pathophysiology of wound healing has pointed to new therapeutic targets. Regenerative medicine has the potential to underpin the design of specific target therapies in acute and chronic wound healing. This personalised approach could eventually reduce the burden of disease associated with wound healing. Further evidence is required in the form of large animal studies and clinical trials to assess long-term efficacy and safety of these new treatments.

Salecan-Based pH-Sensitive Hydrogels for Insulin Delivery

Stimuli-responsive polymeric hydrogels are promising and appealing delivery vehicles for protein/peptide drugs and have made protein/peptide delivery with both dosage- and spatiotemporal-controlled manners possible. Here a series of new Salecan-based pH-sensitive hydrogels were fabricated for controlled insulin delivery via the graft copolymerization reaction between Salecan and 2-acrylamido-2-methyl-1-propanesulfonic acid. In this study, on one hand, Salecan played a key role in modifying the structure and the pore size of the developing hydrogel. On the other hand, Salecan tuned the water content and the water release rate of the obtained hydrogel, leading to a controllable release rate of the insulin. More importantly, in vitro release experiments validated that the release of insulin from this intelligent system could be also tailored by the environmental pH of the release medium. For SGA2, the amount of encapsulated insulin released at gastric conditions (pH 1.2) was relatively low (about 26.1 wt % in 24 h), while that released at intestinal conditions (pH 7.4) increased significantly (over 50 wt % in 6 h). Furthermore, toxicity assays demonstrated that the designed hydrogel carriers were biocompatible. These characteristics make the Salecan-based hydrogel a promising candidate for protein/peptide drug delivery device.

Cationic Salecan-based hydrogels for release of 5-fluorouracil

We designed novel Salecan-based hydrogels for controlled release of 5-fluorouracil.

Amphiphilic and Hydrophilic Block Copolymers from Aliphatic N-Substituted 8-Membered Cyclic Carbonates: A Versatile Macromolecular Platform for Biomedical Applications

Introduction of hydrophilic components, particularly amines and zwitterions, onto a degradable polymer platform, while maintaining precise control over the polymer composition, has been a challenge. Recognizing the importance of these hydrophilic residues in multiple aspects of the nanobiomedicine field, herein, a straightforward synthetic route to access well-defined amphiphilic and hydrophilic degradable block copolymers from diethanolamine-derived functional eight-membered N-substituted aliphatic cyclic carbonates is reported. By this route, tertiary amine, secondary amine, and zwitterion residues can be incorporated across the polymer backbone. Demonstration of pH-responsiveness of these hydrophilic residues and their utility in the development of drug-delivery vehicles, catered for the specific requirements of respective model drugs (doxorubicin and diclofenac sodium salt) are shown. As hydrophilic components in degradable polymers play crucial roles in the biological interactions, these materials offers opportunities to expand the scope and applicability of aliphatic cyclic carbonates. Our approach to these functional polycarbonates will expand the range of biocompatible and biodegradable synthetic materials available for nanobiomedicine, including drug and gene delivery, antimicrobials, and hydrophilic polymers as poly(ethylene glycol) (PEG) alternatives.

Synthesis of Polycarbonates and Poly(ether carbonate)s Directly from Carbon Dioxide and Diols Promoted by a Cs2CO3/CH2Cl2 System

Recently, polycarbonates have attracted considerable research interest because of their potential biodegradability and sustainability. Here, we present a direct route for the synthesis of polycarbonates and poly(ether carbonate)s from carbon dioxide (CO₂) and diols, promoted by Cs₂CO₃ and CH₂Cl₂ under 1 atm of CO₂. Quantitative conversion of diols and polymers with up to 11 kg/mol molecular weight could be obtained. While benzylic diols lead to predominantly carbonate linkage, aliphatic diols result in the incorporation of the methylene unit of CH₂Cl₂ that produces poly(ether carbonate)s. Both primary and secondary diols have been successfully incorporated into the polymer chain.

Poly(amino carbonate urethane)-based biodegradable, temperature and pH-sensitive injectable hydrogels for sustained human growth hormone delivery

In this study, a new pH-/temperature-sensitive, biocompatible, biodegradable, and injectable hydrogel based on poly(ethylene glycol)-poly(amino carbonate urethane) (PEG-PACU) copolymers has been developed for the sustained delivery of human growth hormone (hGH). In aqueous solutions, PEG-PACU-based copolymers existed as sols at low pH and temperature (pH 6.0, 23 °C), whereas they formed gels in the physiological condition (pH 7.4, 37 °C). The physicochemical characteristics, including gelation rate, mechanical strength and viscosity, of the PEG-PACU hydrogels could be finely tuned by varying the polymer weight, pH and temperature of the copolymer. An in vivo injectable study in the back of Sprague-Dawley (SD) rats indicated that the copolymer could form an in situ gel, which exhibited a homogenous porous structure. In addition, an in vivo biodegradation study of the PEG-PACU hydrogels showed controlled degradation of the gel matrix without inflammation at the injection site and the surrounding tissue. The hGH-loaded PEG-PACU copolymer solution readily formed a hydrogel in SD rats, which subsequently inhibited the initial hGH burst and led to the sustained release of hGH. Overall, the PEG-PACU-based copolymers prepared in this study are expected to be useful biomaterials for the sustained delivery of hGH.

Self assembly and hydrogelation of spermine functionalized aromatic peptidomimetics against planktonic and sessile methicillin resistant S. aureus

Novel spermine conjugated shortest nanofibres NF-3 and NF-4 showed potent activity against clinically relevant MRSA with a membrane disruptive mode of action.

Room temperature synthesis of non-isocyanate polyurethanes (NIPUs) using highly reactive N-substituted 8-membered cyclic carbonates

Non-isocyanate polyurethanes (NIPUs) were prepared via polyaddition of highly reactive 8-membered ‘bis-cyclic’ carbonates and various diamines under catalyst-free and room temperature conditions.

Development of polycarbonate-containing block copolymers for thin film self-assembly applications

High quality block copolymers are needed for thin film self-assembly and directed self-assembly applications.

Intrinsically Antibacterial Poly(ionic liquid) Membranes: The Synergistic Effect of Anions

The development of materials with intrinsically antimicrobial activities has attracted great interest. Herein, we report the synthesis of free-standing and robust poly(ionic liquid) (PIL) membranes with high antibacterial activities by in situ photo-cross-linking of an ionic liquid monomer and followed by anion-exchange with an amino acid (l-proline (Pro) or l-tryptophan (Trp)). The resultant PIL-based membranes with excellent robustness exhibit high antimicrobial properties against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) and present no significant hemolysis and cytotoxicity toward human red blood and skin fibroblast cells, as well as low adsorption of bovine serum albumin. The synthesized PIL-Trp membranes exhibit the highest antibacterial efficiency due to the synergistic attributes of both imidazolium cation and Trp^- anion. Furthermore, all the PIL-based membranes exhibit long-term antibacterial stability, which demonstrates clinical feasibility in topical applications.

Biodegradable Block Copolyelectrolyte Hydrogels for Tunable Release of Therapeutics and Topical Antimicrobial Skin Treatment

Biodegradable polycarbonate-based ABA triblock copolyelectrolytes were synthesized and formulated into physically cross-linked hydrogels. These biocompatible, cationically, and anionically charged hydrogel materials exhibited pronounced shear-thinning behavior, making them useful for a variety of biomedical applications. For example, we investigated the antimicrobial activity of positively charged thiouronium functionalized hydrogels by microbial growth inhibition assays against several clinically relevant Gram-negative and Gram-positive bacteria. It is noteworthy that these hydrogels exhibited broad spectrum killing efficiencies approaching 100%, thereby rendering these thixotropic materials attractive for treatment of skin and other surface bound infections. Finally, cationic trimethylammonium containing hydrogels and anionic carboxylic acid functionalized hydrogels were utilized to sustain the release of negatively charged (diclofenac) and positively charged (vancomycin) therapeutics, respectively. Collectively, the present work introduces a simple method for formulating charged hydrogel materials that are capable of interacting with various analytes of interest through noncovalent interactions.