Preparation and Characterization of Methyl Substituted Maleic Anhydride: Modified Collagens Destined for Medical Applications

Characterization and application of photocrosslinkable collagen maleate as bioink in extrusion-based 3D bioprinting

3D bioprinting, a significant advancement in biofabrication, is renowned for its precision in creating tissue constructs. Collagen, despite being a gold standard biomaterial, faces challenges in bioink formulations due to its unique physicochemical properties. This study introduces a novel, neutral-soluble, photocrosslinkable collagen maleate (ColME) that is ideal for 3D bioprinting. ColME was synthesized by chemically modifying bovine type I collagen with maleic anhydride, achieving a high substitution ratio that shifted the isoelectric point to enhance solubility in physiological pH environments. This modification was confirmed to preserve the collagen's triple-helix structure substantially. Bioprinting parameters for ColME were optimized, focusing on adjustments to the bioink concentration, extrusion pressure, nozzle speed, and temperature. Results demonstrated that lower temperatures and smaller nozzle sizes substantially improved the print quality of grid structures. Additionally, the application of intermittent photo-crosslinking facilitated the development of structurally robust 3D multilayered constructs, enabling the stable fabrication of complex tissues. Cell viability assays showed that encapsulated cells within the ColME matrix maintained high viability after printing. When compared to methacrylated gelatin, ColME exhibited superior mechanical strength, resistance to enzymatic digestion, and overall printability, positioning it as an outstanding bioink for the creation of durable, bioactive 3D tissues.

Development of an In Situ Photo-Crosslinking Antimicrobial Collagen Hydrogel for the Treatment of Infected Wounds

Antimicrobial hydrogels have received considerable attention in the treatment of bacteria-infected wounds. Herein, we develop a neutral, soluble collagen via modification with maleic anhydride, serving as a hydrogel precursor. Maleic anhydride-modified collagen (ColME) could form a gel after exposure to UV light and be loaded with the antimicrobial agents, nisin and levofloxacin, to acquire antimicrobial ability. The ColME hydrogel containing nisin and levofloxacin had good cytocompatibility and effectively killed pathogenic bacterial strains, such as Escherichia coli and Staphylococcus aureus. The antimicrobial ColME hydrogels effectively supported the healing of a full-thickness skin wound infected with S. aureus in a mouse model. Our results demonstrate the potential of antimicrobial hydrogels as effective wound dressings via in situ photogelation for the healing of infected wounds.

Cyclic Anhydrides as Powerful Tools for Bioconjugation and Smart Delivery

Cyclic anhydrides are potent tools for bioconjugation; therefore, they are broadly used in the functionalization of biomolecules and carriers. The pH-dependent stability and reactivity, as well as the physical properties, can be tuned by the structure of the cyclic anhydride used; thus, their application in smart delivery systems has become very important. This review intends to cover the last updates in the use of cyclic anhydrides as pH-sensitive linkers, their differences in reactivity, and the latest applications found in bioconjugation chemistry or chemical biology, and when possible, in drug delivery.

pH-Responsive 2-hydroxyethyl methacrylate/citraconic anhydride–modified collagen hydrogels as ciprofloxacin carriers for wound dressings

pH-Sensitive hydrogels of 2-hydroxyethyl methacrylate/citraconic anhydride–modified collagen were obtained by free radical copolymerization/crosslinking in the presence of ammonium persulfate/ N,N,N′, N′-tetramethylethylenediamine redox initiator system. Their pH-responsiveness was demonstrated by swelling behavior and ciprofloxacin release tests. Both unloaded and loaded hydrogels were characterized by Fourier transform infrared, scanning electron microscopy, and biocompatibility tests. The enzymatic degradation in the presence of Clostridium histolyticum mainly depends on initiator content. In vivo biocompatibility tests involving intraperitoneal hydrogels’ implantation in rats following the analysis by the granuloma test, leukocyte formula, immune parameters, and hepatic transaminases demonstrated their non-toxicity and biocompatibility with living tissues. The in vitro antimicrobial activity, in vivo biocompatibility, and in vitro biodegradability tests attest the possibility to use these new polymeric hydrogels with tailored properties as matrices for bioactive products in medical and pharmaceutical applications as wound care and targeting drug delivery systems. The ciprofloxacin release studies proved their potential as materials for wound dressings.