Polyester-based photocrosslinkable bioadhesives for wound closure and tissue regeneration support

One-Pot Synthesis of Antibacterial and Antioxidant Self-Healing Bioadhesives Using Ugi Four-Component Reactions

Bioadhesive materials are extensively utilized as alternatives to surgical sutures and wound dressings. Despite significant advancements in their synthesis, current bioadhesives suffer from inadequate mechanical stability, suboptimal wet tissue adhesion, and a lack of inherent antibacterial and antioxidant properties, while requiring multistep synthesis processes, complicating their production for biomedical applications. To address these limitations, we developed a new bioadhesive, named UgiGel, synthesized through a one-pot Ugi four-component reaction (Ugi-4CR). Our strategy utilized gelatin as the backbone, 4-formylphenylboronic acid (4-FPBA) as an aldehyde source for improved adhesion and antibacterial activity, gallic acid (GA) as a carboxylic acid source for improved antioxidant activity and wound healing, and cyclohexyl isocyanide (CyIso) to induce pseudopeptide structures. The internal crosslinking between GA and 4-FPBA via dynamic boronate ester bond formation, triggered by slight pH changes (7.4-7.8) and temperature elevation (25°C-40°C), resulted in the formation of viscoelastic and self-healing hydrogels with water as the only byproduct without the need for initiator/light activation. UgiGel showed higher adhesion to porcine skin tissue (139.8 ± 8.7 kPa) as compared to commercially available bioadhesives, Evicel (26.3 ± 2.6 kPa) and Coseal (19.3 ± 9.9 kPa). It also demonstrated effective antibacterial properties against both Gram-negative and Gram-positive bacteria, as well as antioxidant activity. Additionally, the in vitro studies using NIH-3T3 cells confirmed the biocompatibility of the UgiGel over 7 days of culture. Moreover, in vivo biocompatibility and biodegradation of UgiGel were confirmed via subcutaneous implantation in rats for up to 28 days. Our results demonstrated that UgiGel outperformed commercially available bioadhesives in terms of adhesion, self-healing, and antibacterial activity, without compromising biocompatibility or physical properties, representing a promising multifunctional bioadhesive for wound sealing and repair.

Degradable polymer bone adhesives

Highly comminuted fractures and bone defects pose a significant challenge for orthopedic surgery. Current surgical procedures commonly rely on metal implants (such as bone plates, nails and pins) for fracture internal and external fixations, but they are likely to result in problems, such as stress shielding and poor bone healing. Bone adhesive represents an attractive alternative for the treatment of fracture. The ideal bone adhesive should satisfy several performance requirements, including high adhesion strength for bone tissues, rapid in-situ curing in a physiological environment, good biocompatibility with no toxicity, degradability, and good stability in vivo. Among these requirements, degradability is a crucial characteristic of bone adhesives. This property enables the material to be easily removed without the need for surgery at a later stage, ensuring the regeneration of bone tissue without any hindrance. The degradation rate of bone adhesive varies depending on the application scenarios and tissues, ranging from weeks to years. Many bone adhesives are unable to guarantee degradability while achieving other necessary performances. Therefore, this article provides a detailed overview of the strategies to fabricate biodegradable polymer bone adhesives that can maintain high bulk and adhesion strength, biocompatibility and other properties. Finally, the current challenges in the clinical translation of bone adhesives and their future development directions are discussed.

Non-Isocyanate Urethane Acrylate Derived from Isophorone Diamine: Synthesis, Characterization and Its Application in 3D Printing

In this paper, urethane-based acrylates (UA) were prepared via an environmentally friendly non-isocyanate route. Isophorone diamine (IPDA) reacted with ethylene carbonate (EC), producing carbamate containing amine and hydroxyl groups, which further reacted with neopentyl glycol diacrylate (NPGDA) by aza Michael addition, forming UA. The structures of the obtained intermediates and UA were characterized by 1H NMR and electrospray ionization high-resolution mass spectrometry (ESI-HRMS). The photopolymerization kinetics of UA were investigated by infrared spectroscopy. The composite with obtained UA can be UV cured quickly to form a transparent film with a tensile strength of 21 MPa and elongation at break of 16%. After UV curing, the mono-functional urethane acrylate was copolymerized into the cross-linked network in the form of side chains. The hydroxyl and carbamate bonds on the side chains have high mobility, which make them easy to form stronger dynamic hydrogen bonds during the tensile process, giving the material a higher tensile strength and elongation at break. Therefore, the hydrogen bonding model of a cross-linked network is proposed. The composite with UA can be 3D printed into models.

Degradable biomedical elastomers: paving the future of tissue repair and regenerative medicine

Degradable biomedical elastomers (DBE), characterized by controlled biodegradability, excellent biocompatibility, tailored elasticity, and favorable network design and processability, have become indispensable in tissue repair. This review critically examines the recent advances of biodegradable elastomers for tissue repair, focusing mainly on degradation mechanisms and evaluation, synthesis and crosslinking methods, microstructure design, processing techniques, and tissue repair applications. The review explores the material composition and cross-linking methods of elastomers used in tissue repair, addressing chemistry-related challenges and structural design considerations. In addition, this review focuses on the processing methods of two- and three-dimensional structures of elastomers, and systematically discusses the contribution of processing methods such as solvent casting, electrostatic spinning, and three-/four-dimensional printing of DBE. Furthermore, we describe recent advances in tissue repair using DBE, and include advances achieved in regenerating different tissues, including nerves, tendons, muscle, cardiac, and bone, highlighting their efficacy and versatility. The review concludes by discussing the current challenges in material selection, biodegradation, bioactivation, and manufacturing in tissue repair, and suggests future research directions. This concise yet comprehensive analysis aims to provide valuable insights and technical guidance for advances in DBE for tissue engineering.

Synthesis and Characterization of Poly(DL-lactide) Containing Fluorene Structures

9,9-bis[4-(2-hydroxy-3-acryloyloxypropoxy)phenyl]fluorene (BPF) hydroxyl groups (-OH) were used as initiators in the ring-opening polymerization reaction with DL-lactide monomers at different molar ratios to synthesize a Poly(DL-lactide) polymer containing bisphenol fluorene structure and acrylate functional groups (DL-BPF). The polymer's structure and molecular weight range were analyzed using NMR (¹H, ¹³C) and gel permeation chromatography. DL-BPF was then subjected to photocrosslinking using the photoinitiator Omnirad 1173, resulting in the formation of an optically transparent crosslinked polymer. Characterization of the crosslinked polymer involved analyzing its gel content, refractive index, thermal stability (via differential scanning thermometry (DSC) and thermogravimetric analysis (TGA)), as well as conducting cytotoxicity tests. The crosslinked copolymer exhibited a maximum refractive index of 1.5276, a maximum glass transition temperature of 61.1 °C, and cell survival rates higher than 83% in the cytotoxicity tests.

Bioactive and Physico-Chemical Assessment of Innovative Poly(lactic acid)-Based Biocomposites Containing Sage, Coconut Oil, and Modified Nanoclay

The bioactivity of the versatile biodegradable biopolymer poly(lactic acid) (PLA) can be obtained by combining it with natural or synthetic compounds. This paper deals with the preparation of bioactive formulations involving the melt processing of PLA loaded with a medicinal plant (sage) and an edible oil (coconut oil), together with an organomodifed montmorillonite nanoclay, and an assessment of the resulting structural, surface, morphological, mechanical, and biological properties of the biocomposites. By modulating the components, the prepared biocomposites show flexibility, both antioxidant and antimicrobial activity, as well as a high degree of cytocompatibility, being capable to induce the cell adherence and proliferation on their surface. Overall, the obtained results suggest that the developed PLA-based biocomposites could potentially be used as bioactive materials in medical applications.

Special Features of Polyester-Based Materials for Medical Applications

This article presents current possibilities of using polyester-based materials in hard and soft tissue engineering, wound dressings, surgical implants, vascular reconstructive surgery, ophthalmology, and other medical applications. The review summarizes the recent literature on the key features of processing methods and potential suitable combinations of polyester-based materials with improved physicochemical and biological properties that meet the specific requirements for selected medical fields. The polyester materials used in multiresistant infection prevention, including during the COVID-19 pandemic, as well as aspects covering environmental concerns, current risks and limitations, and potential future directions are also addressed. Depending on the different features of polyester types, as well as their specific medical applications, it can be generally estimated that 25-50% polyesters are used in the medical field, while an increase of at least 20% has been achieved since the COVID-19 pandemic started. The remaining percentage is provided by other types of natural or synthetic polymers; i.e., 25% polyolefins in personal protection equipment (PPE).