Photocrosslinkable biodegradable elastomers based on cinnamate-functionalized polyesters

Synthesis of photo-responsive κ-carrageenan-based hydrogels for drug delivery application

Natural polymer-based hydrogels may act as versatile platforms in controlled drug delivery. In this regard, photoactive κ-carrageenan (κ-Crg) hydrogels modified with cinnamate (CN) groups are developed for pH-sensitive release of drugs. κ-Crg-CN derivatives containing 17 %, 33 %, and 49 % cinnamate contents, named κ-Crg-CN1, κ-Crg-CN2, and κ-Crg-CN3, respectively, are prepared and cross-linked by UV-induced [2π + 2π] cycloaddition. Fourier transform infrared (FTIR) spectroscopy, Nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and elemental analysis are conducted for structural characterization. Rheological measurements showed an increased degree of cross-linking density with the increase in cinnamate content, as represented by storage modulus (G') values of 226 Pa for κ-Crg-CN1, 631 Pa for κ-Crg-CN2, and 967 Pa for κ-Crg-CN3. Also, drug encapsulation efficiency using theophylline was significantly improved: 48 % for κ-Crg-CN1, 63 % for κ-Crg-CN2, and 85 % for κ-Crg-CN3. Theophylline release studies showed that at pH 1.2, it was slower than pH 7.2, with a release rate inversely proportional to the cinnamate content. Kinetic modeling showed a non-Fickian transport mechanism that involved diffusion and polymer relaxation. These results show that κ-Crg-CN hydrogels can act as tunable, pH-sensitive drug delivery systems, with mechanical properties and release profiles precisely tailored by cinnamate functionalization for applications in controlled drug delivery.

Polyglycerol Sebacate Elastomer: A Critical Overview of Synthetic Methods and Characterisation Techniques

Poly (glycerol sebacate) is a widely studied elastomeric copolymer obtained from the polycondensation of two bioresorbable monomers, glycerol and sebacic acid. Due to its biocompatibility and the possibility to tailor its biodegradability rate and mechanical properties, PGS has gained lots of interest in the last two decades, especially in the soft tissue engineering field. Different synthetic approaches have been proposed, ranging from classic thermal polyesterification and curing to microwave-assisted organic synthesis, UV crosslinking and enzymatic catalysis. Each technique, characterized by its advantages and disadvantages, can be tailored by controlling the crosslinking density, which depends on specific synthetic parameters. In this work, classic and alternative synthetic methods, as well as characterisation and tailoring techniques, are critically reviewed with the aim to provide a valuable tool for the reproducible and customized production of PGS for tissue engineering applications.

Photocrosslinkable and hydroplasicable UV-shielding nanocellulose films facilitated by hydroxyl-yne click reaction

Sustainably-sourced functional nanocellulose materials are vitally important for the green and sustainable development. Herein, we reported photocrosslinkable and hydroplasticable TEMPO-oxidized cellulose nanofiber phenyl propylene ketone ethers (TOCNPPK) films with excellent ultraviolet (UV) shielding, highly reversible processability, and extended mechanical properties, which were facilitated by green hydroxyl-yne click reaction. The introduction of conjugated aromatic ring and vinyl bonds (-C=C-) had been demonstrated the key for the improved overall performance of resultant TOCNPPK, which not only endowed the TOCNPPK with nearly 100 % UV shielding, but also enabled it to be formed into diverse 3D shapes (helix, ring and letters "N, F, U") via the facile hydrosetting method. The photocrosslinkable-enhanced mechanical performance of TOCNPPK films was also attributed to -C=C- which could crosslink via [2π + 2π] cycloaddition reactions under UV-irradiation. The ultimate stress of TOCNPPK films was as high as 210.0 ± 22.8 MPa and the Young's modulus was 11.5 ± 0.7 GPa, much superior to those of 128.6 ± 8.5 MPa and 9.2 ± 0.6 GPa for pristine TOCN films. Furthermore, the TOCNPPK had been demonstrated as efficient nanofillers for both hydrophilic polyvinyl alcohol and lipophilic polycaprolactone to develop advanced biodegradable composite films with the integration of good water-wetting resistance, excellent UV blocking, and photo-enhanced mechanical performance.

Electrical stimulation via repeated biphasic conducting materials for peripheral nerve regeneration

Improved materials for peripheral nerve repair are needed for the advancement of new surgical techniques in fields spanning from oncology to trauma. In this study, we developed bioresorbable materials capable of producing repeated electric field gradients spaced 600 μm apart to assess the impact on neuronal cell growth, and migration. Electrically conductive, biphasic composites comprised of poly (glycerol) sebacate acrylate (PGSA) alone, and doped with poly (pyrrole) (PPy), were prepared to create alternating segments with high and low electrically conductivity. Conductivity measurements demonstrated that 0.05% PPy added to PSA achieved an optimal value of 1.25 × 10-4 S/cm, for subsequent electrical stimulation. Tensile testing and degradation of PPy doped and undoped PGSA determined that 35-40% acrylation of PGSA matched nerve mechanical properties. Both fibroblast and neuronal cells thrived when cultured upon the composite. Biphasic PGSA/PPy sheets seeded with neuronal cells stimulated for with 3 V, 20 Hz demonstrated a 5x cell increase with 1 day of stimulation and up to a 10x cell increase with 3 days stimulation compared to non-stimulated composites. Tubular conduits composed of repeated high and low conductivity materials suitable for implantation in the rat sciatic nerve model for nerve repair were evaluated in vivo and were superior to silicone conduits. These results suggest that biphasic conducting conduits capable of maintaining mechanical properties without inducing compression injuries while generating repeated electric fields are a promising tool for acceleration of peripheral nerve repair to previously untreatable patients.

Strategies for Development of Synthetic Heart Valve Tissue Engineering Scaffolds

The current clinical solutions, including mechanical and bioprosthetic valves for valvular heart diseases, are plagued by coagulation, calcification, nondurability, and the inability to grow with patients. The tissue engineering approach attempts to resolve these shortcomings by producing heart valve scaffolds that may deliver patients a life-long solution. Heart valve scaffolds serve as a three-dimensional support structure made of biocompatible materials that provide adequate porosity for cell infiltration, and nutrient and waste transport, sponsor cell adhesion, proliferation, and differentiation, and allow for extracellular matrix production that together contributes to the generation of functional neotissue. The foundation of successful heart valve tissue engineering is replicating native heart valve architecture, mechanics, and cellular attributes through appropriate biomaterials and scaffold designs. This article reviews biomaterials, the fabrication of heart valve scaffolds, and their in-vitro and in-vivo evaluations applied for heart valve tissue engineering.

A photo-activable nano-agonist for the two-signal model of T cell in vivo activation

The two-signal model of T cell activation has helped shape our understanding of the adaptive immune response for over four decades. According to the model, activation of T cells requires a stimulus through the T cell receptor/CD3 complex (signal 1) and a costimulatory signal 2. Stimulation of activatory signals via T cell agonists has thus emerged. However, for a robust T cell activation, it necessitates not only the presence of both signal 1 and signal 2, but also a high signaling strength. Herein, we report a photo-activable nano-agonist for the two-signal model of T cell in vivo activation. A UV-crosslinkable polymer is coated onto upconversion nanoparticles with satisfactory NIR-to-UV light conversion efficiency. Then dual signal molecules, i.e., signal 1 and signal 2, are conjugated to the polymer end to yield the photo-activable T cell nano-agonist. In melanoma and breast cancer models, photo-activable nano-agonist could bind onto corresponding activatory receptors on the surface of T cells, but has limited activity without the application of NIR light (absence of photo-crosslinking of receptors and consequently a poor signaling strength). While when the NIR light is switched on locally, T cells in tumor are remarkably activated and kill tumor cells effectively. Moreover, we do not observe any detectable toxicities related to the photo-activable nano-agonist. We believe with two activatory signals being simultaneously strengthened by local photo-switched crosslinking, T cells realize a robust and selective activation in tumor and, consequently contribute to an enhanced and safe tumor immunotherapy.

Functionalization of cellulose nanocrystals extracted from pineapple leaves as a UV-absorbing agent in poly(lactic acid)

The cinnamate functionalization of cellulose nanocrystals (Cin-CNCs) was investigated as a potential organic reinforcing and UV-shielding agent in polylactic acid (PLA) films. Acid hydrolysis was used to extract cellulose nanocrystals (CNCs) from pineapple leaves. Through esterification with cinnamoyl chloride, the cinnamate group was grafted onto the CNC surface and the resulting Cin-CNCs were incorporated in PLA films as reinforcing and UV-shielding agents. The PLA nanocomposite films were prepared using a solution-casting method and were tested for mechanical/thermal properties, gas permeability, and UV absorption. Importantly, the functionalization of cinnamate on CNCs substantially improved the dispersion of fillers on the PLA matrix. The PLA films containing 3 wt% Cin-CNCs exhibited high transparency and UV absorption in the visible region. On the other hand, PLA films filled with pristine CNCs did not exhibit any UV-shielding properties. The mechanical properties revealed that adding 3 wt% Cin-CNCs to PLA increased its tensile strength and Young's modulus by 70% and 37%, respectively, compared to neat PLA. In addition, the incorporation of Cin-CNCs substantially improved water vapor and oxygen permeability. At 3 wt% Cin-CNC addition, the water vapor and oxygen permeability of PLA films were reduced by 54% and 55%, respectively. This study demonstrated the great potential in utilizing Cin-CNCs as effective gas barriers, dispersible nanoparticles, and UV-absorbing, nano-reinforcing agents in PLA films.

A Review: Optimization for Poly(glycerol sebacate) and Fabrication Techniques for Its Centered Scaffolds

Poly(glycerol sebacate) (PGS), an emerging promising thermosetting polymer synthesized from sebacic acid and glycerol, has attracted considerable attention due to its elasticity, biocompatibility, and tunable biodegradation properties. But it also has some drawbacks such as harsh synthesis conditions, rapid degradation rates, and low stiffness. To overcome these challenges and optimize PGS performance, various modification methods and fabrication techniques for PGS-based scaffolds have been developed in recent years. Outlining the current modification approaches of PGS and summarizing the fabrication techniques for PGS-based scaffolds are of great importance to accelerate the development of new materials and enable them to be appropriately used in potential applications. Thus, this review comprehensively overviews PGS derivatives, PGS composites, PGS blends, processing for PGS-based scaffolds, and their related applications. It is envisioned that this review could instruct and inspire the design of the PGS-based materials and facilitate tissue engineering advances into clinical practice.

Review on the Impact of Polyols on the Properties of Bio-Based Polyesters

Bio-based polyol polyesters are biodegradable elastomers having potential utility in soft tissue engineering. This class of polymers can serve a wide range of biomedical applications. Materials based on these polymers are inherently susceptible to degradation during the period of implantation. Factors that influence the physicochemical properties of polyol polyesters might be useful in achieving a balance between durability and biodegradability. The characterization of these polyol polyesters, together with recent comparative studies involving creative synthesis, mechanical testing, and degradation, have revealed many of their molecular-level differences. The impact of the polyol component on the properties of these bio-based polyesters and the optimal reaction conditions for their synthesis are only now beginning to be resolved. This review describes our current understanding of polyol polyester structural properties as well as a discussion of the more commonly used polyol monomers.

Photopolymerizable Biomaterials and Light-Based 3D Printing Strategies for Biomedical Applications

Since the advent of additive manufacturing, known commonly as 3D printing, this technology has revolutionized the biofabrication landscape and driven numerous pivotal advancements in tissue engineering and regenerative medicine. Many 3D printing methods were developed in short course after Charles Hull first introduced the power of stereolithography to the world. However, materials development was not met with the same enthusiasm and remained the bottleneck in the field for some time. Only in the past decade has there been deliberate development to expand the materials toolbox for 3D printing applications to meet the true potential of 3D printing technologies. Herein, we review the development of biomaterials suited for light-based 3D printing modalities with an emphasis on bioprinting applications. We discuss the chemical mechanisms that govern photopolymerization and highlight the application of natural, synthetic, and composite biomaterials as 3D printed hydrogels. Because the quality of a 3D printed construct is highly dependent on both the material properties and processing technique, we included a final section on the theoretical and practical aspects behind light-based 3D printing as well as ways to employ that knowledge to troubleshoot and standardize the optimization of printing parameters.

Recent advances in neural interfaces-Materials chemistry to clinical translation

Implantable neural interfaces are important tools to accelerate neuroscience research and translate clinical neurotechnologies. The promise of a bidirectional communication link between the nervous system of humans and computers is compelling, yet important materials challenges must be first addressed to improve the reliability of implantable neural interfaces. This perspective highlights recent progress and challenges related to arguably two of the most common failure modes for implantable neural interfaces: (1) compromised barrier layers and packaging leading to failure of electronic components; (2) encapsulation and rejection of the implant due to injurious tissue-biomaterials interactions, which erode the quality and bandwidth of signals across the biology-technology interface. Innovative materials and device design concepts could address these failure modes to improve device performance and broaden the translational prospects of neural interfaces. A brief overview of contemporary neural interfaces is presented and followed by recent progress in chemistry, materials, and fabrication techniques to improve in vivo reliability, including novel barrier materials and harmonizing the various incongruences of the tissue-device interface. Challenges and opportunities related to the clinical translation of neural interfaces are also discussed.

Photoinduced Surface Zwitterionization for Antifouling of Porous Polymer Substrates

Surface functionalization of polymeric porous substrates is one of the most important requirements to enhance their applications in the biomedical field. In this study, we achieved photoinduced surface modification using a highly efficient reaction of hydrophilic polymers bearing phosphorylcholine groups. Polymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) units and 2-( N-ethylanilino)ethyl methacrylate units were synthesized with attention to the polymer architectures. The surface modification of the porous polyethylene (PE) substrates was carried out by the coating of the MPC polymers with a photochemical radical generator, followed by photoirradiation for a few minutes. Surface analysis by attenuated total reflectance Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy indicated that the MPC polymer layer was generated on the PE surface. Cross-sectional confocal microscopy images showed that the MPC polymers were coated on the polymer surface, even inside the porous structure of the PE substrate. After modification, the porous PE substrates showed a significant increase in hydrophilicity and the water-penetration rate through the pores. Furthermore, the amount of protein adsorbed on the PE substrate was reduced significantly by the surface modification. These functionalities were dependent on the MPC polymer architectures. Thus, we concluded that the photoreactive polymer system developed furnished the porous substrates with antifouling properties.

Advances in Materials and Structures for Ingestible Electromechanical Medical Devices

Ingestible biomedical devices that diagnose, prevent, or treat diseases has been a dream of engineers and clinicians for decades. The increasing apparent importance of gut health on overall well-being and the prevalence of many gastrointestinal diseases have renewed focus on this emerging class of medical devices. Several prominent examples of commercially successful ingestible medical devices exist. However, many technical challenges remain before ingestible medical devices can achieve their full clinical potential. This Minireview summarizes recent discoveries in this interdisciplinary topic including novel materials, advanced materials processing techniques, and select examples of integrated ingestible electromechanical systems. After a brief historical perspective, these topics will be reviewed with a dedicated focus on advanced functional materials and fabrication strategies in the context of clinical translation and potential regulatory considerations. Future perspectives, challenges, and opportunities related to ingestible medical devices will also be summarized.

Urethane-based low-temperature curing, highly-customized and multifunctional poly(glycerol sebacate)-co-poly(ethylene glycol) copolymers

Poly (glycerol sebacate) (PGS), a tough elastomer, has been widely explored in tissue engineering due to the desirable mechanical properties and biocompatibility. However, the complex curing procedure (high temperature and vacuum) and limited hydrophilicity (∼90° of wetting angle) greatly impede its functionalities. To address these challenges, a urethane-based low-temperature setting, PEGylated PGS bioelastomer was developed with and without solvent. By simultaneously tailoring PEG and hexamethylene diisocyanate (HDI) contents, the elastomers X-P-mUs (X referred to the PEG content and m referred to HDI content) with a broad ranging mechanical properties and customized hydrophilicity were constructed. The X-P-mUs synthesized exhibited adjustable tensile Young's modulus, ultimate tensile strength and elongation at break in the range of 1.0 MPa-14.2 MPa, 0.3 MPa-7.6 MPa and 53.6%-272.8%, with the water contact angle varying from 28.6° to 71.5°, respectively. Accordingly, these elastomers showed favorable biocompatibility in vitro and mild host response in vivo. Furthermore, the potential applications of X-P-mU elastomers prepared with solvent-base and solvent-free techniques in biomedical fields were investigated. The results showed that these X-P-mU elastomers with high molding capacity at mild temperature could be easily fabricated into various shapes, used as reinforcement for fragile materials, and controllable delivery of drugs and proteins with excellent bioactivity, demonstrating that the X-P-mU elastomers could be tailored as potential building blocks for diverse applications in biomedical research.

STATEMENT OF SIGNIFICANCE

Poly(glycerol sebacate) (PGS), a tough biodegradable elastomer, has received great attentions in biomedical field. But the complex curing procedure and limited hydrophilicity greatly hamper its functionality. Herein, a urethane-based low-temperature setting, PEGylated PGS (PEGS-U) bioelastomer with highly-customized mechanical properties, hydrophilicity and biodegradability was first explored. The synthesized PEGS-U showed favorable biocompatibility both in vitro and in vivo. Furthermore, the PEGS-U elastomer could be easily fabricated into various shapes, used as reinforcement for fragile materials, and controllable delivery of drugs and proteins with excellent bioactivity. This versatile, user-tunable bioelastomers should be a promising biomaterials for biomedical applications.

Norbornene-modified poly(glycerol sebacate) as a photocurable and biodegradable elastomer

Photocurable norbornene-functionalized poly(glycerol sebacate) (Nor-PGS) has been developed to fabricate cytocompatible, biodegradable and elastomeric scaffolds for tissue engineering applications.

Synthesis and characterization of poly(glycerol sebacate)-based elastomeric copolyesters for tissue engineering applications

A poly(glycerol sebacate)-based elastomeric copolyesters with improved mechanical properties and higher water uptake capacity.

Photo-irradiation paradigm: Mapping a remarkable facile technique used for advanced drug, gene and cell delivery

Undoubtedly, the progression of photo-irradiation technique has provided a smart engineering tool for the state-of-the-art biomaterials that guide the biomedical and therapeutic domains for promoting the modern pharmaceutical industry. Many investigators had exploited such a potential technique to create/ameliorate numerous pharmaceutical carriers. These carriers show promising applications that vary from small drug to therapeutic protein delivery and from gene to living cell encapsulation design. Harmony between the properties of precisely engineered precursors and the formed network structure broadens the investigator's intellect for both brilliant creations and effective applications. As well, controlling photo-curing at the formulation level, through manipulating the absorption of light stimuli, photoinitiator system and photo-responsive precursor, facilitates the exploration of novel distinctive biomaterials. Discussion of utilizing different photo-curing procedures in designing/formulation of different pharmaceutical carriers is the main emphasis of this review. In addition, recent applications of these intelligent techniques in targeted, controlled, and sustained drug delivery with understanding of photo-irradiation concept and mechanism are illustrated.

Poly(glycerol sebacate)-modified polylactic acid scaffolds with improved hydrophilicity, mechanical strength and bioactivity for bone tissue regeneration

Polylactic acid (PLA) has been extensively researched in biomedical engineering applications due to its superior mechanical strength and biocompatibility in vivo.

Fibroblast cell proliferation on photo-cured trehalose cinnamoyl ester thin films

Trehalose cinnamoyl esters (TCs) were synthesized by esterification of trehlaose with cinnamoyl chloride. Two TCs with different degrees of substitution were synthesized, and trehalose cinnamoyl ester thin film-coated glass plates were prepared by a dip-coating method. Photocuring of the TCs was confirmed by ultraviolet–visible spectral changes. The surface of photo-cured TCs were found smooth as observed in a scanning electron microscope. The cell proliferation on the photo-cured TCs was investigated using 3T3 Swiss Albino mouse embryo fibroblasts. The results of the cell proliferation assay revealed that the photo-cured TCs with higher degrees of substitution promoted the cell proliferation compared with a polystyrene culture plate and the photo-cured TCs with lower degrees of substitution. The contact angle of the photo-cured TCs with higher degrees of substitution was 101.0° ± 1.6°, which is much higher than that of the polystyrene culture plate, and it is out of the range known to be suitable for cell adhesion. Nevertheless, the cell unexpectedly grew best on the photo-cured TCs with higher degrees of substitution. Fibronectin binding assay was carried out using fluorescent probe-modified fibronectin, and more fibronectin was found adsorbed onto photo-cured TCs than a polystyrene culture plate.

Photoreconfigurable polymers for biomedical applications: chemistry and macromolecular engineering

Stimuli-responsive polymers play an important role in many biomedical technologies. Light responsive polymers are particularly desirable because the parameters of irradiated light and diverse photoactive chemistries produce a large number of combinations between functional materials and associated stimuli. This Review summarizes recent advances in utilizing photoactive chemistries in macromolecules for prospective use in biomedical applications. Special focus is granted to selection criterion when choosing photofunctional groups. Synthetic strategies to incorporate these functionalities into polymers and networks with different topologies are also highlighted herein. Prospective applications of these materials are discussed including programmable matrices for controlled release, dynamic scaffolds for tissue engineering, and functional coatings for medical devices. The article concludes by summarizing the state of the art in photoresponsive polymers for biomedical applications including current challenges and future opportunities.