Cross-linking Capability Research Articles

Development of printable bacterial nanocellulose bioinks for bioprinting applications

This research has developed a printable bioink formulated with bacterial nanocellulose (BNC) and sodium alginate. The bioink composition offers a unique combination of printability, mechanical strength, and high BNC content. A low-cost 3D bioprinting platform, with in-situ crosslinking capabilities, was designed and fabricated to facilitate the creation of complex constructs. Rheological analysis revealed shear-thinning behaviour, a critical property for efficient 3D bioprinting. The printed constructs exhibited exceptional resolution, printability, and self-supporting features at BNC loadings up to 72 wt.% in dried structures. The optimal ink composition was found, containing 7.8 wt.% BNC and 3 wt.% sodium alginate. These findings highlight the potential for this BNC-alginate bioink for bio-fabrication applications demanding both printability and high biomaterial content.Graphical

Enzymatic Routes to Designer Hemicelluloses for Use in Biobased Materials.

Various enzymes can be used to modify the structure of hemicelluloses directly in vivo or following extraction from biomass sources, such as wood and agricultural residues. Generally, these enzymes can contribute to designer hemicelluloses through four main strategies: (1) enzymatic hydrolysis such as selective removal of side groups by glycoside hydrolases (GH) and carbohydrate esterases (CE), (2) enzymatic cross-linking, for instance, the selective addition of side groups by glycosyltransferases (GT) with activated sugars, (3) enzymatic polymerization by glycosynthases (GS) with activated glycosyl donors or transglycosylation, and (4) enzymatic functionalization, particularly via oxidation by carbohydrate oxidoreductases and via amination by amine transaminases. Thus, this Perspective will first highlight enzymes that play a role in regulating the degree of polymerization and side group composition of hemicelluloses, and subsequently, it will explore enzymes that enhance cross-linking capabilities and incorporate novel chemical functionalities into saccharide structures. These enzymatic routes offer a precise way to tailor the properties of hemicelluloses for specific applications in biobased materials, contributing to the development of renewable alternatives to conventional materials derived from fossil fuels.

Polymers for Perovskite Solar Cells.

Perovskite solar cells (PSCs) are recognized as one of the most promising next-generation photovoltaics, primarily due to their exceptional power conversion efficiency, ease of processing, and cost-effectiveness. Despite these advantages, challenges remain in achieving high-quality films and ensuring the long-term stability of PSCs, which hinder their widespread commercialization. Polymers, characterized by multifunctional groups, superior thermal stability, flexible long chains, and cross-linking capabilities, offer significant potential to enhance the performance and reliability of PSCs. This review comprehensively presents the multifaceted roles that polymers play in PSCs. Through carefully controlling interactions between polymers and perovskites, crucial aspects such as film crystallization kinetics, carrier transport process, ion migration issues, and mechanical properties under bending can be effectively regulated to maximize the device performance. Furthermore, the hydrophobic properties and strong chelated cross-linking networks of polymers significantly enhance the stability of PSCs under various environmental conditions while effectively mitigating lead leakage, thereby addressing environmental concerns and long-term durability. Moreover, this Perspective identifies potential pathways for further advancing polymer-based strategies in PSC applications.

Development of dual-crosslinked Pluronic F127/Chitosan injectable hydrogels incorporating graphene nanosystems for breast cancer photothermal therapy and antibacterial applications

Nanomaterials with responsiveness to near-infrared light can mediate the photoablation of cancer cells with an exceptional spatio-temporal resolution. However, the therapeutic outcome of this modality is limited by the nanostructures’ poor tumor uptake. To address this bottleneck, it is appealing to develop injectable in situ forming hydrogels due to their capacity to perform a tumor-confined delivery of the nanomaterials with minimal off-target leakage. In particular, injectable in situ forming hydrogels based on Pluronic F127 have been emerging due to their FDA-approval status, biocompatibility, and thermosensitive sol–gel transition. Nevertheless, the application of Pluronic F127 hydrogels has been limited due to their fast dissociation in aqueous media. Such limitation may be addressed by combining the thermoresponsive sol–gel transition of Pluronic F127 with other polymers with crosslinking capabilities. In this work, a novel dual-crosslinked injectable in situ forming hydrogel based on Pluronic F127 (thermosensitive gelation) and Chitosan (ionotropic gelation in the presence of NaHCO3), loaded with Dopamine-reduced graphene oxide (DOPA-rGO; photothermal nanoagent), was developed for application in breast cancer photothermal therapy. The dual-crosslinked hydrogel incorporating DOPA-rGO showed a good injectability (through 21 G needles), in situ gelation capacity and cytocompatibility (viability > 73 %). As importantly, the dual-crosslinking improved the hydrogel’s porosity and prevented its premature degradation. After irradiation with near-infrared light, the dual-crosslinked hydrogel incorporating DOPA-rGO produced a photothermal heating (ΔT ≈ 22 °C) that reduced the breast cancer cells’ viability to just 32 %. In addition, this formulation also demonstrated a good antibacterial activity by reducing the viability of S. aureus and E. coli to 24 and 33 %, respectively. Overall, the dual-crosslinked hydrogel incorporating DOPA-rGO is a promising macroscale technology for breast cancer photothermal therapy and antimicrobial applications.

Comparative efficacy of citric acid/tartaric acid/malic acid additive-based polyvinyl alcohol-starch composite films

To ascertain upon the ideal configuration of physico-mechanical qualities, efficient processing techniques, and network stability of the prepared bio-composite films in real-world applications, the polymeric materials shall be subjected to a careful manipulation. Such bio-composite films have outstanding combinations of biocompatibility and toxicity-associated safety qualities. Such research interventions will be beneficial for the packaging, pharmaceutical, and biomedical industries that wish to target and adopt them for commercial applications. In this article, three alternate organic acids, i.e., citric acid (CA), tartaric acid (TA), and malic acid (MA), are blended separately into polyvinyl alcohol (PVA)-starch (St)-glycerol (Gl) composite films and for the targeted purpose of enhanced crosslinking, plasticizing, and antibacterial capability of the polymer network. The organic acid-based bio-composite polymeric films were assessed in terms of swelling index (SI), in vitro degradation, tensile strength (TS), percentage elongation (%E), antibacterial activity, and cytotoxicity attributes. Among these, the MA-based PVA composite films outperformed the CA-based PVA composite film in terms of absorbency (SI 739.29%), mechanical strength (TS 4.88 MPa), and elasticity (%E 103.68%). Furthermore, following a 24-h incubation period, the MA-based films exhibited the highest proliferative effect of 215.59% for the HEK cells. In conclusion, the MA has been inferred to be the most relevant organic acid for the desired optimality of film composition, physical and biological properties, and cost.

Tailoring polyamide membranes via dynamic interfacial manipulation with functional Fe3O4 nanoparticles for elevated Nanofiltration performance

This study investigates the enhancement of thin-film-composite polyamide (TFC-PA) membranes for nanofiltration (NF) by conducting direct interfacial polymerization (IP) at a substrate-free water/n-hexane interface. Fe3O4 nanoparticles, stabilized with surfactants sodium laurate (SL) and hexadecyltrimethylammonium bromide (CTAB), were employed to dynamically influence the diffusion of piperazine (PIP) monomers. The incorporation of these nanoparticles enabled the modulation of the IP process, yielding membranes with distinct morphologies and performance characteristics. Specifically, membranes with SL-stabilized Fe3O4 (SLF) demonstrated enhanced cross-linking and superior salt rejection capabilities for divalent cations, with MgCl2 and CaCl2 rejection rates notably increasing to 95.5 % and 93.4 % respectively. Conversely, CTAB-stabilized Fe3O4 (CTABF) membranes, characterized by smoother surfaces and a looser structure, exhibited increases in water permeance up to 140 % relative to controls, but with a significant reduction in salt rejection efficacy as nanoparticle concentration increased. This study highlights the crucial impact of surfactant-stabilized nanoparticle modifications in manipulating the IP process and tailoring the filtration properties of PA membranes, offering promising avenues for optimizing NF membrane technology.

Physicochemical evaluation of polyvinyl alcohol films crosslinked with saturated and unsaturated dicarboxylic acids: A comparative study

AbstractIn this study, crosslinked films of polyvinyl alcohol (PVA) were prepared using two dicarboxylic acids: saturated succinic acid (SA) and unsaturated maleic acid (MAL) as crosslinkers. The crosslinking capabilities of these acids were compared through physical, chemical, mechanical, morphological, thermal analysis, and swelling measurements to investigate their impact on the physicochemical properties of the resulting films. Attenuated total reflectance fourier transform infrared spectroscopy (FTIR) confirmed the occurrence of an esterification reaction between PVA and the dicarboxylic acids. Based on the degree of crosslinking and thermal properties, it was noted that the crosslinking achieved with maleic acid is more effective for PVA compared with succinic acid. The crosslinking degree of PVA‐MAL was determined to be 6.47 times higher than that of the PVA‐SA film. In terms of thermal stability, the decomposition temperature for crosslinked PVA‐MAL was measured at 365.57°C, whereas PVA‐SA exhibited a slightly lower decomposition temperature of 362.58°C. The findings indicate that the PVA‐MAL film displays lower crystallinity and a higher contact angle (80.60°) in contrast to PVA‐SA (76.0°) and PVA (30.4°). Atomic force microscopy analysis indicated that the PVA‐SA film exhibited more surface roughness compared with the smoother PVA‐MAL film. Also, crosslinked films displayed enhanced elasticity and resilience in comparison with neat PVA, which may be due to the difference in crosslinking density, disruption in intermolecular hydrogen bonding due to crosslinking, and incorporation of flexible crosslinkers.Highlights PVA was crosslinked using SA and MAL. Unsaturated MAL exhibited superior crosslinking density over saturated SA. PVA‐SA film exhibited a porous surface compared to PVA‐MAL film. PVA crosslinked with unsaturated MAL showed higher thermal stability than SA. Both the films showed enhanced elasticity and resilience compared with neat PVA.

Development of High-Performance Coconut Oil-Based Rigid Polyurethane-Urea Foam: A Novel Sequential Amidation and Prepolymerization Process.

The utilization of coconut diethanolamide (p-CDEA) as a substitute polyol for petroleum-based polyol in fully biobased rigid polyurethane-urea foam (RPUAF) faces challenges due to its short chain and limited cross-linking capability. This leads to compromised cell wall resistance during foam expansion, resulting in significant ruptured cells and adverse effects on mechanical and thermal properties. To address this, a novel sequential amidation-prepolymerization route was employed on coconut oil, yielding a hydroxyl-terminated poly(urethane-urea) prepolymer polyol (COPUAP). Compared to p-CDEA, COPUAP exhibited a decreased hydroxyl value (496.3-473.2 mg KOH/g), an increase in amine value (13.464-24.561 mg KOH/g), and an increase in viscosity (472.4-755.8 mPa·s), indicating enhanced functionality of 34.3 mgKOH/g and chain lengthening. Further, COPUAP was utilized as the sole B-side polyol in the production of RPUAF (PU-COPUAP). The improved functionality of COPUAP and its improved cross-linking capability during foaming have significantly improved cell morphology, resulting in a remarkable 4.7-fold increase in compressive strength (132-628 kPa), a 3.5-fold increase in flexural strength (232-828 kPa), and improved insulation properties with a notable decrease in thermal conductivity (48.02-34.52 mW/m·K) compared to PU-CDEA in the literature. Additionally, PU-COPUAP exhibited a 16.5% increase in the water contact angle (114.93° to 133.87°), attributing to the formation of hydrophobic biuret segments and a tightly packed, highly cross-linked structure inhibiting water penetration. This innovative approach sets a new benchmark for fully biobased rigid foam production, delivering high load-bearing capacity, exceptional insulation, and significantly improved hydrophobicity.

Annexin A7 mediates lysosome repair independently of ESCRT-III.

Lysosomes are crucial organelles essential for various cellular processes, and any damage to them can severely compromise cell viability. This study uncovers a previously unrecognized function of the calcium- and phospholipid-binding protein Annexin A7 in lysosome repair, which operates independently of the Endosomal Sorting Complex Required for Transport (ESCRT) machinery. Our research reveals that Annexin A7 plays a role in repairing damaged lysosomes, different from its role in repairing the plasma membrane, where it facilitates repair through the recruitment of ESCRT-III components. Notably, our findings strongly suggest that Annexin A7, like the ESCRT machinery, is dispensable for membrane contact site formation within the newly discovered phosphoinositide-initiated membrane tethering and lipid transport (PITT) pathway. Instead, we speculate that Annexin A7 is recruited to damaged lysosomes and promotes repair through its membrane curvature and cross-linking capabilities. Our findings provide new insights into the diverse mechanisms underlying lysosomal membrane repair and highlight the multifunctional role of Annexin A7 in membrane repair.

Comparative analysis of self-cure and dual cure-dental composites on their physico-mechanical behaviour.

Clinical practitioners may have become familiar with the rapid transformation of dental composites. However, they may not scientifically understand the factors influencing the mechanical and physical properties. Scientific knowledge of filler-resin interaction can significantly improve clinical understanding of resin composites. Several independent studies have examined the mechanical and physico-mechanical properties of dental resin composites; however, no comprehensive study has examined the influence of fillers and resin materials on the physico-mechanical properties of both self-cure and dual-cure composites. This study performed investigations on the physico-mechanical behaviour of four commercially available dual-cure dental composites (Bioactive, Fill Up!, Surefil One, Cention N) and two commercially available self-cure dental composites (Stela Capsule and Stela Automix). Test specimens for flexural and compressive strength, microhardness, fracture toughness, and hydrolytic behaviour were prepared and tested as per respective standards. The data sets were statistically analysed using one-way ANOVA and Tukey's post-hoc comparison. There was a substantial variation in flexural strength and modulus values in this study, ranging from 32.0 to 113.4 MPa and 2.36 to 12.07 GPa, respectively. Similarly, there were significant differences in compressive strength between the materials in this study, ranging from 119.3 to 223.5 MPa. The highest fracture toughness value was found to be 1.41 MPa.m0.5, while the lowest value was 0.43 MPa.m0.5. Variations in surface microhardness were significant (24.11-68.0 N/mm2), which correlated with the filler content. Water sorption and solubility demonstrated high variations among materials, with Surefil One exceeding ISO 4049 thresholds significantly. A linear correlation can be established between surface microhardness (HV) and flexural and compressive moduli, as well as filler content (wt.%). However, both flexural and compressive strengths are impacted by the resin's constituent monomers and the resin-filler matrix's cross-linking capability. Additionally, factors such as filler size, shape, and the cross-linking ability of the resin-filler matrix play a crucial role in fracture toughness and the propagation of cracks within the restoration. Also, resin monomers and filler particle size affect the hydrolytic degradation characteristics of composites, which can also affect their mechanical properties. © 2023 Australian Dental Association.

Synergistic Defect Healing and Device Encapsulation via Structure Regulation by Silicone Polymer Enables Durable Inverted Perovskite Photovoltaics with High Efficiency

AbstractPolymers play a crucial role in promoting the progress of high‐performance inverted perovskite solar cells (PSCs). However, few polymers have simultaneously achieved defect passivation and device encapsulation in PSCs. Herein, a telechelic silicone polymer (poly(dimethylsiloxane‐co‐methylsiloxane acrylate) [PDMA]) is introduced, which possesses crosslinking capability to enable structure regulation through a condensation reaction. By leveraging the advantages of the polymers before and after crosslinking, a synergistic strategy of defect healing and device encapsulation for PSCs is developed via the application of the targeted polymer. PDMA as additives anchors tightly at the grain boundaries (GBs) and bridges the perovskite grains, achieving defect passivation and GBs crosslinking, increasing the efficiency of inverted PSCs from 22.32% to 24.41%. Crosslinked PDMA (CPDMA) is used as an encapsulant to encapsulate the entire device, enabling non‐destructive encapsulation at room temperature and inhibiting perovskite degradation under photothermal aging. Remarkably, the PDMA‐modified device with CPDMA encapsulation maintains 98% of its initial efficiency after 1200 h under continuous illumination at 55 ± 5 °C and retains 95% of its original efficiency after 1000 h of damp heat testing, meeting one of the IEC61215:2016 standards.

Ferulated Poly(vinyl alcohol) based hydrogels

New graft copolymers were prepared by reaction of poly (vinyl alcohol) (PVA) with mono-imidazolide or bis-imidazolide derivatives of ferulic acid (FA) with the formation of ester bonds. The obtained graft copolymers, thanks to the crosslinking capability of FA, formed in water strong gels as verified by rheological analyses. The resulting hydrogels were characterized to evaluate their applicability as wound dressing. In this perspective, their capability to absorb and retain a large amount of fluid without dissolving was verified by swelling kinetics and Moisture Vapour Transmission Rate measurements. Their stability towards mechanical solicitations was assessed by quantifying elasticity, compliance, stress-relaxation, and adhesivity properties. The analyses pointed out that hydrogel PVA-FA2-3 obtained by feruloylation of PVA with bis-imidazole derivative of ferulic acid using an acylation agent/polymer molar ratio 0.03/1 resulted the best candidate for the foreseen application.

Substrate stiffness modulates cardiac fibroblast activation, senescence, and proinflammatory secretory phenotype.

In vitro cultures of primary cardiac fibroblasts (CFs), the major extracellular matrix (ECM)-producing cells of the heart, are used to determine molecular mechanisms of cardiac fibrosis. However, the supraphysiologic stiffness of tissue culture polystyrene (TCPS) triggers the conversion of CFs into an activated myofibroblast-like state, and serial passage of the cells results in the induction of replicative senescence. These phenotypic switches confound the interpretation of experimental data obtained with cultured CFs. In an attempt to circumvent TCPS-induced activation and senescence of CFs, we used poly(ethylene glycol) (PEG) hydrogels as cell culture platforms with low and high stiffness formulations to mimic healthy and fibrotic hearts, respectively. Low hydrogel stiffness converted activated CFs into a quiescent state with a reduced abundance of α-smooth muscle actin (α-SMA)-containing stress fibers. Unexpectedly, lower substrate stiffness concomitantly augmented CF senescence, marked by elevated senescence-associated β-galactosidase (SA-β-Gal) activity and increased expression of p16 and p21, which are antiproliferative markers of senescence. Using dynamically stiffening hydrogels with phototunable cross-linking capabilities, we demonstrate that premature, substrate-induced CF senescence is partially reversible. RNA-sequencing analysis revealed widespread transcriptional reprogramming of CFs cultured on low-stiffness hydrogels, with a reduction in the expression of profibrotic genes encoding ECM proteins, and an attendant increase in expression of NF-κB-responsive inflammatory genes that typify the senescence-associated secretory phenotype (SASP). Our findings demonstrate that alterations in matrix stiffness profoundly impact CF cell state transitions, and suggest mechanisms by which CFs change phenotype in vivo depending on the stiffness of the myocardial microenvironment in which they reside.NEW & NOTEWORTHY Our findings highlight the advantages and pitfalls associated with culturing cardiac fibroblasts on hydrogels of varying stiffness. The findings also define stiffness-dependent signaling and transcriptional networks in cardiac fibroblasts.

Catecholamine Derivatives as Novel Crosslinkers for the Synthesis of Versatile Biopolymers.

Catecholamine metabolites are not only involved in primary metabolism, but also in secondary metabolism, serving a diverse array of physiologically and biochemically important functions. Melanin, which originates from dopa and dopamine, found in the hair, eye, and skin of all animals, is an important biopolymeric pigment. It provides protection against damaging solar radiation to animals. N-Acetyldopamine and N-β-alanyldopamine play a crucial role in the hardening of the exoskeletons of all insects. In addition, insects and other arthropods utilize the melanogenic process as a key component of their defense systems. Many marine organisms utilize dopyl peptides and proteins as bonding materials to adhere to various substrata. Moreover, the complex dopa derivatives that are precursors to the formation of the exoskeletons of numerous marine organisms also exhibit antibiotic properties. The biochemistry and mechanistic transformations of different catecholamine derivatives to produce various biomaterials with antioxidant, antibiotic, crosslinking, and gluing capabilities are highlighted. These reactivities are exhibited through the transient and highly reactive quinones, quinone methides, and quinone methide imine amide intermediates, as well as chelation to metal ions. A careful consideration of the reactivities summarized in this review will inspire numerous strategies for synthesizing novel biomaterials for future medical and industrial use.

Development of 4,4′-dibromobinaphthalene analogues with potent photo-inducible DNA cross-linking capability and cytotoxicity towards breast MDA-MB 468 cancer cells

Photoinduced DNA cross-linking process showed advantages of high spatio-temporal resolution and control. We have designed, synthesized, and characterized several 4,4′-dibromo binaphthalene analogues (1a-f) that can be activated by 350 nm irradiation to induce various DNA damage, including DNA interstrand cross-links (ICL) formation, strand cleavages, and alkaline labile DNA lesions. The degree and types of DNA damage induced by these compounds depend on the leaving groups of the substrates, pH value of the buffer solution, and DNA sequences. The DNA ICL products were produced from the carbocations formed via the oxidation of free radicals photo-generated from 1a-f. Most of these compounds alone exhibited minimum cytotoxicity towards cancer cells while 350 nm irradiation greatly improved their anticancer effects (up to 40-fold enhancement) because of photo-induced cellular DNA damage. This work provides guidance for further design of photo-inducible DNA cross-linking agents as potent photo-activated anticancer prodrugs with good control over toxicity and selectivity.

Dual Noncanonical Amino Acid Incorporation Enabling Chemoselective Protein Modification at Two Distinct Sites in Yeast.

Incorporation of more than one noncanonical amino acid (ncAA) within a single protein endows the resulting construct with multiple useful features such as augmented molecular recognition or covalent cross-linking capabilities. Herein, for the first time, we demonstrate the incorporation of two chemically distinct ncAAs into proteins biosynthesized in Saccharomyces cerevisiae. To complement ncAA incorporation in response to the amber (TAG) stop codon in yeast, we evaluated opal (TGA) stop codon suppression using three distinct orthogonal translation systems. We observed selective TGA readthrough without detectable cross-reactivity from host translation components. Readthrough efficiency at TGA was modulated by factors including the local nucleotide environment, gene deletions related to the translation process, and the identity of the suppressor tRNA. These observations facilitated systematic investigation of dual ncAA incorporation in both intracellular and yeast-displayed protein constructs, where we observed efficiencies up to 6% of wild-type protein controls. The successful display of doubly substituted proteins enabled the exploration of two critical applications on the yeast surface─(A) antigen binding functionality and (B) chemoselective modification with two distinct chemical probes through sequential application of two bioorthogonal click chemistry reactions. Lastly, by utilizing a soluble form of a doubly substituted construct, we validated the dual incorporation system using mass spectrometry and demonstrated the feasibility of conducting selective labeling of the two ncAAs sequentially using a "single-pot" approach. Overall, our work facilitates the addition of a 22nd amino acid to the genetic code of yeast and expands the scope of applications of ncAAs for basic biological research and drug discovery.

Designing Versatile Superhydrophilic Structures via an Alginate-Based Hydrophilic Plasticene.

The rational design of superhydrophilic materials with a controllable structure is a critical component in various applications, including solar steam generation, liquid spontaneous transport, etc. The arbitrary manipulation of the 2D, 3D, and hierarchical structures of superhydrophilic substrates is highly desirable for smart liquid manipulation in both research and application fields. To design versatile superhydrophilic interfaces with various structures, here we introduce a hydrophilic plasticene that possesses high flexibility, deformability, water absorption, and crosslinking capabilities. Through a pattern-pressing process with a specific template, 2D prior fast spreading of liquids at speeds up to 600 mm/s was achieved on the superhydrophilic surface with designed channels. Additionally, 3D superhydrophilic structures can be facilely designed by combining the hydrophilic plasticene with a 3D-printed template. The assembly of 3D superhydrophilic microstructure arrays were explored, providing a promising route to facilitate the continuous and spontaneous liquid transport. The further modification of superhydrophilic 3D structures with pyrrole can promote the applications of solar steam generation. The optimal evaporation rate of an as-prepared superhydrophilic evaporator reached ~1.60 kg·m-2·h-1 with a conversion efficiency of approximately 92.96%. Overall, we envision that the hydrophilic plasticene should satisfy a wide range of requirements for superhydrophilic structures and update our understanding of superhydrophilic materials in both fabrication and application.

ACTIVE-BAPO - A Versatile Transfer Agent for Photoactive Bis(acyl)phosphane Oxide Units.

A N-hydroxy succinimide (NHS) ester substituted bis(acyl)phosphane oxide (ACTIVE-BAPO) was prepared by phospha-Michael addition and used for an easy one-step BAPO ligation with substrates containing primary amino groups, such as amino acids, proteins, and poly(amidoamine) (PAMAM) dendrimers. Thereby, a range of new molecular and polymeric photoinitators was obtained. Real-time photo-rheology experiments demonstrated the outstanding efficiency of the PAMAM BAPOs as photoinitiators for free radical polymerization. Remarkably, it is found that PAMAM BAPOs also act as crosslinking agents to convert monofunctional methacrylate monomers into thermosetting networks without any further additives. Depending on the number of the attached BAPOs, thermosets with a different degree of crosslinking and swelling capability in water were obtained.

New strategies for surface modification of poly (vinyl alcohol) toward click chemistry applications

AbstractIn this study, new synthesis strategies for poly (vinyl alcohol) (PVA) functionalized with azidation (Az) and alkynation (Alk) were carried out for surface functionality modification. These two functionalization routes utilize azide and alkyne groups, respectively, and offer simple way to enhance the PVA crosslinking capabilities toward producing new functional polymer‐based materials. The Az functionalized PVA was prepared in two steps and denoted by PVA‐Az, while Alk functionalized PVA was prepared in one step to produce PVA‐Alk. Surfaces modification of PVA by using Az and Alk functional groups was confirmed by spectral analysis (Fourier transform infrared and 13C‐NMR). Results showed that Alk prompted excellent chemical modifications on the surface of PVA while the thermal stability was enhanced by functionalizing the Az and Alk into PVA. Furthermore, X‐ray photoelectron spectroscopy investigations showed a successful functionalization and new functional groups addition to PVA surface. Scanning electron microscope images were used to analyze the surface morphology of PVA by incorporating the Az and Alk groups, which indicated rougher surfaces compared to that of PVA backbone. In terms of efficiency and simplicity, the techniques used in this study appear to be entirely satisfactory.

An Overview of Collagen-Based Composite Scaffold for Bone Tissue Engineering.

Bone regeneration or restoration is a series of well-ordered physiological activities that occur throughout a person's life, they are continuously being repaired and remodeled. A conventional bone repair procedure, such as autograft and allograft bone transplant, has failed to address bone reconstruction disputes and complexity. On the other hand, Tissue Engineering is a potential therapy option for repairing rather than replacing the damaged tissue. Biomaterials in bone tissue engineering (BTE) help pave the way for damaged tissues as an artificial extracellular matrix, facilitating new tissue growth. Collagen-based biomaterials for repair and replacement have inspired much interest in the hunt for versatile biomaterials compatible with human tissue. It is a major organic component of extracellular matrix in bone and has been employed as scaffolding material in BTE for decades. In this review, we documented the role of collagen in BTE, focusing on collagen type I, its crosslinking capability, collagen-based biomaterials, and fabrication methods. It also considers osteoblast citration a critical process in bone formation, a unique perspective for an old relationship.