Combinatorial approach to develop tailored biodegradable poly(xylitol dicarboxylate) polyesters

Harnessing the power of polyol-based polyesters for biomedical innovations: synthesis, properties, and biodegradation

Polyesters based on polyols have emerged as promising biomaterials for various biomedical applications, such as tissue engineering, drug delivery systems, and regenerative medicine, due to their biocompatibility, biodegradability, and versatile physicochemical properties. This review article provides an overview of the synthesis methods, performance, and biodegradation mechanisms of polyol-based polyesters, highlighting their potential for use in a wide range of biomedical applications. The synthesis techniques, such as simple polycondensation and enzymatic polymerization, allow for the fine-tuning of polyester structure and molecular weight, thereby enabling the tailoring of material properties to specific application requirements. The physicochemical properties of polyol-based polyesters, such as hydrophilicity, crystallinity, and mechanical properties, can be altered by incorporating different polyols. The article highlights the influence of various factors, such as molecular weight, crosslinking density, and degradation medium, on the biodegradation behavior of these materials, and the importance of understanding these factors for controlling degradation rates. Future research directions include the development of novel polyesters with improved properties, optimization of degradation rates, and exploration of advanced processing techniques for fabricating scaffolds and drug delivery systems. Overall, polyol-based polyesters hold significant potential in the field of biomedical applications, paving the way for groundbreaking advancements and innovative solutions that could revolutionize patient care and treatment outcomes.

Biomaterials with Stiffness Gradient for Interface Tissue Engineering

Interface tissue engineering is a rapidly growing field that aims to develop engineered tissue alternates with the goal of promoting integration between multiple tissue types. Engineering interface tissues is a complex process, which requires a specialized biomaterials with organized material composition, stiffness, cell types, and signaling molecules. Among these, stiffness-controllable substrates have been developed to investigate the effect of stiffness on cell behavior. Especially these substrates with graded stiffness are advantageous since they allow the differentiation of multiple cell phenotypes and subsequent tissue development. In this review, we highlight the various types of manufacturing techniques that can be leveraged to fabricate scaffolds with stiffness gradient, discuss methods to characterize them, and gradient biomaterials for controlling cellular behavior including attachment, migration, proliferation, and differentiation. We also address fundamentals of interface tissue organization, and stiffness gradient biomaterials for interface tissue regeneration. Potential challenges and future directions in this emerging field are also discussed.

Activation of cryptic xylose metabolism by a transcriptional activator Znf1 boosts up xylitol production in the engineered Saccharomyces cerevisiae lacking xylose suppressor BUD21 gene

Background

Xylitol is a valuable pentose sugar alcohol, used in the food and pharmaceutical industries. Biotechnological xylitol production is currently attractive due to possible conversion from abundant and low-cost industrial wastes or agricultural lignocellulosic biomass. In this study, the transcription factor Znf1 was characterised as being responsible for the activation of cryptic xylose metabolism in a poor xylose-assimilating S. cerevisiae for xylitol production.

Results

The results suggest that the expression of several xylose-utilising enzyme genes, encoding xylose reductases for the reduction of xylose to xylitol was derepressed by xylose. Their expression and those of a pentose phosphate shunt and related pathways required for xylose utilisation were strongly activated by the transcription factor Znf1. Using an engineered S. cerevisiae strain overexpressing ZNF1 in the absence of the xylose suppressor bud21Δ, xylitol production was maximally by approximately 1200% to 12.14 g/L of xylitol, corresponding to 0.23 g/g xylose consumed, during 10% (w/v) xylose fermentation. Proteomic analysis supported the role of Znf1 and Bud21 in modulating levels of proteins associated with carbon metabolism, xylose utilisation, ribosomal protein synthesis, and others. Increased tolerance to lignocellulosic inhibitors and improved cell dry weight were also observed in this engineered bud21∆ + pLJ529-ZNF1 strain. A similar xylitol yield was achieved using fungus-pretreated rice straw hydrolysate as an eco-friendly and low-cost substrate.

Conclusions

Thus, we identified the key modulators of pentose sugar metabolism, namely the transcription factor Znf1 and the suppressor Bud21, for enhanced xylose utilisation, providing a potential application of a generally recognised as safe yeast in supporting the sugar industry and the sustainable lignocellulose-based bioeconomy.

Graphical Abstract

Controlled Branching by Step-Growth Polymerization of Xylitol and Succinic Acid via Microwave Irradiation

Copolymerization of xylitol usually yields cross-linked materials. In this work, microwave-assisted polyesterification of xylitol and succinic acid produced materials with diverse molecular weights and different branching degrees, and more importantly, no cross-linking was observed, as supported by the solubility behavior and spectroscopic data. Reactions were carried out for short times, less than 20 min, which is not common for production of industrial polyesters. Control over the branching degree was achieved by tuning the reaction conditions, such as temperature, time of exposure, and monomer ratio, during microwave irradiation. No solvent or catalyst was employed during the step-growth polymerization.

E-Beam Effects on Poly(Xylitol Dicarboxylate-co-diol Dicarboxylate) Elastomers Tailored by Adjusting Monomer Chain Length

Poly(xylitol dicarboxylate-co-diol dicarboxylate) elastomers can by synthesized using wide variety of monomers with different chain lengths. Obtained materials are all biodegradable, thermally stable elastomers, but their specific properties like glass transition temperature, degradation susceptibility, and mechanical moduli can be tailored for a specific application. Therefore, we synthesized eight elastomers using a combination of two dicarboxylic acids, namely suberic and sebacic acid, and four different diols, namely ethanediol, 1,3-propanediol, 1,4-buanediol, and 1,5-pentanediol. Materials were further modified by e-beam treatment with a dose of 100 kGy. Materials both before and after radiation modification were tested using tensile tests, gel fraction determination, ¹H NMR, and ¹³C NMR. Thermal properties were tested by Differential Scanning Calorimetry (DSC), Dynamic Thermomechanical Analysis (DMTA) and Thermogravimetric Analysis (TGA). Degradation susceptibility to both enzymatic and hydrolytic degradation was also determined.

Physical Effects of Radiation Modification of Biodegradable Xylitol-Based Materials Synthesized Using a Combination of Different Monomers

There is a possibility of obtaining xylitol-based elastomers sharing common characteristics of biodegradability, thermal stability, and elastomeric behavior by using monomers with different chain-lengths. Therefore, we have synthesized eight elastomers using a combination of four different diols (ethanediol, 1.3-propanediol, 1.4-buanediol, and 1.5-pentanediol) and two different dicarboxylic acids (succinic acid and adipic acid). The obtained materials were further modified by performing e-beam treatment with a dose of 100 kGy. Materials both before and after radiation modification were tested by DSC, DMTA, TGA, tensile tests, gel fraction determination, hydrolytic and enzymatic degradation tests, ¹H NMR and ¹³C NMR and FTIR.

Biobased poly(ester-co-glycoside) from reactive natural Brønsted acidic deep eutectic solvent analogue

{glucose : malic acid : water} [(1 : 1 : x), x ≤ 9] mixtures are Brønsted Acidic Natural Low Transition Temperature (NaLTTM) that react in solvent/catalyst free conditions to prepare all-natural poly(ester-co-glycoside) branched and crosslinked polymers.

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.

Influence of e-Beam Irradiation on the Physicochemical Properties of Poly(polyol Succinate-co-Butylene Succinate) Ester Elastomers

The purpose of this research was synthesis and electron beam modification of novel ester elastomers consisting of sugar alcohol–succinic acid block and butylene glycol–succinic acid block. Four different alditols were used in the synthesis—sorbitol, erythritol, xylitol, and glycerol. The materials were irradiated with doses of 50, 100, and 150 kGy in order to determine which dose is the most beneficial. As expected, irradiation of the materials has led to the cross-link density becoming higher and improvement of the mechanical properties. Additionally, the materials were also sterilized in the process. The great advantage of elastomers described in the paper is the fact that they do not need chemical cross-linking agents or sensitizers in order to undergo radiation modification. The following tests were performed on cross-linked poly(polyol succinate-co-butylene succinate) elastomers: quasi-static tensile test, determination of cross-link density, differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMTA), wettability (water contact angle), and Fourier transform infrared spectroscopy (FTIR). In order to confirm successful synthesis, prepolymers were analyzed by nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR).

Tailoring the Physico-Chemical Properties of Poly(xylitol-dicarboxylate-co-butylene dicarboxylate) Polyesters by Adjusting the Cross-Linking Time

Determining the cross-linking time resulting in the best achievable properties in elastomers is a very important factor when considering their mass production. In this paper, five biodegradable polymers were synthesized-poly(xylitol-dicarboxylate-co-butylene dicarboxylate) polymers, based on xylitol obtained from renewable sources. Five different dicarboxylic acids with even numbers of carbon atoms in the aliphatic chain were used: succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Samples were taken directly after polycondensation (prepolymer samples) and at different stages of the cross-linking process. Physiochemical properties were determined by a gel fraction test, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), quasi-static tensile tests, nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR), and an in vitro biodegradation test. The best cross-linking time was determined to be 288h. Properties and degradation time can be tailored for specific applications by adjusting the dicarboxylic acid chain length.

Effect of E-Beam Irradiation on Thermal and Mechanical Properties of Ester Elastomers Containing Multifunctional Alcohols

The aim of this work was to investigate the thermal and mechanical properties of novel, electron beam-modified ester elastomers containing multifunctional alcohols. Polymers tested in this work consist of two blocks: sebacic acid-butylene glycol block and sebacic acid-sugar alcohol block. Different sugar alcohols were utilized in the polymer synthesis: glycerol, sorbitol, xylitol, erythritol, and mannitol. The polymers have undergone an irradiation procedure. The materials were irradiated with doses of 50 kGy, 100 kGy, and 150 kGy. The expected effect of using ionizing radiation was crosslinking process and improvement of the mechanical properties. Additionally, a beneficial side effect of the irradiation process is sterilization of the affected materials. It is also worth noting that the materials described in this paper do not require either sensitizers or cross-linking agent in order to perform radiation modification. Radiation-modified poly(polyol sebacate-co-butylene sebacate) elastomers have been characterized in respect to the mechanical properties (quasi-static tensile tests), cross-link density, thermal properties (Differential Scanning Calorimetry (DSC)), chemical properties: Fourier transform infrared spectroscopy (FTIR), and wettability (water contact angle). Poly(polyol sebacate-co-butylene sebacate) preopolymers were characterized with nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR) and gel permeation chromatography (GPC). Thermal stability of cross-linked materials (directly after synthesis process) was tested with thermogravimetric analysis (TGA).

Structure and Properties of Biodegradable Poly (Xylitol Sebacate-Co-Butylene Sebacate) Copolyester

In this work, a bio-based copolyester with good mechanical properties was synthesized and characterized in terms of structure, main properties and biodegradability Determining the chemical structure of such materials is important to understand their behavior and properties. Performing an extraction of insoluble cross-linked polymer using different solvents allowed us to analyze how the polymer behaves when subjected to different chemical environments, and to obtain soluble samples suitable for more in-depth analysis. Chemical structure of poly (xylitol sebacate-co-butylene sebacate) was determined by a 1H NMR and FTIR analysis of both prepolymer gel sample and samples obtained by extraction of cross-linked polymer using different solvents. Block structure of the copolymer was confirmed by both NMR and DSC. Gel fraction, swelling value, water contact angle, and mechanical properties were also analyzed. Biodegradability of this material was confirmed by performing enzymatic and hydrolytic degradation. Synthesizing sugar-alcohol based copolyester using three monomers leads to obtaining a material with interesting chemical structure and desirable mechanical properties comparable to conventional elastomers.

A Highly Elastic and Autofluorescent Poly(xylitol-dodecanedioic Acid) for Tissue Engineering

In spite of the vast research on developing a highly elastic polymer for tissue regeneration, using a renewable resource and a simple, environment-friendly synthesis route to synthesize an elastic polymer has not been successfully achieved yet. The objective of this study was to use a simple melt condensation polymerization method to develop an elastic polymer for tissue regeneration applications. A nature-derived renewable, nontoxic, and inexpensive monomer, xylitol, and a cross-linking agent, dodecanedioic acid, were used to synthesize the new polymer named poly(xylitol-dodecanedioic acid) (PXDDA). Its physicochemical and biological properties were fully characterized. Fourier transform infrared (FTIR) results confirmed the formation of ester bonding in the polymer structure, and thermal analysis results demonstrated that the polymer was completely amorphous. The polymer is highly elastic. Increasing the molar ratio of dodecanedioic acid resulted in lower elasticity, higher hydrophobicity, and lower glass transition temperature. Further, the polymer degradation rate and in vitro dye release from the polymer also became slower when the amount of dodecanedioic acid in the composite increased. Biocompatibility studies showed that both the polymeric materials and the degraded products of the polymer did not show any toxicity. Instead, this new polymer significantly promoted cell adhesion and proliferation, compared to a widely used polymer, poly(lactic acid), and tissue culture plates. Interestingly, the PXDDA polymer demonstrated autofluorescent properties. Overall, these results suggest that a new, elastic, biodegradable polymer has been successfully synthesized, and it holds great promise for biomedical applications in drug delivery and tissue engineering.

Gradient platform for combinatorial screening of thermoset polymers for biomedical applications

The goal of this work was to design a device for rapid screening of crosslinked thermoset polymers. This gradient curing platform is capable of yielding a library of polyesters with systematically varying mechanical and physicochemical properties and the resultant cellular response. A library of poly(xylitolsebacate) polyesters was prepared in this device by differential curing to yield a gradient polymer. The resultant polymer exhibits a gradient in the storage modulus (1 to 5 MPa), wettability (70° < water contact angle < 110°), degree of crosslinking, degradation rate (3-25% in 7 days), drug release and biological response (ability to support stem cell proliferation and differentiation) from one end of the polymer to the other. Primary human mesenchymal stem cells were cultured to assess the cellular response in vitro. Maximal stem cell proliferation and osteogenesis was observed on the highly crosslinked polyester segments that provide high stiffness, are hydrophobic and are slow degrading as compared to the lower cured counterparts. Under in vivo conditions, this material showed differential response across the gradient without displaying significant concerns for inflammation or infection. This gradient curing device is capable of ascertaining suitable curing conditions to obtain appropriate polymers for application specific requirements. This gradient platform was further used to identify optimal processing parameters to prepare three-dimensional tissue scaffolds such as electrospun fiber mats and porous foams. Thus, this versatile combinatorial platform is well suited for rapid screening of thermoset polymers for biomedical applications.

Synthetic nanoparticles of bovine serum albumin with entrapped salicylic acid

Bovine serum albumin (BSA) is highly water soluble and binds drugs or inorganic substances noncovalently for their effective delivery to various affected areas of the body. Due to the well-defined structure of the protein, containing charged amino acids, albumin nanoparticles (NPs) may allow electrostatic adsorption of negatively or positively charged molecules, such that substantial amounts of drug can be incorporated within the particle, due to different albumin-binding sites. During the synthesis procedure, pH changes significantly. This variation modifies the net charge on the surface of the protein, varying the size and behavior of NPs as the drug delivery system. In this study, the synthesis of BSA NPs, by a desolvation process, was studied with salicylic acid (SA) as the active agent. SA and salicylates are components of various plants and have been used for medication with anti-inflammatory, antibacterial, and antifungal properties. However, when administered orally to adults (usual dose provided by the manufacturer), there is 50% decomposition of salicylates. Thus, there has been a search for some time to develop new systems to improve the bioavailability of SA and salicylates in the human body. Taking this into account, during synthesis, the pH was varied (5.4, 7.4, and 9) to evaluate its influence on the size and release of SA of the formed NPs. The samples were analyzed using field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, zeta potential, and dynamic light scattering. Through fluorescence, it was possible to analyze the release of SA in vitro in phosphate-buffered saline solution. The results of chemical morphology characterization and in vitro release studies indicated the potential use of these NPs as drug carriers in biological systems requiring a fast release of SA.

Physical insights into salicylic acid release from poly(anhydrides)

Salicylic acid (SA) based biodegradable polyanhydrides (PAHs) are of great interest for drug delivery in a variety of diseases and disorders owing to the multi-utility of SA. There is a need for the design of SA-based PAHs for tunable drug release, optimized for the treatment of different diseases. In this study, we devised a simple strategy for tuning the release properties and erosion kinetics of a family of PAHs. PAHs incorporating SA were derived from related aliphatic diacids, varying only in the chain length, and prepared by simple melt condensation polymerization. Upon hydrolysis induced erosion, the polymer degrades into cytocompatible products, including the incorporated bioactive SA and diacid. The degradation follows first order kinetics with the rate constant varying by nearly 25 times between the PAH obtained with adipic acid and that with dodecanedioic acid. The release profiles have been tailored from 100% to 50% SA release in 7 days across the different PAHs. The release rate constants of these semi-crystalline, surface eroding PAHs decreased almost linearly with an increase in the diacid chain length, and varied by nearly 40 times between adipic acid and dodecanedioic acid PAH. The degradation products with SA concentration in the range of 30-350 ppm were used to assess cytocompatibility and showed no cytotoxicity to HeLa cells. This particular strategy is expected to (a) enable synthesis of application specific PAHs with tunable erosion and release profiles; (b) encompass a large number of drugs that may be incorporated into the PAH matrix. Such a strategy can potentially be extended to the controlled release of other drugs that may be incorporated into the PAH backbone and has important implications for the rational design of drug eluting bioactive polymers.

Polyol-based biodegradable polyesters: a short review

Catalyst-free thermal polyesterification has recently emerged as a potential strategy for designing biodegradable thermoset polymers, particularly polyol-based polyesters for biomedical applications. These thermoset polyesters are synthesized through polycondensation of polyol and polyacid without the presence of catalyst or solvents. The mechanical properties, degradation rates, crystallinity, hydrophilicity, and biocompatibility can be controlled by adjusting the monomer feed ratios and curing conditions. These polyesters often degrade via surface erosion that allows the polymers to maintain structural integrity throughout hydrolysis. Additionally, polyol-based polyesters demonstrated good biocompatibility as non-toxic catalysts and/or solvents involved in the reaction, and the monomers used are endogenous to human metabolism which can be resorbed and metabolized in various physiological pathways. This review summarizes the polyol-based biodegradable polyesters that were synthesized by catalyst-free polyesterification.

Controlled release kinetics of p-aminosalicylic acid from biodegradable crosslinked polyesters for enhanced anti-mycobacterial activity

Unlike conventional polymeric drug delivery systems, where drugs are entrapped in polymers, this study focuses on the incorporation of the drug into the polymer backbone to achieve higher loading and sustained release. Crosslinked, biodegradable, xylitol based polyesters have been synthesized in this study. The bioactive drug moiety, p-aminosalicylic acid (PAS), was incorporated in xylitol based polyesters to impart its anti-mycobacterial activity. To understand the influence of the monomer chemistry on the incorporation of PAS and its subsequent release from the polymer, different diacids have been used. Controlled release profiles of the drug from these polyesters were studied under normal physiological conditions. The degradation of the polyesters varied from 48% to 76% and the release of PAS ranged from 54% to 65% of its initial loading in 7days. A new model was developed to explain the release kinetics of PAS from the polymer that accounted for the polymer degradation and drug concentration. The thermal, mechanical, drug release and cytocompatibility properties of the polymers indicate their suitability in biomedical applications. The released products from these polymers were observed to be pharmacologically active against Mycobacteria. The high drug loading and sustained release also ensured enhanced efficacy. These polymers form biocompatible, biodegradable polyesters where the sustained release of PAS may be tailored for potential treatment of mycobacterial infections.

STATEMENT OF SIGNIFICANCE

In the present work, we report on novel polyesters with p-aminosalicylic acid (PAS) incorporated in the polymer backbone. The current work aims to achieve controlled release of PAS and ensures the delivered PAS is stable and pharmacologically active. The novelty of this work primarily involves the synthetic chemistry of polymerization and detailed analysis and efficacy of active PAS delivery. A new kinetic model has been developed to explain the PAS release profiles. These polymers are biodegradable, cytocompatible and anti-mycobacterial in nature.

Maltitol-based biodegradable polyesters with tailored degradation and controlled release for bone regeneration

Polyesters based on maltitol and different dicarboxylic acids promoted mineral deposition and directed cells towards osteogenic lineage.

Controlled Release of Salicylic Acid from Biodegradable Cross-Linked Polyesters

The purpose of this work was to develop a family of cross-linked poly(xylitol adipate salicylate)s with a wide range of tunable release properties for delivering pharmacologically active salicylic acid. The synthesis parameters and release conditions were varied to modulate polyester properties and to understand the mechanism of release. Varying release rates were obtained upon longer curing (35% in the noncured polymer to 10% in the cured polymer in 7 days). Differential salicylic acid loading led to the synthesis of polymers with variable cross-linking and the release could be tuned (100% release for the lowest loading to 30% in the highest loading). Controlled release was monitored by changing various factors, and the release profiles were dependent on the stoichiometric composition, pH, curing time, and presence of enzyme. The polymer released a combination of salicylic acid and disalicylic acid, and the released products were found to be nontoxic. Minimal hemolysis and platelet activation indicated good blood compatibility. These polymers qualify as "bioactive" and "resorbable" and can, therefore, find applications as immunomodulatory resorbable biomaterials with tunable release properties.