The ad hoc chemical design of random PBS-based copolymers influences the activation of cardiac differentiation while altering the HYPPO pathway target genes in hiPSCs

Cardiac tissue engineering is a cutting-edge technology aiming to replace irreversibly damaged cardiac tissue and restore contractile functionality. However, cardiac tissue engineering porous and perfusable scaffolds to enable oxygen supply in vitro and eventually promote angiogenesis in vivo are still desirable. Two fully-aliphatic random copolymers of poly(butylene succinate) (PBS), poly(butylene succinate/Pripol), P(BSBPripol), and poly(butylene/neopentyl glycol succinate), P(BSNS), containing two different subunits, neopentyl glycol and Pripol 1009, were successfully synthesized and then electrospun in tridimentional fibrous mats. The copolymers show different thermal and mechanical behaviours as result of their chemical structure. In particular, copolymerization led to a reduction in crystallinity and consequently PBS stiffness, reaching values of elastic modulus very close to those of soft tissues. Then, to check the biological suitability, human induced Pluripotent Stem Cells (hiPSCs) were directly seeded on both PBS-based copolymeric scaffolds. The results confirmed the ability of both the scaffolds to sustain cell viability and to maintain their stemness during cell expansion. Furthermore, gene expression and immunofluorescence analysis showed that P(BSBPripol) scaffold promoted an upregulation of the early cardiac progenitor and later-stage markers with a simultaneously upregulation of HYPPO pathway gene expression, crucial for mechanosensing of cardiac progenitor cells. These results suggest that the correct ad-hoc chemical design and, in turn, the mechanical properties of the matrix, such as substrate stiffness, together with surface porosity, play a critical role in regulating the behaviour of cardiac progenitors, which ultimately offers valuable insights into the development of novel bio-inspired scaffolds for cardiac tissue regeneration.

A Review on Current Strategies for the Modulation of Thermomechanical, Barrier, and Biodegradation Properties of Poly (Butylene Succinate) (PBS) and Its Random Copolymers

The impact of plastics on the environment can be mitigated by employing biobased and/or biodegradable materials (i.e., bioplastics) instead of the traditional "commodities". In this context, poly (butylene succinate) (PBS) emerges as one of the most promising alternatives due to its good mechanical, thermal, and barrier properties, making it suitable for use in a wide range of applications. Still, the PBS has some drawbacks, such as its high crystallinity, which must be overcome to position it as a real and viable alternative to "commodities". This contribution covers the actual state-of-the-art of the PBS through different sections. The first section reviews the different synthesis routes, providing a complete picture regarding the obtained molecular weights and the greener alternatives. Afterward, we examine how different strategies such as random copolymerization and the incorporation of fillers can effectively modulate PBS properties to satisfy the needs for different applications. The impact of these strategies is evaluated in the crystallization behavior, crystallinity, mechanical and barrier properties, and biodegradation. The biodegradation is carefully analyzed, highlighting the wide variety of methodologies existing in the literature to measure PBS degradation through different routes (hydrolytic, enzymatic, and soil).

Polybutylene succinate artificial scaffold for peripheral nerve regeneration

Regeneration and recovery of nerve tissues are a great challenge for medicine, and positively affect the quality of life of patients. The development of tissue engineering offers a new approach to the problem with the creation of multifunctional artificial scaffolds that act on various levels in the damaged tissue, providing physical and biochemical support for the growth of nerve cells. In this study, the effects of the use of a tubular scaffold made of polybutylene succinate (PBS), surgically positioned at the level of a sciatic nerve injured in rat, between the proximal stump and the distal one, was investigated. Scaffolds characterization was carried out by scanning electron microscopy and X‐ray microcomputed tomography and magnetic resonance imaging, in vivo. The demonstration of the nerve regeneration was based on the evaluation of electroneurography, measuring the weight of gastrocnemius and tibialis anterior muscles, histological examination of regenerated nerves and observing the recovery of the locomotor activity of animals. The PBS tubular scaffold minimized iatrogenic trauma on the nerve, acting as a directional guide for the regenerating fibers by conveying them toward the distal stump. In this context, neurotrophic and neurotropic factors may accumulate and perform their functions, while invasion by macrophages and scar tissue is hampered.

Elastomeric Electrospun Scaffolds of a Biodegradable Aliphatic Copolyester Containing PEG-Like Sequences for Dynamic Culture of Human Endothelial Cells

In the field of artificial prostheses for damaged vessel replacement, polymeric scaffolds showing the right combination of mechanical performance, biocompatibility, and biodegradability are still demanded. In the present work, poly(butylene-co-triethylene trans-1,4-cyclohexanedicarboxylate), a biodegradable random aliphatic copolyester, has been synthesized and electrospun in form of aligned and random fibers properly designed for vascular applications. The obtained materials were analyzed through tensile and dynamic-mechanical tests, the latter performed under conditions simulating the mechanical contraction of vascular tissue. Furthermore, the in vitro biological characterization, in terms of hemocompatibility and cytocompatibility in static and dynamic conditions, was also carried out. The mechanical properties of the investigated scaffolds fit within the range of physiological properties for medium- and small-caliber blood vessels, and the aligned scaffolds displayed a strain-stiffening behavior typical of the blood vessels. Furthermore, all the produced scaffolds showed constant storage and loss moduli in the investigated timeframe (24 h), demonstrating the stability of the scaffolds under the applied conditions of mechanical deformation. The biological characterization highlighted that the mats showed high hemocompatibility and low probability of thrombus formation; finally, the cytocompatibility tests demonstrated that cyclic stretch of electrospun fibers increased endothelial cell activity and proliferation, in particular on aligned scaffolds.

Full biodegradable elastomeric nanocomposites fabricated by chitin nanocrystal and poly(caprolactone-diol citrate) elastomer

Chitin nanocrystal is a biocompatible and biodegradable nanofiller, with great potential in enhancing the mechanical and biological properties of polymers. Poly(caprolactone-diol citrate) is a kind of citrate-based biodegradable elastomer prepared by an additive-free melt polycondensation of polycaprolactone-diol and citric acid coupled with subsequent thermocuring. Here, a facile casting/evaporation method was utilized to prepare full biodegradable poly(caprolactone-diol citrate)/chitin nanocrystal nanocomposites, and their structure and properties were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, uniaxial tensile test, dynamic mechanical analysis, surface wettability and swelling analysis, thermogravimetric analysis, in vitro degradation, and cytocompatibility test. The results showed the chitin nanocrystals were uniformly distributed in the poly(caprolactone-diol citrate) matrix; with increasing chitin nanocrystal loading, the tensile modulus and strength significantly increased; furthermore, the incorporation of chitin nanocrystals endowed the poly(caprolactone-diol citrate) with more hydrophilicity, lower swelling in phosphate buffered saline solution, slow degradation rate, and greatly improved cytocompatibility. Thus, the chitin nanocrystal was a good bio-based nanofiller that could be used to tune the properties of poly(caprolactone-diol citrate) degradable bioelastomer.

Recent Advances in Nanocomposites Based on Aliphatic Polyesters: Design, Synthesis, and Applications in Regenerative Medicine

In the last decade, biopolymer matrices reinforced with nanofillers have attracted great research efforts thanks to the synergistic characteristics derived from the combination of these two components. In this framework, this review focuses on the fundamental principles and recent progress in the field of aliphatic polyester-based nanocomposites for regenerative medicine applications. Traditional and emerging polymer nanocomposites are described in terms of polymer matrix properties and synthesis methods, used nanofillers, and nanocomposite processing and properties. Special attention has been paid to the most recent nanocomposite systems developed by combining alternative copolymerization strategies with specific nanoparticles. Thermal, electrical, biodegradation, and surface properties have been illustrated and correlated with the nanoparticle kind, content, and shape. Finally, cell-polymer (nanocomposite) interactions have been described by reviewing analysis methodologies such as primary and stem cell viability, adhesion, morphology, and differentiation processes.

Enzymatic Degradation of Poly(butylene succinate) Copolyesters Synthesized with the Use of Candida antarctica Lipase B

Biodegradable polymers are an active area of investigation, particularly ones that can be produced from sustainable, biobased monomers, such as copolymers of poly(butylene succinate) (PBS). In this study, we examine the enzymatic degradation of poly(butylene succinate-dilinoleic succinate) (PBS-DLS) copolymers obtained by "green" enzymatic synthesis using lipase B from Candida antarctica (CALB). The copolymers differed in their hard to soft segments ratio, from 70:30 to 50:50 wt %. Enzymatic degradation was carried out on electrospun membranes (scaffolds) and compression-moulded films using lipase from Pseudomomas cepacia. Poly(ε-caprolactone) (PCL) was used as a reference aliphatic polyester. The degradation process was monitored gravimetrically via water uptake and mass loss. After 24 days, approx. 40% mass loss was observed for fibrous materials prepared from the PBS-DLS 70:30 copolymer, as compared to approx. 10% mass loss for PBS-DLS 50:50. Infrared spectroscopy (FTIR) and size exclusion chromatography (SEC) analysis were used to examine changes in chemical structure. Differential scanning calorimetry (DSC) and scanning light microscopy (LSM) revealed changes in degree of crystallinity, and changes in surface morphology, consistent with a surface erosion mechanism. We conclude that the obtained copolymers are suitable for tissue engineering applications thanks to tuneable degradation and lack of acidification during breakdown.

GBR membrane of novel poly (butylene succinate-co-glycolate) co-polyester co-polymer for periodontal application

In periodontics, osteoconductive biodegradable guided bone regeneration (GBR) membranes with acceptable physico-mechanical properties are required to fix alveolar bone defects. The objectives of the present study were to produce and characterize a novel co-polyester—poly (butylene succinate-co-glycolate) (PBSGL), and fabricate a PBSGL membrane by electrospinning. We then aimed to evaluate the in vitro effect of the glycolate ratio on the biocompatibility and osteogenic differentiation of mesenchymal stem cells (MSCs), and evaluate in vivo bone regeneration using these membranes in rabbit calvarial defects by histology. Increasing the glycolate ratio of electrospun PBSGL membranes resulted in better cell attachment, greater cell metabolic activity, and enhanced osteogenic potential at both transcriptional and translational levels. Histologic and histomorphometric evaluations revealed further that bone defects covered with fibers of higher glycolate ratios showed more bone formation, with no adverse inflammatory response. These results suggest that novel PBSGL electrospun nanofibers show great promise as GBR membranes for bone regeneration.

Influence of the nanofiber chemistry and orientation of biodegradable poly(butylene succinate)-based scaffolds on osteoblast differentiation for bone tissue regeneration

Innovative nanofibrous scaffolds have attracted considerable attention in bone tissue engineering, due to their ability to mimic the hierarchical architecture of an extracellular matrix. Aiming at investigating how the polymer chemistry and fiber orientation of electrospun scaffolds (ES) based on poly(butylene succinate) (PBS) and poly(butylene succinate/diglycolate) (P(BS80BDG20)) affect human osteoblast differentiation, uniaxially aligned (a-) and randomly (r-) distributed nanofibers were produced. Although human osteoblastic SAOS-2 cells were shown to be viable and adherent onto all ES materials, a-P(BS80BDG20) exhibited the best performance both in terms of cellular phosphorylated focal adhesion kinase expression and in terms of alkaline phosphatase activity, calcified bone matrix deposition and quantitative gene expression of bone specific markers during differentiation. It has been hypothesized that the presence of ether linkages may lead to an increased density of hydrogen bond acceptors along the P(BS80BDG20) backbone, which, by interacting with cell membrane components, can in turn promote a better cell attachment on the copolymer mats with respect to the PBS homopolymer. Furthermore, although displaying the same chemical structure, r-P(BS80BDG20) scaffolds showed a reduced cell attachment and osteogenic differentiation in comparison with a-P(BS80BDG20), evidencing the importance of nanofiber alignment. Thus, the coupled action of polymer chemical structure and nanofiber alignment played a significant role in promoting the biological interaction.

LAPONITE® nanorods regulating degradability, acidic-alkaline microenvironment, apatite mineralization and MC3T3-E1 cells responses to poly(butylene succinate) based bio-nanocomposite scaffolds

Novel bio-nanocomposite scaffolds for bone tissue engineering were prepared by incorporation of LAPONITE® (LAP) nanorods into poly(butylene succinate) (PBSu). The results showed that the scaffolds had well interconnected macroporous structures with macropore size in the range of 200–400 μm and porosity of around 70%. In addition, the water absorption, degradability and apatite mineralization ability of the scaffolds were clearly enhanced with the increase of LAP content. Moreover, the degradation of LAP produced alkaline products, which neutralized the acidic degradable products of PBSu, and formed a weak alkaline microenvironment similar to a biological environment. Furthermore, the adhesion, proliferation and differentiation of MC3T3-E1 cells onto the scaffolds were significantly promoted with the increase of LAP content, in which the scaffold with 30 wt% LAP (sPL30) exhibited the best stimulation effect on the cells responses. The results suggested that the promotion of cells responses could be ascribed to the improvements of surface characteristics (including roughness, hydrophilicity, ions release and apatite formation, etc.) of the scaffolds. The sPL30 scaffold with excellent biocompatibility, bioactivity and degradability had great potential for applications in bone tissue engineering.

PBSu/LAP bio-nanocomposite scaffolds were prepared, and the sPL30 scaffolds significantly stimulated cell adhesion and proliferation.

Efficient biomaterials for tissue engineering of female reproductive organs

Current investigations on the bioengineering of female reproductive tissues have created new hopes for the women suffering from reproductive organ failure including congenital anomaly of the female reproductive tract or serious injuries. There are many surgically restore forms that constitute congenital anomaly, however, to date, there is no treatment except surgical treatment of transplantation for patients who are suffering from anomaly or dysfunction organs like vagina and uterus. Restoring and maintaining the normal function of ovary and uterus require the establishment of biological substitutes that can cover the roles of structural support for cells and passage of secreting molecules. As in the case of constructing other functional organs, reproductive organ manufacturing also needs biological matrices which can provide an appropriate condition for attachment, growth, proliferation and signaling of various kinds of grafted cells. Among the organs, uterus needs special features such as plasticity due to their amazing changes in volume when they are in the state of pregnancy. Although numerous natural and synthetic biomaterials are still at the experimental stage, some biomaterials have already been evaluated their efficacy for the reconstruction of female reproductive tissues. In this review, all the biomaterials cited in recent literature that have ever been used and that have a potential for the tissue engineering of female reproductive organs were reviewed, especially focused on bioengineered ovary and uterus.

Synthesis of bio-based thermoplastic polyurethane elastomers containing isosorbide and polycarbonate diol and their biocompatible properties

A new family of highly elastic polyurethanes (PUs) partially based on renewable isosorbide were prepared by reacting hexamethylene diisocyanate with a various ratios of isosorbide and polycarbonate diol 2000 (PCD) via a one-step bulk condensation polymerization without catalyst. The influence of the isorsorbide/PCD ratio on the properties of the PU was evaluated. The successful synthesis of the PUs was confirmed by Fourier transform-infrared spectroscopy and 1H nuclear magnetic resonance. The resulting PUs showed high number-average molecular weights ranging from 56,320 to 126,000 g mol−1 and tunable Tg values from −34 to −38℃. The thermal properties were determined by differential scanning calorimetry and thermogravimetric analysis. The PU films were flexible with breaking strains from 955% to 1795% at from 13.5 to 54.2 MPa tensile stress. All the PUs had 0.9–2.8% weight lost over 4 weeks and continual slow weight loss of 1.1–3.6% was observed within 8 weeks. Although the cells showed a slight lower rate of proliferation than that of the tissue culture polystyrene as a control, the PU films were considered to be cytocompatible and nontoxic. These thermoplastic PUs were soft, flexible and biocompatible polymers, which open up a range of opportunities for soft tissue augmentation and regeneration.

Synthesis, properties and applications of biodegradable polymers derived from diols and dicarboxylic acids: from polyesters to poly(ester amide)s

Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. Most of these polymers can be prepared from biobased diols and dicarboxylic acids such as 1,4-butanediol, succinic acid and carbohydrates. This review provides a current status report concerning synthesis, biodegradation and applications of a series of polymers that cover a wide range of properties, namely, materials from elastomeric to rigid characteristics that are suitable for applications such as hydrogels, soft tissue engineering, drug delivery systems and liquid crystals. Finally, the incorporation of aromatic units and α-amino acids is considered since stiffness of molecular chains and intermolecular interactions can be drastically changed. In fact, poly(ester amide)s derived from naturally occurring amino acids offer great possibilities as biodegradable materials for biomedical applications which are also extensively discussed.

Mechanostimulation protocols for cardiac tissue engineering

Owing to the inability of self-replacement by a damaged myocardium, alternative strategies to heart transplantation have been explored within the last decades and cardiac tissue engineering/regenerative medicine is among the present challenges in biomedical research. Hopefully, several studies witness the constant extension of the toolbox available to engineer a fully functional, contractile, and robust cardiac tissue using different combinations of cells, template bioscaffolds, and biophysical stimuli obtained by the use of specific bioreactors. Mechanical forces influence the growth and shape of every tissue in our body generating changes in intracellular biochemistry and gene expression. That is why bioreactors play a central role in the task of regenerating a complex tissue such as the myocardium. In the last fifteen years a large number of dynamic culture devices have been developed and many results have been collected. The aim of this brief review is to resume in a single streamlined paper the state of the art in this field.

The synthesis and characterization of a thermally responsive hyaluronic acid/Pluronic copolymer and an evaluation of its potential as an artificial vitreous substitute

A smart in situ polymerizable artificial vitreous substitute was synthesized via the copolymerization of hyaluronic acid and Pluronic® F-127. This copolymer has a unique sol–gel transition at different temperatures. The liquid was injected into a vitreous cavity at room temperature and forms a hydrogel at physiological temperatures. The chemical, rheological, and optical properties and the biodegradability and biocompatibility were studied to determine the optimum formulation for the hydrogel. The H1F20 hydrogel optical properties were similar to those of the vitreous humor. Biodegradability studies indicate that the H1F20 hydrogel maintains 60% of the mass in 10,000 U mL−1 of lysozyme solution, after 7 days. The H1F20 hydrogel had the highest human retinal pigment epithelial cell (ARPE-19) viability, which was significantly higher than that of the control ( p < 0.01). In summary, H1F20 appears to be a suitable artificial vitreous substitute.

Application of high-strength biodegradable polyurethanes containing different ratios of biobased isomannide and poly (ϵ-caprolactone) diol

Biodegradable–biocompatible polyurethanes were prepared with fixed hexamethylene diisocyanate and varying ratios of isomannide and poly(ϵ-caprolactone) diol using a simple one-step polymerization without a catalyst. The polyurethane structures were confirmed by ¹H-nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The glass transition temperatures were determined by thermal analysis to be between 25°C and 30°C. Degradation tests performed at 37°C in phosphate buffer produced mass losses of 5%–10% after 8 weeks. After 5 days of culture, using osteoblastic cells, the relative cell number on all the polyurethane films was only slightly lower than that of an optimized tissue culture plastic. These polymers offer significant promise with a simplistic synthesis and controlled degradation.