Selectively Biodegradable Polyesters: Nature-Inspired Construction Materials for Future Biomedical Applications

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Smart Hydrogels for Tissue Regeneration

The rapid growth in the portion of the aging population has led to a consequent increase in demand for biomedical hydrogels, together with an assortment of challenges that need to be overcome in this field. Smart hydrogels can autonomously sense and respond to the physiological/pathological changes of the tissue microenvironment and continuously adapt the response according to the dynamic spatiotemporal shifts in conditions. This along with other favorable properties, make smart hydrogels excellent materials for employing toward improving the precision of treatment for age-related diseases. The key factor during the smart hydrogel design is on accurately identifying the characteristics of natural tissues and faithfully replicating the composition, structure, and biological functions of these tissues at the molecular level. Such hydrogels can accurately sense distinct physiological and external factors such as temperature and biologically active molecules, so they may in turn actively and promptly adjust their response, by regulating their own biological effects, thereby promoting damaged tissue repair. This review summarizes the design strategies employed in the creation of smart hydrogels, their response mechanisms, as well as their applications in field of tissue engineering; and concludes by briefly discussing the relevant challenges and future prospects.

Recent Advances in Polycaprolactones for Anticancer Drug Delivery

Poly(ε-Caprolactone)s are biodegradable and biocompatible polyesters that have gained considerable attention for drug delivery applications due to their slow degradation and ease of functionalization. One of the significant advantages of polycaprolactone is its ability to attach various functionalities to its backbone, which is commonly accomplished through ring-opening polymerization (ROP) of functionalized caprolactone monomer. In this review, we aim to summarize some of the most recent advances in polycaprolactones and their potential application in drug delivery. We will discuss different types of polycaprolactone-based drug delivery systems and their behavior in response to different stimuli, their ability to target specific locations, morphology, as well as their drug loading and release capabilities.

The Evolution and Recent Trends in Acoustic Targeting of Encapsulated Drugs to Solid Tumors: Strategies beyond Sonoporation

Despite recent advancements in ultrasound-mediated drug delivery and the remarkable success observed in pre-clinical studies, no delivery platform utilizing ultrasound contrast agents has yet received FDA approval. The sonoporation effect was a game-changing discovery with a promising future in clinical settings. Various clinical trials are underway to assess sonoporation's efficacy in treating solid tumors; however, there are disagreements on its applicability to the broader population due to long-term safety issues. In this review, we first discuss how acoustic targeting of drugs gained importance in cancer pharmaceutics. Then, we discuss ultrasound-targeting strategies that have been less explored yet hold a promising future. We aim to shed light on recent innovations in ultrasound-based drug delivery including newer designs of ultrasound-sensitive particles specifically tailored for pharmaceutical usage.

Polylevolysine and Fibronectin-Loaded Nano-Hydroxyapatite/PGLA/Dextran-Based Scaffolds for Improving Bone Regeneration: A Histomorphometric in Animal Study

The regeneration of large bone defects is still demanding, requiring biocompatible scaffolds, with osteoconductive and osteoinductive properties. This study aimed to assess the pre-clinical efficacy of a nano-hydroxyapatite (nano-HA)/PGLA/dextran-based scaffold loaded with Polylevolysine (PLL) and fibronectin (FN), intended for bone regeneration of a critical-size tibial defect, using an ovine model. After physicochemical characterization, the scaffolds were implanted in vivo, producing two monocortical defects on both tibiae of ten adult sheep, randomly divided into two groups to be euthanized at three and six months after surgery. The proximal left and right defects were filled, respectively, with the test scaffold (nano-HA/PGLA/dextran-based scaffold loaded with PLL and FN) and the control scaffold (nano-HA/PGLA/dextran-based scaffold not loaded with PLL and FN); the distal defects were considered negative control sites, not receiving any scaffold. Histological and histomorphometric analyses were performed to quantify the bone ingrowth and residual material 3 and 6 months after surgery. In both scaffolds, the morphological analyses, at the SEM, revealed the presence of submicrometric crystals on the surfaces and within the scaffolds, while optical microscopy showed a macroscopic 3D porous architecture. XRD confirmed the presence of nano-HA with a high level of crystallinity degree. At the histological and histomorphometric evaluation, new bone formation and residual biomaterial were detectable inside the defects 3 months after intervention, without differences between the scaffolds. At 6 months, the regenerated bone was significantly higher in the defects filled with the test scaffold (loaded with PLL and FN) than in those filled with the control scaffold, while the residual material was higher in correspondence to the control scaffold. Nano-HA/PGLA/dextran-based scaffolds loaded with PLL and FN appear promising in promoting bone regeneration in critical-size defects, showing balanced regenerative and resorbable properties to support new bone deposition.

Green preparation of electrically conductive solution blow spun nanofibers from recycled polyethylene terephthalate via plasma-assisted oxidation-reduction

Simple and green strategy was described for the development of multifunctional polyester nanofibers (PNFs). Solution blow spinning (SBS) technology was applied to in situ immobilize nanocomposites of polyaniline (PANi) and silver nanoparticles (AgNPs) into plasma-treated polyester nanoscaled fibers prepared. The polyester nanofibers were prepared from recycled polyethylene terephthalate waste, which was exposed plasma-curing and a REDOX reaction in the presence of AgNO₃, aniline, and CH₃COONH₄. Plasma-catalyzed oxidative polymerization of aniline to polyaniline together with a reductive process of Ag⁺ to silver nanoparticles led to their enduring insoluble dispersion into the surface of polyester nanofibers. By taking the advantage of the PANi oxidation, AgNPs were precipitated from an aqueous medium of AgNPs. The morphological properties were investigated by various analytical techniques. The polyester fiber diameter was determined in the range of 450-650 nm. In addition, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were utilized to examine AgNPs, demonstrating diameters of 4-20 nm. The plasma-uncured AgNPs/PANi immobilized nanofibrous film displayed weak absorption bands at 399 nm and 403 nm upon increasing the concentration of AgNPs. On the other hand, the plasma-cured AgNPs/PANi immobilized nanofibers displayed strong absorption bands at 526 nm and 568 nm upon increasing the concentration of AgNPs. The AgNP-induced antimicrobial performance and the PANi-induced electrically conductivity were explored. The prepared PNFs showed high UV protection.

Smart Poly(lactide)-b-poly(triethylene glycol methyl ether methacrylate) (PLA-b-PTEGMA) Block Copolymers: One-Pot Synthesis, Temperature Behavior, and Controlled Release of Paclitaxel

This paper introduces a new class of amphiphilic block copolymers created by combining two polymers: polylactic acid (PLA), a biocompatible and biodegradable hydrophobic polyester used for cargo encapsulation, and a hydrophilic polymer composed of oligo ethylene glycol chains (triethylene glycol methyl ether methacrylate, TEGMA), which provides stability and repellent properties with added thermo-responsiveness. The PLA-b-PTEGMA block copolymers were synthesized using ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization (ROP-RAFT), resulting in varying ratios between the hydrophobic and hydrophilic blocks. Standard techniques, such as size exclusion chromatography (SEC) and ¹H NMR spectroscopy, were used to characterize the block copolymers, while ¹H NMR spectroscopy, 2D nuclear Overhauser effect spectroscopy (NOESY), and dynamic light scattering (DLS) were used to analyze the effect of the hydrophobic PLA block on the LCST of the PTEGMA block in aqueous solutions. The results show that the LCST values for the block copolymers decreased with increasing PLA content in the copolymer. The selected block copolymer presented LCST transitions at physiologically relevant temperatures, making it suitable for manufacturing nanoparticles (NPs) and drug encapsulation-release of the chemotherapeutic paclitaxel (PTX) via temperature-triggered drug release mechanism. The drug release profile was found to be temperature-dependent, with PTX release being sustained at all tested conditions, but substantially accelerated at 37 and 40 °C compared to 25 °C. The NPs were stable under simulated physiological conditions. These findings demonstrate that the addition of hydrophobic monomers, such as PLA, can tune the LCST temperatures of thermo-responsive polymers, and that PLA-b-PTEGMA copolymers have great potential for use in drug and gene delivery systems via temperature-triggered drug release mechanisms in biomedicine applications.

Biomolecular Liquid-Liquid Phase Separation for Biotechnology

The liquid-liquid phase separation (LLPS) of biomolecules induces condensed assemblies called liquid droplets or membrane-less organelles. In contrast to organelles with lipid membrane barriers, the liquid droplets induced by LLPS do not have distinct barriers (lipid bilayer). Biomolecular LLPS in cells has attracted considerable attention in broad research fields from cellular biology to soft matter physics. The physical and chemical properties of LLPS exert a variety of functions in living cells: activating and deactivating biomolecules involving enzymes; controlling the localization, condensation, and concentration of biomolecules; the filtration and purification of biomolecules; and sensing environmental factors for fast, adaptive, and reversible responses. The versatility of LLPS plays an essential role in various biological processes, such as controlling the central dogma and the onset mechanism of pathological diseases. Moreover, biomolecular LLPS could be critical for developing new biotechnologies such as the condensation, purification, and activation of a series of biomolecules. In this review article, we introduce some fundamental aspects and recent progress of biomolecular LLPS in living cells and test tubes. Then, we discuss applications of biomolecular LLPS toward biotechnologies.

Exploring the Application of Micellar Drug Delivery Systems in Cancer Nanomedicine

Various formulations of polymeric micelles, tiny spherical structures made of polymeric materials, are currently being investigated in preclinical and clinical settings for their potential as nanomedicines. They target specific tissues and prolong circulation in the body, making them promising cancer treatment options. This review focuses on the different types of polymeric materials available to synthesize micelles, as well as the different ways that micelles can be tailored to be responsive to different stimuli. The selection of stimuli-sensitive polymers used in micelle preparation is based on the specific conditions found in the tumor microenvironment. Additionally, clinical trends in using micelles to treat cancer are presented, including what happens to micelles after they are administered. Finally, various cancer drug delivery applications involving micelles are discussed along with their regulatory aspects and future outlooks. As part of this discussion, we will examine current research and development in this field. The challenges and barriers they may have to overcome before they can be widely adopted in clinics will also be discussed.

Overview of Antimicrobial Biodegradable Polyester-Based Formulations

As the clinical complications induced by microbial infections are known to have life-threatening side effects, conventional anti-infective therapy is necessary, but not sufficient to overcome these issues. Some of their limitations are connected to drug-related inefficiency or resistance and pathogen-related adaptive modifications. Therefore, there is an urgent need for advanced antimicrobials and antimicrobial devices. A challenging, yet successful route has been the development of new biostatic or biocide agents and biomaterials by considering the indisputable advantages of biopolymers. Polymers are attractive materials due to their physical and chemical properties, such as compositional and structural versatility, tunable reactivity, solubility and degradability, and mechanical and chemical tunability, together with their intrinsic biocompatibility and bioactivity, thus enabling the fabrication of effective pharmacologically active antimicrobial formulations. Besides representing protective or potentiating carriers for conventional drugs, biopolymers possess an impressive ability for conjugation or functionalization. These aspects are key for avoiding malicious side effects or providing targeted and triggered drug delivery (specific and selective cellular targeting), and generally to define their pharmacological efficacy. Moreover, biopolymers can be processed in different forms (particles, fibers, films, membranes, or scaffolds), which prove excellent candidates for modern anti-infective applications. This review contains an overview of antimicrobial polyester-based formulations, centered around the effect of the dimensionality over the properties of the material and the effect of the production route or post-processing actions.

Factors Controlling Degradation of Biologically Relevant Synthetic Polymers in Solution and Solid State

The field of biodegradable synthetic polymers, which is central for regenerative engineering and drug delivery applications, encompasses a multitude of hydrolytically sensitive macromolecular structures and diverse processing approaches. The ideal degradation behavior for a specific life science application must comply with a set of requirements, which include a clinically relevant kinetic profile, adequate biocompatibility, benign degradation products, and controlled structural evolution. Although significant advances have been made in tailoring materials characteristics to satisfy these requirements, the impacts of autocatalytic reactions and microenvironments are often overlooked resulting in uncontrollable and unpredictable outcomes. Therefore, roles of surface versus bulk erosion, in situ microenvironment, and autocatalytic mechanisms should be understood to enable rational design of degradable systems. In an attempt to individually evaluate the physical state and form factors influencing autocatalytic hydrolysis of degradable polymers, this Review follows a hierarchical analysis that starts with hydrolytic degradation of water-soluble polymers before building up to 2D-like materials, such as ultrathin coatings and capsules, and then to solid-state degradation. We argue that chemical reactivity largely governs solution degradation while diffusivity and geometry control the degradation of bulk materials, with thin "2D" materials remaining largely unexplored. Following this classification, this Review explores techniques to analyze degradation in vitro and in vivo and summarizes recent advances toward understanding degradation behavior for traditional and innovative polymer systems. Finally, we highlight challenges encountered in analytical methodology and standardization of results and provide perspective on the future trends in the development of biodegradable polymers.

Polyglycerol Adipate-Grafted Polycaprolactone Nanoparticles as Carriers for the Antimicrobial Compound Usnic Acid

Nanoparticle (NP) drug delivery systems are known to potentially enhance the efficacy of therapeutic agents. As for antimicrobial drugs, therapeutic solutions against drug-resistant microbes are urgently needed due to the worldwide antimicrobial resistance issue. Usnic acid is a widely investigated antimicrobial agent suffering from poor water solubility. In this study, polymer nanoparticles based on polyglycerol adipate (PGA) grafted with polycaprolactone (PCL) were developed as carriers for usnic acid. We demonstrated the potential of the developed systems in ensuring prolonged bactericidal activity against a model bacterial species, Staphylococcus epidermidis. The macromolecular architecture changes produced by PCL grafted from PGA significantly influenced the drug release profile and mechanism. Specifically, by varying the length of PCL arms linked to the PGA backbone, it was possible to tune the drug release from a burst anomalous drug release (high PCL chain length) to a slow diffusion-controlled release (low PCL chain length). The developed nanosystems showed a prolonged antimicrobial activity (up to at least 7 days) which could be used in preventing/treating infections occurring at different body sites, including medical device-related infection and mucosal/skin surface, where Gram-positive bacteria are commonly involved.

Biodegradable Polymer Composites for Electrophysiological Signal Sensing

Electrophysiological signals are collected to characterize human health and applied in various fields, such as medicine, engineering, and pharmaceuticals. Studies of electrophysiological signals have focused on accurate signal acquisition, real-time monitoring, and signal interpretation. Furthermore, the development of electronic devices consisting of biodegradable and biocompatible materials has been attracting attention over the last decade. In this regard, this review presents a timely overview of electrophysiological signals collected with biodegradable polymer electrodes. Candidate polymers that can constitute biodegradable polymer electrodes are systemically classified by their essential properties for collecting electrophysiological signals. Moreover, electrophysiological signals, such as electrocardiograms, electromyograms, and electroencephalograms subdivided with human organs, are discussed. In addition, the evaluation of the biodegradability of various electrodes with an electrophysiology signal collection purpose is comprehensively revisited.

Regeneration of Articular Cartilage Using Membranes of Polyester Scaffolds in a Rabbit Model

One promising method for cartilage regeneration involves combining known methods, such as the microfracture technique with biomaterials, e.g., scaffolds (membranes). The most important feature of such implants is their appropriate rate of biodegradation, without the production of toxic metabolites. This study presents work on two different membranes made of polyester (L-lactide-co-ε-caprolactone-PLCA) named “PVP and “Z”. The difference between them was the use of different pore precursors—polyvinylpyrrolidone in the “PVP” scaffold and gelatin in the “Z” scaffold. These were implemented in the articular cartilage defects of rabbit knee joints (defects were created for the purpose of the study). After 8, 16, and 24 weeks of observation, and the subsequent termination of the animals, histopathology and gel permeation chromatography (GPC) examinations were performed. Statistical analysis proved that the membranes support the regeneration process. GPC testing proved that the biodegradation process is progressing exponentially, causing the membranes to degrade at the appropriate time. The surgical technique we used meets all the requirements without causing the membrane to migrate after implantation. The “PVP” membrane is better due to the fact that after 24 weeks of observation there was a statistical trend for higher histological ratings. It is also better because it is easier to implant due to its lower fragility then membrane “Z”. We conclude that the selected membranes seem to support the regeneration of articular cartilage in the rabbit model.

Synthesis and Properties of Phosphorus-Containing Pseudo-Poly(Amino Acid)sof Polyester Type Based on N-Derivatives of Glutaminic Acid

Poly(phosphoeter)s (PPE)s are a class of polymers possessing a high chemical functionality and biodegradability. Novel, glutamic acid based poly(phosphoeter)s were synthesized by the Steglich reaction. The developed synthetic approach allows controlling the composition and the structure of PPEs, and therefore their physical and colloidal properties. The studies on solubilization and cytotoxicity in vitro proved the potential of PPEs for drug delivery applications.

Enzymatic Poly(octamethylene suberate) Synthesis by a Two-Step Polymerization Method Based on the New Greener Polymer-5B Technology

Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis of the final polymers confirmed the successful POS synthesis and a high degree of monomer conversion. This innovative two-step polymerization strategy opens up a new opportunity for implementing greener and more environmentally friendly processes for synthesizing biodegradable polyesters.

Improved Synthesis of a Novel Biodegradable Tunable Micellar Polymer Based on Partially Hydrogenated Poly(β-malic Acid-co-benzyl Malate)

Poly(benzyl malate) (PBM), together with its derivatives, have been studied as nanocarriers for biomedical applications due to their superior biocompatibility and biodegradability. The acquisition of PBM is primarily from chemical routes, which could offer polymer-controlled molecular weight and a unique controllable morphology. Nowadays, the frequently used synthesis from L-aspartic acid gives an overall yield of 4.5%. In this work, a novel synthesis route with malic acid as the initiator was successfully designed and optimized, increasing the reaction yield up to 31.2%. Furthermore, a crystalline form of PBM (PBM-2) that polymerized from high optical purity benzyl-β-malolactonate (MLABn) was discovered during the optimization process. X-ray diffraction (XRD) patterns revealed that the crystalline PBM-2 had obvious diffraction peaks, demonstrating that its internal atoms were arranged in a more orderly manner and were different from the amorphous PBM-1 prepared from the racemic MLABn. The differential scanning calorimetry (DSC) curves and thermogravimetric curves elucidated the diverse thermal behaviors between PBM-1 and PBM-2. The degradation curves and scanning electron microscopy (SEM) images further demonstrated the biodegradability of PBM, which have different crystal structures. The hardness of PBM-2 implied the potential application in bone regeneration, while it resulted in the reduction of solubility when compared with PBM-1, which made it difficult to be dissolved and hydrogenated. The solution was therefore heated up to 75 °C to achieve benzyl deprotection, and a series of partially hydrogenated PBM was sequent prepared. Their optimal hydrogenation rates were screened to determine the optimal conditions for the formation of micelles suitable for drug-carrier applications. In summary, the synthesis route from malic acid facilitated the production of PBM for a shorter time and with a higher yield. The biodegradability, biosafety, mechanical properties, and adjustable hydrogenation widen the application of PBM with tunable properties as drug carriers.

Enzymatic Synthesis of Polyesters and Their Bioapplications: Recent Advances and Perspectives

This article reviews the most important advances in the enzymatic synthesis of polyesters. In first place, the different processes of polyester enzymatic synthesis, i.e., polycondensation, ring opening, and chemoenzymatic polymerizations, and the key parameters affecting these reactions, such as enzyme, concentration, solvent, or temperature, are analyzed. Then, the latest articles on the preparation of polyesters either by direct synthesis or via modification are commented. Finally, the main bioapplications of enzymatically obtained polyesters, i.e., antimicrobial, drug delivery, or tissue engineering, are described. It is intended to point out the great advantages that enzymatic polymerization present to obtain polymers and the disadvantages found to develop applied materials.

Insights into the toxicity of biomaterials microparticles with a combination of cellular and oxidative biomarkers

Considering that the extensive biomedical, pharmaceutics, cosmetic and other industrial applications of biomaterials (BMs) is of great concern nowadays, regarding their environmental risk, the present study aimed to investigate the effects of four BMs, poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBSu), chitosan (CS) and modified chitosan (succinic acid grafted chitosan) (CS-Suc) in the form of microplastics (particle sizes less than 1 mm) on biochemical parameters of snails Cornu aspersum hemocytes. Due to the absence of knowledge about the environmentally relevant concentrations of BMs, snails were initially treated through their food with a wide range of nominal concentrations of each BM to define the half maximal effective concentration (NRRT₅₀), according to the destabilization degree of hemocytes' lysosomal membranes (by mean of neutral red retention time/NRRT assay). Thereafter, snails were treated with each BM, at concentrations lower than the estimated NRRT₅₀ values in all cases, for periods up to 15 days. After the end of the exposure period, a battery of stress indices were measured in hemocytes of challenged snails. According to the results, all parameters tested in BMs-treated snails statistically differed from those measured in BMs-free snails, thus indicating the pro-oxidant potential of BMs, as well as their ability to affect animals' physiology. The most considerable effect in most cases seems to be caused by modified chitosan and PCL, while chitosan appears to be the least toxic. A common response mechanism of snails' blood cells against the 4 BMs used in the present study was shown. After exposure to each of the studied BMs a significant augmentation in protein carbonyls, MDA equivalents and DNA damage, while a significant reduction in NRRT values was determined in the snails hemocytes, in relation to the unexposed animals. From the biochemical parameters examined, MDA equivalents and DNA damage seem to be more susceptible than the other parameters studied, to respond to BMs effect, with MDA to react with more sensitivity to PCL and CS, while DNA damage to CS-Suc and PBSu. Our results could suggest the simultaneous use of the latter biomarkers in biomonitoring studies of terrestrial ecosystems against the specific BMs.

PLGA Microspheres Containing Hydrophobically Modified Magnesium Hydroxide Particles for Acid Neutralization-Mediated Anti-Inflammation

BACKGROUND

Poly(lactic-co-glycolic acid) (PLGA) microspheres have been actively used in various pharmaceutical formulations because they can sustain active pharmaceutical ingredient release and are easy to administer into the body using a syringe. However, the acidic byproducts produced by the decomposition of PLGA cause inflammatory reactions in surrounding tissues, limiting biocompatibility. Magnesium hydroxide (MH), an alkaline ceramic, has attracted attention as a potential additive because it has an acid-neutralizing effect.

METHODS

To improve the encapsulation efficiency of hydrophilic MH, the MH particles were capped with hydrophobic ricinoleic acid (RA-MH). PLGA microspheres encapsulated with RA-MH particles were manufactured by the O/W method. To assess the in vitro cytotoxicity of the degradation products of PLGA, MH/PLGA, and RA-MH/PLGA microspheres, CCK-8 and Live/Dead assays were performed with NIH-3T3 cells treated with different concentrations of their degradation products. In vitro anti-inflammatory effect of RA-MH/PLGA microspheres was evaluated with quantitative measurement of pro-inflammatory cytokines.

RESULTS

The synthesized RA-MH was encapsulated in PLGA microspheres and displayed more than four times higher loading content than pristine MH. The PLGA microspheres encapsulated with RA-MH had an acid-neutralizing effect better than that of the control group. In an in vitro cell experiment, the degradation products obtained from RA-MH/PLGA microspheres exhibited higher biocompatibility than the degradation products obtained from PLGA microspheres. Additionally, the RA-MH/PLGA microsphere group showed an excellent anti-inflammatory effect.

CONCLUSION

Our results proved that RA-MH-encapsulated PLGA microspheres showed excellent biocompatibility with an anti-inflammatory effect. This technology can be applied to drug delivery and tissue engineering to treat various incurable diseases in the future.

Achievements and Trends in Biocatalytic Synthesis of Specialty Polymers from Biomass-Derived Monomers Using Lipases

New technologies for the conversion of biomass into high-value chemicals, including polymers and plastics, is a must and a challenge. The development of green processes in the last decade involved a continuous increase of the interest towards the synthesis of polymers using in vitro biocatalysis. Among the remarkable diversity of new bio-based polymeric products meeting the criteria of sustainability, biocompatibility, and eco-friendliness, a wide range of polyesters with shorter chain length were obtained and characterized, targeting biomedical and cosmetic applications. In this review, selected examples of such specialty polymers are presented, highlighting the recent developments concerning the use of lipases, mostly in immobilized form, for the green synthesis of ε-caprolactone co-polymers, polyesters with itaconate or furan units, estolides, and polyesteramides. The significant process parameters influencing the average molecular weights and other characteristics are discussed, revealing the advantages and limitations of biocatalytic processes for the synthesis of these bio-based polymers.

Connecting primitive phase separation to biotechnology, synthetic biology, and engineering

One aspect of the study of the origins of life focuses on how primitive chemistries assembled into the first cells on Earth and how these primitive cells evolved into modern cells. Membraneless droplets generated from liquid-liquid phase separation (LLPS) are one potential primitive cell-like compartment; current research in origins of life includes study of the structure, function, and evolution of such systems. However, the goal of primitive LLPS research is not simply curiosity or striving to understand one of life's biggest unanswered questions, but also the possibility to discover functions or structures useful for application in the modern day. Many applicational fields, including biotechnology, synthetic biology, and engineering, utilize similar phaseseparated structures to accomplish specific functions afforded by LLPS. Here, we briefly review LLPS applied to primitive compartment research and then present some examples of LLPS applied to biomolecule purification, drug delivery, artificial cell construction, waste and pollution management, and flavor encapsulation. Due to a significant focus on similar functions and structures, there appears to be much for origins of life researchers to learn from those working on LLPS in applicational fields, and vice versa, and we hope that such researchers can start meaningful cross-disciplinary collaborations in the future.

Human metabolite-derived alkylsuccinate/dilinoleate copolymers: from synthesis to application

The advances in polymer chemistry have allowed the preparation of biomedical polymers using human metabolites as monomers that can hold unique properties beyond the required biodegradability and biocompatibility. Herein, we demonstrate the use of endogenous human metabolites (succinic and dilinoleic acids) as monomeric building blocks to develop a new series of renewable resource-based biodegradable and biocompatible copolyesters. The novel copolyesters were characterized in detail employing several standard techniques, namely 1H NMR, 13C NMR, and FTIR spectroscopy and SEC, followed by an in-depth thermomechanical and surface characterization of their resulting thin films (DSC, TGA, DMTA, tensile tests, AFM, and contact angle measurements). Also, their anti-fungal biofilm properties were assessed via an anti-fungal biofilm assay and the biological properties were evaluated in vitro using relevant human-derived cells (human mesenchymal stem cells and normal human dermal fibroblasts). These novel highly biocompatible polymers are simple and cheap to prepare, and their synthesis can be easily scaled-up. They presented good mechanical, thermal and anti-fungal biofilm properties while also promoting cell attachment and proliferation, outperforming well-known polymers used for biomedical applications (e.g. PVC, PLGA, and PCL). Moreover, they induced morphological changes in the cells, which were dependent on the structural characteristics of the polymers. In addition, the obtained physicochemical and biological properties can be design-tuned by the synthesis of homo- and -copolymers through the selection of the diol moiety (ES, PS, or BS) and by the addition of a co-monomer, DLA. Consequently, the copolyesters presented herein have high application potential as renewable and cost-effective biopolymers for various biomedical applications.

Design of Bio-Conjugated Hydrogels for Regenerative Medicine Applications: From Polymer Scaffold to Biomolecule Choice

Bio-conjugated hydrogels merge the functionality of a synthetic network with the activity of a biomolecule, becoming thus an interesting class of materials for a variety of biomedical applications. This combination allows the fine tuning of their functionality and activity, whilst retaining biocompatibility, responsivity and displaying tunable chemical and mechanical properties. A complex scenario of molecular factors and conditions have to be taken into account to ensure the correct functionality of the bio-hydrogel as a scaffold or a delivery system, including the polymer backbone and biomolecule choice, polymerization conditions, architecture and biocompatibility. In this review, we present these key factors and conditions that have to match together to ensure the correct functionality of the bio-conjugated hydrogel. We then present recent examples of bio-conjugated hydrogel systems paving the way for regenerative medicine applications.

Forensic Engineering of Advanced Polymeric Materials-Part VII: Degradation of Biopolymer Welded Joints

Welding technology may be considered as a promising processing method for the formation of packaging products from biopolymers. However, the welding processes used can change the properties of the polymer materials, especially in the region of the weld. In this contribution, the impact of the welding process on the structure and properties of biopolymer welds and their ability to undergo hydrolytic degradation will be discussed. Samples for the study were made from polylactide (PLA) and poly(3-hydroxyalkanoate) (PHA) biopolymers which were welded using two methods: ultrasonic and heated tool welding. Differential scanning calorimetry (DSC) analysis showed slight changes in the thermal properties of the samples resulting from the processing and welding method used. The results of hydrolytic degradation indicated that welds of selected biopolymers started to degrade faster than unwelded parts of the samples. The structure of degradation products at the molecular level was confirmed using mass spectrometry. It was found that hydrolysis of the PLA and PHA welds occurs via the random ester bond cleavage and leads to the formation of PLA and PHA oligomers terminated by hydroxyl and carboxyl end groups, similarly to as previously observed for unwelded PLA and PHA-based materials.

Magnetic Temperature-Sensitive Solid-Lipid Particles for Targeting and Killing Tumor Cells

Magnetic and temperature-sensitive solid lipid particles (mag. SLPs) were prepared in the presence of oleic acid-coated iron oxide (IO-OA) nanoparticles with 1-tetradecanol and poly(ethylene oxide)-block-poly(ε-caprolactone) as lipid and stabilizing surfactant-like agents, respectively. The particles, typically ~850 nm in hydrodynamic size, showed heat dissipation under the applied alternating magnetic field. Cytotoxic activity of the mag.SLPs, non-magnetic SLPs, and iron oxide nanoparticles was compared concerning the mammalian cancer cell lines and their drug-resistant counterparts using trypan blue exclusion test and MTT assay. The mag.SLPs exhibited dose-dependent cytotoxicity against human leukemia cell lines growing in suspension (Jurkat and HL-60/wt), as well as the doxorubicin (Dox)- and vincristine-resistant HL-60 sublines. The mag.SLPs showed higher cytotoxicity toward drug-resistant sublines as compared to Dox. The human glioblastoma cell line U251 growing in a monolayer culture was also sensitive to mag.SLPs cytotoxicity. Staining of U251 cells with the fluorescent dyes Hoechst 33342 and propidium iodide (PI) revealed that mag.SLPs treatment resulted in an increased number of cells with condensed chromatin and/or fragmented nuclei as well as with blebbing of the plasma membranes. While the Hoechst 33342 staining of cell suggested the pro-apoptotic activity of the particles, the PI staining indicated the pro-necrotic changes in the target cells. These conclusions were confirmed by Western blot analysis of apoptosis-related proteins, study of DNA fragmentation (DNA laddering due to the inter-nucleosomal cleavage and DNA comets due to single strand breaks), as well as by FACS analysis of the patterns of cell cycle distribution (pre-G1 phase) and Annexin V/PI staining of the treated Jurkat cells. The induction of apoptosis or necrosis by the particles used to treat Jurkat cells depended on the dose of the particles. Production of the reactive oxygen species (ROS) was proposed as a potential mechanism of mag.SLPs-induced cytotoxicity. Accordingly, hydrogen peroxide and superoxide radical levels in mag.SLPs-treated Jurkat leukemic cells were increased by ~20–40 and ~70%, respectively. In contrast, the non-magnetic SLPs and neat iron oxides did not influence ROS levels significantly. Thus, the developed mag.SLPs can be used for effective killing of human tumor cells, including drug-resistant ones.

Synthesis and Characterization of Polyfumarateurethane Nanoparticles for Sustained Release of Bupivacaine

Biodegradable polyfumarateurethane (PFU) for use as a bupivacaine delivery vehicle, synthesized using di-(2-hydroxypropyl fumarate) (DHPF), polyethylene glycol (PEG) and 1,6-hexamethylene diisocyanate (HMDI), was designed to be degradable through the hydrolysis and enzymatic degradation of the ester bonds in its polymer backbone. Using a water-in-oil-in-water double emulsion techniques, nanoparticles encapsulating water or fluorescein isothiocyanate (FITC) were fabricated to avoid the immune system owing to the presence of PEG on their surface. The morphologies of these nanoparticles were characterized by DLS, TEM, FE-SEM, and fluorescent microscopies. The present study explored the encapsulation, loading efficiency and in vitro drug release of bupivacaine encapsulated with biodegradable PFU nanoparticles for the treatment of local anesthesia. Various concentrations of bupivacaine were encapsulated into nanoparticles and their encapsulation efficiencies and drug loading were investigated. Encapsulation efficiency was highest when 2.5% bupivacaine was encapsulated. Drug release behavior from the bupivacaine-loaded PFU nanoparticles followed a sustained release profile.

Parallel evolution of polymer chemistry and immunology: Integrating mechanistic biology with materials design

To develop new therapeutics involves the interaction of multiple disciplines to yield safe, functional devices and formulations. Regardless of drug function and potency, administration with controlled timing, dosing, and targeting is required to properly treat or regulate health and disease. Delivery approaches can be optimized through advances in materials science, clinical testing, and basic biology and immunology. Presently, laboratories focused on developing these technologies are composed of, or collaborate with, chemists, biologists, materials scientists, engineers, and physicians to understand the way our body interacts with drug delivery devices, and how to synthesize new, rationally designed materials to improve targeted and controlled drug delivery. In this review, we discuss both device-based and micro/nanoparticle-based materials in the clinic, our biologic understanding of how our immune system interacts with these materials, how this diverse set of immune cells has become a target and variable in drug delivery design, and new directions in polymer chemistry to address these interactions and further our advances in medical therapeutics.

Trends in Polymers 2017/2018: Polymer Synthesis

Polymer synthesis is a substantial area in polymer science and marks the starting point for all sorts of polymer materials that have a plethora of applications in everyday life but also in academic research [...].