Biodegradable polymers-an overview

Aromatic poly (amino acids) as an effective low-temperature demulsifier for treating crude oil-in-water emulsions

Amphiphilic aromatic poly (amino acids) polymers were designed as biodegradability demulsifiers with higher aromaticity, stronger polarity, and side chain-like combs. The effects of demulsifier dosage, structural characteristics and emulsion properties such as pH, salinity, and oil content on the demulsification efficiency were investigated. The results show that the poly (L-glutamic-benzyl ester)-block-poly (L-phenylalanine) (PBLG15-b-PPA15) as the demulsifier can remove more than 99.97% of the oil in a 5.0 wt% oil-in-water (O/W) emulsion at room temperature within 2 min. The poly (L-tyrosine)-block-poly (L-phenylalanine) (PTyr15-b-PPA15) with environmental durability demonstrates high effectiveness, universality, and demulsification speed. It achieves a remarkable demulsification efficiency of up to 99.99% for a 20.0 wt% O/W emulsion at room temperature. The demulsification mechanism indicates that demulsifiers have sufficient interfacial activity can quickly migrate to the oil-water interface after being added to the emulsions. Additionally, when demulsifiers are present in a continuous phase in the molecular form, their "teeth" side chains are beneficial for increasing coalescence and flocculation capacities. Furthermore, according to the Density Functional Theory (DFT) calculations, enhancing the intermolecular interactions between demulsifiers and the primary native surfactants that form an oil-water interfacial film is a more efficient approach to reducing demulsification temperature and improving demulsification efficiency and rate.

Additive Manufacturing of Wet-Spun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-Based Scaffolds Loaded with Hydroxyapatite

Tissue engineering represents an advanced therapeutic approach for the treatment of bone tissue defects. Polyhydroxyalkanoates are a promising class of natural polymers in this context thanks to their biocompatibility, processing versatility, and mechanical properties. The aim of this study is the development by computer-aided wet-spinning of novel poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based composite scaffolds for bone engineering. In particular, PHBV scaffolds are loaded with hydroxyapatite (HA), an osteoinductive ceramic, in order to tailor their biological activity and mechanical properties. PHBV blending with poly(lactide-co-glycolide) (PLGA) is also explored to increase the processing properties of the polymeric mixture used for composite scaffold fabrication. Different HA percentages, up to 15% wt., can be loaded into the PHBV or PHBV/PLGA scaffolds without compromising their interconnected porous architecture, as well as the polymer morphological and thermal properties, as demonstrated by scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, HA loading results in increased scaffold compressive stiffness to levels comparable to those of trabecular bone tissue, as well as in higher in vitro MC3T3-E1 cell viability and production of mineralized extracellular matrix, in comparison to what observed for unloaded scaffolds. The observed mechanical and biological properties suggest the suitability of the developed scaffolds for bone engineering.

How Biodegradable Polymers Can be Effective Drug Delivery Systems for Cannabinoids? Prospectives and Challenges

Cannabinoids are compounds found in and derived from the Cannabis plants that have become increasingly recognised as significant modulating factors of physiological mechanisms and inflammatory reactions of the organism, thus inevitably affecting maintenance of homeostasis. Medical Cannabis popularity has surged since its legal regulation growing around the world. Numerous promising discoveries bring more data on cannabinoids' pharmacological characteristics and therapeutic applications. Given the current surge in interest in the medical use of cannabinoids, there is an urgent need for an effective method of their administration. Surpassing low bioavailability, low water solubility, and instability became an important milestone in the advancement of cannabinoids in pharmaceutical applications. The numerous uses of cannabinoids in clinical practice remain restricted by limited administration alternatives, but there is hope when biodegradable polymers are taken into account. The primary objective of this review is to highlight the wide range of indications for which cannabinoids may be used, as well as the polymeric carriers that enhance their effectiveness. The current review described a wide range of therapeutic applications of cannabinoids, including pain management, neurological and sleep disorders, anxiety, and cancer treatment. The use of these compounds was further examined in the area of dermatology and cosmetology. Finally, with the use of biodegradable polymer-based drug delivery systems (DDSs), it was demonstrated that cannabinoids can be delivered specifically to the intended site while also improving the drug's physicochemical properties, emphasizing their utility. Nevertheless, additional clinical trials on novel cannabinoids' formulations are required, as their full spectrum therapeutical potential is yet to be unravelled.

Recent Advances in the Degradability and Applications of Tissue Adhesives Based on Biodegradable Polymers

In clinical practice, tissue adhesives have emerged as an alternative tool for wound treatments due to their advantages in ease of use, rapid application, less pain, and minimal tissue damage. Since most tissue adhesives are designed for internal use or wound treatments, the biodegradation of adhesives is important. To endow tissue adhesives with biodegradability, in the past few decades, various biodegradable polymers, either natural polymers (such as chitosan, hyaluronic acid, gelatin, chondroitin sulfate, starch, sodium alginate, glucans, pectin, functional proteins, and peptides) or synthetic polymers (such as poly(lactic acid), polyurethanes, polycaprolactone, and poly(lactic-co-glycolic acid)), have been utilized to develop novel biodegradable tissue adhesives. Incorporated biodegradable polymers are degraded in vivo with time under specific conditions, leading to the destruction of the structure and the further degradation of tissue adhesives. In this review, we first summarize the strategies of utilizing biodegradable polymers to develop tissue adhesives. Furthermore, we provide a symmetric overview of the biodegradable polymers used for tissue adhesives, with a specific focus on the degradability and applications of these tissue adhesives. Additionally, the challenges and perspectives of biodegradable polymer-based tissue adhesives are discussed. We expect that this review can provide new inspirations for the design of novel biodegradable tissue adhesives for biomedical applications.

Targeting Diverse Wounds and Scars: Recent Innovative Bio-design of Microneedle Patch for Comprehensive Management

Wounds and the subsequent formation of scars constitute a unified and complex phased process. Effective treatment is crucial; however, the diverse therapeutic approaches for different wounds and scars, as well as varying treatment needs at different stages, present significant challenges in selecting appropriate interventions. Microneedle patch (MNP), as a novel minimally invasive transdermal drug delivery system, has the potential for integrated and programmed treatment of various diseases and has shown promising applications in different types of wounds and scars. In this comprehensive review, the latest applications and biotechnological innovations of MNPs in these fields are thoroughly explored, summarizing their powerful abilities to accelerate healing, inhibit scar formation, and manage related symptoms. Moreover, potential applications in various scenarios are discussed. Additionally, the side effects, manufacturing processes, and material selection to explore the clinical translational potential are investigated. This groundwork can provide a theoretical basis and serve as a catalyst for future innovations in the pursuit of favorable therapeutic options for skin tissue regeneration.

Effect of Nano Spinel Ferrites Co0.9Cu0.1Fe2O4 on Non-Isothermal Cold Crystallization Behaviours and Kinetics of Its Composites with Polylactic Acid

Nanoparticles of spinel ferrites with a composition of Co0.9Cu0.1Fe2O4 (AM NPs) were effectively synthesized via a hydrothermal route. The structure of ferrite nanoparticles was characterized with X-ray diffraction, which showed a single cubic spinel phase. Energy-dispersive X-ray (EDX) spectroscopy and field emission-scanning electron microscopy (FE-SEM) were employed to analyse elemental composition and surface morphology, respectively. Moreover, the effects of the Co0.9Cu0.1Fe2O4 on the morphology of [PLA = polylactic acid] nanocomposites were examined through polarized light optical microscopy (POM) and X-ray diffraction (XRD). The thermal behaviours for tested samples were studied through [DSC = differential scanning calorimetry] and [TGA = thermal gravimetric analysis]. A great number of minor PLA spherulites were detected using POM in the presence of the Co0.9Cu0.1Fe2O4 ceramic magnetic nanoparticles (AM), increasing with AM nanoparticle contents. X-ray diffraction (XRD) analysis showed that the presence of nanoparticles led to an increase in the intensity of diffraction peaks. The DSC findings implied that the crystallization behaviours for the efficient PLA as well as its nanocomposites were affected by the addition of AM nanoparticles. They act as efficient nucleating agents because they shift the temperature of crystallization to a lower value. The Avrami models were used to analyse kinetics data. The experimental data were well described using the Avrami method for all samples tested. The addition of AM to the PLA matrix resulted in a decrease in the crystallization half-time t1/2 values, indicating a faster crystallization rate. TGA data showed that the occurrence of AM nanoparticles decreased the thermal stability of PLA.

Poly-Gamma-Glutamic Acid Nanopolymer Effect against Bacterial Biofilms: In Vitro and In Vivo Study

In this study, a biodegradable poly-gamma-glutamic-acid nanopolymer (Ɣ-PGA NP) was investigated for its activity against clinical strains of Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Klebsiella pneumoniae and Escherichia coli), and reference strains of S. aureus ATCC 6538, S. pyogenes ATCC 19615 (Gram-positive), and Gram-negative E. coli ATCC 25922, and K. pneumoniae ATCC 13884 bacterial biofilms. The minimum inhibitory concentration (MIC) effect of Ɣ-PGA NP showed inhibitory effects of 0.2, 0.4, 1.6, and 3.2 μg/mL for S. pyogenes, S. aureus, E. coli, and K. pneumoniae, respectively. Also, MIC values were 1.6, 0.8, 0.2, and 0.2 μg/mL for K. pneumoniae ATCC 13884, E. coli ATCC 25922, S. aureus ATCC 6538, and S. pyogenes ATCC 19615, respectively. Afterwards, MBEC (minimum biofilm eradication concentration) and MBIC (minimum biofilm inhibitory concentration) were investigated to detect Ɣ-PGA NPs efficiency against the biofilms. MBEC and MBIC increased with increasing Ɣ-PGA NPs concentration or time of exposure. Interestingly, MBIC values were at lower concentrations of Ɣ-PGA NPs than those of MBEC. Moreover, MBEC values showed that K. pneumoniae was more resistant to Ɣ-PGA NPs than E. coli, S. aureus, and S. pyogenes, and the same pattern was observed in the reference strains. The most effective results for MBEC were after 48 h, which were 1.6, 0.8, 0.4, and 0.2 µg/mL for K. pneumoniae, E. coli, S. aureus, and S. pyogenes, respectively. Moreover, MBIC results were the most impactful after 24 h but some were the same after 48 h. MBIC values after 48 h were 0.2, 0.2, 0.2, and 0.1 μg/mL for K. pneumoniae, E. coli, S. aureus, and S. pyogenes, respectively. The most effective results for MBEC were after 24 h, which were 1.6, 0.8, 0.4, and 0.4 µg/mL for K. pneumoniae ATCC 13884, E. coli ATCC 25922, S. aureus ATCC 6538, and S. pyogenes ATCC 19615, respectively. Also, MBIC results were the most impactful after an exposure time of 12 h. MBIC values after exposure time of 12 h were 0.4, 0.4, 0.2, and 0.2 μg/mL for K. pneumoniae ATCC 13884, E. coli ATCC 25922, S. aureus ATCC 6538, and S. pyogenes ATCC 19615, respectively. Besides that, results were confirmed using confocal laser scanning microscopy (CLSM), which showed a decrease in the number of living cells to 80% and 60% for MBEC and MBIC, respectively, for all the clinical bacterial strains. Moreover, living bacterial cells decreased to 70% at MBEC while decreasing up to 50% at MBIC with all bacterial refence strains. These data justify the CFU quantification. After that, ImageJ software was used to count the attached cells after incubating with the NPs, which proved the variation in live cell count between the manual counting and image analysis methods. Also, a scanning electron microscope (SEM) was used to detect the biofilm architecture after incubation with the Ɣ-PGA NP. In in vivo wound healing experiments, treated wounds of mice showed faster healing (p < 0.00001) than both the untreated mice and those that were only wounded, as the bacterial count was eradicated. Briefly, the infected mice were treated faster (p < 0.0001) when infected with S. pyogenes > S. aureus > E. coli > K. pneumoniae. The same pattern was observed for mice infected with the reference strains. Wound lengths after 2 h showed slightly healing (p < 0.001) for the clinical strains, while treatment became more obvious after 72 h > 48 h > 24 h (p < 0.0001) as wounds began to heal after 24 h up to 72 h. For reference strains, wound lengths after 2 h started to heal up to 72 h.

Poly(d,l-lactide-co-glycolide) Surface-Anchored Biotin-Loaded Irinotecan Nanoparticles for Active Targeting of Colon Cancer

A poly(d,l-lactide-co-glycolide) (PLGA) copolymer was synthesized using the ring-opening polymerization of d,l-lactide and glycolide monomers in the presence of zinc proline complex in bulk through the green route and was well characterized using attenuated total reflectance-Fourier transform infrared, 1H and 13C nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, X-ray diffraction, matrix-assisted laser desorption/ionization time-of-flight, etc. Furthermore, PLGA-conjugated biotin (PLGA-B) was synthesized using the synthesized PLGA and was employed to fabricate nanoparticles for irinotecan (Ir) delivery. These nanoparticles (PLGA-NP-Ir and PLGA-B-NP-Ir) were tested for physicochemical and biological characteristics. PLGA-B-NP-Ir exhibited a stronger cellular uptake and anticancer activity as compared to PLGA-NP-Ir in CT-26 cancer cells (log p < 0.05). The accumulation and retention of fluorescence-labeled nanoparticles were observed to be better in CT-26-inoculated solid tumors in Balb/c mice. The PLGA-B-NP-Ir-treated group inhibited tumor growth significantly more (log p < 0.001) than the untreated control, PLGA-NP-Ir, and Ir-treated groups. Furthermore, no body weight loss, hematological, and blood biochemical tests demonstrated the nanocarriers' nontoxic nature. This work presents the use of safe PLGA and the demonstration of a proof-of-concept of biotin surface attached PLGA nanoparticle-mediated active targeted Ir administration to combat colon cancer. To treat colon cancer, PLGA-B-NP-Ir performed better due to specific active tumor targeting and greater cellular uptake due to biotin.

Development of hybrid 3D printing approach for fabrication of high-strength hydroxyapatite bioscaffold using FDM and DLP techniques

This study develops a hybrid 3D printing approach that combines fused deposition modeling (FDM) and digital light processing (DLP) techniques for fabricating bioscaffolds, enabling rapid mass production. The FDM technique fabricates outer molds, while DLP prints struts for creating penetrating channels. By combining these components, hydroxyapatite (HA) bioscaffolds with different channel sizes (600, 800, and 1000μm) and designed porosities (10%, 12.5%, and 15%) are fabricated using the slurry casting method with centrifugal vacuum defoaming for significant densification. This innovative method produces high-strength bioscaffolds with an overall porosity of 32%-37%, featuring tightly bound HA grains and a layered surface structure, resulting in remarkable cell viability and adhesion, along with minimal degradation rates and superior calcium phosphate deposition. The HA scaffolds show hardness ranging from 1.43 to 1.87 GPa, with increasing compressive strength as the designed porosity and channel size decrease. Compared to human cancellous bone at a similar porosity range of 30%-40%, exhibiting compressive strengths of 13-70 MPa and moduli of 0.8-8 GPa, the HA scaffolds demonstrate robust strengths ranging from 40 to 73 MPa, paired with lower moduli of 0.7-1.23 GPa. These attributes make them well-suited for cancellous bone repair, effectively mitigating issues like stress shielding and bone atrophy.

Degradation of Polylactic Acid/Polypropylene Carbonate Films in Soil and Phosphate Buffer and Their Potential Usefulness in Agriculture and Agrochemistry

Blends of poly(lactic acid) (PLA) with poly(propylene carbonate) (PPC) are currently in the phase of intensive study due to their promising properties and environmentally friendly features. Intensive study and further commercialization of PPC-based polymers or their blends, as usual, will soon face the problem of their waste occurring in the environment, including soil. For this reason, it is worth comprehensively studying the degradation rate of these polymers over a long period of time in soil and, for comparison, in phosphate buffer to understand the difference in this process and evaluate the potential application of such materials toward agrochemical and agricultural purposes. The degradation rate of the samples was generally accompanied by weight loss and a decrease in molecular weight, which was facilitated by the presence of PPC. The incubation of the samples in the aqueous media yielded greater surface erosions compared to the degradation in soil, which was attributed to the leaching of the low molecular degradation species out of the foils. The phytotoxicity study confirmed the no toxic impact of the PPC on tested plants, indicating it as a "green" material, which is crucial information for further, more comprehensive study of this polymer toward any type of sustainable application.

Inducing in situ M2 macrophage polarization to promote the repair of bone defects via scaffold-mediated sustained delivery of luteolin

Immunoregulation mediated bone tissue engineering (BTE) has demonstrated huge potential in promoting repair of critical-size bone defects (CSBDs). The trade-off between stable immunoregulation function and extended immunoregulation period has posed a great challenge to this strategy. Here, we reported a 3D porous biodegradable Poly(HEMA-co-3APBA)/LUT scaffold, in which reversible boronic acid ester bond was formed between the 3APBA moiety and the catechol moiety of luteolin (LUT). The boronic acid ester bond not only protected the bioactivity of LUT but also extended the release period of LUT. The rationale behind the phenomenon of sustained LUT release was explained using a classical transition state theory. In vitro/in vivo assays proved the immunoregulation function of the scaffold in inducing M2 polarization of both M0 and M1 Mφ. The crosstalk between the scaffold treated Raw 264.7 and BMSCs were also investigated through the in vitro co-culture assay. The results demonstrated that the scaffold could induce immunoregulation mediated osteogenic differentiation of BMSCs. In addition, CSBDs model of SD rats was also applied, and the corresponding data proved that the scaffold could accelerate new bone formation, therefore promoting repair of CSBDs. The as-prepared scaffold might be a promising candidate for repair of CSBDs in the future.

Synthesis and characterization of Alg/Gel/n-HAP/MNPs porous nanocomposite adsorbent for efficient water conservancy and removal of methylene blue in aqueous environments: Kinetic modeling and artificial neural network predictions

In this study, a new porous nanocomposite adsorbent for water conservancy was synthesized using the freeze-drying technique to adsorb a cationic dye (Methylene Blue) in an aqueous environment. The nanocomposite adsorbent was synthesized using natural polymers, gelatin, and sodium alginate, and hydroxyapatite and magnetic iron oxide nanoparticles was incorporated into the polymer network to improve mechanical properties and increase the surface-to-volume ratio. To confirm the structure and morphology of the sample, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques were employed. In addition, the magnetic properties of the synthesis of MNPs and porous nanocomposite were determined using value stream mapping (VSM) and dynamic light scattering (DLS). The adsorption of Methylene Blue (MB) was studied as a function of effective physical and variable parameters, such as time, temperature, pH, and initial concentration. The synthesized porous nanocomposite adsorbent exhibited a high adsorption capacity of 473.2 mg g-1 and followed pseudo-second-order kinetics. Additionally, the maximum adsorption capacity was observed at an initial concentration of 534.9 mg g-1. The adsorbent was also sensitive to temperature changes and was well-described thermodynamically and isothermally by the Freundlich isotherm model. Two artificial neural networks (ANNs) were also developed to investigate the properties of the synthesized nanocomposites. In the first ANN, the properties of the nanocomposites, including pore size, porosity, compressive strength, and elastic modulus, were predicted based on the variations in the weight percentages of gelatin and hydroxyapatite. In the second ANN, the effects of changes in temperature and initial concentration on the adsorption of MB by the synthesized nanocomposite samples were predicted. The ANNs' predictions indicated that increasing the weight percentage of hydroxyapatite nanoparticles and gelatin enhances the physical, mechanical, and adsorption performance of the synthesized porous nanocomposites. The best results were achieved for the sample containing 40 wt % of gelatin and 30 wt % of hydroxyapatite nanoparticles. Furthermore, the ANN models demonstrated that increasing the temperature and initial concentration resulted in an increase in the amount of MB adsorbed.

Development of Poly(sorbitol adipate)-g-poly(ethylene glycol) Mono Methyl Ether-Based Hydrogel Matrices for Model Drug Release

Hydrogels were prepared by Steglich esterification and by crosslinking pre-synthesized poly(sorbitol adipate)-graft-poly(ethylene glycol) mono methyl ether (PSA-g-mPEG) using different-chain-length-based disuccinyl PEG. PSA and PSA-g-mPEG were investigated for polymer degradation as a function of time at different temperatures. PSA-g-mPEG hydrogels were then evaluated for their most crucial properties of swelling that rendered them suitable for many pharmaceutical and biomedical applications. Hydrogels were also examined for their Sol-Gel content in order to investigate the degree of cross-linking. Physical structural parameters of the hydrogels were theoretically estimated using the modified Flory-Rehner theory to obtain approximate values of polymer volume fraction, the molecular weight between two crosslinks, and the mesh size of the hydrogels. X-ray diffraction was conducted to detect the presence or absence of crystalline regions in the hydrogels. PSA-g-mPEG hydrogels were then extensively examined for higher and lower molecular weight solute release through analysis by fluorescence spectroscopy. Finally, the cytotoxicity of the hydrogels was also investigated using a resazurin reduction assay. Experimental results show that PSA-g-mPEG provides an option as a biocompatible polymer to be used for pharmaceutical applications.

Bone Regeneration Induced by Patient-Adapted Mg Alloy-Based Scaffolds for Bone Defects: Present and Future Perspectives

Treatment of bone defects resulting after tumor surgeries, accidents, or non-unions is an actual problem linked to morbidity and the necessity of a second surgery and often requires a critical healthcare cost. Although the surgical technique has changed in a modern way, the treatment outcome is still influenced by patient age, localization of the bone defect, associated comorbidities, the surgeon approach, and systemic disorders. Three-dimensional magnesium-based scaffolds are considered an important step because they can have precise bone defect geometry, high porosity grade, anatomical pore shape, and mechanical properties close to the human bone. In addition, magnesium has been proven in in vitro and in vivo studies to influence bone regeneration and new blood vessel formation positively. In this review paper, we describe the magnesium alloy's effect on bone regenerative processes, starting with a short description of magnesium's role in the bone healing process, host immune response modulation, and finishing with the primary biological mechanism of magnesium ions in angiogenesis and osteogenesis by presenting a detailed analysis based on a literature review. A strategy that must be followed when a patient-adapted scaffold dedicated to bone tissue engineering is proposed and the main fabrication technologies are combined, in some cases with artificial intelligence for Mg alloy scaffolds, are presented with examples. We emphasized the microstructure, mechanical properties, corrosion behavior, and biocompatibility of each study and made a basis for the researchers who want to start to apply the regenerative potential of magnesium-based scaffolds in clinical practice. Challenges, future directions, and special potential clinical applications such as osteosarcoma and persistent infection treatment are present at the end of our review paper.

Hybrid Coatings for Active Protection against Corrosion of Mg and Its Alloys

A novel approach to surface modification was developed to improve the corrosion performance of biodegradable magnesium alloys. Additively manufactured magnesium samples and Mg-Mn-based magnesium alloys were used in this study. This method involves the combination of plasma electrolytic oxidation to create a porous ceramic-like matrix, followed by treatment with protective biocompatible agents. The most efficient method for the PEO-layer impregnation using sodium oleate and polycaprolactone was selected and optimized. The correlation between the structure, composition, and protective properties of the hybrid coatings was established. The composition of the formed polymer-containing layers was established using XPS and Raman microspectroscopy. The presence of sodium oleate and its distribution across the coating surface was confirmed at the microscale. The corrosion-protection level of the hybrid layers was assessed using potentiodynamic polarization measurements, electrochemical impedance spectroscopy, hydrogen evolution testing, and gravimetry (mass-loss tests) in vitro. The oleate-containing polycaprolactone layers (HC-SO 0.1-2) demonstrated stable corrosion behavior even after 7 days of immersion in Hank's balanced salt solution. The corrosion-current density and impedance modulus measured at a frequency of 0.1 Hz for the samples with hybrid coating after 7 days of exposure were equal to 5.68 × 10^-8 A∙cm^-2 and 2.03 × 10⁶ Ω∙cm², respectively. The developed method of surface modification demonstrates the coating's self-healing properties. The effectiveness of employing hybrid anticorrosive bioactive PEO coatings for biomedical products made from magnesium and its alloys was demonstrated.

Fabrication and optimization of 3D printed gelatin methacryloyl microneedle arrays based on vat photopolymerization

Microneedles (MNs) are micrometer-sized arrays that can penetrate the skin in a minimally invasive manner; these devices offer tremendous potential for the transdermal delivery of therapeutic molecules. Although there are many conventional techniques for manufacturing MNs, most of them are complicated and can only fabricate MNs with specific geometries, which restricts the ability to adjust the performance of the MNs. Herein, we present the fabrication of gelatin methacryloyl (GelMA) MN arrays using the vat photopolymerization 3D printing technique. This technique allows for the fabrication of high-resolution and smooth surface MNs with desired geometries. The existence of methacryloyl groups bonded to the GelMA was verified by ¹H NMR and FTIR analysis. To examine the effects of varying needle heights (1000, 750, and 500 µm) and exposure times (30, 50, and 70 s) on GelMA MNs, the height, tip radius, and angle of the needles were measured; their morphological and mechanical properties were also characterized. It was observed that as the exposure time increased, the height of the MNs increased; moreover, sharper tips were obtained and tip angles decreased. In addition, GelMA MNs exhibited good mechanical performance with no breakage up to 0.3 mm displacement. These results indicate that 3D printed GelMA MNs have great potential for transdermal delivery of various therapeutics.

Polymer-Based Nanostructures for Pancreatic Beta-Cell Imaging and Non-Invasive Treatment of Diabetes

Diabetes poses major economic, social, and public health challenges in all countries worldwide. Besides cardiovascular disease and microangiopathy, diabetes is a leading cause of foot ulcers and lower limb amputations. With the continued rise of diabetes prevalence, it is expected that the future burden of diabetes complications, early mortality, and disabilities will increase. The diabetes epidemic is partly caused by the current lack of clinical imaging diagnostic tools, the timely monitoring of insulin secretion and insulin-expressing cell mass (beta (β)-cells), and the lack of patients' adherence to treatment, because some drugs are not tolerated or invasively administrated. In addition to this, there is a lack of efficient topical treatment capable of stopping the progression of disabilities, in particular for treating foot ulcers. In this context, polymer-based nanostructures garnered significant interest due to their tunable physicochemical characteristics, rich diversity, and biocompatibility. This review article emphasizes the last advances and discusses the prospects in the use of polymeric materials as nanocarriers for β-cell imaging and non-invasive drug delivery of insulin and antidiabetic drugs in the management of blood glucose and foot ulcers.

Biocompatible and biodegradable copper-protocatechuic metal-organic frameworks as rifampicin carrier

Tuberculosis (TB) is a disease caused by the M. tuberculosis bacteria infection and is listed as one of the deadliest diseases to date. Despite the development of antituberculosis drugs, the need for long-term drug consumption and low patient commitment are obstacles to the success of TB treatment. A continuous drug delivery system that has a long-term effect is needed to reduce routine drug consumption intervals, suppress infection, and prevent the emergence of drug-resistant strains of M. tuberculosis. For this reason, biomolecule metal-organic framework (BioMOF) with good biocompatibility, nontoxicity, bioactivity, and high stability are becoming potential drug carriers. This study used a bioactive protocatechuic acid (PCA) as organic linker to prepare copper-based BioMOF Cu-PCA under base-modulated conditions. Detailed crystal analysis by the powder X-ray diffraction demonstrated that the Cu-PCA, with a chemical formula of C₁₄H₁₆O₁₃Cu₃, crystalizes as triclinic in space group P1. Comprehensive physicochemical characterizations were provided using FTIR, SEM, XPS, TGA, EA, and N₂ sorption. As a drug carrier, Cu-PCA showed a high maximum rifampicin (RIF) drug loading of 443.01 mg/g. Upon resuspension in PBS, the RIF and linkers release profile exhibited two-stage release kinetic profiles, which are well described by the Biphasic Dose Response (BiDoseResp) model. A complete release of these compounds (RIF and PCA) was achieved after ~9 h of mixing in PBS. Cu-PCA and RIF@Cu-PCA possessed antibacterial activity against Escherichia coli, and good biocompatibility is evidenced by the high viability of MH-S mice alveolar macrophage cells upon supplementations.

Assessment of the structures contribution (crystalline and mesophases) and mechanical properties of polycaprolactone/pluronic blends

Films of biodegradable blends of polycaprolactone (PCL) and Pluronics F68 and F127 were manufactured by an industrial thermo-mechanical process to be applied as potential delivery systems. The effects of Pluronics on the structure (mesophase organization), and thermal and mechanical properties of polycaprolactone were investigated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), polarized optical microscopy (POM) and tensile mechanical tests. The addition of Pluronics affected the crystallization process by changing the relative amounts of crystalline, amorphous, and meso- (condis + plastic) phases. The melting transition and XRD profiles were deconvoluted to assess the individual contribution of the different crystal morphologies. Furthermore, it was found that the mechanical properties of the blends depended on the ratio and type of Pluronic. Thus, Pluronic F127 showed a larger mesophase content than its F68 counterpart with PCL and blends with enhanced ductility.

Aryloxy Ionic Liquid-Catalyzed Homogenous Esterification of Cellulose with Low-Reactive Acyl Donors

Ionic liquids (ILs) are recyclable, non-volatile, and can dissolve cellulose, a natural polymer that is insoluble in versatile solvents. Therefore, ILs have been used to modify cellulose. However, 1-ethyl-3-methylimidazolium acetate (EmimOAc), a commercially available IL often used to dissolve and modify cellulose to prepare cellulose-based materials, causes the undesired introduction of an acetyl group derived from the acetate anion of EmimOAc onto the hydroxy group of cellulose during esterification. In this study, for cellulose esterification, we prepared aryloxy ILs as non-carboxylate-type and basic ILs, which can theoretically prevent the undesired introduction of an acyl group from the IL onto the hydroxy group of cellulose. The optimized 1-ethyl-3-methylimidazolium 2-pyridinolate (Emim2OPy) and mixed solvent system achieved rapid cellulose esterification (within 30 min) with an excellent degree of substitution (DS) value (up to >2.9) derived from the employed low-reactive vinyl esters and bio-based unsaturated aldehydes, without any undesired substituent introduction from side reactions.

Inorganic/organic combination: Inorganic particles/polymer composites for tissue engineering applications

Biomaterials have ushered the field of tissue engineering and regeneration into a new era with the development of advanced composites. Among these, the composites of inorganic materials with organic polymers present unique structural and biochemical properties equivalent to naturally occurring hybrid systems such as bones, and thus are highly desired. The last decade has witnessed a steady increase in research on such systems with the focus being on mimicking the peculiar properties of inorganic/organic combination composites in nature. In this review, we discuss the recent progress on the use of inorganic particle/polymer composites for tissue engineering and regenerative medicine. We have elaborated the advantages of inorganic particle/polymer composites over their organic particle-based composite counterparts. As the inorganic particles play a crucial role in defining the features and regenerative capacity of such composites, the review puts a special emphasis on the various types of inorganic particles used in inorganic particle/polymer composites. The inorganic particles that are covered in this review are categorised into two broad types (1) solid (e.g., calcium phosphate, hydroxyapatite, etc.) and (2) porous particles (e.g., mesoporous silica, porous silicon etc.), which are elaborated in detail with recent examples. The review also covers other new types of inorganic material (e.g., 2D inorganic materials, clays, etc.) based polymer composites for tissue engineering applications. Lastly, we provide our expert analysis and opinion of the field focusing on the limitations of the currently used inorganic/organic combination composites and the immense potential of new generation of composites that are in development.

Polyanhydride Chemistry

Polyanhydrides (PAs) are a class of synthetic biodegradable polymers employed as controlled drug delivery vehicles. They can be synthesized and scaled up from low-cost starting materials. The structure of PAs can be manipulated synthetically to meet desirable characteristics. PAs are biocompatible, biodegradable, and generate nontoxic metabolites upon degradation, which are easily eliminated from the body. The rate of water penetrating into the polyanhydride (PA) matrix is slower than the anhydride bond cleavage. This phenomenon sets PAs as "surface-eroding drug delivery carriers." Consequently, a variety of PA-based drug delivery carriers in the form of solid implants, pasty injectable formulations, microspheres, nanoparticles, etc. have been developed for the sustained release of small molecule drugs, and vaccines, peptide drugs, and nucleic acid-based active agents. The rate of drug delivery is often controlled by the polymer erosion rate, which is influenced by the polymer structure and composition, crystallinity, hydrophobicity, pH of the release medium, device size, configuration, etc. Owing to the above-mentioned interesting physicochemical and mechanical properties of PAs, the present review focuses on the advancements made in the domain of synthetic biodegradable biomedical PAs for therapeutic delivery applications. Various classes of PAs, their structures, their unique characteristics, their physicochemical and mechanical properties, and factors influencing surface erosion are discussed in detail. The review also summarizes various methods involved in the synthesis of PAs and their utility in the biomedical domain as drug, vaccine, and peptide delivery carriers in different formulations are reviewed.

Multifunctional Filter Membranes Based on Self-Assembled Core-Shell Biodegradable Nanofibers for Persistent Electrostatic Filtration through the Triboelectric Effect

The massive production of polymer-based respiratory masks during the COVID-19 pandemic has rekindled the issue of environmental pollution from nonrecyclable plastic waste. To mitigate this problem, conventional filters should be redesigned with improved filtration performance over the entire operational life while also being naturally degradable at the end. Herein, we developed a functional and biodegradable polymeric filter membrane consisting of a polybutylene adipate terephthalate (PBAT) matrix blended with cetyltrimethylammonium bromide (CTAB) and montmorillonite (MMT) clay, whose surface properties have been modified through cation exchange reactions for good miscibility with PBAT in an organic solvent. Particularly, the spontaneous evolution of a partial core-shell structure (i.e., PBAT core encased by CTAB-MMT shell) during the electrospinning process amplified the triboelectric effect as well as the antibacterial/antiviral activity that was not observed in naive PBAT. Unlike the conventional face mask filter that relies on the electrostatic adsorption mechanism, which deteriorates over time and/or due to external environmental factors, the PBAT@CTAB-MMT nanofiber membrane (NFM)-based filter continuously retains electrostatic charges on the surface due to the triboelectric effect of CTAB-MMT. As a result, the PBAT@CTAB-MMT NFM-based filter showed high filtration efficiencies (98.3%, PM_0.3) even at a low differential pressure of 40 Pa or less over its lifetime. Altogether, we not only propose an effective and practical solution to improve the performance of filter membranes while minimizing their environmental footprint but also provide valuable insight into the synergetic functionalities of organic-inorganic hybrid materials for applications beyond filter membranes.

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.

Hydrophilic Natural Polylysine as Drug Nanocarrier for Preparation of Helical Delivery System

Polypeptide materials have clear secondary structure and biodegradability, which can be further modified and functionalized, so that they can be employed as therapeutic agents in clinical applications. PEGylation of polylysine (PEG-PLL) is a kind of safe and effective nanocarrier that is utilized for gene and drug delivery. However, PEG-PLL needs to be produced through chemical synthesis, which is expensive and difficult to obtain. We hope to simplify the nanocarrier and use hydrophilic natural polylysine (PLL) to develop a high-efficacy delivery system. To evaluate the possibility of PLL as nanocarriers, methotrexate (MTX) is selected as a model drug and PEG-PLL is utilized as control nanocarriers. The experimental results showed that PLL is an ideal polypeptide to prepare MTX-loaded PLL nanoparticles (PLL/MTX NPs). Compared with PEG-PLL as nanocarriers, PLL/MTX NPs showed higher drug-loading content (58.9%) and smaller particle sizes (113.7 nm). Moreover, the shape of PLL/MTX NPs was a unique helical nanorod. The PLL/MTX NPs had good storage stability, media stability, and sustained release effect. Animal research demonstrated that PLL/MTX NPs could improve the anti-tumor activity of MTX, the antitumor efficacy is enhanced 1.9-fold and 1.2-fold compared with MTX injection and PEG-PLL/MTX NPs, respectively. To sum up, natural polymer PLL is an ideal nano drug delivery carrier which has potential clinical applications.

Synthetic biodegradable polyesters for implantable controlled-release devices

INTRODUCTION

: Implantable devices can be designed to release drugs to localized regions of tissue at sustained and reliable rates. Advances in polymer engineering have led to the design and development of drug-loaded implants with predictable, desirable release profiles. Biodegradable polyesters exhibit chemical, physical, and biological properties suitable for developing implants for pain management, cancer therapy, contraception, antiviral therapy, and other applications.

AREAS COVERED

: This article reviews the use of biodegradable polyesters for drug-loaded implants by discussing the properties of commonly used polymers, techniques for implant formulation and manufacturing, mechanisms of drug release, and clinical applications of implants as drug delivery devices.

EXPERT OPINION

: Drug delivery implants are unique systems for safe and sustained drug release, providing high bioavailability and low toxicity. Depending on the implant design and tissue site of deployment, implants can offer either localized or systemic drug release. Due to the long history of use of degradable polyesters in medical devices, polyester-based implants represent an important class of controlled release technologies. Further, polyester-based implants are the largest category of drug delivery implants to reach the point of testing in humans or approval for human use.

Additive Manufacturing of Anatomical Poly(d,l-lactide) Scaffolds

Poly(lactide) (PLA) is one of the most investigated semicrystalline polymers for material extrusion (MEX) additive manufacturing (AM) techniques based on polymer melt processing. Research on its application for the development of customized devices tailored to specific anatomical parts of the human body can provide new personalized medicine strategies. This research activity was aimed at testing a new multifunctional AM system for the design and fabrication by MEX of anatomical and dog-bone-shaped PLA samples with different infill densities and deposition angles. In particular, a commercial PLA filament was employed to validate the computer-aided design (CAD) and manufacturing (CAM) process for the development of scaffold prototypes modeled on a human bone defect. Physical-chemical characterization of the obtained samples by 1H-NMR spectroscopy, size exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) demonstrated a small reduction of polymer molecular weight (~5%) due to thermal processing, as well as that the commercial polymer employed was a semicrystalline poly(d,l-lactide). Mechanical characterization highlighted the possibility of tuning elastic modulus and strength, as well as the elongation at break up to a 60% value by varying infill parameters.

Bio-based materials for barrier coatings on paper packaging

Research into alternative packaging materials is becoming more and more popular as a result of growing eco-friendly concerns regarding the usage of some petroleum-based polymeric packaging materials and coatings, as well as growing buyer demands for products with nutritious quality and extended shelf lives. Barrier coatings made of naturally renewable biopolymers can be applied to paper packing materials. These biopolymer coatings have the potential to replace the current synthetic paper and paperboard coatings, are strong oxygen and oil barriers, and may prevent the unintended moisture transfer in food goods. An appealing method of controlling the growth and spread of microorganisms in food packaging is the integration of antimicrobial compounds into coatings to create active/functional paper-based packaging materials. Here, in this review of the oxygen/moisture barrier, mechanical, and other characteristics of paper coated with bio-based materials. Examples are used to discuss the current and future uses of bio-based material coatings on paper packaging materials to improve barrier performance.

The Preparation and Characterization of Chitooligosaccharide–Polylactide Polymers, and In Vitro Release of Microspheres Loaded with Vancomycin

Drug-loaded microspheres are an ideal bone tissue delivery material. In this study, a biodegradable Schiff base chitosan–polylactide was used as the encapsulation material to prepare drug-loaded microspheres as biocompatible carriers for controlled vancomycin release. In this regard, Schiff base chitosan was prepared by the Schiff base method, and then different proportions of the Schiff base chitosan–polylactide polymer were prepared by ring-opening polymerization. Drug-loaded microspheres were prepared by the W/O emulsion method, and the polymers and polymer microspheres were characterized and studied by NMR, IR, and antibacterial methods. The drug loading and release rates of microspheres were determined to investigate the drug loading, encapsulation efficiency, and release rate of drug microspheres at different ratios. In this study, different proportions of Schiff base chitosan–polylactic acid materials are successfully prepared, and vancomycin-loaded microspheres are successfully prepared using them as carriers. This study proves that the materials have antibacterial activities against Staphylococcus aureus and Escherichia coli. The particle size of drug-loaded microspheres was below 10 μm, and the particle size decreased with decreasing molecular weight. The obtained results show that 1:100 microspheres have the highest drug-loading and encapsulation efficiencies, the drug-loaded microspheres have no burst release within 24 h, and the release quantity reaches more than 20%. After 30 days of release, the release amounts of 1:10, 1:20, 1:40, 1:60, and 1:100 drug-loaded microspheres were 64.80 ± 0.29%, 54.43 ± 0.54%, 44.60 ± 0.43%, 42.53 ± 0.40% and 69.73 ± 0.45%, respectively, and the release amount of 1:100 was the highest.

Additive Manufacturing of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Poly(D,L-lactide-co-glycolide) Biphasic Scaffolds for Bone Tissue Regeneration

Polyhydroxyalkanoates are biopolyesters whose biocompatibility, biodegradability, environmental sustainability, processing versatility, and mechanical properties make them unique scaffolding polymer candidates for tissue engineering. The development of innovative biomaterials suitable for advanced Additive Manufacturing (AM) offers new opportunities for the fabrication of customizable tissue engineering scaffolds. In particular, the blending of polymers represents a useful strategy to develop AM scaffolding materials tailored to bone tissue engineering. In this study, scaffolds from polymeric blends consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(D,L-lactide-co-glycolide) (PLGA) were fabricated employing a solution-extrusion AM technique, referred to as Computer-Aided Wet-Spinning (CAWS). The scaffold fibers were constituted by a biphasic system composed of a continuous PHBV matrix and a dispersed PLGA phase which established a microfibrillar morphology. The influence of the blend composition on the scaffold morphological, physicochemical, and biological properties was demonstrated by means of different characterization techniques. In particular, increasing the content of PLGA in the starting solution resulted in an increase in the pore size, the wettability, and the thermal stability of the scaffolds. Overall, in vitro biological experiments indicated the suitability of the scaffolds to support murine preosteoblast cell colonization and differentiation towards an osteoblastic phenotype, highlighting higher proliferation for scaffolds richer in PLGA.

A Key Role by Polymers in Microneedle Technology: A New Era

The skin serves as the major organ in the targeted transdermal drug delivery system for many compounds. The microneedle acts as a novel technique to deliver drugs across the different layers of the skin, including the major barrier stratum corneum, in an effective manner. A microneedle array patch comprises dozens to hundreds of micron-sized needles with numerous structures and advantages resulting from their special and smart designs. Microneedle approach is much more advanced than conventional transdermal delivery pathways due to several benefits like minimally invasive, painless, self-administrable, and enhanced patient compliance. The microneedles are classified into hollow, solid, coated, dissolving, and hydrogel. Several polymers are used to fabricate microneedle, such as natural, semi-synthetic, synthetic, biodegradable, and swellable polymers. Researchers in the preparation of microneedles also explored the combinations of polymers. The safety of the polymer used in microneedle is a crucial aspect to prevent toxicity in vivo. Thus, this review aims to provide a detailed review of microneedles and mainly focus on the various polymers used in the fabrication of microneedles.

Polyacrylic Acid Nanoplatforms: Antimicrobial, Tissue Engineering, and Cancer Theranostic Applications

Polyacrylic acid (PAA) is a non-toxic, biocompatible, and biodegradable polymer that gained lots of interest in recent years. PAA nano-derivatives can be obtained by chemical modification of carboxyl groups with superior chemical properties in comparison to unmodified PAA. For example, nano-particles produced from PAA derivatives can be used to deliver drugs due to their stability and biocompatibility. PAA and its nanoconjugates could also be regarded as stimuli-responsive platforms that make them ideal for drug delivery and antimicrobial applications. These properties make PAA a good candidate for conventional and novel drug carrier systems. Here, we started with synthesis approaches, structure characteristics, and other architectures of PAA nanoplatforms. Then, different conjugations of PAA/nanostructures and their potential in various fields of nanomedicine such as antimicrobial, anticancer, imaging, biosensor, and tissue engineering were discussed. Finally, biocompatibility and challenges of PAA nanoplatforms were highlighted. This review will provide fundamental knowledge and current information connected to the PAA nanoplatforms and their applications in biological fields for a broad audience of researchers, engineers, and newcomers. In this light, PAA nanoplatforms could have great potential for the research and development of new nano vaccines and nano drugs in the future.

Pharmaceutical, Biomedical and Ophthalmic Applications of Biodegradable Polymers (BDPs): Literature and Patent Review

In the last few decades, the interest in biodegradable materials for biomedical applications has increased significantly. Both natural and synthetic biodegradable polymers (BDPs) have been broadly explored for various biomedical applications. These include sutures and wound dressings, screws for bone fracture, scaffolds in tissue engineering, implants, and other carriers for targeted and sustained release drug delivery. Owing to their unique characteristics, including their surface charge variable copolymer block and composition and film-forming properties, BDPs have been widely used as favourable materials for ophthalmic drug delivery. Mucoadhesive BDPs have been used in ophthalmic formulations to prolong drug retention time and improve bioavailability, allowing ophthalmic controlled release systems to design. Furthermore, BDPs-based implants, microneedles, and injectable nano- and micro-particles enabled ocular posterior segment targeting and, most importantly, circumvented the need for removing the delivery systems after application. This review outlines the major advances of BDPs and highlights the latest progress of employing natural and synthetic BDPs for various biomedical applications, emphasising the treatment and management of ophthalmic conditions.

Biodegradable Polymers for Microencapsulation Systems

Environmentally friendly alternatives have become sought after upon the development of scientific research and industrial processes. Recent trends suggest biodegradable polymers as the most promising solution for synthetic microcapsule systems. Safety, efficiency, biocompatibility, and biodegradability are some of the properties that biodegradable systems in microencapsulation can provide for a broad spectrum of applications. The controlled release of encapsulated active agents is a research field that, over the years, has been constantly innovating due to the promising applications in the areas of pharmaceutical, cosmetic, textile industry, among others. This article presents an overview of different polymers with potential for microcapsule synthesis, namely, biodegradable polymers. First, natural polymers are discussed, which are divided into two categories: polysaccharide-based polymers (cellulose, starch, chitosan, and alginate) and protein polymers (gelatin). Second, synthetic polymers are described, where biodegradable polymers such as polyesters, polyamides, among others appear as examples. For each polymer, this review presents its origin, relevant properties, applications, and examples found in the literature regarding its use in biodegradable microencapsulation systems.

Meniscus regeneration by 3D printing technologies: Current advances and future perspectives

Meniscal tears are a frequent orthopedic injury commonly managed by conservative strategies to avoid osteoarthritis development descending from altered biomechanics. Among cutting-edge approaches in tissue engineering, 3D printing technologies are extremely promising guaranteeing for complex biomimetic architectures mimicking native tissues. Considering the anisotropic characteristics of the menisci, and the ability of printing over structural control, it descends the intriguing potential of such vanguard techniques to meet individual joints’ requirements within personalized medicine. This literature review provides a state-of-the-art on 3D printing for meniscus reconstruction. Experiences in printing materials/technologies, scaffold types, augmentation strategies, cellular conditioning have been compared/discussed; outcomes of pre-clinical studies allowed for further considerations. To date, translation to clinic of 3D printed meniscal devices is still a challenge: meniscus reconstruction is once again clear expression of how the integration of different expertise (e.g., anatomy, engineering, biomaterials science, cell biology, and medicine) is required to successfully address native tissues complexities.

Molecular self-assembly under nanoconfinement: indigo carmine scroll structures entrapped within polymeric capsules

Molecular self-assembly forms structures of well-defined organization that allow control over material properties, affording many advanced technological applications. Although the self-assembly of molecules is seemingly spontaneous, the structure into which they assemble can be altered by carefully modulating the driving forces. Here we study the self-assembly within the constraints of nanoconfined closed spherical volumes of polymeric nanocapsules, whereby a mixture of polyester-polyether block copolymer and methacrylic acid methyl methacrylate copolymer forms the entrapping capsule shell of nanometric dimensions. We follow the organization of the organic dye indigo carmine that serves as a model building unit due to its tendency to self-assemble into flat lamellar molecular sheets. Analysis of the structures formed inside the nanoconfined space using cryogenic-transmission electron microscopy (cryo-TEM) and cryogenic-electron tomography (cryo-ET) reveal that confinement drives the self-assembly to produce tubular scroll-like structures of the dye. Combined continuum theory and molecular modeling allow us to estimate the material properties of the confined nanosheets, including their elasticity and brittleness. Finally, we comment on the formation mechanism and forces that govern self-assembly under nanoconfinement.

Compatibilization of Starch/Synthetic Biodegradable Polymer Blends for Packaging Applications: A Review

The health and environmental concerns of the usage of non-biodegradable plastics have driven efforts to explore replacing them with renewable polymers. Although starch is a vital renewable polymer, poor water resistivity and thermo-mechanical properties have limited its applications. Recently, starch/synthetic biodegradable polymer blends have captured greater attention to replace inert plastic materials; the question of ‘immiscibility’ arises during the blend preparation due to the mixing of hydrophilic starch with hydrophobic polymers. The immiscibility issue between starch and synthetic polymers impacts the water absorption, thermo-mechanical properties, and chemical stability demanded by various engineering applications. Numerous studies have been carried out to eliminate the immiscibility issues of the different components in the polymer blends while enhancing the thermo-mechanical properties. Incorporating compatibilizers into the blend mixtures has significantly reduced the particle sizes of the dispersed phase while improving the interfacial adhesion between the starch and synthetic biodegradable polymer, leading to fine and homogeneous structures. Thus, Significant improvements in thermo-mechanical and barrier properties and water resistance can be observed in the compatibilized blends. This review provides an extensive discussion on the compatibilization processes of starch and petroleum-based polymer blends.

Hydrogel, Electrospun and Composite Materials for Bone/Cartilage and Neural Tissue Engineering

Injuries of the bone/cartilage and central nervous system are still a serious socio-economic problem. They are an effect of diversified, difficult-to-access tissue structures as well as complex regeneration mechanisms. Currently, commercially available materials partially solve this problem, but they do not fulfill all of the bone/cartilage and neural tissue engineering requirements such as mechanical properties, biochemical cues or adequate biodegradation. There are still many things to do to provide complete restoration of injured tissues. Recent reports in bone/cartilage and neural tissue engineering give high hopes in designing scaffolds for complete tissue regeneration. This review thoroughly discusses the advantages and disadvantages of currently available commercial scaffolds and sheds new light on the designing of novel polymeric scaffolds composed of hydrogels, electrospun nanofibers, or hydrogels loaded with nano-additives.

Instantaneous Degelling Thermoresponsive Hydrogel

Responsive polymeric hydrogels have found wide application in the clinic as injectable, biocompatible, and biodegradable materials capable of controlled release of therapeutics. In this article, we introduce a thermoresponsive polymer hydrogel bearing covalent disulfide bonds. The cold aqueous polymer solution forms a hydrogel upon heating to physiological temperatures and undergoes slow degradation by hydrolytic cleavage of ester bonds. The disulfide functionality allows for immediate reductive cleavage of the redox-sensitive bond embedded within the polymer structure, affording the option of instantaneous hydrogel collapse. Poly(ethylene glycol)-b-poly(lactic acid)-S-S-poly(lactic acid)-b-poly(ethylene glycol) (PEG-PLA-SS-PLA-PEG) copolymer was synthesized by grafting PEG to PLA-SS-PLA via urethane linkages. The aqueous solution of the resultant copolymer was a free-flowing solution at ambient temperatures and formed a hydrogel above 32 °C. The immediate collapsibility of the hydrogel was displayed via reaction with NaBH4 as a relatively strong reducing agent, yet stability was displayed even in glutathione solution, in which the polymer degraded slowly by hydrolytic degradation. The polymeric hydrogel is capable of either long-term or immediate degradation and thus represents an attractive candidate as a biocompatible material for the controlled release of drugs.

Polyamide/Poly(Amino Acid) Polymers for Drug Delivery

Polymers have always played a critical role in the development of novel drug delivery systems by providing the sustained, controlled and targeted release of both hydrophobic and hydrophilic drugs. Among the different polymers, polyamides or poly(amino acid)s exhibit distinct features such as good biocompatibility, slow degradability and flexible physicochemical modification. The degradation rates of poly(amino acid)s are influenced by the hydrophilicity of the amino acids that make up the polymer. Poly(amino acid)s are extensively used in the formulation of chemotherapeutics to achieve selective delivery for an appropriate duration of time in order to lessen the drug-related side effects and increase the anti-tumor efficacy. This review highlights various poly(amino acid) polymers used in drug delivery along with new developments in their utility. A thorough discussion on anticancer agents incorporated into poly(amino acid) micellar systems that are under clinical evaluation is included.

Synthesis, Properties, and Applications of Bio-Based Cyclic Aliphatic Polyesters

Cyclic polymers have long been reported in the literature, but their development has often been stunted by synthetic difficulties such as the presence of linear contaminants. Research into the synthesis of these polymers has made great progress in the past decade, and this review covers the synthesis, properties, and applications of cyclic polymers, with an emphasis on bio-based aliphatic polyesters. Synthetic routes to cyclic polymers synthesized from bioderived monomers, alongside mechanistic descriptions for both ring closure and ring expansion polymerization approaches, are reviewed. The review also highlights some of the unique physical properties of cyclic polymers together with potential applications. The findings illustrate the substantial recent developments made in the syntheses of cyclic polymers, as well as the progress which can be made in the commercialization of bio-based polymers through the versatility this topology provides.

Amino acid derived biopolymers: Recent advances and biomedical applications

Over the past few years, amino acids (AA) have emerged as promising biomaterials for the synthesis of functional polymers. Owing to the diversity of functional groups in amino acids, various polymerization methods may be used to make a wide range of well-defined functional amino-acid/peptide-based optically active polymers with varying polymer lengths, compositions, and designs. When incorporated with chirality and self-assembly, they offer a wide range of applications and are particularly appealing in the field of drug delivery, tissue engineering, and biosensing. There are several classes of these polymers that include polyamides (PA), polyesters (PE), poly(ester-amide)s (PEA)s, polyurethanes (PU)s, poly(depsipeptide)s (PDP)s, etc. They offer the ability to control functionality, conjugation, crosslinking, stimuli responsiveness, and tuneable mechanical/thermal properties. In this review, we present the recent advancements in the synthesis strategies for obtaining these amino acid-derived bio-macromolecules, their self-assembly properties, and the wealth of prevalent applications.