Poly(lactic acid) based hydrogels

Research Progress in Hydrogels for Cartilage Organoids

The repair and regeneration of cartilage has always been a hot topic in medical research. Cartilage organoids (CORGs) are special cartilage tissue created using tissue engineering techniques outside the body. These engineered organoids tissues provide models that simulate the complex biological functions of cartilage, opening new possibilities for cartilage regenerative medicine and treatment strategies. However, it is crucial to establish suitable matrix scaffolds for the cultivation of CORGs. In recent years, utilizing hydrogel to culture stem cells and induce their differentiation into chondrocytes has emerged as a promising method for the in vitro construction of CORGs. In this review, the methods for establishing CORGs are summarized and an overview of the advantages and limitations of using matrigel in the cultivation of such organoids is provided. Furthermore, the importance of cartilage tissue ECM and alternative hydrogel substitutes for Matrigel, such as alginate, peptides, silk fibroin, and DNA derivatives is discussed, and the pros and cons of using these hydrogels for the cultivation of CORGs are outlined. Finally, the challenges and future directions in hydrogel research for CORGs are discussed. It is hoped that this article provides valuable references for the design and development of hydrogels for CORGs.

Poly-(lactic acid) composite films comprising carvacrol and cellulose nanocrystal-zinc oxide with synergistic antibacterial effects

Herein, carvacrol (CRV) and modified cellulose nanocrystal-zinc oxide (CNC-ZnO) were incorporated into a poly (lactic acid) (PLA) matrix to prepare a PLA-based composite film using a simple solution casting method to achieve antimicrobial effects for application in antimicrobial food packaging. Compared with films obtained from neat PLA, the PLA@CRV20%@CNC-ZnO3% composite film shows better performance in terms of mechanical properties, ultraviolet (UV) blocking, and antimicrobial effects. The PLA composites containing CRV and 3 wt% CNC-ZnO blends exhibit improved tensile strength (21.8 MPa) and elongation at break (403.1 %) as well as excellent UV resistance. In particular, CRV and the CNC-ZnO hybrid endow the obtained PLA composite films with a synergistic antibacterial effect, resulting in good antibacterial properties for microbes, such as Escherichia coli, Staphylococcus aureus and Aspergillus niger. The diameters of the inhibition zone of the PLA@CRV20%@CNC-ZnO3% composite films against E. coli, S. aureus, and A. niger were 4.9, 5.0, and 3.4 cm, respectively. Appling the PLA@CRV20%@CNC-ZnO3% composite film as an antibacterial food packaging material, the storage period for strawberries was considerably extended. This study provides a theoretical basis for developing new organic/inorganic composite antimicrobial film materials from PLA.

Insulin Extended Release from PLA-PEG Stereocomplex Nanoparticles

This report addresses the challenges of controlled drug delivery for peptide and protein therapeutics by introducing a novel approach of nano formulation fabricated in aqueous media applying stereo-interaction mechanism with poly(D-lactide)-polyethylene glycol (D-PLA-PEG). To overcome the inherent poor stability of peptide and protein therapeutics, stereocomplexation of the peptide, insulin, is applied, onto D-PLA-PEG in aqueous media. Nanoparticles of ≈400 nm are spontaneously formed when water-soluble D configured PLA-PEG diblock copolymer and L- configured insulin interlock into a stereocomplex, owing to their concave convex fitness. In vitro release of insulin from stereocomplex in phosphate buffer solution (PBS) pH 7.4 solution shows sustained release for 14 weeks. The therapeutic efficacy of the PLA-insulin stereocomplex nanoparticles are evaluated in diabetic Akita mice. Blood glucose levels and body weight are closely monitored for a period of 17 weeks, revealing a significant reduction in glucose levels of the Akita mice treated with insulin stereocomplex, as well as normal body weight gain. These findings suggest that the stereocomplex nanoparticles of insulin-D-PLA-PEG present a promising and effective sustained and extended release platform for insulin. Notably, the use of water-soluble D-PLA-PEG for stereocomplexation in water expands the applicability of this approach to fabricate controlled delivery systems for peptide and protein therapeutics.

Synthesis of MPEG-b-PLLA Diblock Copolymers and Their Crystallization Performance with PDLA and PLLA Composite Films

Methoxy poly(ethylene glycol)-block-poly(L-lactide) (MPEG-b-PLLA) has a wide range of applications in pharmaceuticals and biology, and its structure and morphology have been thoroughly studied. In the experiment, we synthesized MPEG-b-PLLA with different block lengths using the principle of ring-opening polymerization by controlling the amount of lactic acid added. The thermodynamic properties of copolymers and the crystallization properties of blends were studied separately. The crystallization kinetics of PDLA/MPEG-b-PLA and PLLA/MPEG-b-PLA composite films were studied using differential scanning calorimetry (DSC). The results indicate that the crystallization kinetics of composite films are closely related to the amount of block addition. The crystallinity of the sample first increases and then decreases with an increase in MPEG-b-PLLA content. These results were also confirmed in polarized optical microscope (POM) and wide-angle X-ray diffraction (WAXD) tests. When 3% MPEG-b-PLLA was added to the PDLA matrix, the blend exhibited the strongest crystallization performance.

Nanotherapeutics against malaria: A decade of advancements in experimental models

Malaria, caused by different species of protists of the genus Plasmodium, remains among the most common causes of death due to parasitic diseases worldwide, mainly for children aged under 5. One of the main obstacles to malaria eradication is the speed with which the pathogen evolves resistance to the drug schemes developed against it. For this reason, it remains urgent to find innovative therapeutic strategies offering sufficient specificity against the parasite to minimize resistance evolution and drug side effects. In this context, nanotechnology-based approaches are now being explored for their use as antimalarial drug delivery platforms due to the wide range of advantages and tuneable properties that they offer. However, major challenges remain to be addressed to provide a cost-efficient and targeted therapeutic strategy contributing to malaria eradication. The present work contains a systematic review of nanotechnology-based antimalarial drug delivery systems generated during the last 10 years. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Exploring the Potentials of Chitin and Chitosan-Based Bioinks for 3D-Printing of Flexible Electronics: The Future of Sustainable Bioelectronics

Chitin and chitosan-based bioink for 3D-printed flexible electronics have tremendous potential for innovation in healthcare, agriculture, the environment, and industry. This biomaterial is suitable for 3D printing because it is highly stretchable, super-flexible, affordable, ultrathin, and lightweight. Owing to its ease of use, on-demand manufacturing, accurate and regulated deposition, and versatility with flexible and soft functional materials, 3D printing has revolutionized free-form construction and end-user customization. This study examined the potential of employing chitin and chitosan-based bioinks to build 3D-printed flexible electronic devices and optimize bioink formulation, printing parameters, and postprocessing processes to improve mechanical and electrical properties. The exploration of 3D-printed chitin and chitosan-based flexible bioelectronics will open new avenues for new flexible materials for numerous industrial applications.

In Vitro and In Vivo Hydrolytic Degradation Behaviors of a Drug-Delivery System Based on the Blend of PEG and PLA Copolymers

This paper presents the in vitro and in vivo degradation of BEPO, a marketed in situ forming depot technology used for the formulation of long-acting injectables. BEPO is composed of a solution of a blend of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) triblock and diblock in an organic solvent, where a therapeutic agent may be dissolved or suspended. Upon contact with an aqueous environment, the solvent diffuses and the polymers precipitate, entrapping the drug and forming a reservoir. Two representative BEPO compositions were subjected to a 3-month degradation study in vitro by immersion in phosphate-buffered saline at 37 °C and in vivo after subcutaneous injection in minipig. The material erosion rate, as a surrogate of the bioresorption, determined via the depot weight loss, changed substantially, depending on the composition and content of polymers within the test item. The swelling properties and internal morphology of depots were shown to be highly dependent on the solvent exchange rate during the precipitation step. Thermal analyses displayed an increase of the depot glass transition temperature over the degradation process, with no crystallinity observed at any stage. The chemical composition of degraded depots was determined by 1H NMR and gel permeation chromatography and demonstrated an enrichment in homopolymers, i.e., free PLA and (m)PEG, to the detriment of (m)PEG-PLA copolymers in both formulations. It was observed that the relative ratio of the degradants within the depot is driven by the initial polymer composition. Interestingly, in vitro and in vivo results showed very good qualitative consistency. Taken together, the outcomes from this study demonstrate that the different hydrolytic degradation behaviors of the BEPO compositions can be tuned by adjusting the polymer composition of the formulation.

Simulated gastrointestinal digestion of polylactic acid (PLA) biodegradable microplastics and their interaction with the gut microbiota

The accumulation of microplastics (MPs) in the environment as well as their presence in foods and humans highlight the urgent need for studies on the effects of these particles on humans. Polylactic acid (PLA) is the most widely used bioplastic in the food industry and medical field. Despite its biodegradability, biocompatibility, and "Generally Recognized As Safe" (GRAS) status, recent animal model studies have shown that PLA MPs can alter the intestinal microbiota; however, to date, no studies have been reported on the possible gut and health consequences of its intake by humans. This work simulates the ingestion of a realistic daily amount of PLA MPs and their pass through the gastrointestinal tract by combining the INFOGEST method and the gastrointestinal simgi® model to evaluate possible effects on the human colonic microbiota composition (16S rRNA gene sequencing analysis) and metabolic functionality (lactic acid and short-chain fatty acids (SCFA) production). Although PLA MPs did not clearly alter the microbial community homeostasis, increased Bifidobacterium levels tended to increase in presence of millimetric PLA particles. Furthermore, shifts detected at the functional level suggest an alteration of microbial metabolism, and a possible biotransformation of PLA by the human microbial colonic community. Raman spectroscopy and field emission scanning electron microscopy (FESEM) characterization revealed morphological changes on the PLA MPs after the gastric phase of the digestion, and the adhesion of organic matter as well as a microbial biofilm, with surface biodegradation, after the intestinal and colonic phases. With this evidence and the emerging use of bioplastics, understanding their impact on humans and potential biodegradation through gastrointestinal digestion and the human microbiota merits critical investigation.

Biomimetic Hydrogel Applications and Challenges in Bone, Cartilage, and Nerve Repair

Tissue engineering and regenerative medicine is a highly sought-after field for researchers aiming to compensate and repair defective tissues. However, the design and development of suitable scaffold materials with bioactivity for application in tissue repair and regeneration has been a great challenge. In recent years, biomimetic hydrogels have shown great possibilities for use in tissue engineering, where they can tune mechanical properties and biological properties through functional chemical modifications. Also, biomimetic hydrogels provide three-dimensional (3D) network spatial structures that can imitate normal tissue microenvironments and integrate cells, scaffolds, and bioactive substances for tissue repair and regeneration. Despite the growing interest in various hydrogels for biomedical use in previous decades, there are still many aspects of biomimetic hydrogels that need to be understood for biomedical and clinical trial applications. This review systematically describes the preparation of biomimetic hydrogels and their characteristics, and it details the use of biomimetic hydrogels in bone, cartilage, and nerve tissue repair. In addition, this review outlines the application of biomimetic hydrogels in bone, cartilage, and neural tissues regarding drug delivery. In particular, the advantages and shortcomings of biomimetic hydrogels in biomaterial tissue engineering are highlighted, and future research directions are proposed.

Robust Osteoconductive β-Tricalcium Phosphate/L-poly(lactic acid) Membrane via Orientation-Strengthening Technology

L-poly(lactic acid) (PLLA) is a biodegradable material with multiple biomedical application potentials, especially as a membrane for guided bone regeneration. In terms of its low strength and poor osteogenic activity, improving these two properties is the key to resolve the limitations of PLLA for bone-associated applications. Herein, an orientation-strengthening technology (OST) was developed to reinforce PLLA's mechanical strength by introducing biocompatible β-tricalcium phosphate (β-TCP) to improve the crystallinity of PLLA, allowing for the formation of a highly oriented architecture to acquire an advanced membrane with high mechanical property. Furthermore, the addition of β-TCP nanoparticles significantly promotes the osteogenic activity of the composites. The tensile strength of the membrane containing 5 wt % β-TCP was 220 MPa, which was 4-folds that of the native polylactic acid fabricated via the conventional method. The oriented microstructure enhanced both the mechanical strength and the osteogenic activity of the material. The parallel grooves on the material surface are similar to the mineralized collagen fibers on the bone surface, which promoted the growth and differentiation of osteoblasts, with β-TCP further contributing to the osteoconductive effect. The combination of β-TCP and orientation-strengthening effect endows the material with higher mechanical properties and bioactivities, which provides an advanced manufacturing strategy for the preparation of PLLA-based materials for bone repair.

Hydrogel device for analgesic drugs with in-situ loading and polymerization

The high prevalence of opioid addiction and the shortcomings of systemic opioids has increased the pace of the search for alternative methods of pain management. The local delivery of pain medications has started to be used as a tool for pain management and to decrease the use of systemic opioids for these patients. Here, we explored an in-situ polymerizable hydrogel system for the local delivery of analgesics and nonsteroid anti-inflammatory drugs (NSAID) for orthopaedic applications. We synthesized a series of methacrylated oligomeric polyethylene glycol-co-lactic acid polymer using microwave radiation for the delivery of bupivacaine hydrochloride as an analgesic and ketorolac tromethamine as an NSAID. We determined drug elution and gel degradation profiles in vitro. Biocompatibility was assessed against osteoblasts in vitro and by histological analysis after subcutaneous implantation for 4 weeks in vivo. Intra-articular and systemic concentrations and pharmacokinetic parameters were estimated using a two-compartment pharmacodynamic model based on in-vitro elution profiles. This type of in-situ applicable hydrogels is promising for extending the local efficacy of pain medication and further reducing the need for opioids.

Polysaccharides, proteins, and synthetic polymers based multimodal hydrogels for various biomedical applications: A review

Nature-derived or biologically encouraged hydrogels have attracted considerable interest in numerous biomedical applications owing to their multidimensional utility and effectiveness. The internal architecture of a hydrogel network, the chemistry of the raw materials involved, interaction across the interface of counter ions, and the ability to mimic the extracellular matrix (ECM) govern the clinical efficacy of the designed hydrogels. This review focuses on the mechanistic viewpoint of different biologically driven/inspired biomacromolecules that encourages the architectural development of hydrogel networks. In addition, the advantage of hydrogels by mimicking the ECM and the significance of the raw material selection as an indicator of bioinertness is deeply elaborated in the review. Furthermore, the article reviews and describes the application of polysaccharides, proteins, and synthetic polymer-based multimodal hydrogels inspired by or derived from nature in different biomedical areas. The review discusses the challenges and opportunities in biomaterials along with future prospects in terms of their applications in biodevices or functional components for human health issues. This review provides information on the strategy and inspiration from nature that can be used to develop a link between multimodal hydrogels as the main frame and its utility in biomedical applications as the primary target.

Self-Immolative Hydrogels with Stimulus-Mediated On-Off Degradation

Hydrogels are of interest for a wide range of applications from sensors to drug delivery and tissue engineering. Self-immolative polymers, which depolymerize from end-to-end following a single backbone or end-cap cleavage, offer advantages such as amplification of the stimulus-mediated cleavage event through a cascade degradation process. It is also possible to change the active stimulus by changing only a single end-cap or linker unit. However, there are very few examples of self-immolative polymer hydrogels, and the reported examples exhibited relatively poor stability in their nontriggered state or slow degradation after triggering. Described here is the preparation of hydrogels composed of self-immolative poly(ethyl glyoxylate) (PEtG) and poly(ethylene glycol) (PEG). Hydrogels formed from 2 kg/mol 4-arm PEG and 1.2 kg/mol PEtG with a light-responsive linker end-cap had high gel content (90%), an equilibrium water content of 89%, and a compressive modulus of 26 kPa. The hydrogel degradation could be turned on and off repeatedly through alternating cycles of irradiation and dark storage. Similar cycles could also be used to control the release of the anti-inflammatory drug celecoxib. These results demonstrate the potential for self-immolative hydrogels to afford a high degree of control over responses to stimuli in the context of smart materials for a variety of applications.

Stereo-Complex and Click-Chemical Bicrosslinked Amphiphilic Network Gels with Temperature/pH Response

Stimulus-responsive hydrogels have been widely used in the field of drug delivery because of their three-dimensional pore size and the ability to change the drug release rate with the change in external environment. In this paper, the temperature-sensitive monomer 2-methyl-2-acrylate-2-(2-methoxyethoxy-ethyl) ethyl ester (MEO2MA) and oligoethylene glycol methyl ether methacrylate (OEGMA) as well as the pH-sensitive monomer N,N-Diethylaminoethyl methacrylate (DEAEMA) were used to make the gel with temperature and pH response. Four kinds of physicochemical double-crosslinked amphiphilic co-network gels with different polymerization degrees were prepared by the one-pot method using the stereocomplex between polylactic acid as physical crosslinking and click chemistry as chemical crosslinking. By testing morphology, swelling, thermal stability and mechanical properties, the properties of the four hydrogels were compared. Finally, the drug release rate of the four gels was tested by UV-Vis spectrophotometer. It was found that the synthetic hydrogels had a good drug release rate and targeting, and had great application prospect in drug delivery.

Biodegradable Polylactic Acid and Its Composites: Characteristics, Processing, and Sustainable Applications in Sports

Polylactic acid (PLA) is a biodegradable polyester polymer that is produced from renewable resources, such as corn or other carbohydrate sources. However, its poor toughness limits its commercialization. PLA composites can meet the growing performance needs of various fields, but limited research has focused on their sustainable applications in sports. This paper reviews the latest research on PLA and its composites by describing the characteristics, production, degradation process, and the latest modification methods of PLA. Then, it discusses the inherent advantages of PLA composites and expounds on different biodegradable materials and their relationship with the properties of PLA composites. Finally, the importance and application prospects of PLA composites in the field of sports are emphasized. Although PLA composites mixed with natural biomass materials have not been mass produced, they are expected to be sustainable materials used in various industries because of their simple process, nontoxicity, biodegradability, and low cost.

Poly Ethylene Glycol (PEG)-Based Hydrogels for Drug Delivery in Cancer Therapy: A Comprehensive Review

Hydrogel-based drug delivery systems (DDSs) can leverage therapeutically beneficial outcomes in cancer therapy. In this domain, polyethylene glycol (PEG) has become increasingly popular as a biomedical polymer and has found clinical use. Owing to their excellent biocompatibility, facile modifiability, and high drug encapsulation rate, PEG hydrogels have shown great promise as drug delivery platforms. Here, the progress in emerging novel designs of PEG-hydrogels as DDSs for anti-cancer therapy is reviewed and discussed, focusing on underpinning multiscale release mechanisms categorized under stimuli-responsive and non-responsive drug release. The responsive drug delivery approaches are discussed, and the underpinning release mechanisms are elucidated, covering the systems functioning based on either exogenous stimuli-response, such as photo- and magnetic-sensitive PEG hydrogels, or endogenous stimuli-response, such as enzyme-, pH-, reduction-, and temperature-sensitive PEG hydrogels. Special attention is paid to the commercial potential of PEG-based hydrogels in cancer therapy, highlighting the limitations that need to be addressed in future research for their clinical translation.

3D Bioprinting of Hyaline Articular Cartilage: Biopolymers, Hydrogels, and Bioinks

The musculoskeletal system, consisting of bones and cartilage of various types, muscles, ligaments, and tendons, is the basis of the human body. However, many pathological conditions caused by aging, lifestyle, disease, or trauma can damage its elements and lead to severe disfunction and significant worsening in the quality of life. Due to its structure and function, articular (hyaline) cartilage is the most susceptible to damage. Articular cartilage is a non-vascular tissue with constrained self-regeneration capabilities. Additionally, treatment methods, which have proven efficacy in stopping its degradation and promoting regeneration, still do not exist. Conservative treatment and physical therapy only relieve the symptoms associated with cartilage destruction, and traditional surgical interventions to repair defects or endoprosthetics are not without serious drawbacks. Thus, articular cartilage damage remains an urgent and actual problem requiring the development of new treatment approaches. The emergence of biofabrication technologies, including three-dimensional (3D) bioprinting, at the end of the 20th century, allowed reconstructive interventions to get a second wind. Three-dimensional bioprinting creates volume constraints that mimic the structure and function of natural tissue due to the combinations of biomaterials, living cells, and signal molecules to create. In our case-hyaline cartilage. Several approaches to articular cartilage biofabrication have been developed to date, including the promising technology of 3D bioprinting. This review represents the main achievements of such research direction and describes the technological processes and the necessary biomaterials, cell cultures, and signal molecules. Special attention is given to the basic materials for 3D bioprinting-hydrogels and bioinks, as well as the biopolymers underlying the indicated products.

PolySMart: a general coarse-grained molecular dynamics polymerization scheme

The development of simulation methods to study the structure and dynamics of a macroscopically sized piece of polymer material is important as such methods can elucidate structure-property relationships. Several methods have been reported to construct initial structures for homo- and co-polymers; however, most of them are only useful for short linear polymers since one needs to pack and equilibrate the far-from-equilibrium initial structures, which is a tedious task for long or hyperbranched polymers and unfeasible for polymer networks. In this method article, we present PolySMart, i.e., an open-source python package, which can effectively produce fully equilibrated homo- and hetero-polymer melts and solutions with no limitation on the polymer topology and size, at a coarse-grained resolution and through a bottom-up approach. This python package is also capable of exploring the polymerization kinetics through its reactive scheme in realistic conditions so that it can model the multiple co-occurring polymerization reactions (with different reaction rates) as well as consecutive polymerizations under stoichiometric and non-stoichiometric conditions. Thus, the equilibrated polymer models are generated through correct polymerization kinetics. A benchmark and verification of the performance of the program for several realistic cases, i.e., for homo-polymers, co-polymers, and crosslinked networks, is given. We further discuss the capability of the program to contribute to the discovery and design of new polymer materials.

Global hotspots and emerging trends in 3D bioprinting research

Three-dimensional (3D) bioprinting is an advanced tissue engineering technique that has received a lot of interest in the past years. We aimed to highlight the characteristics of articles on 3D bioprinting, especially in terms of research hotspots and focus. Publications related to 3D bioprinting from 2007 to 2022 were acquired from the Web of Science Core Collection database. We have used VOSviewer, CiteSpace, and R-bibliometrix to perform various analyses on 3,327 published articles. The number of annual publications is increasing globally, a trend expected to continue. The United States and China were the most productive countries with the closest cooperation and the most research and development investment funds in this field. Harvard Medical School and Tsinghua University are the top-ranked institutions in the United States and China, respectively. Dr. Anthony Atala and Dr. Ali Khademhosseini, the most productive researchers in 3D bioprinting, may provide cooperation opportunities for interested researchers. Tissue Engineering Part A contributed the largest publication number, while Frontiers in Bioengineering and Biotechnology was the most attractive journal with the most potential. As for the keywords in 3D bioprinting, Bio-ink, Hydrogels (especially GelMA and Gelatin), Scaffold (especially decellularized extracellular matrix), extrusion-based bioprinting, tissue engineering, and in vitro models (organoids particularly) are research hotspots analyzed in the current study. Specifically, the research topics "new bio-ink investigation," "modification of extrusion-based bioprinting for cell viability and vascularization," "application of 3D bioprinting in organoids and in vitro model" and "research in personalized and regenerative medicine" were predicted to be hotspots for future research.

Application of Silk-Fibroin-Based Hydrogels in Tissue Engineering

Silk fibroin (SF) is an excellent protein-based biomaterial produced by the degumming and purification of silk from cocoons of the Bombyx mori through alkali or enzymatic treatments. SF exhibits excellent biological properties, such as mechanical properties, biocompatibility, biodegradability, bioabsorbability, low immunogenicity, and tunability, making it a versatile material widely applied in biological fields, particularly in tissue engineering. In tissue engineering, SF is often fabricated into hydrogel form, with the advantages of added materials. SF hydrogels have mostly been studied for their use in tissue regeneration by enhancing cell activity at the tissue defect site or counteracting tissue-damage-related factors. This review focuses on SF hydrogels, firstly summarizing the fabrication and properties of SF and SF hydrogels and then detailing the regenerative effects of SF hydrogels as scaffolds in cartilage, bone, skin, cornea, teeth, and eardrum in recent years.

Current advances in nanodrug delivery systems for malaria prevention and treatment

Malaria is a life-threatening, blood-borne disease with over two hundred million cases throughout the world and is more prevalent in Sub-Saharan Africa than anywhere else in the world. Over the years, several treatment agents have been developed for malaria; however, most of these active pharmaceutical ingredients exhibit poor aqueous solubility and low bioavailability and may result in drug-resistant parasites, thus increasing malaria cases and eventually, deaths. Factors such as these in therapeutics have led to a better appreciation of nanomaterials. The ability of nanomaterials to function as drug carriers with a high loading capacity and targeted drug delivery, good biocompatibility, and low toxicity renders them an appealing alternative to conventional therapy. Nanomaterials such as dendrimers and liposomes have been demonstrated to be capable of enhancing the efficacy of antimalarial drugs. This review discusses the recent development of nanomaterials and their benefits in drug delivery for the potential treatment of malaria.

From crosslinking strategies to biomedical applications of hyaluronic acid-based hydrogels: A review

Hyaluronic acid (HA) is not only a natural anionic polysaccharide with excellent biocompatibility, biodegradability, and moisturizing effect, but also an essential factor that can affect angiogenesis, inflammation, cell behavior, which has a wide range of applications in the biomedical field. Among them, HA-based hydrogels formed by various physical or chemical crosslinking strategies are particularly striking. They not only retain the physiological function of HA, but also have the skeleton function of hydrogel, which further expands the application of HA. However, HA-based natural hydrogels generally have problems such as insufficient mechanical strength and susceptibility to degradation by hyaluronidase, which limits their application to a certain extent. To solve such problems, researchers have prepared a variety of HA-based multifunctional hydrogels with remarkable properties in recent years by adopting various structural modification methods or novel crosslinking strategies, as well as introducing functionally reactive molecules or moieties, which have extended the application scope. This manuscript systematically introduced common crosslinking strategies of HA-based hydrogels and highlighted the development of novel HA-based hydrogels in anticancer drug delivery, cartilage repair, three-dimensional cell culture, skin dressing and other fields. We hope to provide some references for the subsequent development of HA-based hydrogels in the biomedical field.

Aggregation and Gelation Behavior of Stereocomplexed Four-Arm PLA-PEG Copolymers Containing Neutral or Cationic Linkers

Poly(lactide) (PLA) and poly(ethylene glycol) (PEG)-based hydrogels were prepared by mixing phosphate buffer saline (PBS, pH 7.4) solutions of four-arm (PEG-PLA)₂-R-(PLA-PEG)₂ enantiomerically pure copolymers having the opposite chirality of the poly(lactide) blocks. Dynamic Light Scattering, rheology measurements, and fluorescence spectroscopy suggested that, depending on the nature of the linker R, the gelation process followed rather different mechanisms. In all cases, mixing of equimolar amounts of the enantiomeric copolymers led to micellar aggregates with a stereocomplexed PLA core and a hydrophilic PEG corona. Yet, when R was an aliphatic heptamethylene unit, temperature-dependent reversible gelation was mainly induced by entanglements of PEG chains at concentrations higher than 5 wt.%. When R was a linker containing cationic amine groups, thermo-irreversible hydrogels were promptly generated at concentrations higher than 20 wt.%. In the latter case, stereocomplexation of the PLA blocks randomly distributed in micellar aggregates is proposed as the major determinant of the gelation process.

Evaluation of Ibuprofen Prolonged Release of Biomedical PLA-PEG-PLA Hydrogel via Degradation Mechanism

A micellar hydrogel has long been considered an intelligent hydrophobic drug delivery material. In this study, synthesized PLA₁₇₅₀-PEG₁₇₅₀-PLA₁₇₅₀ micellar hydrogel aims to encapsulate ibuprofen (IBU) in the core PLA hydrophobic of the micelle and prolong the drug release time by an injectable route. The structure and morphology of the PLA₁₇₅₀-PEG₁₇₅₀-PLA₁₇₅₀ copolymer hydrogel were demonstrated by ¹H NMR and TEM data. The hydrogel also achieved a gel state at a high concentration of 25 wt.% under the physiological conditions of the body (37°C, pH 7.4). Besides, the biocompatibility test displayed that the hydrogel slightly affected mice after injection one week and fully recovered after four weeks. Furthermore, the in vitro degradation of the hydrogel showed apparent gel erosion after the first three weeks, which is related to the IBU release rate: slow for the first three weeks and then fast. As a result, the total drug release after three and four weeks was 18 wt.% and 41 wt.%, respectively. However, in the first 24 hours, the amount of the drug released was 10 wt.%, suggesting that the IBU drug diffused from the surface hydrogel to the buffer solution. These show that PLA₁₇₅₀-PEG₁₇₅₀-PLA₁₇₅₀ hydrogel can be a potential IBU drug delivery candidate.

Research progress on albumin-based hydrogels: Properties, preparation methods, types and its application for antitumor-drug delivery and tissue engineering

Albumin is derived from blood plasma and is the most abundant protein in blood plasma, which has good mechanical properties, biocompatibility and degradability, so albumin is an ideal biomaterial for biomedical applications, and drug-carriers based on albumin can better reduce the cytotoxicity of drug. Currently, there are numerous reviews summarizing the research progress on drug-loaded albumin molecules or nanoparticles. In comparison, the study of albumin-based hydrogels is a relatively small area of research, and few articles have systematically summarized the research progress of albumin-based hydrogels, especially for drug delivery and tissue engineering. Thus, this review summarizes the functional features and preparation methods of albumin-based hydrogels, different types of albumin-based hydrogels and their applications in antitumor drugs, tissue regeneration engineering, etc. Also, potential directions for future research on albumin-based hydrogels are discussed.

Extracellular vesicle-loaded hydrogels for tissue repair and regeneration

Extracellular vesicles (EVs) are a collective term for nanoscale or microscale vesicles secreted by cells that play important biological roles. Mesenchymal stem cells are a class of cells with the potential for self-healing and multidirectional differentiation. In recent years, numerous studies have shown that EVs, especially those secreted by mesenchymal stem cells, can promote the repair and regeneration of various tissues and, thus, have significant potential in regenerative medicine. However, due to the rapid clearance capacity of the circulatory system, EVs are barely able to act persistently at specific sites for repair of target tissues. Hydrogels have good biocompatibility and loose and porous structural properties that allow them to serve as EV carriers, thereby prolonging the retention in certain specific areas and slowing the release of EVs. When EVs are needed to function at specific sites, the EV-loaded hydrogels can stand as an excellent approach. In this review, we first introduce the sources, roles, and extraction and characterization methods of EVs and describe their current application status. We then review the different types of hydrogels and discuss factors influencing their abilities to carry and release EVs. We summarize several strategies for loading EVs into hydrogels and characterizing EV-loaded hydrogels. Furthermore, we discuss application strategies for EV-loaded hydrogels and review their specific applications in tissue regeneration and repair. This article concludes with a summary of the current state of research on EV-loaded hydrogels and an outlook on future research directions, which we hope will provide promising ideas for researchers.

Insights on Some Polysaccharide Gel Type Materials and Their Structural Peculiarities

Global resources have to be used in responsible ways to ensure the world's future need for advanced materials. Ecologically friendly functional materials based on biopolymers can be successfully obtained from renewable resources, and the most prominent example is cellulose, the well-known most abundant polysaccharide which is usually isolated from highly available biomass (wood and wooden waste, annual plants, cotton, etc.). Many other polysaccharides originating from various natural resources (plants, insects, algae, bacteria) proved to be valuable and versatile starting biopolymers for a wide array of materials with tunable properties, able to respond to different societal demands. Polysaccharides properties vary depending on various factors (origin, harvesting, storage and transportation, strategy of further modification), but they can be processed into materials with high added value, as in the case of gels. Modern approaches have been employed to prepare (e.g., the use of ionic liquids as "green solvents") and characterize (NMR and FTIR spectroscopy, X ray diffraction spectrometry, DSC, electronic and atomic force microscopy, optical rotation, circular dichroism, rheological investigations, computer modelling and optimization) polysaccharide gels. In the present paper, some of the most widely used polysaccharide gels will be briefly reviewed with emphasis on their structural peculiarities under various conditions.

Polylactide Perspectives in Biomedicine: From Novel Synthesis to the Application Performance

The incessant developments in the pharmaceutical and biomedical fields, particularly, customised solutions for specific diseases with targeted therapeutic treatments, require the design of multicomponent materials with multifunctional capabilities. Biodegradable polymers offer a variety of tailored physicochemical properties minimising health adverse side effects at a low price and weight, which are ideal to design matrices for hybrid materials. PLAs emerge as an ideal candidate to develop novel materials as are endowed withcombined ambivalent performance parameters. The state-of-the-art of use of PLA-based materials aimed at pharmaceutical and biomedical applications is reviewed, with an emphasis on the correlation between the synthesis and the processing conditions that define the nanostructure generated, with the final performance studies typically conducted with either therapeutic agents by in vitro and/or in vivo experiments or biomedical devices.

Eco-friendly whey/polysaccharide-based hydrogel with poly(lactic acid) for improvement of agricultural soil quality and plant growth

A set of renewable and biodegradable hydrogels based on acid whey and cellulose derivatives blended with poly(lactic acid) (PLA) were designed as eco-friendly biopolymeric material for sustainable agricultural applications. The physico-chemical properties of the hydrogel were evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and rheological measurements. The effect of the whey/polysaccharide/PLA hydrogel on soil quality improvement (water retention study, biodegradability, loading capacity and release of the fertilizers) and the growth pattern of Raphanus sativus and Phaseolus vulgaris has been also studied. The addition of PLA has been found to improve mechanical properties of the hydrogel. The introduction of 20% wt PLA extended decomposition time of hydrogels by 25% which makes the material more stable in the environment and maintaining the soil humidity for longer. The increasing the amount of PLA led to a rise in hydrogel viscosity brought about better entrapment efficiency of the fertilizers (86-92% for KNO₃ and 87-96% for urea, resp.) compared to control (82% for KNO₃ and 85% for urea, resp.). The novel hydrogels with swelling ratio of up to 500% showed potential as a sustainable water reservoir for plants improving water retention capacity of the soil by 30%.

Synergistic effects of PEG middle-blocks and talcum on crystallizability and thermomechanical properties of flexible PLLA-b-PEG-b-PLLA bioplastic

In this study, talcum was melt-blended with a flexible poly(l-lactide)-b-polyethylene glycol-b-poly(l-lactide) triblock copolymer (PLLA-PEG-PLLA) with 1, 2, 4, and 8 wt% talcum, for improvement of the crystallization and thermomechanical properties of PLLA-PEG-PLLA compared with PLLA. The crystallizability of PLLA-PEG-PLLA/talcum composites was better than that of PLLA/talcum composites as determined from differential scanning calorimetry. X-ray diffractometry showed that the PLLA-PEG-PLLA/talcum films had a higher degree of crystallinity than the PLLA/talcum films. PEG middle-blocks and talcum showed a synergistic effect for crystallization of PLLA end-blocks. The PLLA-PEG-PLLA/talcum films showed better thermomechanical properties than those of the PLLA/talcum films as determined from dynamic mechanical analysis. This was confirmed from the results of dimensional stability to heat. In summary, the PLLA-PEG-PLLA/talcum composites have potential for use as flexible bioplastics with good dimensional stability to heat.

Preparation and characterization of a novel drug-loaded Bi-layer scaffold for cartilage regeneration

The incidence of articular cartilage defects is increasing year by year. In order to repair the cartilage tissue at the defect, scaffolds with nanofiber structure and biocompatibility have become a research hotspot. In this study, we designed and fabricated a bi-layer scaffold prepared from an upper layer of drug-dispersed gelatin methacrylate (GELMA) hydrogel and a lower layer of a drug-encapsulated coaxial fiber scaffold prepared from silk fiber (SF) and polylactic acid (PLA). These bi-layer scaffolds have porosity (91.26 ± 3.94%) sufficient to support material exchange and pore size suitable for cell culture and infiltration, as well as mechanical properties (2.65 ± 0.31 MPa) that meet the requirements of cartilage tissue engineering. The coaxial fiber structure exhibited excellent drug release properties, maintaining drug release for 14 days in PBS. In vitro experiments indicated that the scaffolds were not toxic to cells and were amenable to chondrocyte migration. Notably, the growth of cells in a bi-layer scaffold presented two states. In the hydrogel layer, cells grow through interconnected pores and take on a connective tissue-like shape. In the coaxial fiber layer, cells grow on the surface of the coaxial fiber mats and appeared tablet-like. This is similar to the structure of the functional partitions of natural cartilage tissue. Together, the bi-layer scaffold can play a positive role in cartilage regeneration, which could be a potential therapeutic choice to solve the current problems of clinical cartilage repair.

Tunable microphase-regulated silk fibroin/poly (lactic acid) biocomposite materials generated from ionic liquids

One of the most effective and promising strategies to develop novel biomaterials with unique, tunable structure and physicochemical properties is by creating composite materials that combine synthetic polymers with natural proteins using ionic liquids. In this study, biodegradable poly(d,l-lactic acid) (PDLLA) was blended with silk fibroin (SF) to create biocompatible films using an ionic liquid-based binary solvent system (1-butyl-3-methylimidazolium chloride/N,N-dimethylformamide), which can maintain the molecular weights of the proteins/polymers and encourage intermolecular interactions between the molecules. The effects of varying the ratio of PLA to SF were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), water contact angle testing, and cytotoxicity analysis as well as enzymatic degradation. Results showed that the composite films were homogeneously blended on the macroscopic scale and exhibited typical fully miscible polymer blend characteristics. By increasing the SF content in the composites, the amounts of β-sheets in the films were significantly increased, allowing for SF to act as a physical crosslinker to maintain the stability of the protein-polymer network. Additionally, SF significantly improved the hydrophilicity and biocompatibility of the material and promoted the self-assembly of micelle structures in the biocomposites. Different topologies in the films also provided beneficial surface morphology for cell adhesion, growth, and proliferation. Overall, this study demonstrated an effective fabrication method for a fine-tuned polymer blends combining synthetic polymer and protein for a wide variety of biomedical and green material applications.

One-Pot Preparation of Hydrophilic Polylactide Porous Scaffolds by Using Safe Solvent and Choline Taurinate Ionic Liquid

Polylactides (PLAs) are a class of polymers that are very appealing in biomedical applications due to their degradability in nontoxic products, tunable structural, and mechanical properties. However, they have some drawbacks related to their high hydrophobicity, lack of functional groups able to graft bioactive molecules, and solubility in unsafe solvents. To circumvent these shortcomings, porous scaffolds for tissue engineering were prepared by vigorously mixing a solution of isotactic and atactic PLA in nontoxic ethyl acetate at 70 °C with a water solution of choline taurinate. The partial aminolysis of the polymer ester bonds by taurine –NH₂ brought about the formation of PLA oligomers with surfactant activity that stabilized the water-in-oil emulsion. Upon drying, a negligible shrinking occurred, and mechanically stable porous scaffolds were obtained. By varying the polymer composition and choline taurinate concentration, it was possible to modulate the pore dimensions (30–50 µm) and mechanical properties (Young’s moduli: 1–6 MPa) of the samples. Furthermore, the grafted choline taurinate made the surface of the PLA films hydrophilic, as observed by contact angle measurements (advancing contact angle: 76°; receding contact angle: 40°–13°). The preparation method was very simple because it was based on a one-pot mild reaction that did not require an additional purification step, as all the employed chemicals were nontoxic.

Microwave-Assisted Synthesis of Modified Glycidyl Methacrylate-Ethyl Methacrylate Oligomers, Their Physico-Chemical and Biological Characteristics

In this study, well-known oligomers containing ethyl methacrylate (EMA) and glycidyl methacrylate (GMA) components for the synthesis of the oligomeric network [P(EMA)-co-(GMA)] were used. In order to change the hydrophobic character of the [P(EMA)-co-(GMA)] to a more hydrophilic one, the oligomeric chain was functionalized with ethanolamine, xylitol (Xyl), and L-ornithine. The oligomeric materials were characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy, scanning electron microscopy, and differential thermogravimetric analysis. In the final stage, thanks to the large amount of -OH groups, it was possible to obtain a three-dimensional hydrogel (HG) network. The HGs were used as a matrix for the immobilization of methylene blue, which was chosen as a model compound of active substances, the release of which from the matrix was examined using spectrophotometric detection. The cytotoxic test was performed using fluid extracts of the HGs and human skin fibroblasts. The cell culture experiment showed that only [P(EMA)-co-(GMA)] and [P(EMA)-co-(GMA)]-Xyl have the potential to be used in biomedical applications. The studies revealed that the obtained HGs were porous and non-cytotoxic, which gives them the opportunity to possess great potential for use as an oligomeric network for drug reservoirs in in vitro application.

The isothermal crystallization kinetic of poly(L-lactide)-block-poly(ethylene glycol) block copolymers (PLLA-PEG): Effect of block lengths of PEG and PLLA

Poly(ethylene glycol)-block-poly(L-lactide) (PEG-PLLA) is a biodegradable copolymer which widely applied to medicine and drug system, and the morphology, organization and mechanical properties were extensively investigated. However, the crystallization kinetic were...

Recent advances of 3D hydrogel culture systems for mesenchymal stem cell-based therapy and cell behavior regulation

Mesenchymal stem cells (MSCs) have been increasingly recognized as resources for disease treatments and regenerative medicine. Meanwhile, the unique chemical and physical properties of hydrogels provide innate advantages to achieve...

Green Copolymers Based on Poly(Lactic Acid)-Short Review

Polylactic acid (PLA) is a biodegradable and biocompatible polymer that can be applied in the field of packaging and medicine. Its starting substrate is lactic acid and, on this account, PLA can also be considered an ecological material produced from renewable resources. Apart from several advantages, polylactic acid has drawbacks such as brittleness and relatively high glass transition and melting temperatures. However, copolymerization of PLA with other polymers improves PLA features, and a desirable material marked by preferable physical properties can be obtained. Presenting a detailed overview of the accounts on the PLA copolymerization accomplishments is the innovation of this paper. Scientific findings, examples of copolymers (including branched, star, grafted or block macromolecules), and its applications are discussed. As PLA copolymers can be potentially used in pharmaceutical and biomedical areas, the attention of this article is also placed on the advances present in this field of study. Moreover, the subject of PLA synthesis is described. Three methods are given: azeotropic dehydrative condensation, direct poly-condensation, and ring-opening polymerization (ROP), along with its mechanisms. The applied catalyst also has an impact on the end product and should be adequately selected depending on the intended use of the synthesized PLA. Different ways of using stannous octoate (Sn(Oct)₂) and examples of the other inorganic and organic catalysts used in PLA synthesis are presented.

Self-Assembly Dipeptide Hydrogel: The Structures and Properties

Self-assembly peptide-based hydrogels are well known and popular in biomedical applications due to the fact that they are readily controllable and have biocompatibility properties. A dipeptide is the shortest self-assembling motif of peptides. Due to its small size and simple synthesis method, dipeptide can provide a simple and easy-to-use method to study the mechanism of peptides' self-assembly. This review describes the design and structures of self-assembly linear dipeptide hydrogels. The strategies for preparing the new generation of linear dipeptide hydrogels can be divided into three categories based on the modification site of dipeptide: 1) COOH-terminal and N-terminal modified dipeptide, 2) C-terminal modified dipeptide, and 3) uncapped dipeptide. With a deeper understanding of the relationship between the structures and properties of dipeptides, we believe that dipeptide hydrogels have great potential application in preparing minimal biocompatible materials.

Simultaneous incorporation of PTH(1-34) and nano-hydroxyapatite into Chitosan/Alginate Hydrogels for efficient bone regeneration

Tissue regeneration based on the utilization of artificial soft materials is considered a promising treatment for bone-related diseases. Here, we report cranial bone regeneration promoted by hydrogels that contain parathyroid hormone (PTH) peptide PTH(1-34) and nano-hydroxyapatite (nHAP). A combination of the positively charged natural polymer chitosan (CS) and negatively charged sodium alginate led to the formation of hydrogels with porous structures, as shown by scanning electron microscopy. Rheological characterizations revealed that the mechanical properties of the hydrogels were almost maintained upon the addition of nHAP and PTH(1-34). In vitro experiments showed that the hydrogel containing nHAP and PTH(1-34) exhibited strong biocompatibility and facilitated osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) via the Notch signaling pathway, as shown by the upregulated expression of osteogenic-related proteins. We found that increasing the content of PTH(1-34) in the hydrogels resulted in enhanced osteogenic differentiation of BMSCs. Implantation of the complex hydrogel into a rat cranial defect model led to efficient bone regeneration compared to the rats treated with the hydrogel alone or with nHAP, indicating the simultaneous therapeutic effect of nHAP and PTH during the treatment process. Both the in vitro and in vivo results demonstrated that simultaneously incorporating nHAP and PTH into hydrogels shows promise for bone regeneration, suggesting a new strategy for tissue engineering and regeneration in the future.

(Macro)molecular self-assembly for hydrogel drug delivery

Hydrogels prepared via self-assembly offer scalable and tunable platforms for drug delivery applications. Molecular-scale self-assembly leverages an interplay of attractive and repulsive forces; drugs and other active molecules can be incorporated into such materials by partitioning in hydrophobic domains, affinity-mediated binding, or covalent integration. Peptides have been widely used as building blocks for self-assembly due to facile synthesis, ease of modification with bioactive molecules, and precise molecular-scale control over material properties through tunable interactions. Additional opportunities are manifest in stimuli-responsive self-assembly for more precise drug action. Hydrogels can likewise be fabricated from macromolecular self-assembly, with both synthetic polymers and biopolymers used to prepare materials with controlled mechanical properties and tunable drug release. These include clinical approaches for solubilization and delivery of hydrophobic drugs. To further enhance mechanical properties of hydrogels prepared through self-assembly, recent work has integrated self-assembly motifs with polymeric networks. For example, double-network hydrogels capture the beneficial properties of both self-assembled and covalent networks. The expanding ability to fabricate complex and precise materials, coupled with an improved understanding of biology, will lead to new classes of hydrogels specifically tailored for drug delivery applications.

Non-Isothermal Crystallization Kinetics of Poly(Ethylene Glycol)-Poly(l-Lactide) Diblock Copolymer and Poly(Ethylene Glycol) Homopolymer via Fast-Scan Chip-Calorimeter

The non-isothermal crystallization kinetics of double-crystallizable poly(ethylene glycol)-poly(l-lactide) diblock copolymer (PEG-PLLA) and poly(ethylene glycol) homopolymer (PEG) were studied using the fast cooling rate provided by a Fast-Scan Chip-Calorimeter (FSC). The experimental data were analyzed by the Ozawa method and the Kissinger equation. Additionally, the total crystallization rate was represented by crystallization half time t1/2. The Ozawa method is a perfect success because secondary crystallization is inhibited by using fast cooling rate. The first crystallized PLLA block provides nucleation sites for the crystallization of PEG block and thus promotes the crystallization of the PEG block, which can be regarded as heterogeneous nucleation to a certain extent, while the method of the PEG block and PLLA block crystallized together corresponds to a one-dimensional growth, which reflects that there is a certain separation between the crystallization regions of the PLLA block and PEG block. Although crystallization of the PLLA block provides heterogeneous nucleation conditions for PEG block to a certain extent, it does not shorten the time of the whole crystallization process because of the complexity of the whole crystallization process including nucleation and growth.