Sustain release of loaded insulin within biomimetic hydrogel microsphere for sciatic tissue engineering in vivo

Recent advances in bioactive hydrogel microspheres: Material engineering strategies and biomedical prospects

Hydrogel microspheres are a class of hydrophilic polymeric particles in microscale, which has been developed as a new type of functional biomaterials for wide-range biomedical applications in recent years. This review provides a comprehensive overview of the preparation methods for hydrogel microspheres, including droplet microfluidics, electrospray and emulsion was first summarized. At the same time, we analyze the impacts of these methods on the properties of hydrogel microspheres and explore various functionalization strategies for enhancing their bioactivity and expanding their biomedical applications. In addition, we discuss the recent advances and the further prospect of hydrogel microspheres in life science applications, particularly in cell biology research, bioanalysis and detection, as well as tissue repair and regeneration. By synthesizing the latest developments, this review aims to offer valuable insights and strategies for optimizing hydrogel microspheres in diverse application scenarios and inspire future research and practical innovations.

Cellulose-based hydrogels enhanced with bioactive molecules for optimal chronic diabetic wound management

Hydrogels are three-dimensional structures that replicate natural tissues' extracellular matrix (ECM). They are essential for transporting exudates, gases, and moisture and facilitating cellular interactions in tissue engineering and wound healing. The choice of primary material in designing the scaffold is necessary to be paid more attention rather than common sources, including plant fibres like cotton, bamboo, and algae, as well as bacterial and marine-derived materials. Among them, cellulose-based polymers are especially valued for their biocompatibility and ability to promote wound healing. Chronic diabetic wounds pose unique treatment challenges, such as necrosis and infection risks. Consequently, a growing interest is in incorporating bioactive molecules into cellulose-based hydrogels. This article investigates how these infused hydrogels enhance the healing process in chronic diabetic wounds, examining various loading and crosslinking techniques alongside their clinical applications. It also discusses the benefits and limitations of bioactive molecules and their interactions with hydrogels to improve treatment strategies.

Ultra-small starch microspheres with narrow size distribution prepared in aqueous two-phase system of starch-PVP

It is challenging to fabricate uniform starch microspheres (SMs) with sub-10 μm diameters in starch-polyethylene glycol (PEG) aqueous two-phase system (ATPS). To address this issue, a refined approach using starch-polyvinylpyrrolidone (PVP) ATPS is presented in this work. Phase diagrams were constructed for ATPSs containing PVPs of varying molecular weights, which provided crucial insights into the influence of PVP on SM formation. The results revealed that increasing both the molecular weight and concentration of PVP led to higher starch and PVP contents within the dispersed phase, significantly influencing the final yield of SMs. The morphology, size, crystallinity, and swelling behavior of SMs prepared in the starch-PVP ATPS were comprehensively characterized. Increasing PVP molecular weight resulted in smaller SMs with enhanced crystallinity and reduced swelling capacity. Notably, SMs prepared with 58 kDa PVP exhibited an average particle size (D[4,3) of 5.13 μm, a narrow size distribution (Span value = 1.33), a B + V crystal type, and a relative crystallinity of 20.9 %. Furthermore, no residual PVP was detected in the final SMs. This innovative starch-PVP ATPS approach offers a promising route for the controlled fabrication of sub-10 μm SMs with tightly controlled size distributions. This method holds significant potential for applications demanding well-defined starch-based materials in various fields. This innovative starch-PVP ATPS approach offers a promising route for controlled fabrication of uniform SMs with sub-10 μm diameters, which could be advantageous for drug encapsulation and delivery systems requiring high structural stability.

Fabrication of stable hydrogel microspheres with hydrophobic shell using water-in-water (W/W) Pickering emulsion template

Hydrogel microspheres are promising for food applications. The water-in-oil (W/O) emulsion template is commonly used to prepare the hydrogel microspheres. However, this method often involves synthetic surfactants and toxic organic solvents to remove the oil phase. The swelling problem of the resultant microspheres is another obstacle. In this study the water-in-water (W/W) emulsion template of gelatin-in-dextran was used to prepare the hydrogel microspheres, without the addition of surfactants, toxic reagents and high energy input. To prevent swelling, zein particles modified with alginate were served as a hydrophobic shell of the gelatin core. The formation evolution of these core-shell microspheres and its relevant factors including phase behavior of the immiscible gelatin/dextran, the binding of zein/alginate and the addition of the modified zein particles were investigated. It was found that small amount of alginate could induce zein particles to adsorb on the gelatin surface, whereas the excess led to adsorption competition. When using 0.6 wt% particles with zein/alginate ratio of 1:0.5, the ideal core-shell microspheres which were fully covered by the particles and with a self-supporting architecture in uniform size (18.8 ± 0.1 μm) and spherical shape were obtained. These microspheres showed remarkable stability under the conditions of heat treatment, varied pHs and salt concentrations and long-term storage either in refrigerator or room environment. Their sizes were easily manipulated by adjusting the concentration and molar mass of the biopolymers. It is believed that the desired stability and tunable sizes of these edible core-shell microspheres could contribute the development of their applications in foods.

Effectiveness of the injectable hyaluronic acid-based microparticles loaded with cannabidiol on rat sciatic nerve injury model

We have developed an innovative peripheral nerve tissue repair approach by designing biomimetic microparticles loaded with cannabidiol (CBD) using horseradish peroxidase-mediated crosslinking within a microfluidic device. This method utilizes a water-in-oil emulsion system where a mixture of phenol-substituted hyaluronic acid (HAPh), CBD, and laccase is channeled into oil flow, forming hydrogel microparticles. The physical properties, such as their swelling rate, mechanical strength, and the sustained release of CBD, emphasize their potential in tissue engineering and drug delivery applications. Cellular proliferation studies within the microparticles demonstrate their cytocompatibility, making them suitable for developing microtissues. The microparticles also served as a controlled release mechanism for CBD-targeted delivery to the injured locations, showcasing the effectiveness and ability to aid in the regeneration of the sciatic nerve tissue. In vivo, histopathological analysis of treated sciatic nerve injuries showed enhanced axonal restoring and remyelination with HAPh microparticles containing CBD in contrast to control groups. Furthermore, microparticles enhanced various functional aspects of locomotor activities, such as functional sciatic index (SFI) values, response to heat stimulation, and muscle mass retention. In conclusion, results indicate that these composite biomimetic microparticles with CBD effectively promote nerve structural restoration and increase the reconstruction process in a sciatic nerve injury model.

Design and preparation of hydrogel microspheres for spinal cord injury repair

A severe disorder known as spinal cord damage causes both motor and sensory impairment in the limbs, significantly reducing the patients' quality of life. After a spinal cord injury, functional recovery and therapy have emerged as critical concerns. Hydrogel microspheres have garnered a lot of interest lately because of their enormous promise in the field of spinal cord injury rehabilitation. The material classification of hydrogel microspheres (natural and synthetic macromolecule polymers) and their synthesis methods are examined in this work. This work also covers the introduction of several kinds of hydrogel microspheres and their use as carriers in the realm of treating spinal cord injuries. Lastly, the study reviews the future prospects for hydrogel microspheres and highlights their limitations and problems. This paper can offer feasible ideas for researchers to advance the application of hydrogel microspheres in the field of spinal cord injury.

Preparation and characterization of polysaccharide-based conductive hydrogels for nerve repair

Peripheral nerve injury is a serious medical condition, but the limited availability of autologous grafts often delays timely treatment for many patients. The implantation of functional hydrogels with good biocompatibility provides an effective solution to this challenge. In this study, a novel chitosan derivative, choline functionalized catechol carboxymethyl chitosan (CF-Catechol-CMCS), was synthesized by modifying carboxymethyl chitosan (CMCS) with choline functionalized (CF) molecule and catechol. CF-Catechol-CMCS, sodium alginate (SA), and pyrrole monomer (Py) were then combined, crosslinked with Fe3+ and Ca2+, and polymerized in situ to form polypyrrole (PPy), resulting in the CF-Catechol-CMCS/SA/PPy hydrogel. This hydrogel exhibits excellent thermal stability, with a maximum thermal degradation temperature of 580 °C. By adjusting the ratio of PPy to CF-Catechol-CMCS/SA in the hydrogel, its degradation properties, swelling behavior, mechanical properties, and electrical conductivity can be fine-tuned. Specifically, when the mass ratio of PPy to CF-Catechol-CMCS/SA is 8:10, the hydrogel achieves optimal conductivity within a safe range (1.82 × 10-3 S·cm-1). By controlling the mass ratio of CF-Catechol-CMCS to SA in the hydrogel, the acetylcholine concentration can be regulated. When the CF-Catechol-CMCS:SA ratio is 2:1, the measured Sciatic Function Index (SFI) value is -34.54, indicating that the CF-Catechol-CMCS/SA/PPy hydrogel has excellent nerve repair potential.

Sustained co-release of ciprofloxacin and dexamethasone in rabbit maxillary sinus using polyvinyl alcohol-based hydrogel microparticle

Topical delivery to paranasal sinuses through sustained-release stents is one of the new horizons in treating chronic rhinosinusitis (CRS). This study aims to introduce and evaluate sustained co-release of encapsulated ciprofloxacin (CIP) and dexamethasone (DEX) in polyvinyl alcohol-based carriers within the maxillary sinus of rabbit animals. DEX and CIP were loaded in a tyramine-substituted polyvinyl alcohol microparticle (PVATyr MP). The mechanical stability, degradability, and sustained-release patterns of both drugs as well as cellular cytocompatibility were assessed in vitro. The PVATyr MPs were then injected into the maxillary sinus of rabbits and they were monitored weekly for 21 days. Nasal endoscopy, MRI imaging, and tissue microscopy were used to follow the changes and compared them with the control condition. Also, the concentrations of drugs were evaluated in the maxillary sinus and blood samples over the study period. Produced PVA-based MPs possessed a relatively narrow particle size distribution (CV 7.7%) with proper physical stability until 30 days of incubation. The uniform-sized PVATyr MPs and their surrounding hydrogel showed sustained-release profiles for DEX and CIP for up to 32 days in vitro. The injected drugs-loaded hydrogel showed complete clearance from the maxillary sinus of rabbits within 28 days. The concentrations of DEX and CIP in mucosal remained within the therapeutic window when measured on days 7, 14, and 21, which were well above the plasma concentrations without any pathological changes in endoscopy, MRI imaging, and histological examinations. DEX/CIP loaded PVATyr MPs provided an effective, controlled, and safe sustained-drug delivery in both in vitro and in vivo analyses at therapeutic concentrations with minimal systemic absorption, suggesting a promising treatment approach for CRS.

Hybrid-Aligned Fibers of Electrospun Gelatin with Antibiotic and Polycaprolactone Composite Membranes as an In Vitro Drug Delivery System to Assess the Potential Repair Capacity of Damaged Cornea

The cornea lacks the ability to repair itself and must rely on transplantation to repair damaged tissue. Therefore, creating alternative therapies using dressing membranes based on tissue engineering concepts to repair corneal damage before failure has become a major research goal. Themost outstanding features that are important in reconstructing a damaged cornea are the mechanical strength and transparency of the membrane, which are the most important standard considerations. In addition, preventing infection is an important issue, especially in corneal endothelial healing processes. The purpose of this study was to produce aligned fibers via electrospinning technology using gelatin (Gel) composite polycaprolactone (PCL) as an optimal transport and antibiotic release membrane. The aim of the composite membrane is to achieve good tenacity, transparency, antibacterial properties, and in vitro biocompatibility. Results showed that the Gel and PCL composite membranes with the same electrospinning flow rate had the best transparency. The Gel impregnated with gentamicin antibiotic in composite membranes subsequently exhibited transparency and enhanced mechanical properties provided by PCL and could sustainably release the antibiotic for 48 h, achieving good antibacterial effects without causing cytotoxicity. This newly developed membrane has the advantage of preventing epidermal tissue infection during clinical operations and is expected to be used in the reconstruction of damaged cornea in the future.

Dexamethasone release from hyaluronic acid microparticle and proanthocyanidin-gelatin hydrogel in sciatic tissue regeneration

Biodegradable microparticles are useful vehicles for the controlled release of bioactive molecules in drug delivery, tissue engineering and biopharmaceutical applications. We developed dexamethasone (Dex) encapsulation into tyramine-substituted hyaluronic acid microparticles (Dex-HA-Tyr Mp) mediated by horseradish peroxidase (HRP) crosslinking using a microfluidic device and infollowing crosslinked gelatin (Gela) with proanthocyanidin (PA) as a semi-confined bed hydrogel for the repair of sciatic tissue injury. It was found that the simultaneous use of Dex-HA-Tyr Mp and cross-linked Gela-PA hydrogel improved the physical properties of the hydrogel, including mechanical strength and degradability. The designed composite also provided a sustained release system for Dex delivery to the surrounding sites, demonstrating the applicability of the fabricated hydrogel composite for sciatic nerve tissue engineering and regeneration. The encapsulated cells were viable and showed adequate growth ability and morphogenesis during prolonged incubation in Gela-PA/HA-Tyr Mp hydrogel compared to control conditions. Interestingly, histological analysis revealed a significant increase in the number of axons in the injured sciatic nerve following treatment with Dex-HA-Tyr Mp and injectable Gela-PA hydrogel compared to other control groups. In conclusion, the results demonstrated that fabricated Dex-loaded MPs and injectable hydrogel from biomimetic components are suitable systems for sustained delivery of Dex with adequate biocompatibility and the approach may have potential therapeutic applications in peripheral nerve regeneration.

Gelatin microsphere-alginate hydrogel combined system for sustained and gastric targeted delivery of 5-fluorouracil

In the current study, novel gelatin microspheres/methacrylated alginate hydrogel combined system (5-FU-GELms/Alg-MA) was developed for gastric targeted delivery of 5-fluorouracil as an anticancer agent. While water-in-oil emulsification method was used for the production of 5-FU-GELms, Alg-MA was synthesized through methacrylation reaction occurred by epoxide ring-opening mechanism. Then, 5-FU-GELms/Alg-MA hydrogel system was fabricated by the encapsulation of 5-FU-GELms into Alg-MA hydrogel network via UV-crosslinking. To evaluate applicability of fabricated 5-FU-GELms/Alg-MA as gastric targeted drug delivery vehicle, both swelling and in vitro drug release experiments were carried out at pH 1.2 medium resembling gastric fluid. Compared to drug release directly from 5-FU-GELms, 5-FU-GELms/Alg-MA hydrogel system showed more controlled and sustained drug release profile with lower amount of cumulative release starting from early stages, since hydrogel matrix created a barrier to the diffusion of 5-FU included in microspheres. Drug release kinetic results obtained by applying various kinetic models to release data showed that the mechanism of 5-FU release from 5-FU-GELms/Alg-MA hydrogel system is controlled by Fickian diffusion. All results revealed that 5-FU-GELms/Alg-MA hydrogel integrated system could be potentially utilized as gastric targeted drug carrier to enhance therapeutic efficacy and reduce systemic side effects in gastric cancer treatments for future studies.

Fabrication and optimization of multilayered composite scaffold made of sulfated alginate-based nanofiber/decellularized Wharton's jelly ECM for tympanic membrane tissue engineering

In this study, we fabricated a novel multilayer polyvinyl alcohol (PVA)/alginate sulfate (ALG-S) nanofiber/decellularized Wharton's Jelly ECM (d-ECM) composite for tympanic membrane perforations (TMPs) tissue engineering (TE). Initially, electrospun PVA/ALG-S scaffolds with different blend ratios were fabricated. The influence of ALG-S ratio on surface morphology, mechanical, physical and biological properties of the nanofibers was studied. Secondly, 3-layer composites were developed as a combination of PVA/ALG-S nanofibers and d-ECM to take synergic advantages of electrospun mats and d-ECM. As part of the evaluation of the effects of d-ECM incorporation, the composite's mechanical properties, in vitro degradation, swelling ratio, and biological activities were assessed. The MTT assay showed that PVA/ALG-S nanofibers with 50:50 ratio provided a more desirable environment to support cell growth. A composite containing 25 mg/cm2 d-ECM was determined as the optimal composite through MTT assay, and this composite was used for animal studies inducing TMP regeneration. According to the in vivo studies, the optimal composite not only stimulated the healing of TMPs but also shortened the healing period. These results suggest that a multilayer nanofiber/hydrogel composite could be a potential platform for regenerating TMPs.

Sustain release of dexamethasone from polyvinyl alcohol microparticle produced via coaxial microfluidic system

OBJECTIVE

Polyvinyl alcohol (PVA) as a synthetic biopolymer has unique physicochemical properties to achieve an efficient drug carrier. In this study phenol-substituted polyvinyl alcohol (PVAPh) microparticle was made through a microfluidic system and peroxidase-mediated reaction in the presence of hydrogen peroxide and in following dexamethasone (Dex) release characteristics from this vehicle were elaborated for sustained drug delivery applications.

RESULTS

PVAPh was synthesized by esterification and amidation reactions respectively. Then, the synthesized PVAPh solution containing peroxidase and Dex flowed within the inner channel of the coaxial microfluidic device while liquid paraffin saturated with H2O2 flowed from the outer channel. The monodisperse microparticles were produced in a spherical shape with an average diameter of 160 μm. The Dex was successfully encapsulated in PVAPh MP and its sustained release profile was maintained for up to 7 days. It was found that exposure of Dex-loaded PVAPh MPs to subcultured mouse embryonic fibroblast 10T1/2 cells had no deleterious effects on cell viability, morphology and growth rate. Moreover, the sustained release of Dex and the high mechanical durability of PVAPh MPs suggest an excellent prospect for the synthesized PVAPh and the developed method as a biocompatible carrier required for drug delivery and regenerative medicine.

Fucoidan-functionalized gelatin methacryloyl microspheres ameliorate intervertebral disc degeneration by restoring redox and matrix homeostasis of nucleus pulposus

Loss of extracellular matrix (ECM) and dehydration of the nucleus pulposus (NP) are major pathological characteristics of intervertebral disc degeneration (IVDD), the leading cause of low back pain. Excessive reactive oxygen species (ROS) induced by proinflammatory cytokines substantially contribute to IVDD pathogenesis. This study aimed to examine the potential of fucoidan in protecting the matrix metabolism of NP cells and its therapeutic efficacy in the prevention of IVDD. In an inflammatory environment induced by interleukin (IL)-1β, fucoidan treatments demonstrated a dose-dependent enhancement of ECM production in NP cells, while concurrently reducing the expression of matrix degradation enzymes. The protective effect of fucoidan was mediated through the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and subsequent induction of antioxidant enzymes, whereas silencing Nrf2 abrogated the protection of fucoidan on NP cells against IL-1β-induced oxidative stress. Moreover, a novel fucoidan-functionalized gelatin methacryloyl microsphere (Fu@GelMA-MS) was synthesized. The in vivo application of Fu@GelMA-MS via in situ injection in a rat caudal IVD model effectively conserved the ECM components and maintained the hydration of the NP tissue, thereby preventing IVDD caused by puncture. Collectively, fucoidan-functionalized hydrogel microspheres represent a promising strategy for the regeneration of NP and the treatment of IVDD.

Preparation strategy of hydrogel microsphere and its application in skin repair

In recent years, hydrogel microsphere has attracted much attention due to its great potential in the field of skin repair. This paper reviewed the recent progress in the preparation strategy of hydrogel microsphere and its application in skin repair. In this review, several preparation methods of hydrogel microsphere were summarized in detail. In addition, the related research progress of hydrogel microspheres for skin repair was reviewed, and focused on the application of bioactive microspheres, antibacterial microspheres, hemostatic microspheres, and hydrogel microspheres as delivery platforms (hydrogel microspheres as a microcarrier of drugs, bioactive factors, or cells) in the field of skin repair. Finally, the limitations and future prospects of the development of hydrogel microspheres and its application in the field of skin repair were presented. It is hoped that this review can provide a valuable reference for the development of the preparation strategy of hydrogel microspheres and promote the application of hydrogel microspheres in skin repair.

Alginate-Chitosan Hydrogels Containing shRNA Plasmid for Inhibition of CTNNB1 Expression in Breast Cancer Cells

The hydrogels prepared with alginate and chitosan polymers were prepared to deliver the shRNA-encoding plasmid (pshRNA) to MDA-MB-231 cells for the inhibition of β-catenin (CTNNB1), which was reported to be overexpressed in breast cancer. Polyion complex hydrogels prepared using sodium alginate and chitosan were characterized by Fourier transform infrared spectrometry (FTIR) analysis, scanning electron microscope (SEM) analysis, swelling, and degradation properties. After the release properties and serum stability of pshRNA-loaded hydrogels were determined, their cytotoxicity, transfection efficacy, and effects on CTNNB1 expression were investigated in MDA-MB-231 cells. All hydrogels were shown to protect pshRNA from the enzymatic activity of serum and to deliver pshRNA to cells efficiently. As a result of transfection studies, pshRNA-loaded hydrogels reduced CTNNB1 expression by up to 30.25%. Cell viability also decreased by 38% in cells treated with 2.5% (w/v) alginate-chitosan hydrogel containing pshRNA targeting CTNNB1. Alginate-chitosan hydrogels were shown to be a suitable matrix system for local gene delivery.

Development and In Vitro Analysis of Layer-by-Layer Assembled Membranes for Potential Wound Dressing: Electrospun Curcumin/Gelatin as Middle Layer and Gentamicin/Polyvinyl Alcohol as Outer Layers

Nanofibrous membranes made of hydrogels have high specific surface areas and are suitable as drug carriers. Multilayer membranes fabricated by continuous electrospinning could delay drug release by increasing diffusion pathways, which is beneficial for long-term wound care. In this experiment, polyvinyl alcohol (PVA) and gelatin were used as membrane substrates, and a sandwich PVA/gelatin/PVA structure of layer-by-layer membranes was prepared by electrospinning under different drug loading concentrations and spinning times. The outer layers on both sides were citric-acid-crosslinked PVA membranes loaded with gentamicin as an electrospinning solution, and the middle layer was a curcumin-loaded gelatin membrane for the study of release behavior, antibacterial activity, and biocompatibility. According to the in vitro release results, the multilayer membrane could release curcumin slowly; the release amount was about 55% less than that of the single layer within 4 days. Most of the prepared membranes showed no significant degradation during immersion, and the phosphonate-buffered saline absorption rate of the multilayer membrane was about five to six times its weight. The results of the antibacterial test showed that the multilayer membrane loaded with gentamicin had a good inhibitory effect on Staphylococcus aureus and Escherichia coli. In addition, the layer-by-layer assembled membrane was non-cytotoxic but detrimental to cell attachment at all gentamicin-carrying concentrations. This feature could be used as a wound dressing to reduce secondary damage to the wound when changing the dressing. This multilayer wound dressing could be applied to wounds in the future to reduce the risk of bacterial infection and help wounds heal.

In Vitro Characterizations of Post-Crosslinked Gelatin-Based Microspheres Modified by Phosphatidylcholine or Diammonium Phosphate as Antibiotic Delivery Vehicles

Hydrogel-based microspheres prepared by emulsification have been widely used as drug carriers, but biocompatibility remains a challenging issue. In this study, gelatin was used as the water phase, paraffin oil was used as the oil phase, and Span 80 was used as the surfactant. Microspheres were prepared using a water-in-oil (W/O) emulsification. Diammonium phosphate (DAP) or phosphatidylcholine (PC) were further used to improve the biocompatibility of post-crosslinked gelatin microspheres. The biocompatibility of DAP-modified microspheres (0.5-10 wt.%) was better than that of PC (5 wt.%). The microspheres soaked in phosphate-buffered saline (PBS) lasted up to 26 days before fully degrading. Based on microscopic observation, the microspheres were all spherical and hollow inside. The particle size distribution ranged from 19 μm to 22 μm in diameter. The drug release analysis showed that the antibiotic gentamicin loaded on the microspheres was released in a large amount within 2 h of soaking in PBS. It was stabilized until the amount of microspheres integrated was significantly reduced after soaking for 16 days and then released again to form a two-stage drug release curve. In vitro experiments showed that DAP-modified microspheres at concentrations less than 5 wt.% had no cytotoxicity. Antibiotic-impregnated and DAP-modified microspheres had good antibacterial effects against Staphylococcus aureus and Escherichia coli, but these drug-impregnated groups hinder the biocompatibility of hydrogel microspheres. The developed drug carrier can be combined with other biomaterial matrices to form a composite for delivering drugs directly to the affected area in the future to achieve local therapeutic effects and improve the bioavailability of drugs.