Hyaluronic acid/gelatin microcapsule functionalized with carbon nanotube through laccase-catalyzed crosslinking for fabrication of cardiac microtissue

Engineering functional electroconductive hydrogels for targeted therapy in myocardial infarction repair

Myocardial infarction (MI) is characterized by a paucity of cardiomyocyte regeneration, leading to significant morbidity and mortality. Contemporary therapeutic modalities, while mitigating ischemic effects, fail to reconstitute the impaired electromechanical coupling within the infracted myocardium. Emerging evidence supports the utility of electroconductive hydrogels (ECHs) in facilitating post-MI cardiac function recovery by restoring the conductive microenvironment of the infarcted tissue. This comprehensive review delineates the taxonomy of ECHs predicated on their constituent conductive materials. It also encapsulates prevailing research trends in ECH-mediated MI repair, encompassing innovative design paradigms and microenvironment-sensitive strategies. The review also provides a critical appraisal of various implantation techniques, underscored by a thorough examination of the attendant considerations. It elucidates the mechanistic underpinnings by which hydrogels exert salutary effects on myocardial repair, namely by augmenting mechanical and electrical integrity, exerting anti-inflammatory actions, fostering angiogenesis, and curtailing adverse remodeling processes. Furthermore, the review engages with the pressing challenge of optimizing ECH functionality to achieve superior reparative outcomes post-MI. The discourse concludes with an anticipatory perspective on the evolution of ECH scaffolds, advocating for a tailored approach that integrates multifaceted physicochemical properties to cater to the nuances of personalized medicine.

Injectable hyaluronic acid-based microcapsules loaded with human endometrial stem cells improves cardiac function after myocardial infarction

Therapeutic efficacy of human endometrial stem cells (hEnSCs) encapsulated in hyaluronic acid (HA)-based microcapsules for cardiac regeneration in a rat model of MI is investigated. Cell-enclosed microcapsules were made by loading hEnSCs within hydrogel membrane produced from modified HA possessing phenolic hydroxyl moieties (HA-Ph). The hEnSC-loaded HA-Ph microcapsules (≈150 μm) injected intramyocardially into the peri-infarct area post-MI. The encapsulated cells showed mechanical stability and >87 % cell viability with cellular aggregation in size of about 100 μm until 7 days of culture. Transthoracic echocardiography evaluation indicated a significant increase in ejection fraction in encapsulated cells, compared to the other groups. Histological investigation of fibrosis and scar area by Masson trichrome and hematoxylin and eosin (H&E) staining illustrated less fibrosis and scarring area in the encapsulated cell group compared with the other groups. Furthermore, the cell-laden microcapsules significantly enhance expression intensities of actin and troponin as well as vascular endothelial-specific marker, all of which promote cardiac functions and contribute to a better therapeutic effect than the free-cell injection group in a rat model of MI. Our findings demonstrated that both hEnSCs and specifically hEnSC-loaded HA-based hydrogel vehicle can provide a promising novel therapy for functional restoration in MI instances.

3D-Printed Gelatin-Based Scaffold Crosslinked by Genipin: Evaluation of Mechanical Properties and Biological Effect

In this study, scaffolds based on natural polymer gelatin A, blended with polyvinylpyrrolidone were crosslinked by genipin (0.5 and 1 wt%), in order to investigate their mechanical performance and potential for biomedical application. Semi-solid extrusion (SSE) 3D printing technique was used, enabling in situ crosslinking of the blend during processing. Swelling test showed that the swelling ratio reduces with higher concentration of genipin due to an increased crosslinking. The FTIR analysis confirmed the crosslinking of scaffolds by genipin. DSC analysis and mechanical testing have shown improved thermal and mechanical properties. Morphological analysis of scaffolds by FESEM showed increased toughening of the material with the crosslinking. Tensile strength and microhardness showed a significant rise in scaffolds with the increase in genipin content, which was up to 93.8% and 125.3%, respectively. These findings were in accordance with morphological features present in samples. The biological effect of the scaffold matrix system was evaluated by qualitative and quantitative cytotoxicity assessment in vitro, demonstrating the absence of cytotoxicity in tested preparations in a direct test. The cytotoxicity index based on the metabolic activity of cells in an indirect test showed up to 20% reduction of viability compared with the control, confirming the absence of cytotoxicity, which was additionally verified by propidium iodine staining of the cells exposed to scaffolds. The presented gelatin-based crosslinked scaffolds obtained by 3D printing represent good candidates for biomedical application and future research that includes further in vitro and in vivo analysis.

Effectiveness of Insolubilized Poly(vinyl alcohol)-Based Electrospun Fiber-Loaded Methylprednisolone by Enzyme-Catalyzed Cross-Linking in a Rat Spinal Cord Injury Model

Spinal cord injury (SCI) has been implicated in neural loss and, consequently, motor/sensory impairment. Here, we propose an improved formation for fibrous mat fabrication from the derivatives of poly(vinyl alcohol) (PVA) and gelatin (Gela) through horseradish peroxidase-mediated cross-linking, providing a sustained release of methylprednisolone (MP) for SCI repair. After 28 days, the animals were evaluated in terms of remyelination and apoptosis and underwent behavioral tests. The mechanical properties, hydrophobicity, and degradation rate of PVAPh/GelaPh fibrous mats were significantly improved as compared with those of PVAPh samples. This could provide the desired structure for a sustained MP release. The seeded cells could adhere and proliferate to the composite fibers, which indicates the cytocompatibility of the resultant PVAPh/GelaPh fibrous mat. The results showed significant reductions in the number of apoptotic neurons and a substantial improvement in remyelination in the SCI+ PVAPh/GelaPh + MP group. The behavioral tests confirmed improvement in locomotor hindlimb function following treatment. The MP-loaded PVAPh/GelaPh mat developed through the long-term release of MP and the biocompatible fabricated mat could inhibit axonal demyelination, attenuate apoptosis, and improve the functional outcome, which verified the potential of PVAPh/GelaPh + MP nanocomposites as a bioactive scaffold for SCI regeneration.

Regulation of mechanical properties of microcapsules and their applications

Microcapsules encapsulating payloads are one of the most promising delivery methods. The mechanical properties of microcapsules often determine their application scenarios. For example, microcapsules with low mechanical strength are more widely used in biomedical applications due to their superior biocompatibility, softness, and deformability. In contrast, microcapsules with high mechanical strength are often mixed into the matrix to enhance the material. Therefore, characterizing and regulating the mechanical properties of microcapsules is essential for their design optimization. This paper first outlines four methods for the mechanical characterization of microcapsules: nanoindentation technology, parallel plate compression technology, microcapillary technology, and deformation in flow. Subsequently, the mechanisms of regulating the mechanical properties of microcapsules and the progress of applying microcapsules with different degrees of softness and hardness in food, textile, and pharmaceutical formulations are discussed. These regulation mechanisms primarily include altering size and morphology, introducing sacrificial bonds, and construction of hybrid shells. Finally, we envision the future applications and research directions for microcapsules with tunable mechanical properties.

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.

Fabrication of alginate-based hydrogel microparticle via ruthenium-catalyzed photocrosslinking

In this study, we developed an alginate-based microparticle production process via sodium ruthenium(II) tris-bipyridyl dication (Ru)/ammonium persulfate (SPS)-mediated visible light crosslinking system using a microfluidic device. Microparticles were prepared by crosslinking phenolic-substituted alginate (AlgPh) and incorporated gelatin (GelPh) in an aqueous solution containing SPS, which flowed into an ambient immiscible liquid paraffin-containing Ru using coaxial double orifice microfluidic device. The hydrogel microparticles appeared with the desired geometries and dimensions under optimal conditions. The concentration of AlgPh and light intensity were the most critical parameters for harvesting spherical microparticles with homogeneous size distribution. The physical properties of the prepared AlgPh microparticles were characterized and compared with Alg-Ca microparticles. Cell viability and proliferation preserved on AlgPh/GelPh hydrogel surfaces. Also, encapsulated cells in microparticles were also viable and proliferated well over 13 days after encapsulation. In brief, the results proved the feasibility of fabricating AlgPh vehicles via Ru/SPS-mediated system and visible light irradiation as a simple and efficient three-dimensional platform, which are applicable for various tissue engineering and cell delivery purposes.

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.

Chitosan-Polyethylene Glycol Inspired Polyelectrolyte Complex Hydrogel Templates Favoring NEO-Tissue Formation for Cardiac Tissue Engineering

Neo-tissue formation and host tissue regeneration determine the success of cardiac tissue engineering where functional hydrogel scaffolds act as cardiac (extracellular matrix) ECM mimic. Translationally, the hydrogel templates promoting neo-cardiac tissue formation are currently limited; however, they are highly demanding in cardiac tissue engineering. The current study focused on the development of a panel of four chitosan-based polyelectrolyte hydrogels as cardiac scaffolds facilitating neo-cardiac tissue formation to promote cardiac regeneration. Chitosan-PEG (CP), gelatin-chitosan-PEG (GCP), hyaluronic acid-chitosan-PEG (HACP), and combined CP (CoCP) polyelectrolyte hydrogels were engineered by solvent casting and assessed for physiochemical, thermal, electrical, biodegradable, mechanical, and biological properties. The CP, GCP, HACP, and CoCP hydrogels exhibited excellent porosity (4.24 ± 0.18, 13.089 ± 1.13, 12.53 ± 1.30 and 15.88 ± 1.10 for CP, GCP, HACP and CoCP, respectively), water profile, mechanical strength, and amphiphilicity suitable for cardiac tissue engineering. The hydrogels were hemocompatible as evident from the negligible hemolysis and RBC aggregation and increased adsorption of plasma albumin. The hydrogels were cytocompatible as evident from the increased viability by MTT (>94% for all the four hydrogels) assay and direct contact assay. Also, the hydrogels supported the adhesion, growth, spreading, and proliferation of H9c2 cells as unveiled by rhodamine staining. The hydrogels promoted neo-tissue formation that was proven using rat and swine myocardial tissue explant culture. Compared to GCP and CoCP, CP and HACP were superior owing to the cell viability, hemocompatibility, and conductance, resulting in the highest degree of cytoskeletal organization and neo-tissue formation. The physiochemical and biological performance of these hydrogels supported neo-cardiac tissue formation. Overall, the CP, GCP, HACP, and CoCP hydrogel systems promise novel translational opportunities in regenerative cardiology.

Carbon nanotube nanocomposite scaffolds: advances in fabrication and applications for tissue regeneration and cancer therapy

Carbon nanotube (CNT) nanocomposite scaffolds have emerged as highly promising frameworks for tissue engineering research. By leveraging their intrinsic electrical conductivity and valuable mechanical properties, CNTs are commonly dispersed into polymers to create robust, electrically conductive scaffolds that facilitate tissue regeneration and remodeling. This article explores the latest progress and challenges related to CNT dispersion, functionalization, and scaffold printing techniques, including electrospinning and 3D printing. Notably, these CNT scaffolds have demonstrated remarkable positive effects across various cell culture systems, stimulating neuronal growth, promoting cardiomyocyte maturation, and facilitating osteocyte differentiation. These encouraging results have sparked significant interest within the regenerative medicine field, including neural, cardiac, muscle, and bone regenerations. However, addressing the concern of CNT cytotoxicity in these scaffolds remains critical. Consequently, substantial efforts are focused on exploring strategies to minimize cytotoxicity associated with CNT-based scaffolds. Moreover, researchers have also explored the intriguing possibility of utilizing the natural cytotoxic properties of CNTs to selectively target cancer cells, opening up promising avenues for cancer therapy. More research should be conducted on cutting-edge applications of CNT-based scaffolds through phototherapy and electrothermal ablation. Unlike drug delivery systems, these novel methodologies can combine 3D additive manufacturing with the innate physical properties of CNT in response to electromagnetic stimuli to efficiently target localized tumors. Taken together, the unique properties of CNT-based nanocomposite scaffolds position them as promising candidates for revolutionary breakthroughs in both regenerative medicine and cancer treatment. Continued research and innovation in this area hold significant promise for improving healthcare outcomes.

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.

Horseradish Peroxidase-Mediated Bioprinting via Bioink Gelation by Alternately Extruded Support Material

Horseradish peroxidase (HRP)-mediated extrusion bioprinting has a significant potential in tissue engineering and regenerative medicine. However, they often face challenges in terms of printing fidelity and structural integrity when using low-viscosity inks. To address this issue, a method that alternately extrudes bioinks and support material was developed in this study. The bioinks consisting of cells, HRP, and phenolated polymers, and the support material contained hydrogen peroxide (H2O2). The support material not only prevented the collapse of the constructs but also supplied H2O2 to facilitate the enzymatic reaction. 3D constructs with tall and complex shapes were successfully printed from a low-viscosity ink containing 10 U/mL HRP and 1.0% w/v phenolated hyaluronic acid (HA-Ph), with a support material containing 10 mM H2O2. Over 90% viability of mouse fibroblasts (10T1/2) was achieved following the printing process, along with a morphology and proliferation rate similar to that of nontreated cells. Furthermore, human hepatoblastoma (HepG2) cells showed an increased spheroid size over 14 days in the printed constructs. The 10T1/2 cells adhered and proliferated on the constructs printed from inks containing both phenolated gelatin and HA-Ph. These results demonstrate the great potential of this HRP-mediated extrusion bioprinting technique for tissue engineering applications.

Chitosan-collagen-fibrinogen uncrosslinked scaffolds possessing skin regeneration and vascularization potential

Clinical success of regenerative medicine for treating deep-tissue skin injuries depends on the availability of skin grafts. Though bioengineered constructs are tested clinically, lack of neovascularization provide only superficial healing. Thus constructs, which promotes wound healing and supports vascularization has gained priority in tissue engineering. In this study, chitosan-collagen-fibrinogen (CCF) scaffold was fabricated using freeze-drying method without using any chemical crosslinkers. CCF scaffolds proved cytocompatibility and faster healing in in vitro scratch assay of primary human adult dermal fibroblasts cells with progressively increasing vascular endothelial growth factor-A and reducing vascular endothelial growth factor receptor 1 expressions. Skin regeneration evaluated on in vivo full thickness wound model confirmed faster remodeling with angiogenic signatures in CCF scaffold-implanted mice. Histopathological observations corroborated with stereo-zoom and SS-optical coherence tomography images of wound sites to prove the maturation of healing-bed, after 12 days of CCF implantation. Therefore, it is concluded that CCF scaffolds are promising for skin tissue regeneration and demonstrates pro-angiogenic potential.

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

We developed insulin loaded biomimetic microsphere by laccase-mediated crosslinking using a microfluidic device in the water-in-oil emulsion system as an injectable vehicle for the repair of sciatic tissue. Aqueous polymeric solution of phenol-substituted hyaluronic acid (HAPh) and collagen (ColPh) containing insulin and laccase flowed from the inner channel into oil flow within an outer channel which leads formation of hydrogel microsphere. The physical properties of prepared specimens including swelling rate, mechanical resistance and the prolonged release rate of microspheres proved applicability of fabricated vehicles for tissue engineering and drug delivery systems. The growth profile and behavior of cells in microspheres indicated cytocompatibility of the method and prepared vehicles for microtissue development. Histopathological examination revealed a significant increase in axonal regeneration, and remyelination process in injured sciatic nerve following treatment with HAPh/ColPh microspheres containing insulin compared to control groups. Also, the functional characteristic of sciatic tissue showed that the presence of biomimetic microsphere and insulin simultaneously had improved sciatic tissue functions including functional sciatic index (SFI) values, reaction to hot plate and muscle weight of rats. In summary, the results proved that composite biomimetic microspheres containing insulin effectively improved nerve regeneration in the rat model.