Alginate Hydrogel Research Articles

A stable HOF-embedded alginate hydrogel membrane for selective adsorption of cationic dyes.

Targeted at organic dye pollutants, a stable HOF was combined with an alginate (SA) hydrogel to enhance the affinity for cationic dyes. The as-obtained HOF@SA membrane (weight ratio: 1/1) shows a high adsorption capacity (729.21 mg g-1), adsorption selectivity and good recycling performance towards methylene blue.

DNA Aptamers That Bind to Alginate Hydrogels.

Hydrogels have become common in wound treatment because they form very stable and biocompatible environments that promote healing. However, due to the highly porous hydrogel structure, any therapeutic added to these gels tends to diffuse quickly and impact delivery to the target site. Aptamers are short, single-stranded DNA or RNA sequences that bind specifically to a target, so aptamers that bind to hydrogels could serve as tags for therapeutics to prevent rapid diffusion and allow for extended delivery. An in vitro selection approach was developed to identify DNA aptamers for alginate hydrogels. Two DNA aptamers were shown to bind hydrogels ranging from 0.5 to 2% alginate and could be either encapsulated during gelation or introduced to preformed gels. Both aptamers also showed specificity for binding to alginate compared to agarose. To demonstrate the functional aspect of the aptamers as tethers for other biomolecules, both aptamers were conjugated to BSA. Aptamer-conjugated BSA was retained longer in the hydrogel during week-long diffusion studies both when encapsulated or introduced to preformed gels, which adds flexibility to how these aptamers can be deployed in a clinical setting.

High-Resolution Atomic Force Microscopy Investigation of Alginate Hydrogel Materials in Aqueous Media.

Alginate hydrogels are frequently used in 3D bioprinting and tissue repair and regeneration. Establishing the structure-property-performance correlation of these materials would benefit significantly from high-resolution structural characterization in aqueous environments from the molecular level to continuum. This study overcomes technical challenges and enables high-resolution atomic force microscopy (AFM) imaging of hydrated alginate hydrogels in aqueous media. By combining a new sample preparation protocol with extremely gentle tapping mode AFM imaging, we characterized the morphology and regional mechanical properties of the hydrated alginate. Upon cross-linking, basic units of these hydrogel materials consist of egg-box dimers, which assemble into long fibrils. These fibrils congregate and pile up, forming a sponge-like structure, whose pore size and distribution depend on the cross-linking conditions. At the exterior, surface tension impacts the piling of fibrils, leading to stripe-like features. These structural features contribute to local, regional, and macroscopic mechanics. The outcome provides new insights into its structural characteristics from nanometers to tens of micrometers, i.e., at the dimensions pertaining to biomaterial and hydrogel-cell interactions. Collectively, the results advance our knowledge of the structure and mechanics from the nanometer to continuum, facilitating advanced applications in hydrogel biomaterials.

Spherical Shell Bioprinting to Produce Uniform Spheroids with Controlled Sizes.

Conventional cell spheroid production methods are largely manual, leading to variations in size and shape that compromise consistency and reliability for use in cell-based therapeutic applications. To enhance spheroid production, a spherical shell bioprinting system was implemented, enabling the high-throughput generation of uniform cell spheroids with precisely controlled sizes. The system encapsulates cells within thin alginate hydrogel shells formed through bioprinting and ion crosslinking reactions. Alginate-calcium ion crosslinking created alginate shells that contained gelatin-based bioinks with embedded cells, facilitating spontaneous cell aggregation within the shells and eliminating the need for plastic wells. By adjusting cell concentrations in the alginate-gelatin bioink, we achieved precise control over spheroid size, maintaining a sphericity above 0.94 and size deviations within ±10 µm. This method has been successfully applied to various cell types including cancer cells, fibroblasts, chondrocytes, and epithelial cells, demonstrating its versatility. This scalable approach enhances the reliability of cell therapy and drug screening, offering a robust platform for future biomedical applications.

Impact of extract of cryopreserved pig heart fragments in alginate hydrogel on electrophysiological indicators of rat hearts with myocardial cryonecrosis

Background. The issue of stimulating reparative myocardial regeneration in ischemic heart disease (IHD) is a pressing one, requiring in-depth experimental and clinical research. Consequently, considerable attention is currently being paid to studies on the effectiveness and mechanisms of action of regenerative plastic therapy for pathological conditions of the cardiovascular system. To prevent cardiac aneurysms in the early post-infarction period and to treat progressive chronic heart failure, biodegradable polymer hydrogels, including alginate polysaccharide hydrogels, are used as surgical implants. Purpose – analysis of electrophysiological indicators of the heart during the development of necrosis and organ remodeling in a myocardial cryodestruction model and the introduction of an alginate implant saturated with an extract of cryopreserved pig heart fragments to determine the cardioprotective effect of these factors. Materials and Methods. Electrocardiograms (ECGs) were recorded in three standard leads (I, II, III) and three additional leads (aVR, aVL, aVF) using the «PolySpectrum/8V» hardware-software complex («Poly-Spectrum», Ukraine). The «PolySpectrum-Analysis» software allows for contour analysis of the averaged cardiocomplex. Initially, we conducted an experiment to assess the impact of sodium alginate hydrogel alone on electrocardiographic parameters without heart cryoinjury. Subsequently, the experimental animals were divided into three groups: 1 – control group, animals with myocardial necrosis (MN) without treatment; 2 – rats with MN and an implant (sodium alginate hydrogel) introduced into the cryonecrosis area; 3 – rats with MN and an alginate implant saturated with cryopreserved pig heart extract (CPHE) introduced into the cryonecrosis area. The normal group consisted of 7 rats. Results. The use of an extract from cryopreserved heart fragments of piglets, delivered via an alginate carrier, in the context of myocardial infarction induced by local cryodestruction of the heart, significantly accelerates the recovery of the left ventricular myocardium compared to both the control group and the experimental groups receiving alginate hydrogel alone. This is supported by electrocardiographic evidence: a positive P wave on the first day indicates the preservation of the myocardial excitation source at the sinoatrial node level; recovery of the R wave to normal levels by the seventh day reflects the restoration of myocardial contractile function; and on the 30th day, the group treated with the ECP in alginate gel shows a QRS complex shape that conforms to normal standards, with minimal cardiac remodeling as evidenced by the absence of a Q wave in the ECG. In contrast, up to 40% of animals in other groups exhibit signs of transmural myocardial necrosis, indicated by the persistent presence of the Q wave. Conclusions. Analysis of the electrocardiograms (ECGs) of healthy rats after the introduction of the alginate hydrogel into the heart muscle showed that the correct sinus rhythm is maintained, and the QRS-T complexes retain their shape and duration, indicating that the alginate implant does not cause pathological changes in the ECG. It was demonstrated that the alginate implant, when introduced into the myocardial infarction area, is an indifferent substance that does not exacerbate destructive and inflammatory processes and can be used as a carrier for biologically active substances or drugs for delivery to the damaged area. On the 30th day of observation, in the group with CPHE in the alginate gel, the shape of the QRS complex corresponds to the norm, and signs of heart remodeling are minimal, as evidenced by the absence of animals with a registered Q wave. In contrast, up to 40% of animals in other groups show signs of previous transmural myocardial necrosis with the persistence of the Q wave on the ECG.

Development of Alginate Hydrogels Incorporating Essential Oils Loaded in Chitosan Nanoparticles for Biomedical Applications.

A hybrid alginate hydrogel-chitosan nanoparticle system suitable for biomedical applications was prepared. Chitosan (CS) was used as a matrix for the encapsulation of lavender (Lavandula angustifolia) essential oil (LEO) and Mentha (Mentha arvensis) essential oil (MEO). An aqueous solution of an acidic Natural Deep Eutectic Solvent (NADES), namely choline chloride/ascorbic acid in a 2:1 molar ratio, was used to achieve the acidic environment for the dissolution of chitosan and also played the role of the ionic gelator for the preparation of the chitosan nanoparticles (CS-NPs). The hydrodynamic diameter of the CS-MEO NPs was 130.7 nm, and the size of the CS-LEO NPs was 143.4 nm (as determined using Nanoparticle Tracking Analysis). The CS-NPs were incorporated into alginate hydrogels crosslinked with CaCl2. The hydrogels showed significant water retention capacity (>80%) even after the swollen sample was kept in the aqueous HCl solution (pH 1.2) for 4 h, indicating a good stability of the network. The hydrogels were tested (a) for their ability to absorb dietary lipids and (b) for their antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens. The antimicrobial activity of the hybrid hydrogels was comparable to that of the widely used food preservative sodium benzoate 5% w/v.

Injectable alginate chitosan hydrogel as a promising bioengineered therapy for acute spinal cord injury

Dealing with spinal cord injuries presents problematic due to multiple secondary mechanisms. Beyond primary concerns like paralysis and disability, complications including urinary, gastrointestinal, cardiac, and respiratory disorders, along with substantial economic burdens may occur. Limited research focuses on modeling and treating contusion and compression injuries. Tissue engineering emerges as an innovative treatment, targeting lesion pathophysiology. This study was evaluated implanting injectable biomaterials into injury-induced cavity before glial scar formation, avoiding tissue incisions and minimizing further damage. The efficacy of injectable alginate/thiolated chitosan hydrogel was investigated for acute spinal cord injury induced by Vanický method in Wistar rats. Three days post-injury, hydrogel was administrated through microinjection after laminectomy. After 60 days, the hydrogel group demonstrated notable motor function enhancement compared to the control by the BBB locomotor test (P < 0.05). However, no statistically significant differences were observed in MRI assessment concerning lesion severity. Stereological and histopathological evaluations revealed a reduction in vacuole volume and the presence of axon profiles within the scaffold (P < 0.05), alongside reduced infiltration of inflammatory and Gitter cells in the hydrogel group, although the latter was not statistically significant compared to the control. Thiolated chitosan/ alginate hydrogel implantation may be regarded as a promising treatment to enhance motor function by restraining destructive processes post-acute spinal cord injury.

Green synthesis of benzimidazole derivatives using copper(II)-supported on alginate hydrogel beads

The study addresses the challenge of developing sustainable and efficient catalytic systems for the synthesis of benzimidazole derivatives, which are of significant importance in the field of medicinal chemistry due to their diverse biological activities. The objective is to develop a recyclable and environmentally friendly catalyst utilizing copper(II)-loaded alginate hydrogel beads, which can facilitate the synthesis of these compounds while minimizing environmental impact. The preparation process entails crosslinking sodium alginate with copper(II) ions to form hydrogel beads, which are then washed and characterized through techniques such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Inductively coupled plasma (ICP), and Zeta potential to analyses the morphology, composition and porosity of the beads. The catalytic performance is evaluated through recycling tests, which demonstrate the catalyst's ability to maintain selectivity and activity over multiple reaction cycles. The Cu(II)-Alg hydrogel beads were used for synthesizing substituted benzimidazole derivatives in a water-ethanol solvent at room temperature. This method offers significant advantages, including extremely mild reaction conditions, short reaction times (<1 h), high yields (70–94 %), and ease of processing. The most significant results indicate that the Cu(II)-alginate catalyst exhibits a high loading capacity and retains its catalytic efficiency for at least 3 cycles, thereby highlighting its potential for sustainable applications in organic synthesis.

Enhanced catalytic efficiency and ionic liquid tolerance of entrapped cellulase for single-step mixed cabbage residue saccharification

This study explores the enhancement of catalytic efficiency and 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) tolerance in the single-step saccharification of mixed cabbage residue (MCR) biomass using entrapped cellulase. Entrapping cellulase in calcium alginate hydrogel beads achieved an entrapment efficiency of 75.90 ± 1.83 %. In hydrolysis systems with 2 % and 10 % [Emim][OAc], the entrapped cellulase demonstrated 5.3 % and 6.5 % higher activity than free cellulase, respectively. After five cycles, the entrapped cellulase retained 93 % and 87 % of its initial activity in 0 % and 2 % [Emim][OAc] hydrolysis systems, respectively. Remarkably, cumulative glucose yields with entrapped cellulase were 3.51 and 3.10 times greater than those with free cellulase in 0 % and 2 % [Emim][OAc] hydrolysis systems, respectively. These results highlight the superior performance of entrapped cellulase in maintaining enzyme activity and improving glucose yields. Notably, while [Emim][OAc] is effective in separate pretreatment stages, its addition is unnecessary for the single-step saccharification of MCR biomass. This study underscores the promising potential of entrapped cellulase as a catalyst in enhancing the efficiency of biomass saccharification processes.

The role of multivalent cations in determining the cross-linking affinity of alginate hydrogels: A combined experimental and modeling study

This study explores the development of a comprehensive mathematical model to predict the cross-link density of alginate hydrogels using varying concentrations of divalent and trivalent ions. By systematically investigating the effects of Ca²⁺, Ba²⁺, Cu²⁺, Sr²⁺, Mg²⁺, Fe3⁺ and Al³⁺, the research describes the relationship between ion concentration and cross-link density. Experimental data reveals that the type and concentration of these ions critically influence the mechanical properties of the resulting hydrogels, with trivalent ions such as Fe³⁺ forming stronger, triple cross-links that significantly enhance the hydrogel's mechanical strength. Among the divalent ions, the trend in binding affinity is as follows: Ba²⁺ with the highest affinity followed by Sr²⁺, Ca²⁺ and Cu²⁺, while Mg²⁺ stands out with the lowest affinity, significantly differing from the others. The deviation of Cu²⁺ (transition metal ion) from the expected trend in ion interactions suggests that coordination chemistry, along with ionic radius, valence, and cation coordination abilities, plays a significant role in determining interaction strength with alginate. The proposed model, enhanced with fitting parameters k1 and k2 to account for ion-specific effects, leverages the unique binding affinities and coordination chemistry of each ion to tailor alginate hydrogels for specific applications. The parameter k1 reflects the affinity of the ions for the alginate chains, while k2 captures the coordination abilities and cross-linking efficiency. This work not only advances the understanding of ion-mediated cross-linking in alginate systems but also offers a valuable tool for the design and optimization of hydrogels with precise mechanical properties governed by various applications.

Unraveling size-dependent catalytic activity of monolithic alginate hydrogels for PMS activation and ciprofloxacin removal

Unraveling size-dependent catalytic activity of monolithic alginate hydrogels for PMS activation and ciprofloxacin removal

Optimization of hydrogel extrusion printing process parameters based on numerical simulation

The printing quality of biological scaffold is not only affected by the fluidity of bio-ink but also by the printing process parameters, such as the size of the needle, printing height, extrusion speed, and printing speed. Therefore, optimizing the printing process parameters can further improve the molding quality of the biological scaffold. In this study, the printing and deposition process of sodium alginate hydrogel was modeled and analyzed based on the Herschel–Bulkley model by the finite element simulation method. The orthogonal experiment method, control variable method, and response surface method were used to design experiments, and the influences of different printing process parameters on the hydrogel deposition process were investigated. Finally, the optimal combination of printing process parameters was obtained by taking the molding degree and offset of the hydrogel line as optimization objectives. The results show that the strength relationship of the factors affecting the molding degree of the hydrogel line is as follows: printing height &amp;gt; needle diameter &amp;gt; printing speed &amp;gt; extrusion speed, and the strength relationship of the factors affecting the printing offset is as follows: printing height &amp;gt; needle diameter &amp;gt; extrusion speed &amp;gt; printing speed. The optimal combination of printing process parameters is d = 0.34 mm, H = 0.51 mm, v1 = 10 mm/s, and v2 = 7.91 mm/s. Compared with the printing experiment results of the hydrogel line molding degree under the optimal process parameters, the error range is within −11.55%–1.27%, which further demonstrates the reliability of the optimization method of hydrogel extrusion printing process parameters based on numerical simulation and response surface method.

A Stone‐Cottage‐Inspired Printing Strategy to Build Microsphere Patterned Scaffolds for Accelerated Bone Regeneration

AbstractThe physical microtopography, in an effective and stable manner, can powerfully confer biomaterials with enhanced osteoconduction for the repair of critical‐sized bone defects. However, the realization of the osteoconductive microtopography within a 3D porous scaffold is still unmet. Herein, this work presents a stone‐cottage‐inspired printing strategy to build microsphere patterned scaffolds with a tunable microtopography for accelerated bone regeneration. The customized composite inks of poly (lactic‐co‐glycolic acid) microspheres as “Stone” and alginate hydrogels as “Mortar” endow the fibers of as‐printed scaffolds with a stable and tunable groove‐ridge microstructure. Owing to this microtopography, microsphere patterned scaffolds significantly promote cell recruitment, immune response, angiogenesis, and osteogenesis. Meanwhile, compared to 55 and 85 µm, 25 µm width of groove‐ridge microstructure displays the most osteoconduction for repair of critical bone defects. Mechanistically, while cells prefer to adhere to microstructure with a bigger width and higher modulus in the early phase, this microstructure should also act as a barrier for cell growth and its smaller width is more beneficial for cell communication and differentiation in the later phase. Overall, it provides a robust strategy to fabricate the osteoconductive microtopography within a 3D scaffold, broadening the manipulation of physical morphology in tissue engineering.

Encapsulation of gallic acid in alginate/lactoferrin composite hydrogels: Physical properties and gallic acid diffusion

Alginate hydrogel is commonly utilized to encapsulate hydrophilic polyphenols because of its biocompatibility and flexibility. However, encapsulation with neat alginate gel is prone to uncontrolled compound diffusion during gel formation and storage. Previous research have demonstrated the electrostatic complexation of lactoferrin and alginate, nonetheless, no study has been reported on the combination of these polymers as hydrophilic polyphenol encapsulation agent. Therefore, this research aims to explore the encapsulation of gallic acid (GA), a representative of water-soluble polyphenol, in the lactoferrin-alginate composite hydrogel. The composite hydrogel of sodium alginate-lactoferrin (S-L) was prepared in solid-basis ratios of 1:0, 1:1, 2:0, 2:1, 2:2, and 2:3. The evaluation was conducted on the alginate-lactoferrin mixture viscosity, gel syneresis, gel strength and stiffness, dried gel rehydration properties, porosity, GA diffusion, and gel microstructure. Images of SEM and CLSM microscopy revealed relatively compact structures created by evenly distributed lactoferrin in the hydrogel system. According to the gel electrophoresis analysis, composite alginate-lactoferrin gel hindered the diffusion of compounds with molecular weight >50 kDa. The addition of lactoferrin to the GA-loaded alginate composite hydrogel significantly increased the retention of GA (87.1–92.2%) in the gel. The GA-loaded composite hydrogel with the alginate to lactoferrin ratio of 2:1 and 2:2 (pH 5.24–5.43) exhibited significantly better (P > 0.05) gallic acid retention compared to the neat alginate hydrogel (pH 5.16) in their natural pH. FTIR analysis revealed a hydrogen bond between lactoferrin and the gallic acid phenolic group, while the zeta-potential analysis showed the intermolecular interaction between positive-charged lactoferrin and negative-charged alginate. This work provides important information for the development of hydrogel-based polyphenol encapsulating materials.

Durable fluorinated cobalt oxyhydroxide/calcium alginate hydrogels for activating peroxymonosulfate to enable nearly 100% degradation of ciprofloxacin.

Peroxymonosulfate (PMS) activation by solid catalysts for ciprofloxacin (CIP) removal is a promising method for decontaminating wastewater. However, mainstream catalysts suffer from efficiency and durability issues due to mechanical fragility and structural instability. Here, we have developed a durable calcium alginate hydrogel encapsulating fluorinated cobalt oxyhydroxide (FCO/CAH), fabricated by a simple hydrogen-bond-assisted cross-linking reaction, to enhance PMS activation for complete CIP removal. The optimized 2-FCO/CAH could generate abundant singlet oxygen (1O2) and sulfate radicals (SO4˙-) with PMS, resulting in 0.433 min-1 kinetic constant and approximately 100% CIP degradation within 10 minutes. This exceptional degradation efficiency is due to the even distribution of 2-FCO, which maximizes catalytic sites for PMS activation, and the multichannel cavity structure of CAH, which effectively enriches both PMS and CIP. Furthermore, the durability of 2-FCO/CAH was proved by its negligible decay in CIP removal efficiency (∼100%) and good microstructure retention after 6 consecutive cycles, facilitated by a stable surface reconstructed interphase on the 2-FCO surface and the strong mechanical property of 2-FCO/CAH. Our work showcases a facile approach to constructing durable hydrogel catalysts that improve PMS-mediated antibiotic degradation.

Sensitivity-enhanced optical fiber probe-type humidity sensor based on CaAlg film

Optical fiber probe-type humidity sensors based on calcium alginate (CaAlg) hydrogel films are proposed. The sensor is based on the Michelson interferometer (MI) and constructed by splicing a tapered multimode fiber (MMF) in the middle of two single-mode fibers (SMFs). One of the 1.5 cm long SMFs is coated with CaAlg hydrogel film and can be regarded as the sensor probe. The sensitivity of the sensor is 0.31015 nm/%RH. The high sensitivity, low temperature crosstalk, compact probe structure, and stability of the sensor allow it to be used for humidity monitoring in a variety of complex environments.

3D-printed artificial cornea featuring aligned fibrous structure and enhanced mechanical strength

The global shortage of donor eye bank tissue has significantly impeded advancements in biomaterial for corneal implantation. To address this issue, we have developed a 3D-printed artificial cornea using a composite hydrogel of sodium alginate (SA) and cellulose nanofibers (CNF), crosslinked with poly-L-lysine-co-L-glutamic acid (PLL80GA20, PG) and calcium chloride (CaCl2, CC). The 2 wt% SA/CNF composite hydrogel offers several advantages, including low toxicity, cost-effectiveness, excellent printability, and high mechanical strength, even with low crosslinker concentrations. The PG was synthesized via ring-opening polymerization of L-glutamate N-carboxyl anhydride (BGNCA) and L-lysine N-carboxyl anhydride (CBZNCA). The purity of the monomers was verified through DSC analysis, revealing a melting point of 97 ℃. The molecular weight of the synthesized PG was determined to be 47 kDa. A dual crosslinking strategy was employed, starting with electrostatic crosslinking, followed by ionic crosslinking using varying concentrations of PG and CC at different effective charge concentrations of 6.25 mM, 12.25 mM, and 25 mM. The hydrogel and 3D-printed cornea were comprehensively evaluated for chemical structure, surface functional groups, water content, mechanical strength, orientation, cytotoxicity, biocompatibility, and transparency. Notably, the inclusion of PG significantly enhanced the mechanical properties of the 3D-printed cornea, with the hydrogel achieving a storage modulus of 2,360 kPa at 6.25 mM of PG/CC, while maintaining over 95% water content. The artificial cornea demonstrated 86% transparency, and the cell viability showed 96% viable on Day 7 with degradation rate of 35.9% in 28 days. The superior hydrophilicity, transparency, and mechanical strength of the printed hydrogel highlights its potential for the development of full-thickness corneal structures, making it a promising candidate for future corneal implants.

Alginate-chitosan hydrogel formulations for VEGFA expressed baculovirus delivery promoting angiogenesis for wound healing and revascularization

Abstract Background Baculoviruses, engineered to express growth factors, offer a promising avenue for short-term gene therapy, such as wound dressings, due to their safety and specificity. Encapsulation in natural polymers like alginate and chitosan addresses limitations like serum inactivation and fragility, while promoting sustained delivery and shielding from immune inactivation. Wound healing involves complex processes that can be enhanced by maintaining an antimicrobial, moist environment, which promotes cell migration and angiogenesis. Vascular endothelial cell growth factor A (VEGFA) is known to be one of the most potent pro-angiogenic factors and plays a key role in wound healing. Purpose This investigation seeks to enhance wound healing and angiogenesis, support the revascularization process, and provide anti-inflammatory and anti-microbial effects. Additionally, it aims to assess the preclinical efficacy and safety of the approach. Methods Ionic cross-linking was used for virus encapsulation under aseptic conditions. The capsules were assessed for their surface morphology, particle size, zeta potential, and in vitro release profile. Additionally, their therapeutic potential was studied using cell lines. The efficacy of hydrogel delivery of VEGFA-expressing baculoviruses in promoting cell migration and angiogenesis for wound healing applications was investigated on Human Umbilical Vein Endothelial Cells (HUVECs). Hydrogel morphology, swelling, and encapsulation efficiency were evaluated, along with endothelial tube formation assays and hemocompatibility studies on HUVECs. Results Encapsulation of baculovirus expressing the VEGFA gene in alginate and chitosan–alginate hydrogels achieve a high encapsulation efficiency of 99.9%. This allows for prolonged virus delivery and an increased therapeutic window. The encapsulated baculovirus maintains activity and is released over eight days, with a transduction efficiency of over 40%. This promotes tube formation, cell proliferation, and cell migration for angiogenesis, particularly beneficial for chronic wound-healing applications. The hydrogels also prevented E. coli and C. albicans growth directly below and inhibited C. albicans growth surrounding the alginate–chitosan hydrogels. The hydrogels demonstrated no cytotoxicity and good blood compatibility. Conclusion This proof of concept underscores the potential of encapsulated baculovirus delivery systems for various gene therapy applications including cardiovascular tissue regeneration and revascularization.

Tuning porosity of macroporous hydrogels enables rapid rates of stress relaxation and promotes cell expansion and migration

Extracellular matrix (ECM) viscoelasticity broadly regulates cell behavior. While hydrogels can approximate the viscoelasticity of native ECM, it remains challenging to recapitulate the rapid stress relaxation observed in many tissues without limiting the mechanical stability of the hydrogel. Here, we develop macroporous alginate hydrogels that have an order of magnitude increase in the rate of stress relaxation as compared to bulk hydrogels. The increased rate of stress relaxation occurs across a wide range of polymer molecular weights (MWs), which enables the use of high MW polymer for improved mechanical stability of the hydrogel. The rate of stress relaxation in macroporous hydrogels depends on the volume fraction of pores and the concentration of bovine serum albumin, which is added to the hydrogels to stabilize the macroporous structure during gelation. Relative to cell spheroids encapsulated in bulk hydrogels, spheroids in macroporous hydrogels have a significantly larger area and smaller circularity because of increased cell migration. A computational model provides a framework for the relationship between the macroporous architecture and morphogenesis of encapsulated spheroids that is consistent with experimental observations. Taken together, these findings elucidate the relationship between macroporous hydrogel architecture and stress relaxation and help to inform the design of macroporous hydrogels for materials-based cell therapies.

Alginate Use in Orthopedics and Peripheral Nerve Repair: A Systematic Review.

The use of alginate, a derivative of seaweed, has been proposed for multiple orthopedic indications. We aimed to review the current use of alginate in orthopedics and to focus on the future applications of alginate for peripheral nerve repair. A comprehensive literature search was performed to identify biomechanical, laboratory, animal, and human studies where alginate has been utilized for orthopedic or nerve repair indications. A systematic review of orthopedic indications was conducted for safety and efficacy, and a specific focus was placed on alginate for use in peripheral nerve repair and reconstruction. Thirty-two studies were identified. Alginate has a strong history and safety profile for usage in orthopedic surgery. Its primary usage has been for the repair of articular cartilage, although it has also been used for disc regeneration of the lumbar spine and for cushioning joints in osteoarthritis. The primary indication in peripheral nerve repair is to create an environment that encourages Schwann cell migration and repair in nerve injuries while blocking fibrotic scar tissue formation by inhibiting the activity of fibroblasts. Alginate hydrogel may serve as a potential conduit for nerve regeneration in nerve injuries with small to medium-sized gaps.