Biocompatibility and hemocompatibility of polyvinyl alcohol hydrogel used for vascular grafting--In vitro and in vivo studies

Biointegration of soft tissue-inspired hydrogels on the chorioallantoic membrane: An experimental characterization

Soft scaffold materials for cell cultures grafted onto the chorioallantoic membrane (CAM) provide innovative solutions for creating physiologically relevant environments by mimicking the host tissue. Biocompatible hydrogels represent an ideal medium for such applications, but the relationship between scaffold mechanical properties and reactions at the biological interface remains poorly understood. This study examines the attachment and integration of soft hydrogels on the CAM using an accessible ex ovo system. Composite hydrogels of polyvinyl alcohol and Phytagel were fabricated by sterile freeze-thawing. CAM assays, as an alternative to traditional in vivo models, enabled the evaluation of the compatibility, attachment, and biointegration of hydrogels with three distinct compositions. The mechanomimetic properties of the hydrogels were assessed through cyclic compression-tension tests, with nominal peak stresses ranging from 0 . 26 to 2 . 82  kPa in tension and - 0 . 33 to - 2 . 92  kPa in compression. Mechanical attachment to the CAM was measured by pull-off tests after five days of incubation. On the first day, the interface strength was similar for all hydrogel compositions. On day 5 , softer hydrogels showed the greatest increase ( p = 0 . 008 ), followed by intermediate hydrogels ( p = 0 . 020 ), while the denser hydrogels showed negligible changes ( p = 0 . 073 ). Histological analyses revealed cell infiltration in 100 % of soft, 75 % of intermediate, and 13 % of dense hydrogels, suggesting that softer hydrogels integrate better into the CAM by facilitating cell migration and enhancing interface strength. Chicken embryo survival rates and cytotoxicity assays confirmed the biocompatibility of the hydrogels and supported their potential for use in soft, hydrated three-dimensional scaffolds that mimic tissue environments in dynamic biological systems. Statement of significance Current research on soft scaffold materials for cell cultures often overlooks the critical relationship between mechanical properties and biological integration of these materials with host tissues. Although hydrogels, as soft porous materials, hold promise for creating physiologically relevant environments, the mechanisms driving their attachment and biointegration, especially on the chorioallantoic membrane (CAM), remain largely unexplored. This study addresses this gap by investigating the interaction between soft hydrogels and the CAM, providing valuable insights into how material properties and microstructure influence cellular responses. Our findings emphasize the importance of understanding these dynamics to develop biocompatible scaffolds that better mimic tissue environments, advancing applications in three-dimensional cell cultures on CAM assays and other biological systems.

Highly sensitive photoluminescence sensor based on chitosan biopolymer film for determination of hydrogen peroxide

Determination of hydrogen peroxide (H2O2) is of great importance in many systems for controlling the quality of products, food safety, and medical diagnostics. In this work, a highly sensitive photoluminescence film sensor was synthesized based on chitosan (CS), polyvinyl alcohol (PVA), and terephthalic acid (TPA), in the presence of copper (II) ions for determination of hydrogen peroxide. TPA was used as a sensitive probe for detection of hydroxyl radicals produced in a photo-Fenton-like process. Several important factors that can affect the fluorescence response of the sensor were investigated, including the irradiation time, pH, and the amount of catalyst. The response of the sensor (CS/PVA-Cu-TPA) was greatly improved by UV irradiation. The structure of the film sensor was studied by FT-IR, TGA, SEM, and X-ray mapping analysis. The highest response values were observed under the optimum conditions (0.7 % w/w Cu (II) ions, 4.25 % w/w TPA, 45 min UV irradiation, and excitation at 315 nm). This method can be applied for determination of H2O2 with a limit of detection (LOD) of about 0.1 μM and limit of quantification (LOQ) of about 0.33 μM. The practical value of the highly sensitive fluorescence sensor was illustrated by its application in milk samples.

PEGylated Platinum Nanoparticles: A Comprehensive Study of Their Analgesic and Anti-Inflammatory Effects

Pain and inflammation are common symptoms of a majority of the diseases. Chronic pain and inflammation, as well as related dreadful disorders, remain difficult to control due to a lack of safe and effective medications. In this work, biocompatible platinum nanoparticles with significant analgesic and anti-inflammatory action were synthesized through a wet chemical method using polyethylene glycol-400 as a capping agent and sodium borohydride as a reducing agent. The average particle size of these Pt nanospheres was determined to be 3.26 nm using TEM analysis, and X-ray diffraction confirmed their face-centered cubic crystalline structure. Fourier transform infrared and UV-visible spectroscopy confirm that Pt-NPs are coated with the PEG-400 molecule. The significantly negative zeta potential value (-26.8 mV) indicates the stability of the produced nanoparticles. In vitro cytotoxicity studies on normal cell lines show nontoxic behavior with over 96% cell viability at 100 μg/mL of the test sample. In vitro assays of inhibition of protein denaturation and DPPH free radical scavenging elucidated the anti-inflammatory and antioxidant properties of PEGylated Pt NPs with promising EC50 values 57.99 and 9.324 μg/mL, respectively. In vivo animal trials confirmed that PEG-capped Pt-NPs are more effective than conventional medicines. The in vivo hot plate assay for the analgesic study shows a maximum response time of 14.5 ± 1.22 s (92.54% analgesia) at a dosage of 50 mg/kg and 13.8 ± 0.71 s (86.05% analgesia) at a dosage of 25 mg/kg after 180 and 240 min of administration, respectively. In the rat paw edema model for anti-inflammatory activity, the PEG-capped Pt NPs exhibit significant inhibitory action, with the maximum percentage of edema inhibition at a dosage of 50 mg/kg identical to that of the aspirin-based standard medication administered at a higher dosage of 100 mg/kg, resulting in 42% inhibition, suggesting a versatile solution for inflammation and persistent pain.

Concentric Capillary Microfluidic Devices Designed for Robust Production of Multiple-Emulsion Droplets

Multiple emulsions are used as templates for producing functional microcapsules due to their unique core-shell geometry. Employing glass capillary devices with coaxial channels has proven effective in creating uniform multiple-emulsion droplets. However, the use of partially miscible fluids, crucial for microcapsule production, often results in clogging and disrupts the stability of these devices. Here, we introduce innovative capillary microfluidic devices with concentric capillary channels, specifically designed to optimize the production of multiple-emulsion droplets while mitigating issues of precipitation and clogging. The key aspect of these devices is their configuration of two or three concentrically aligned capillaries, which form separate, coaxial microchannels for fluid injection. This unique alignment, achieved through rotational adjustments that leverage the natural off-center positioning of tapered capillaries, facilitates the simultaneous coaxial injection of various fluids into a droplet-forming junction, significantly reducing fluid contact before emulsification. The devices, featuring double and triple concentric capillary channels, consistently produce highly uniform double-, triple-, and quadruple-emulsion droplets with precisely controlled diameters and layer thicknesses. The minimal contact between fluids prior to emulsification in these devices broadens the usable range of fluid combinations, heralding new possibilities in microcapsule development for pharmaceutical and cosmetic applications.

Engineering Tough and Elastic Polyvinyl Alcohol-Based Hydrogel with Antimicrobial Properties

Hydrogels have been extensively used for tissue engineering applications due to their versatility in structure and physical properties, which can mimic native tissues. Although significant progress has been made towards designing hydrogels for soft tissue repair, engineering hydrogels that resemble load-bearing tissues is still considered a great challenge due to their specific mechano-physical demands. Here, we report microporous, tough, yet highly compressible poly(vinyl alcohol) (PVA)-based hydrogels for potential applications in repairing or replacing different load-bearing tissues. The synergy of freeze-thawing and the Hofmeister effect, which controlled the spatial arrangement and aggregation of polymer chains, facilitated the formation of micro-structured frameworks with tunable porosity. While the maximum mechanical strength, toughness, and stretchability of the engineered hydrogel were ~390 kPa, ~388 kJ/m3, and ~170%, respectively, the Young's modulus based on compression testing was found to be in the range of ~0.02 - 0.30 MPa, highlighting the all-in-one mechanically enriched nature of the hydrogel system. Furthermore, the minimal swelling and degradation rate of the engineered hydrogel met the specific requirements of load-bearing tissues. Finally, excellent antibacterial resistance as well as in vitro biocompatibility of the hydrogel demonstrated its potential for the replacement of load-bearing tissues.

Recent Advances in the Fabrication and Performance Optimization of Polyvinyl Alcohol Based Vascular Grafts

Cardiovascular disease is one of the diseases with the highest morbidity and mortality rates worldwide, and coronary artery bypass grafting (CABG) is a fast and effective treatment. More researchers are investigating in artificial blood vessels due to the limitations of autologous blood vessels. Despite the availability of large-diameter vascular grafts (Ø > 6 mm) for clinical use, small-diameter vascular grafts (Ø < 6 mm) have been a challenge for researchers to overcome in recent years. Vascular grafts made of polyvinyl alcohol (PVA) and PVA-based composites have excellent biocompatibility and mechanical characteristics. In order to gain a clearer and more specific understanding of the progress in PVA vascular graft research, particularly regarding the preparation methods, principles, and functionality of PVA vascular graft, this article discusses the mechanical properties, biocompatibility, blood compatibility, and other properties of PVA vascular graft prepared or enhanced with different blends using various techniques that mimic natural blood vessels. The findings reveal the feasibility and promising potential of PVA or PVA-based composite materials as vascular grafts.

Fabrication, characterization and numerical validation of a novel thin-wall hydrogel vessel model for cardiovascular research based on a patient-specific stenotic carotid artery bifurcation

In vitro vascular models, primarily made of silicone, have been utilized for decades for studying hemodynamics and supporting the development of implants for catheter-based treatments of diseases such as stenoses and aneurysms. Hydrogels have emerged as prominent materials in tissue-engineering applications, offering distinct advantages over silicone models for fabricating vascular models owing to their viscoelasticity, low friction, and tunable mechanical properties. Our study evaluated the feasibility of fabricating thin-wall, anatomical vessel models made of polyvinyl alcohol hydrogel (PVA-H) based on a patient-specific carotid artery bifurcation using a combination of 3D printing and molding technologies. The model's geometry, elastic modulus, volumetric compliance, and diameter distensibility were characterized experimentally and numerically simulated. Moreover, a comparison with silicone models with the same anatomy was performed. A PVA-H vessel model was integrated into a mock circulatory loop for a preliminary ultrasound-based assessment of fluid dynamics. The vascular model's geometry was successfully replicated, and the elastic moduli amounted to 0.31 ± 0.007 MPa and 0.29 ± 0.007 MPa for PVA-H and silicone, respectively. Both materials exhibited nearly identical volumetric compliance (0.346 and 0.342% mmHg-1), which was higher compared to numerical simulation (0.248 and 0.290% mmHg-1). The diameter distensibility ranged from 0.09 to 0.20% mmHg-1 in the experiments and between 0.10 and 0.18% mmHg-1 in the numerical model at different positions along the vessel model, highlighting the influence of vessel geometry on local deformation. In conclusion, our study presents a method and provides insights into the manufacturing and mechanical characterization of hydrogel-based thin-wall vessel models, potentially allowing for a combination of fluid dynamics and tissue engineering studies in future cardio- and neurovascular research.

Implantable, Bioresorbable Radio Frequency Resonant Circuits for Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is widely used in clinical care and medical research. The signal-to-noise ratio (SNR) in the measurement affects parameters that determine the diagnostic value of the image, such as the spatial resolution, contrast, and scan time. Surgically implanted radiofrequency coils can increase SNR of subsequent MRI studies of adjacent tissues. The resulting benefits in SNR are, however, balanced by significant risks associated with surgically removing these coils or with leaving them in place permanently. As an alternative, here the authors report classes of implantable inductor-capacitor circuits made entirely of bioresorbable organic and inorganic materials. Engineering choices for the designs of an inductor and a capacitor provide the ability to select the resonant frequency of the devices to meet MRI specifications (e.g., 200 MHz at 4.7 T MRI). Such devices enhance the SNR and improve the associated imaging capabilities. These simple, small bioelectronic systems function over clinically relevant time frames (up to 1 month) at physiological conditions and then disappear completely by natural mechanisms of bioresorption, thereby eliminating the need for surgical extraction. Imaging demonstrations in a nerve phantom and a human cadaver suggest that this technology has broad potential for post-surgical monitoring/evaluation of recovery processes.

Biosynthesis of MgO Nanoparticles and Their Impact on the Properties of the PVA/Gelatin Nanocomposites for Smart Food Packaging Applications

Fabricating active and intelligent packaging materials has become the highest demand for catering to market needs, especially after the COVID-19 pandemic, for ensuring food safety. Thus, the wider objective of this article was to promote active and smart packaging biofilms possessing antibacterial and humidity-sensing properties for sustainable poly(vinyl alcohol) (PVA)/gelatin (Ge) reinforced with biosynthesized magnesium nanoparticles (MgO NPs) by a solvent-casting route. The UV-visible spectrum has been utilized to determine the optimized biosynthesized MgO NPs and then the nanostructure of optimized MgO NPs investigated by varying techniques such as XRD, SEM-EDX, TEM, FT-IR, and thermogravimetric analysis. Four MgO NPs proportions (i.e., 1, 3, 5, and 10 wt %) were used to fabricate PVA/Ge biofilms. In the biofilms system, the tensile results showcased that the nanocomposite film containing 5 wt % of MgO NPs had the highest tensile strength value (i.e., 22.10 MPs) compared to the other biofilms or the unfilled blank (i.e., 6.30 MPs). Correspondingly, the humidity-sensing data revealed that the PVA/Ge-1% MgO NPs sensor had higher sensitivity over a broad range of relative humidity from (7-97% RH) and at 100 Hz. Additionally, the hydrophobicity of biofilms, measured by water contact angle, UV-stability, and antioxidant and antibacterial properties was also analyzed to possibly use these biofilms in active food packaging with extended shelf life of foodstuffs. However, the PVA/Ge-1% MgO NPs biofilm was predominately found to possess attractive sensing properties and could be considered as a sensor for intelligent food packaging.

Preparation of a Dual-Functional Sulfated Galactofucan Polysaccharide/Poly(vinyl alcohol) Hydrogel to Promote Macrophage Recruitment and Angiogenic Potential in Diabetic Wound Healing

A diabetic foot ulcer is a common high-risk complication in diabetic patients, but there is still no universal dressing for clinical treatment. In this study, a novel dual-functional sulfated galactofucan polysaccharide/poly(vinyl alcohol) hydrogel (DPH20) is developed during freeze-thaw cycles. Experimental results indicated that DPH20 had a high specific surface area, a dense porous structure, and a good swelling property, which could effectively adsorb the exudates and keep the wound moist. Furthermore, DPH20 exhibited remarkably recruited macrophage capability and accelerated the inflammation stage by improving the expression of the mRNA of CCL2, CCR2, and CCL22 in macrophages. DPH20 could promote cell migration and growth factor release to accelerate tube formation under hyperglycemic conditions in cell models of L929s and HUEVCs, respectively. Significantly, DPH20 accelerates the reconstruction of the full-thickness skin wound by accelerating the recruitment of macrophages, promoting angiogenesis, and releasing the growth factor in the diabetic mouse model. Collectively, DPH20 is a promising multifunctional dressing to reshape the damaged tissue environment and accelerate wound healing. This study provides an efficient strategy to repair and regenerate diabetic skin ulcers.

Functionally Graded Bioactive Composites Based on Poly(vinyl alcohol) Made through Thiol-Ene Click Reaction

Functionally graded materials (FGMs) composed of a polymer matrix embedded with calcium phosphate particles are preferred for bone tissue engineering, as they can mimic the hierarchical and gradient structure of bones. In this study, we report the design and development of a FGM based on thiolated poly(vinyl alcohol) (TPVA) and nano-hydroxyapatite (nano-HA) with graded bioactivity, cell compatibility, and degradability properties that are conducive for bone regeneration. The polymer matrix comprises crosslinked poly(vinyl alcohol) with ester and thioether linkages formed via the thiol-ene click reaction, avoiding undesired additives and byproducts. Freshly precipitated and spray-dried HA was mixed with the TPVA hydrogel, and layers of varying concentrations were cast. Upon lyophilization, the hydrogel structure yielded porous sheets of the graded composite of TPVA and nano-HA. The new FGM showed higher values of tensile strength and degradation in phosphate buffer saline (PBS) in vitro, compared to bare TPVA. The bioactive nature of the FGM was confirmed through bioactivity studies in simulated body fluid (SBF), while cytocompatibility was demonstrated with human periodontal ligament cells in vitro. Cumulatively, our results indicate that based on the composition, mechanical properties, bioactivity, and cytocompatibility, the fabricated TPVA-HA composites can find potential use as guided bone regeneration (GBR) membranes.

Enzyme-Catalyzed Polymerization Process: A Novel Approach to the Preparation of Polyaniline Colloidal Dispersions with an Immunomodulatory Effect

A green, nature-friendly synthesis of polyaniline colloidal particles based on enzyme-assisted oxidation of aniline with horseradish peroxidase and chitosan or poly(vinyl alcohol) as steric stabilizers was successfully employed. Physicochemical characterization revealed formation of particles containing the polyaniline emeraldine salt and demonstrated only a minor effect of polymer stabilizers on particle morphology. All tested colloidal particles showed in vitro antioxidation activity determined via scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. In vitro, they were able to reduce oxidative stress and inhibit the production of reactive oxygen species by neutrophils and inflammatory cytokines by macrophages. The anti-inflammatory effect observed was related to their antioxidant activity, especially in the case of neutrophils. The particles can thus be especially advantageous as active components of biomaterials modulating the early stages of inflammation. In addition to the immunomodulatory effect, the presence of intrinsically conducting polyaniline can impart cell-instructive properties to the particles. The approach to particle synthesis that we employed─an original one using environmentally friendly and biocompatible horseradish peroxidase─represents a smart way of preparing conducting particles with unique properties, which can be further modified by the stabilizers used.

A Rare Ultra-Long-Term Complication of Occluder Recanalization Due to Spontaneous Perforation of Polyvinyl Alcohol Membrane of Atrial Septal Defect Occluder: A Case Report and Review of the Literature

Percutaneous closure of atrial septal defect (ASD) has emerged as a feasible alternative strategy to surgical repair in many cardiac centers worldwide. Occluder recanalization due to device failure is a rare and severe complication that often occurs within weeks to years after ASD closure. We reported a rare ultra-long-term complication of occluder recanalization due to delayed spontaneous perforation of polyvinyl alcohol (PVA) membrane of ASD occluder after 18 years of ASD closure. Surgical removal of the faulty device and reconstruction of the atrial septum with a bovine pericardial patch was performed. The patient was discharged and recovered uneventfully without syncope or residual shunt. The cause of this rare complication of spontaneous PVA membrane perforation of the occluder has not been fully detected. To our knowledge, this is the first report about PVA membrane perforation of an occluder that occurred soon after ASD closure.

Development of Lepidium sativum Extracts/PVA Electrospun Nanofibers as Wound Healing Dressing

Lepidium sativum L. (Garden cress/Hab El Rashad) (Ls), family Brassicaceae, has considerable importance in traditional medicine worldwide because of its antioxidant and anti-inflammatory activities. Ls fruits were used in Ayurvedic medicines as a useful drug for injuries, skin, and eye diseases. The aim of this study was to examine the effectiveness of the total ethanol extract (TEE) and polysaccharide (Poly) of Ls seeds loaded on poly(vinyl alcohol) (PVA) nanofibers (NFs) as a wound healing dressing and to correlate the activity with the constituents of each. TEE and Poly were phytochemically analyzed qualitatively and quantitatively. Qualitative analysis proved the presence of phenolic acids, flavonoids, tannins, sterols, triterpenes, and mucilage. Meanwhile, quantitative determinations were carried out spectrophotometrically for total phenolic and total flavonoid contents. High-performance liquid chromatography (HPLC) for TEE identified 15 phenolic acids and flavonoid compounds, with gallic acid and catechin as the majors. Separation, purification, and identification of the major compounds were achieved through a Puriflash system, column Sephadex LH20, and spectroscopic data (¹H, ¹³C NMR, and UV). Eight compounds (gallic acid, catechin, rutin, kaempferol-3-O-rutinoside, quercetin-3-O-rhamnoside, kaempferol-3-O-rhamnoside, quercetin, and kaempferol) were obtained. Gas-liquid chromatography (GLC) analysis for Poly identified 11 compounds, with galactose being the main. The antioxidant activity for both extracts was measured by three different methods based on different mechanisms: 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing ability of plasma (FRAP), and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS). TEE has the highest effectiveness as an antioxidant agent with IC₅₀ 82.6 ± 8.35 μg/mL for DPPH and 772.47 and 758.92 μM Trolox equivalent/mg extract for FRAP and ABTS, respectively. The PVA nanofibers (NFs) for each sample were fabricated by electrospinning. The fabricated NFs were characterized by SEM and Fourier transform infrared spectroscopy (FTIR); the results revealed successful encapsulation of TEE and Poly in the prepared NFs. Moreover, the swelling index of TEE in the prepared NFs shows that it is the most appropriate for use as a wound dressing. Cytotoxicity studies indicated a high cell viability with IC₅₀ 216 μg/mL and 1750 μg/mL for TEE and Poly, respectively. Moreover, the results revealed that nanofibers possess higher cell viability compared to solutions with the same sample quantities: 9-folds for TEE and 4-folds for Poly of amount 400 μg. The in vitro wound healing test showed that the TEE nanofibers performed better than Poly nanofibers in accelerating wound healing, with 90% for TEE, more than that for the Poly extract (82%), after 48 h. These findings implied that the incorporation of TEE in PVA nanofibers was more efficient than incorporation of Poly in improving the biological activity in wound healing. In conclusion, the TEE and polysaccharides of L. sativum L seed are ideal candidates for nanofibrous wound dressings. Furthermore, the contents of phenolic acids and flavonoids in TEE, which have potential antioxidant activity, make the TEE of L. sativum more favorable for wound healing dressing.

Magnetic Soft Materials and Robots

In conventional classification, soft robots feature mechanical compliance as the main distinguishing factor from traditional robots made of rigid materials. Recent advances in functional soft materials have facilitated the emergence of a new class of soft robots capable of tether-free actuation in response to external stimuli such as heat, light, solvent, or electric or magnetic field. Among the various types of stimuli-responsive materials, magnetic soft materials have shown remarkable progress in their design and fabrication, leading to the development of magnetic soft robots with unique advantages and potential for many important applications. However, the field of magnetic soft robots is still in its infancy and requires further advancements in terms of design principles, fabrication methods, control mechanisms, and sensing modalities. Successful future development of magnetic soft robots would require a comprehensive understanding of the fundamental principle of magnetic actuation, as well as the physical properties and behavior of magnetic soft materials. In this review, we discuss recent progress in the design and fabrication, modeling and simulation, and actuation and control of magnetic soft materials and robots. We then give a set of design guidelines for optimal actuation performance of magnetic soft materials. Lastly, we summarize potential biomedical applications of magnetic soft robots and provide our perspectives on next-generation magnetic soft robots.

Low Concentrated Fractionalized Nanofibers as Suitable Fillers for Optimization of Structural–Functional Parameters of Dead Space Gel Implants after Rectal Extirpation

Dead space after rectal resection in colorectal surgery is an area with a high risk of complications. In this study, our goal was to develop a novel 3D implant based on composite hydrogels enriched with fractionalized nanofibers. We employed, as a novel approach in abdominal surgery, the application of agarose gels functionalized with fractionalized nanofibers on pieces dozens of microns large with a well-preserved nano-substructure. This retained excellent cell accommodation and proliferation, while nanofiber structures in separated islets allowed cells a free migration throughout the gel. We found these low-concentrated fractionalized nanofibers to be a good tool for structural and biomechanical optimization of the 3D hydrogel implants. In addition, this nano-structuralized system can serve as a convenient drug delivery system for a controlled release of encapsulated bioactive substances from the nanofiber core. Thus, we present novel 3D nanofiber-based gels for controlled release, with a possibility to modify both their biomechanical properties and drug release intended for 3D lesions healing after a rectal extirpation, hysterectomy, or pelvic exenteration.

Poly(vinyl alcohol)-tannic Acid Cryogel Matrix as Antioxidant and Antibacterial Material

The biocompatible, viscoelastic properties of poly(vinyl alcohol) (PVA) in combination with the antimicrobial and antioxidant natural polyphenolic, tannic acid (TA), and the natural flavonoid and antioxidant curcumin (Cur), were used in the preparation of PVA:TA and PVA:TA:Cur cryogel composites using cryotropic gelation to combine the individually beneficial properties. The effect of TA content on the antioxidant and antimicrobial activities of PVA:TA cryogel composites and the antioxidant activities of PVA:TA:Cur cryogel composites was determined using Trolox equivalent antioxidant capacity (TEAC) and total phenol content (TPC) assays, and were compared. The PVA:TA:Cur cryogel composite showed the highest antioxidant activity, with a TEAC value of 2.10 ± 0.24 and a TPC value of 293 ± 12.00. The antibacterial capacity of the PVA:TA and PVA:TA:Cur 1:1:0.1 cryogel composites was examined against two different species of bacteria, E. coli and S. aureus. It was found that the minimum inhibition concentration (MIC) value of the PVA:TA:Cur 1:1:0.1 cryogel composites varied between 5 and 10 mg/mL based on the type of microorganism, and the minimum bactericidal concentration (MBC) value was 20 mg/mL irrespective of the type of microorganism. Furthermore, the hemocompatibility of the PVA:TA cryogel composites was evaluated by examining their hemolytic and coagulation behaviors. PVA:TA 1:1 cryogels with a value of 95.7% revealed the highest blood clotting index value amongst all of the synthesized cryogels, signifying the potential for blood contacting applications. The release of TA and Cur from the cryogel composites was quantified at different pH conditions, i.e., 1.0, 7.4, and 9.0, and additionally in ethanol (EtOH) and an ethanol-water (EtOH:Wat) mixture. The solution released from the PVA:TA cryogels in PBS was tested for inhibition capability against α-glucosidase (E.C. 3.2.1.20). Concentration-dependent enzyme inhibition was observed, and 70 µL of 83 µg/mL PVA:TA (1:1) cryogel in PBS inhibited α-glucosidase enzyme solution of 0.03 unit/mL in 70 µL by 81.75 ± 0.96%.

Design of 3D Scaffolds for Hard Tissue Engineering: From Apatites to Silicon Mesoporous Materials

Advanced bioceramics for bone regeneration constitutes one of the pivotal interests in the multidisciplinary and far-sighted scientific trajectory of Prof. Vallet Regí. The different pathologies that affect osseous tissue substitution are considered to be one of the most important challenges from the health, social and economic point of view. 3D scaffolds based on bioceramics that mimic the composition, environment, microstructure and pore architecture of hard tissues is a consolidated response to such concerns. This review describes not only the different types of materials utilized: from apatite-type to silicon mesoporous materials, but also the fabrication techniques employed to design and adequate microstructure, a hierarchical porosity (from nano to macro scale), a cell-friendly surface; the inclusion of different type of biomolecules, drugs or cells within these scaffolds and the influence on their successful performance is thoughtfully reviewed.

Subcutaneous toxicity of a dual ionically cross-linked atelocollagen and sodium hyaluronate gel: Rat in vivo study for biological safety evaluation of the injectable hydrogel

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Hydrogel wound dressings are commonly used to stop bleeding and enhance healing.

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Hyaluronic acid and collagen are beneficial for wound healing, however, each polymer has limitations.

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A dual hydrogel combining the benefits of both biopolymers can be more effective for the treatment of various wound types.

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A composite of collagen and sodium hyaluronate did not generate significant subacute toxicity or reactivity in vivo.

Hydrogels are commonly used in wound dressing, as they retain moisture, accelerate healing, and break down necrotic tissue. This process enhances patient comfort levels while simultaneously reducing pain caused by dead tissue. The purpose of this study was to investigate the in vivo toxicity of a dual hydrogel consisting of type I atelocollagen cross-linked with sodium hyaluronate hydrogel used for wound dressing.

Porcine type I atelocollagen was cross-linked with sodium hyaluronate to form the hydrogel. For subcutaneous implantation, 0.5 ml of dual hydrogel was injected into two different sites of twenty rats per group. High density polyethylene rods were implanted subcutaneously to serve as a control material. Hematological assessment, blood biochemistry, histopathological, and histological evaluations were scored and graded after 4 weeks. A bioreactivity rating was used for evaluation of subacute toxicity.

Differences observed in blood chemical analysis and hematological analysis between control and test groups were within normal variations and considered unrelated to the test article implantation. No significant implantation-related lesions were observed in any of the major organs of all test animals. The overall histopathological index of the test article implantation sites was evaluated as 0. The bioreactivity rating was evaluated as non-irritant after 4-week subcutaneous implantation.

Overall, these results indicate that the dual hydrogel of type I atelocollagen and sodium hyaluronate is biologically and chemically safe for clinical application as a wound dressing.

Radiopharmaceutical and Eu3+ doped gadolinium oxide nanoparticles mediated triple-excited fluorescence imaging and image-guided surgery

Cerenkov luminescence imaging (CLI) is a novel optical imaging technique that has been applied in clinic using various radionuclides and radiopharmaceuticals. However, clinical application of CLI has been limited by weak optical signal and restricted tissue penetration depth. Various fluorescent probes have been combined with radiopharmaceuticals for improved imaging performances. However, as most of these probes only interact with Cerenkov luminescence (CL), the low photon fluence of CL greatly restricted it's interaction with fluorescent probes for in vivo imaging. Therefore, it is important to develop probes that can effectively convert energy beyond CL such as β and γ to the low energy optical signals. In this study, a Eu3+ doped gadolinium oxide (Gd2O3:Eu) was synthesized and combined with radiopharmaceuticals to achieve a red-shifted optical spectrum with less tissue scattering and enhanced optical signal intensity in this study. The interaction between Gd2O3:Eu and radiopharmaceutical were investigated using 18F-fluorodeoxyglucose (18F-FDG). The ex vivo optical signal intensity of the mixture of Gd2O3:Eu and 18F-FDG reached 369 times as high as that of CLI using 18F-FDG alone. To achieve improved biocompatibility, the Gd2O3:Eu nanoparticles were then modified with polyvinyl alcohol (PVA), and the resulted nanoprobe PVA modified Gd2O3:Eu (Gd2O3:Eu@PVA) was applied in intraoperative tumor imaging. Compared with 18F-FDG alone, intraoperative administration of Gd2O3:Eu@PVA and 18F-FDG combination achieved a much higher tumor-to-normal tissue ratio (TNR, 10.24 ± 2.24 vs. 1.87 ± 0.73, P = 0.0030). The use of Gd2O3:Eu@PVA and 18F-FDG also assisted intraoperative detection of tumors that were omitted by preoperative positron emission tomography (PET) imaging. Further experiment of image-guided surgery demonstrated feasibility of image-guided tumor resection using Gd2O3:Eu@PVA and 18F-FDG. In summary, Gd2O3:Eu can achieve significantly optimized imaging property when combined with 18F-FDG in intraoperative tumor imaging and image-guided tumor resection surgery. It is expected that the development of the Gd2O3:Eu nanoparticle will promote investigation and application of novel nanoparticles that can interact with radiopharmaceuticals for improved imaging properties. This work highlighted the impact of the nanoprobe that can be excited by radiopharmaceuticals emitting CL, β, and γ radiation for precisely imaging of tumor and intraoperatively guide tumor resection.

Sesquiterpene-Loaded Co-Polymer Hybrid Nanoparticle Effects on Human Mast Cell Surface Receptor Expression, Granule Contents, and Degranulation

Biodegradable polymeric nanoparticles (NPs) such as poly(lactic-co-glycolic acid) (PLGA) and polyvinyl alcohol (PVA) have been used as drug delivery systems for natural and synthetic compounds and are designed to control the loading and release of biodegradable materials to target cells, tissues, and organs. Eremophilane-type sesquiterpenes have anti-inflammatory properties but are lipophilic, cytotoxic, and not biocompatible with many cells. To determine whether biodegradable PLGA/PVA could improve the biocompatibility of sesquiterpenes, sesquiterpene-loaded NPs were synthesized and their effects on human mast cells (LAD2), the major effector cells of allergic inflammation, were determined. NPs composed of PLGA/PVA and two types of sesquiterpenes (fukinone, PLGA/PVA-21 and 10βH-8α,12-epidioxyeremophil-7(11)-en-8β-ol, PLGA/PVA-22) were produced using a microfluidic synthesis method. The NPs’ size distribution and morphology were evaluated by dynamic light scattering and cryogenic transmission electron microscopy (TEM). PLGA/PVA-21 and PLGA/PVA-22 were 60 to 70 nm and were readily internalized by LAD2 as shown by flow cytometry, fluorescence microscopy, and TEM. While unencapsulated sesquiterpenes decreased LAD2 cell viability by 20%, PLGA/PVA-21 and PLGA/PVA-22 did not alter LAD2 viability, showing that encapsulation improved the biocompatibility of the sesquiterpenes. PLGA/PVA-21 and PLGA/PVA-22 decreased the expression of genes encoding the subunits of the high affinity immunoglobulin E receptor (FcεR1α, FcεR1β, FcεR1γ) and the stem cell factor receptor (Kit,), suggesting that hybrid NPs could alter mast cell responses to antigens and shift their maturation. Similarly, PLGA/PVA-21 and PLGA/PVA-22 inhibited tryptase expression but had no effect on chymase expression, thereby promoting a shift to the tryptase-positive phenotype (MC_T). Lastly, PLGA/PVA-21 and PLGA/PVA-22 inhibited mast cell degranulation when the LAD2 cells were activated by IgE crosslinking and FcεRI. Overall, our results suggest that PLGA/PVA-21 and PLGA/PVA-22 alter human mast cell phenotype and activation without modifying viability, making them a more biocompatible approach than treating cells with sesquiterpenes alone.

Bacteriophage-Delivering Hydrogels: Current Progress in Combating Antibiotic Resistant Bacterial Infection

Antibiotic resistance remains as an unresolved global challenge in the health care system, posing serious threats to global health. As an alternative to antibiotics, bacteriophage (phage) therapy is rising as a key to combating antibiotic-resistant bacterial infections. In order to deliver a phage to the site of infection, hydrogels have been formulated to incorporate phages, owing to its favorable characteristics in delivering biological molecules. This paper reviews the formulation of phage-delivering hydrogels for orthopedic implant-associated bone infection, catheter-associated urinary tract infection and trauma-associated wound infection, with a focus on the preparation methods, stability, efficacy and safety of hydrogels as phage carriers.

Polyvinyl alcohol modification with sustainable ketones

Water-degradable polyvinyl ketals with high glass transition temperatures (78–127 °C) were made via ketalization of polyvinyl alcohol (PVA) with sustainable ketones.

Surface modification of electrospun silk/AMOX/PVA nanofibers by dielectric barrier discharge plasma: physiochemical properties, drug delivery and in-vitro biocompatibility

The naturally obtained protein Bombyxmori silk is a biocompatible polymer with excellent mechanical properties and have the potential in controlled drug delivery applications. In this work, we have demonstrated dielectric barrier discharge (DBD) oxygen (O2) plasma surface modified electrospun Bombyxmori silk/Amoxicillin hydrochloride trihydrate (AMOX)/polyvinyl alcohol (PVA) nanofibers for drug release applications with controlled plasma treatment duration (1-10 min). The findings indicate that plasma treated electrospun nanofibers for 1-3 min exhibited significant enhancement in tensile strength, Young's modulus, wettability and surface energy. The plasma treated electrospun nanofibers for 1-5 min showed remarkable increase in AMOX released rate, whereas the electrospun nanofibers treated with plasma irradiation beyond 5 min showed only marginal increase. Moreover, the plasma treated nanofibers also exhibited good antibacterial activity against both E. coli (gram negative) and S. aureus (gram positive) bacteria. The untreated and the plasma treated silk/AMOX/PVA electrospun nanofibers for 1-3 min showed enhanced viability of primary adipose derived mesenchymal stem cells (ADMSCs) growth on them and much less hemolysis activity (< 5%). The in vitro biocompatibility of various electrospun nanofibers were further corroborated by live/dead imaging and cytoskeletal architecture assessment demonstrating enhanced cell adhesion and spreading on the plasma treated nanofibers for 1-3 min. The findings of the present study suggest that the silk/AMOX/PVA electrospun nanofibers with plasma treatment (1-3 min) due to their enhanced drug release ability and biocompatibility can be used as potential wound dressing applications.

Multispecies Evaluation of a Long-Acting Tenofovir Alafenamide Subdermal Implant for HIV Prophylaxis

New HIV-1 infection rates far outpace the targets set by global health organizations, despite important progress in curbing the progression of the epidemic. Long-acting (LA) formulations delivering antiretroviral (ARV) agents for HIV-1 pre-exposure prophylaxis (PrEP) hold significant promise, potentially facilitating adherence due to reduced dosing frequency compared to oral regimens. We have developed a subdermal implant delivering the potent ARV drug tenofovir alafenamide that could provide protection from HIV-1 infection for 6 months, or longer. Implants from the same lot were investigated in mice and sheep for local safety and pharmacokinetics (PKs). Ours is the first report using these animal models to evaluate subdermal implants for HIV-1 PrEP. The devices appeared safe, and the plasma PKs as well as the drug and metabolite concentrations in dermal tissue adjacent to the implants were studied and contrasted in two models spanning the extremes of the body weight spectrum. Drug and drug metabolite concentrations in dermal tissue are key in assessing local exposure and any toxicity related to the active agent. Based on our analysis, both animal models were shown to hold significant promise in LA product development.

Preparation of PU/Fibrin Vascular Scaffold with Good Biomechanical Properties and Evaluation of Its Performance in vitro and in vivo

PURPOSE

The development of tissue-engineered blood vessels provides a new source of donors for coronary artery bypass grafting and peripheral blood vessel transplantation. Fibrin fiber has good biocompatibility and is an ideal tissue engineering vascular scaffold, but its mechanical property needs improvement.

METHODS

We mixed polyurethane (PU) and fibrin to prepare the PU/fibrin vascular scaffolds by using electrospinning technology in order to enhance the mechanical properties of fibrin scaffold. We investigated the morphological, mechanical strength, hydrophilicity, degradation, blood and cell compatibility of PU/fibrin (0:100), PU/fibrin (5:95), PU/fibrin (15:85) and PU/fibrin (25:75) vascular scaffolds. Based on the results in vitro, PU/fibrin (15:85) was selected for transplantation in vivo to repair vascular defects, and the extracellular matrix formation, vascular remodeling, and immune response were evaluated.

RESULTS

The results indicated that the fiber diameter of the PU/fibrin (15:85) scaffold was about 712nm. With the increase of PU content, the mechanical strength of the composite scaffolds increased, however, the degradation rate decreased gradually. The PU/fibrin scaffold showed good hydrophilicity and hemocompatibility. PU/fibrin (15:85) vascular scaffold could promote the adhesion and proliferation of mesenchymal stromal cells (MSCs). Quantitative RT-PCR experimental results showed that the expression of collagen, survivin and vimentin genes in PU/fibrin (15:85) was higher than that in PU/fibrin (25:75). The results in vivo indicated the mechanical properties and compliance of PU/fibrin grafts could meet clinical requirements and the proportion of thrombosis or occlusion was significantly lower. The graft showed strong vasomotor response, and the smooth muscle cells, endothelial cells, and ECM deposition of the neoartery were comparable to that of native artery after 3 months. At 3 months, the amount of macrophages in PU/fibrin grafts was significantly lower, and the secretion of pro-inflammatory and anti-inflammatory cytokines decreased.

CONCLUSION

PU/fibrin (15:85) vascular scaffolds had great potential to be used as small-diameter tissue engineering blood vessels.

Advances in translational orthopaedic research with species-specific multipotent mesenchymal stromal cells derived from the umbilical cord

Compliance with current regulations for the development of innovative medicines require the testing of candidate therapies in relevant translational animal models prior to human use. This poses a great challenge when the drug is composed of cells, not only because of the living nature of the active ingredient but also due to its human origin, which can subsequently lead to a xenogeneic response in the animals. Although immunosuppression is a plausible solution, this is not suitable for large animals and may also influence the results of the study by altering mechanisms of action that are, in fact, poorly understood. For this reason, a number of procedures have been developed to isolate homologous species-specific cell types to address preclinical pharmacodynamics, pharmacokinetics and toxicology. In this work, we present and discuss advances in the methodologies for derivation of multipotent Mesenchymal Stromal Cells derived from the umbilical cord, in general, and Wharton's jelly, in particular, from medium to large animals of interest in orthopaedics research, as well as current and potential applications in studies addressing proof of concept and preclinical regulatory aspects.

Dual drug-loaded nano-platform for targeted cancer therapy: toward clinical therapeutic efficacy of multifunctionality

Background

Poor targeting and penetration of chemotherapy drugs in solid tumors, and the development of resistance to chemotherapeutic agents are currently hindering the therapy of breast cancer; meanwhile, breast cancer metastasis is one of the leading causes of death in breast cancer patients. With the development of nanotechnology, nanomaterials have been widely used in tumor therapy.

Results

A multi-functional nano-platform containing gambogic acid (GA) and paclitaxel (PTX) was characterized by a small size, high encapsulation efficiency, slow release, long systemic circulation time in vivo, showed good targeting and penetrability to tumor tissues and tumor cells, and exhibited higher anti-tumor effect and lower systemic toxicity in BALB/c mice bearing 4T1 tumor. GA not only overcame the multidrug resistance of PTX by inhibiting P-glycoprotein (P-gp) activity in MCF-7/ADR cells, but also inhibited MDA-MB-231 cells migration and invasion, playing a crucial role in preventing and treating the lung metastasis of breast cancer caused by PTX; meanwhile, the synergistic anti-tumor effect of GA and PTX has also been verified in vitro and in vivo experiments.

Conclusion

Our data described the better recognition and penetration of tumor cells of R9dGR-modified versatile nanosystems containing GA and PTX, which exerted one stone three birds clinical therapeutic efficacy of multifunctionality.

Opto-acoustic synergistic irradiation for vaporization of natural melanin-cored nanodroplets at safe energy levels and efficient sono-chemo-photothermal cancer therapy

Rationale: Insufficient penetration and accumulation of theranostic payloads in solid tumors greatly challenge the clinical translation of cancer nanomedicines. To address this challenge, we synthesized natural melanin-cored and doxorubicin-loaded perfluoropentane nanodroplets with good biocompatibility and self-assembling ability. Methods: We used an opto-acoustic synergistic irradiation (OASI) method that was effective at lower energy levels than ultrasound- or laser-only irradiation to safely vaporize the nanodroplets and to cavitate the generated microbubbles for mechanically enhancing intratumoral delivery. The delivered melanin and doxorubicin inside the tumors mediated secondary chemo-photothermal therapy under laser irradiation to fully kill cancer cells. Results: In vivo animal experiments demonstrated direct mechanical disruption of tumor structures (H&E staining), enhanced intratumoral penetration of melanin (photoacoustic imaging), and efficient intratumoral accumulation of doxorubicin (fluorescent imaging). Anti-tumor experiments demonstrated that the nanodroplets combined with OASI treatment and subsequent laser irradiation could efficiently eliminate melanoma tumors. Conclusion: Melanin-cored and doxorubicin-loaded perfluoropentane nanodroplets hold great promise for translational sono-chemo-photothermal cancer therapy.

Synthesis and Characterization of Zwitterionic Polymer Brush Functionalized Hydrogels with Ionic Responsive Coefficient of Friction

Freeze-thaw poly(vinyl alcohol) hydrogels (PVA-H) offer great potential for several biomedical applications due to their biomimetic mechanical properties and biocompatibility. Despite these advantages, the use of PVA-H for load bearing applications has been limited due to poor performance in boundary lubrication compared to natural tissue such as articular cartilage. Recently, zwitterionic polymer brushes have been shown to act as effective boundary lubricants on rigid substrates; however, to the best of our knowledge, the synergistic effects of zwitterionic brushes coupled with the biomimetic fluid load support exhibited by hydrogels have not been reported. We report here on our investigation involving the synthesis and characterization of two unique types of polymer brush functionalized PVA hydrogels. The zwitterionic polymers that were compared contained either [2-(methacryloyloxy)ethyl]dimethyl-3-sulfopropylammonium hydroxide, PMEDSAH, or 2-methacryloyloxyethylphosphorylcholine, PMPC, repeating units. Both hydrogels coated with zwitterionic polymers were found to be cytocompatible. We report further on micrometer-scale surface properties via water contact angle goniometry, surface roughness measurements, and scanning electron microscopy. Finally, the impact of brush functionalization on the mechanics of the tribologically enhanced gels is reported with comparison to natural articular cartilage within the context of Hertzian contact theory.

Self-Powered, Self-Healed, and Shape-Adaptive Ultraviolet Photodetectors

The emergence of self-healing devices in recent years has drawn a great amount of attention in both academics and industry. Self-healed devices can autonomically restore a rupture as unexpected destruction occurs, which can efficiently prolong the life span of the devices; hence, they have an enhanced durability and decreased replacement cost. As a result, integration of wearable devices with self-healed electronics has become an indispensable issue in smart wearable devices. In this study, we present the first self-powered, self-healed, and wearable ultraviolet (UV) photodetector based on the integration of agarose/poly(vinyl alcohol) (PVA) double network (DN) hydrogels, which have the advantages of good mechanical strength, self-healing ability, and tolerability of multiple types of damage. With the integration of a DN hydrogel substrate, the photodetector enables 90% of the initial efficiency to be restored after five healing cycles, and each rapid healing time is suppressed to only 10 s. The proposed device has several merits, including having an all spray coating, self-sustainability, biocompatibility, good sensitivity, mechanical flexibility, and an outstanding healing ability, which are all essential to build smart electronic systems. The unprecedented self-healed photodetector expands the future scope of electronic skin design, and it also offers a new platform for the development of next-generation wearable electronics.

One-Pot Covalent Grafting of Gelatin on Poly(Vinyl Alcohol) Hydrogel to Enhance Endothelialization and Hemocompatibility for Synthetic Vascular Graft Applications

Cardiovascular diseases remain the leading cause of death worldwide. Patency rates of clinically-utilized small diameter synthetic vascular grafts such as Dacron® and expanded polytetrafluoroethylene (ePTFE) to treat cardiovascular disease are inadequate due to lack of endothelialization. Sodium trimetaphosphate (STMP) crosslinked PVA could be potentially employed as blood-compatible small diameter vascular graft for the treatment of cardiovascular disease. However, PVA severely lacks cell adhesion properties, and the efforts to endothelialize STMP-PVA have been insufficient to produce a functioning endothelium. To this end, we developed a one-pot method to conjugate cell-adhesive protein via hydroxyl-to-amine coupling using carbonyldiimidazole by targeting residual hydroxyl groups on crosslinked STMP-PVA hydrogel. Primary human umbilical vascular endothelial cells (HUVECs) demonstrated significantly improved cells adhesion, viability and spreading on modified PVA. Cells formed a confluent endothelial monolayer, and expressed vinculin focal adhesions, cell-cell junction protein zonula occludens 1 (ZO1), and vascular endothelial cadherin (VE-Cadherin). Extensive characterization of the blood-compatibility was performed on modified PVA hydrogel by examining platelet activation, platelet microparticle formation, platelet CD61 and CD62P expression, and thrombin generation, which showed that the modified PVA was blood-compatible. Additionally, grafts were tested under whole, flowing blood without any anticoagulants in a non-human primate, arteriovenous shunt model. No differences were seen in platelet or fibrin accumulation between the modified-PVA, unmodified PVA or clinical, ePTFE controls. This study presents a significant step in the modification of PVA for the development of next generation in situ endothelialized synthetic vascular grafts.

Bi-Layered Polymer Carriers with Surface Modification by Electrospinning for Potential Wound Care Applications

Polymeric wound dressings with advanced properties are highly preferred formulations to promote the tissue healing process in wound care. In this study, a combinational technique was investigated for the fabrication of bi-layered carriers from a blend of polyvinyl alcohol (PVA) and sodium alginate (SA). The bi-layered carriers were prepared by solvent casting in combination with two surface modification approaches: electrospinning or three-dimensional (3D) printing. The bi-layered carriers were characterized and evaluated in terms of physical, physicochemical, adhesive properties and for the safety and biological cell behavior. In addition, an initial inkjet printing trial for the incorporation of bioactive substances for drug delivery purposes was performed. The solvent cast (SC) film served as a robust base layer. The bi-layered carriers with electrospun nanofibers (NFs) as the surface layer showed improved physical durability and decreased adhesiveness compared to the SC film and bi-layered carriers with patterned 3D printed layer. Thus, these bi-layered carriers presented favorable properties for dermal use with minimal tissue damage. In addition, electrospun NFs on SC films (bi-layered SC/NF carrier) provided the best physical structure for the cell adhesion and proliferation as the highest cell viability was measured compared to the SC film and the carrier with patterned 3D printed layer (bi-layered SC/3D carrier). The surface properties of the bi-layered carriers with electrospun NFs showed great potential to be utilized in advanced technical approach with inkjet printing for the fabrication of bioactive wound dressings.

Ovalbumin-Loaded Gelation Microneedles Made of Predictive Formulation by Molecular Dynamics Simulation for Enhancement of Skin Immunization

Gelation microneedle (GMNs) based vaccinations with tumor antigens have been considered to be an attractive method for transcutaneous immunization because of their superior ability to deliver vaccines through the stratum corneum (SC) in a minimally invasive manner, which subsequently induces adaptive antitumor immunity. In this study, molecular dynamics (MD) uniaxial tension simulations were conducted to predict the formulation of poly(vinyl alcohol) (PVA; possesses high water solubility) and poly(methyl vinyl ether-altmaleic anhydride) (PMVEMA; possesses high mechanical strength) blend that has the strongest mechanical properties. To validate the accuracy of the Dreiding potential for these two polymers, their densities and Hildebrand solubility parameters were first predicted using MD simulations. These values exhibited good agreement with the corresponding experimental results, indicating the accuracy of the Dreiding potential for the polymers. Regarding the simulation results, the number density of H-bonds between PVA and PMVEMA was the highest at 50% PMVEMA, which can significantly enhance the mechanical strength of pristine PVA for enhanced skin immunization. In terms of further experimental validation, evidence from mechanical strength, solubility, in vitro porcine skin penetration tests, and in vivo immunization were consistent with our simulation predictions. In addition, our results indicated that delivery of ovalbumin (OVA) using GMN patches fabricated using PVA/PMVEMA (50%/50%) provided even stronger immune responses. Using this molecular simulation procedure, the optimal fraction of PVA/PMVEMA composite for the strongest mechanical properties can be rapidly predicted to reduce research time and costs in related experiments.

Pullulan/Poly(Vinyl Alcohol) Composite Hydrogels for Adipose Tissue Engineering

Composite hydrogels based on pullulan (HP) and poly(vinyl alcohol) (PVA) were both prepared by simple chemical crosslinking with sodium trimethaphosphate (STMP) or by dual crosslinking (simultaneously chemical crosslinking with STMP and physical crosslinking by freeze-thaw technique). The resulting hydrogels and cryogels were designed for tissue engineering applications. PVA, with two different molecular weights (47,000 and 125,000 g/mol; PVA₄₇ and PVA₁₂₅, respectively), as well as different P/PVA weight ratios were tested. The physico-chemical characterization of the hydrogels was performed by FTIR spectroscopy and scanning electron microscopy (SEM). The swelling kinetics, dissolution behavior, and degradation profiles in simulated physiological conditions (phosphate buffer at pH 7.4) were investigated. Pullulan concentration and the crosslinking method had significant effects on the pore size, swelling ratio, and degradation profiles. Cryogels exhibit lower swelling capacities than the conventional hydrogels but have better stability against hydrolitic degradation. Biocompatibility of the hydrogels was also investigated by both MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and LDH (lactaten dehydrogenase) assay. The MTT and LDH assays proved that dual crosslinked HP/PVA₁₂₅ (75:25, w/w) scaffolds are more biocompatible and promote to a greater extent the adhesion and proliferation of L929 murine fibroblast cells than chemically crosslinked HP/PVA₄₇ (50/50, w/w) scaffolds. Moreover, the HP/PVA₁₂₅ cryogel had the best ability for the adipogenic differentiation of cells. The overall results demonstrated that the HP/PVA composite hydrogels or cryogels are suitable biomaterials for tissue engineering applications.

Hydrogel Small-Diameter Vascular Graft Reinforced with a Braided Fiber Strut with Improved Mechanical Properties

Acute thrombosis remains the main limitation of small-diameter vascular grafts (inner diameter <6 mm) for bridging and bypassing of small arteries defects and occlusion. The use of hydrogel tubes represents a promising strategy. However, their low mechanical strength and high swelling tendency may limit their further application. In the present study, a hydrogel vascular graft of Ca alginate/polyacrylamide reinforced with a braided fiber strut was designed and fabricated with the assistance of a customized casting mold. Morphology, structure, swellability, mechanical properties, cyto- and hemocompatibility of the reinforced graft were characterized. The results showed that the reinforced graft was transparent and robust, with a smooth surface. Scanning electron microscopic examination confirmed a uniform porous structure throughout the hydrogel. The swelling of the reinforced grafts could be controlled to 100%, obtaining clinically satisfactory mechanical properties. In particular, the dynamic circumferential compliance reached (1.7 ± 0.1)%/100 mmHg for 50-90 mmHg, a value significantly higher than that of expanded polytetrafluoroethylene (ePTFE) vascular grafts. Biological tests revealed that the reinforced graft was non-cytotoxic and had a low hemolysis percentage (HP) corresponding to (0.9 ± 0.2)%. In summary, the braided fiber-reinforced hydrogel vascular grafts demonstrated both physical and biological superiority, suggesting their suitability for vascular grafts.

The use of fractionated Kraft lignin to improve the mechanical and biological properties of PVA-based scaffolds

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved. The improvements in mechanical properties correlated with the amount of Kraft lignin in PVA matrices. The critical property for any scaffold is its capacity to allow cells to ingrow and survive within its internal structure. The ingrowth of cells was tested using bioreactors creating simulated in vivo conditions. In the context of all the mentioned parameters, the most advantageous properties were exhibited by the scaffold containing 99 wt% PVA and 1 wt% Kraft lignin. The composites with 1 wt% Kraft lignin exhibited sufficient mechanical stability, a lack of cytotoxicity, and mainly the ability to allow the ingrowth of cells into the scaffold in a rotation bioreactor.

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved.

Dental pulp stem cells and Bonelike® for bone regeneration in ovine model

Development of synthetic bone substitutes has arisen as a major research interest in the need to find an alternative to autologous bone grafts. Using an ovine model, the present pre-clinical study presents a synthetic bone graft (Bonelike^®) in combination with a cellular system as an alternative for the regeneration of non-critical defects. The association of biomaterials and cell-based therapies is a promising strategy for bone tissue engineering. Mesenchymal stem cells (MSCs) from human dental pulp have demonstrated both in vitro and in vivo to interact with diverse biomaterial systems and promote mineral deposition, aiming at the reconstruction of osseous defects. Moreover, these cells can be found and isolated from many species. Non-critical bone defects were treated with Bonelike^® with or without MSCs obtained from the human dental pulp. Results showed that Bonelike^® and MSCs treated defects showed improved bone regeneration compared with the defects treated with Bonelike^® alone. Also, it was observed that the biomaterial matrix was reabsorbed and gradually replaced by new bone during the healing process. We therefore propose this combination as an efficient binomial strategy that promotes bone growth and vascularization in non-critical bone defects.

Reactive Ion Plasma Modification of Poly(Vinyl-Alcohol) Increases Primary Endothelial Cell Affinity and Reduces Thrombogenicity

Bulk material properties and luminal surface interaction with blood determine the clinical viability of vascular grafts, and reducing intimal hyperplasia is necessary to improve their long-term patency. Here, the authors report that the surface of a biocompatible hydrogel material, poly(vinyl alcohol) (PVA) can be altered by exposing it to reactive ion plasma (RIP) in order to increase primary endothelial cell attachment. The power and the carrier gas of the RIP treatment are varied and the resultant surface nitrogen, water contact angle, as well as the ability of the RIP-treated surfaces to support primary endothelial colony forming cells is characterized. Additionally, in a clinically relevant shunt model, the amounts of platelet and fibrin attachment to the surface were quantified during exposure to non-anticoagulated blood. Treatments with all carrier gases resulted in an increase in the surface nitrogen. Treating PVA with O2 , N2 , and Ar RIP increased affinity to primary endothelial colony forming cells. The RIP treatments did not increase the thrombogenicity compared to untreated PVA and had significantly less platelet and fibrin attachment compared to the current clinical standard of expanded polytetrafluoroethylene (ePTFE). These findings indicate that RIP-treatment of PVA could lead to increased patency in synthetic vascular grafts.

Human umbilical cord blood plasma as an alternative to animal sera for mesenchymal stromal cells in vitro expansion - A multicomponent metabolomic analysis

Mesenchymal Stromal cells (MSCs) have a potential role in cell-based therapies. Foetal bovine serum (FBS) is used to supplement the basal cell culture medium but presents several disadvantages and risks. Other alternatives have been studied, including human umbilical cord blood plasma (hUCBP), aiming at the development of xeno-free culturing protocols. A comparative characterization of multicomponent metabolic composition of hUCBP and commercial FBS based on Nuclear Magnetic Resonance (NMR) spectroscopy and multivariate statistical analysis was performed. The analysis of ¹H-NMR spectra revealed both similarities and differences between the two proposed supplements. Similar metabolites (amino acids, glucose, lipids and nucleotides) were found in the hUCBP and FBS NMR spectra. The results show that the major difference between the metabolic profiles of the two proposed supplements are due to the significantly higher levels of glucose and lower levels of lactate, glutamate, alanine and branched chain amino acids in hUCBP. Similar or slightly different levels of important proteinogenic amino acids, as well as of nucleotides, lipids were found in the hUCBP and FBS. In order to validate it’s suitability for cell culture, umbilical cord-MSCs (UC-MSCs) and dental pulp stem cells (DPSCs) were expanded using hUCBP. In both hMSCs, in vitro culture with hUCBP supplementation presented similar to improved metabolic performances when compared to FBS. The two cell types tested expressed different optimum hUCBP percentage content. For DPSCs, the optimum hUCBP content was 6% and for UC-MSCs, 4%. Cultured hMSCs displayed no changes in senescence indicators, as well as maintained characteristic surface marker’s expression. FBS substitution was associated with an increase in early apoptosis events, in a dose dependent manner, as well as to slight up- and down-regulation of targeted gene’s expression. Tri-lineage differentiation capacity was also influenced by the substitution of FBS by hUCBP.

Design, characterization and in vivo performance of synthetic 2 mm-diameter vessel grafts made of PVA-gelatin blends

Since the development of the first vascular grafts, fabrication of vessel replacements with diameters smaller than 6 mm remains a challenge. The present work aimed to develop PVA (poly (vinyl alcohol))-gelatin hybrids as tubes suitable for replacement of very small vessels and to evaluate their performance using a rat abdominal aorta interposition model. PVA-gelatin hybrid tubes with internal and external diameters of 1.4 mm and 1.8 mm, respectively, composed of 4 different gelatin ratios were prepared using a one-step strategy with both chemical and physical crosslinking. By 3D Time of Flight MRI, Doppler-Ultrasound, Computed Tomography angiography and histology, we demonstrated good patency rates with the 1% gelatin composition until the end of the study at 3 months (50% compared to 0% of PVA control grafts). A reduction of the patency rate during the time of implantation suggested some loss of properties of the hybrid material in vivo, further confirmed by mechanical evaluation until one year. In particular, stiffening and reduction of compliance of the PVA-gelatin grafts was demonstrated, which might explain the observed long-term changes in patency rate. These encouraging results confirm the potential of PVA-gelatin hybrids as ready-to-use vascular grafts for very small vessel replacement.