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Polyvinyl alcohol hydrogel (PVA-H) has been widely used in clinical transplantation because of its high water content, good biocompatibility and mechanical properties. However, PVA-H have some problems, such as low elongation at break, low fatigue resistance and high friction coefficient, which hinders its application in clinic. In this paper, a novel high-performance PVA hydrogel enhanced by chemical double crosslinking (CDC) method had been synthesized. The influences of chemical crosslinking agent concentration on mechanical properties, friction properties and fatigue properties of materials were systematically investigated, in order to meet the clinical application of artificial meniscus, artificial cartilage, nucleus pulposus and so on. As a result, due to the introduction of chemical bonds, CDC hydrogels have over 600% elongation at break, modulus loss after fatigue test was reduced by 42%, average coefficient during friction was reduced to 0.048, and biocompatibility performance was excellent. The PVA hydrogel enhanced by CDC method provides a new concept for us to prepare high-performance PVA hydrogel and a promising material to replace cartilage, meniscus, nucleus pulposus and other tissues., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Many models describing the deformation of general foam or auxetic materials are based on the assumption of homogeneity and order within the materials. However, non-uniform heterogeneity is often an inherent nature in many porous materials and composites, but difficult to measure. In this work, inspired by the structures of auxetic materials, the porous PVA hydrogels with internal inby-concave pores (IICP) or interconnected pores (ICP) were designed and processed. The deformation of the PVA hydrogels under compression was tested and their Poisson's ratio was characterized. The results indicated that the size, shape and distribution of the pores in the hydrogel matrix had strong influence on the local Poisson's ratio, which varying from positive to negative at micro-scale. The size-dependency of their local Poisson's ratio reflected and quantified the uniformity and heterogeneity of the micro-porous structures in the PVA hydrogels., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In view of the problems that conventional artificial cartilages have no bioactivity and are prone to peel off in repeated uses as a result of insufficient strength to bond with subchondral bone, we have designed and prepared a novel kind of PVA-BG composite hydrogel as bionic artificial articular cartilage/bone composite implants. The effects of processes and conditions of preparation on the mechanical properties of implant were explored. In addition, the relationships between compression strain rate, BG content, PVA hydrogels thickness and compressive tangent modulus were also explicated. We also analyzed the effects of cancellous bone aperture, BG and PVA content on the shear strength of bonding interface of artificial articular cartilage with cancellous bone. Meanwhile, the bonding interface of artificial articular cartilage and cancellous bone was characterized by scanning electron microscopy. It was revealed that the compressive modulus of composite implants was correspondingly increased with the adding of BG content and the augments of PVA hydrogel thickness. The compressive modulus and bonding interface were both related to the apertures of cancellous bone. The compressive modulus of composite implants was 1.6-2.23 MPa and the shear strength of bonding interface was 0.63-1.21 MPa. These results demonstrated that the connection between artificial articular cartilage and cancellous bone was adequately firm.

Due to the non-bioactivity and poor conjunction performance of present cartilage prostheses, the main work here is to develop the bioactive glass-polyvinyl alcohol hydrogel articular cartilage/bone (BG-PVA/bone) composite implants. The essential criterion for a biomaterial to bond with living bone is well-matched mechanical properties as well as biocompatibility and bioactivity. In vitro studies on the formation of a surface layer of carbonate hydroxyl apatite (HCA) and the corresponding variation of the properties of biomaterials are imperative for their clinical application. In this paper, the mineralization behavior and variation of the interface properties of BG-PVA/bone composites were studied in vitro by using simulated body fluid (SBF). The mineralization and HCA layer formed on the interface between the BG-PVA hydrogel and bone in SBF could provide the composites with bioactivity and firmer combination. The compression property, shear strength and interface morphology of BG-PVA/bone composite implants varying with the immersion time in SBF were characterized. Also, the influence laws of the immersion time, content of BG in the composites and aperture of bones to the mineralization behavior and interface properties were investigated. The good mineralization behavior and enhanced conjunction performance of BG-PVA/bone composites demonstrated that this kind of composite implant might be more appropriate cartilage replacements.

The long-term fixation of poly(vinyl alcohol) PVA hydrogels cartilage implants on ambient tissue is a difficult problem, which is one of the obstacles for PVA hydrogels to be used as articular cartilage implants. In this work, a novel bioactive PVA/HA hydrogel was prepared by the in situ sol-gel synthesis method. Simulated experiments were performed to evaluate and compare the bioactive ability and properties of the hydrogels in simulated body fluid (SBF). Gradual-structure PVA/HA cartilage implants were developed and used to repair articular cartilage defects in rabbit knees. In vitro bioactive evaluation showed that PVA/HA hydrogels could be bio-mineralized to form bone-like hydroxyl-carbonate-apatite deposit in SBF solution. The macroscopic and histological observation of animal experiments displayed that the implanted hydrogels combined tightly with ambient tissues, and some bone-like tissue grew into the bottom of the implants from the base bone to form more deep-set binding between replacement and cartilage tissues.

In order to form firm active fixation with the adjacent bone, a new kind of bioactive composite hydrogel was prepared with polyvinyl alcohol (PVA) and bioglass (BG) through ultrasonic dispersion, heat-high-pressure and freeze/thawed technique. A digital speckle correlation method (DSCM) was utilized to characterize the mechanical properties of the series of BG/PVA composites. Results showed that at different load pressures, the composite hydrogel displayed different displacement and deformation in the V field. Results also showed that an increase of PVA percentage (15-30 wt%) or of bioglass percentage (2-10 wt%) in composite hydrogel could lead to an increase in the elastic compression modulus. Scanning electron microscope results indicated that bioglass was uniformly dispersed in the BG/PVA composite hydrogel. The BG/PVA composite hydrogel shows a promising prospect as a new bionic cartilage implantation material.

Poly(vinyl alcohol) (PVA) hydrogel is a kind of material which has excellent biocompatibility and mechanical properties. In this paper, the researches and developments of PVA hydrogel preparation and the modifications of PVA with other material were introduced. The potential for the use of PVA hydrogels as implant materials in cartilage reparation was reviewed.

The structures and properties of polyvinyl alcohol (PVA)/hydroxylapatite(HA) composites were investigated. The components and processing conditions were studied for preparation of optimum compound hydrogels with good lubricating feature and high bioactivity. The properties, such as stretch strength, compress strength, friction, compress stress relaxation of various compound hydrogels were compared. The micro-morphology of PVA hydrogels and PVA/HA hydrogels were investigated by use of SEM. It was found that the addition of HA could improve the lubricating feature and mechanical strength of hydrogels, and its compress stress relaxation properties were closer to those of natural cartilages.

Calcium sulfate hemihydrate (CaSO 4 ·1/2H 2 O; CSH) has been used for filling bone defects because of its excellent biocompatibility and injectability. Researchers have devoted in improving its performance to adapt to various demands. However, up to now, no studies have reported bone cement with expandable ability. In this study, a novel expandable bone cement was prepared with acetalized polyvinyl alchol porous material (APVA-PM) and CSH. By controlling the content of APAV-PM, composite cements with different structures and morphology were obtained and investigated by using SEM, FT-IR, XRD. The physical properties including setting time, porosity and expansion ratio were studied. CSH/APVA-PM bone cement could produce volume expansion in the setting process and form a porous structure after curing. The setting time decreased with the increase of the volume fraction of APVA-PM. APVA-PM improved the toughness of calcium sulfate cement, thus overcoming the present mechanical limitations. In vitro experiments demonstrated the CSH/APVA-PM bone cement did not show cytotoxicity and the porous structure allowed the rat bone marrow stem cells (BMSCs) to grow into the pores. Therefore, CSH/APVA-PM bone cement appeared to be useful for bone tissue engineering and can potentially serve as a new filling material. [ABSTRACT FROM AUTHOR]

This investigation describes an effective strategy to fabricate an electrochemically active hybrid hydrogel made from platinum nanoparticles that are highly dense, uniformly dispersed, and tightly embedded throughout the conducting hydrogel network for the electrochemical oxidation of glucose. A suspension of multiwalled carbon nanotubes and polyvinyl alcohol aqueous was coated on glassy carbon electrode by electrophoretic deposition and then physically crosslinked to form a three-dimensional porous conductive hydrogel network by a process of freezing and thawing. The network offered 3D interconnected mass-transport channels (around 200 nm) and confined nanotemplates for in situ growth of uniform platinum nanoparticles via the moderate reduction agent, ascorbic acid. The resulting hybrid hydrogel electrode membrane demonstrates an effective method for loading platinum nanoparticles on multiwalled carbon nanotubes by the electrostatic adsorption between multiwalled carbon nanotubes and platinum ions within porous hydrogel network. The average diameter of platinum nanoparticles is 37 ± 14 nm, which is less than the particle size by only using the moderate reduction agent. The hybrid hydrogel electrode membrane-coated glassy carbon electrode showed excellent electrocatalytic activity and good long-term stability toward glucose electrochemical oxidation. The glucose oxidation current exhibited a linear relationship with the concentration of glucose in the presence of chloride ions, promising for potential applications of implantable biofuel cells, biosensors, and electronic devices. [ABSTRACT FROM AUTHOR]

Hydrophilic nanofibers derivate from bacterial cellulose (nf-BC) were compounded with PVA colloidal sol to form physical crosslinking hybrid hydrogels. With the hydrophilic and hydrogen bonding interaction between the groups of PVA and nf-BC during the composite gel phase transformation process, a regular and uniform distributed porous structure was formed which interconnected through fibrous funicular cords composed of PVA gel along nf-BC orientation by controlling the content of nf-BC and gel transition condition. The micro-morphology, chemical structure, crystallinity and mechanical properties of the nf-BC/PVA hydrogels changed with the different proportion and distribution of nf-BC. It has been verified that hydrophilic nf-BC acts as “crosslinking agent” and reinforced phase which can guide the composite hydrogels to form more ordered and compact porous structure, via enhancing the interaction of hydrogen bonds and physical crosslinking points between nf-BC and PVA macromolecule, finally resulted in the enhancement of their mechanical performances. The composite hydrogels have broad application prospects in the field of medicine, such as artificial cartilage, blood vessel, wound dressing and so on. [ABSTRACT FROM AUTHOR]