Biomaterial Of Choice Research Articles

Poly(Propylene Carbonate)-Based Biodegradable and Environment-Friendly Materials for Biomedical Applications.

Poly(propylene carbonate) (PPC) is an emerging "carbon fixation" polymer that holds the potential to become a "biomaterial of choice" in healthcare owing to its good biocompatibility, tunable biodegradability and safe degradation products. However, the commercialization and wide application of PPC as a biomedical material are still hindered by its narrow processing temperature range, poor mechanical properties and hydrophobic nature. Over recent decades, several physical, chemical and biological modifications of PPC have been achieved by introducing biocompatible polymers, inorganic ions or small molecules, which can endow PPC with better cytocompatibility and desirable biodegradability, and thus enable various applications. Indeed, a variety of PPC-based degradable materials have been used in medical applications including medical masks, surgical gowns, drug carriers, wound dressings, implants and scaffolds. In this review, the molecular structure, catalysts for synthesis, properties and modifications of PPC are discussed. Recent biomedical applications of PPC-based biomaterials are highlighted and summarized.

Periapical Surgery with BiodentineTM as a Root-End Filling Material

MTA® is considered as the biomaterial of choice because of its excellent characteristics. Biodentine™ has been introduced into periapical surgery and has proven its efficacity in sealing root-end cavities. Despite of the desirable properties of BiodentineTM, there are limited published cases that described the use of BiodentineTM in periapical surgery.

Regeneration of deep intrabony periodontal defects with enamel matrix derivative: A case report

A clinical case of treatment of two severe intrabony defects on the aesthetic zone is reported and followed for one year. The biomaterial of choice was enamel matrix derivative (Emdogain®; Straumann™) alone with a preservation papilla flap and a minimally invasive surgical technique. After surgical treatment, the patient was kept in a supportive periodontal therapy programme with 6-month interval between appointments. In the one year after surgery appointment, clinical and radiographic changes were observed, showing periodontal health and stability.

The Collagen Suprafamily: From Biosynthesis to Advanced Biomaterial Development.

Collagen is the oldest and most abundant extracellular matrix protein that has found many applications in food, cosmetic, pharmaceutical, and biomedical industries. First, an overview of the family of collagens and their respective structures, conformation, and biosynthesis is provided. The advances and shortfalls of various collagen preparations (e.g., mammalian/marine extracted collagen, cell-produced collagens, recombinant collagens, and collagen-like peptides) and crosslinking technologies (e.g., chemical, physical, and biological) are then critically discussed. Subsequently, an array of structural, thermal, mechanical, biochemical, and biological assays is examined, which are developed to analyze and characterize collagenous structures. Lastly, a comprehensive review is provided on how advances in engineering, chemistry, and biology have enabled the development of bioactive, 3D structures (e.g., tissue grafts, biomaterials, cell-assembled tissue equivalents) that closely imitate native supramolecular assemblies and have the capacity to deliver in a localized and sustained manner viable cell populations and/or bioactive/therapeutic molecules. Clearly, collagens have a long history in both evolution and biotechnology and continue to offer both challenges and exciting opportunities in regenerative medicine as nature's biomaterial of choice.

Spatial Differences in Cellular and Molecular Responses as a Function of the Material Used in Conduit‐Mediated Repair and Autograft Treatment of Peripheral Nerve Injuries

AbstractThe treatment of peripheral nerve injuries remains a major problem worldwide despite the availability of a number of Food and Drug Administration (FDA) approved devices which fail to match the efficacy of autografts. Different strategies are used to improve regeneration and functional recovery using biomaterial nerve conduits. However, there is little investigation of the transcriptomic and proteomic changes which occur as a result of these interventions, particularly regarding transection injuries. This study explores differences between autograft‐mediated repair and conduit‐material‐mediated repair of peripheral nerve injuries to understand fundamental differences in their repair mechanisms at the proteomics level at the proximal, middle, and distal components in the early stages of repair. Pathway analysis demonstrates that each material selectively activates different regenerative pathways and alters different biological functions spatially throughout the biomaterial conduits. The analysis highlights some of the deficiencies in conduit‐mediated repair in comparison to autograft (e.g., recycling of myelin and cholesterol, reduction in reactive oxygen species, and higher expression of regenerative proteins). These findings thus suggest that by supplementing the expression of these proteins on the biomaterial of choice, this study can potentially attain regeneration equivalent to autograft. This approach paves the way for incorporating future biomaterial‐specific functionalities in nerve guidance conduits.

Improved Stress Shielding of a Coated Cemented Hip Stem by Functionally Graded Materials

Abstract Surfaces are the primary contact zones between a biomaterial and its host organism. Surface treatment or coating provides a means to fulfill demanding structural and mechanical requirements of the prostheses. As well as, a number of studies have been performed on functionally graded materials (FGM) and their suitability for use as the biomaterial of choice in various prostheses. This study investigates the effect of utilizing the two concepts of FGM and coating, in designing new hip stem material. The results of this study concluded that the optimal FGM cemented stem is consisting of titanium at the upper stem layers graded to collagen at lower stem layers. The optimal functionally graded stem coated with collagen reduced the stress shielding by 51% compared to homogenous titanium stem coated with collagen. However, this optimal graded stem coated with hydroxyapatite showed a reduction of stress shielding by 57% compared to homogenous titanium stem coated with hydroxyapatite.

Stem Cells in Alginate Bioscaffolds

The immobilization of cells into polymeric scaffolds releasing therapeutic factors, such as alginate microcapsules, has been widely employed as a drug-delivery system for numerous diseases for many years. As a result of the potential benefits stem cells offer, during recent decades, this type of cell has gained the attention of the scientific community in the field of cell microencapsulation technology and has opened many perspectives. Stem cells represent an ideal tool for cell immobilization and so does alginate as a biomaterial of choice in the elaboration of these biomimetic scaffolds, offering us the possibility of benefiting from both disciplines in a synergistic way. This review intends to give an overview of the many possibilities and the current situation of immobilized stem cells in alginate bioscaffolds, showing the diverse therapeutic applications they can already be employed in; not only drug-delivery systems, but also tissue engineering platforms.

Polyvinyl alcohol as a viable membrane in artificial tissue design and development

Polyvinyl alcohol (PVA) membranes have long been used in many applications, most notably in a number of recent biomedical applications. These applications include the encapsulation of hybrid-type artificial organs,1-3 the controlled release of specific molecules,4,5 targeted drug delivery systems,6,7 enhanced wound dressings,8,9 and myriad other applications that utilize the semi-permeability and high biocompatibility of PVA. Nevertheless, prior to its designation for use as the biomaterial of choice in the design and development processes of artificial tissue fabrication applications, the exact nature of PVA's physiological properties needs to be ascertained. In particular, the permeability and the diffusion coefficient are two important parameters that need to be analyzed. The experimental results can subsequently be used to determine the appropriate fabrication technique and design geometry for the design and development of the required tissue engineering applications. This study is based on the following presumption: if a researcher could place a semi-permeable membrane at the interface of two chambers (Chambers 1 and 2) that contain different concentrations of the same solution, then the diffusive parameters of the membrane can be measured simply by continuously measuring the changes in solute concentration in the chamber with the lower concentration. If the researcher waits until equilibrium between the two chambers is reached, both of the chambers would then have the same amount of solute (and, therefore, the same concentration of solute). A complete concentration profile will therefore provide the information that is needed to determine (using Fick's Law) the desired parameters of the membrane. Nevertheless, this procedure is highly impractical, due to the long period of time that is required to record the observations and any related changes. On the other hand, by deriving a model of the underlying diffusion process using Fick's Law, the researcher can predict the diffusive parameters based on the collected data over a relatively short period of time. The derivation of the model begins with constructing materials that are balanced on either side of the membrane. The material balance on the higher-concentration chamber (Chamber 1) can be expressed as where V1 is the chamber volume, P is the permeability, A is the exposed area of the membrane, c1 is the concentration in Chamber 1, and c2 is the concentration in Chamber 2. Similarly, the material balance in the lower-concentration chamber (Chamber 2) can be expressed as Assuming the initial conditions of c1 equals c0, and c2 equals zero, the following mathematical model can be derived and used to determine the permeability, P, and thus the diffusion coefficient, D, of the hydrogel membrane. If the ratio of ct/c0 is sufficiently small (as is the case if the period of the experiment is sufficiently short), then the left-hand side of the equation will be equal to –2ct/c0, according to Taylor's series.5,7 In other words, a linear concentration profile can be expected if the experimental period is sufficiently short, and the permeability and diffusion coefficient can be easily determined thereafter. The aim of this technical report was to study the fundamental parameters in the design and development of an aqueous PVA hydrogel membrane to be used in generic artificial tissue engineering applications; these parameters included the permeability and diffusion coefficient of the membrane and were measured using dextran-fluorescein isothiocyanate (Dextran-FITC) as the solute of choice.

Differences between in vitro viability and differentiation and in vivo bone-forming efficacy of human mesenchymal stem cells cultured on PCL–TCP scaffolds

Human mesenchymal stem cells (hMSCs) possess great therapeutic potential for the treatment of bone disease and fracture non-union. Too often however, in vitro evidence alone of the interaction between hMSCs and the biomaterial of choice is used as justification for continued development of the material into the clinic. Clearly for hMSC-based regenerative medicine to be successful for the treatment of orthopaedic trauma, it is crucial to transplant hMSCs with a suitable carrier that facilitates their survival, optimal proliferation and osteogenic differentiation in vitro and in vivo. This motivated us to evaluate the use of polycaprolactone-20% tricalcium phosphate (PCL–TCP) scaffolds produced by fused deposition modeling for the delivery of hMSCs. When hMSCs were cultured on the PCL–TCP scaffolds and imaged by a combination of phase contrast, scanning electron and confocal laser microscopy, we observed five distinct stages of colonization over a 21-day period that were characterized by cell attachment, spreading, cellular bridging, the formation of a dense cellular mass and the accumulation of a mineralized extracellular matrix when induced with osteogenic stimulants. Having established that PCL–TCP scaffolds are able to support hMSC proliferation and osteogenic differentiation, we next tested the in vivo efficacy of hMSC-loaded PCL–TCP scaffolds in nude rat critical-sized femoral defects. We found that fluorescently labeled hMSCs survived in the defect site for up to 3 weeks post-transplantation. However, only 50% of the femoral defects treated with hMSCs responded favorably as determined by new bone volume. As such, we show that verification of hMSC viability and differentiation in vitro is not sufficient to predict the efficacy of transplanted stem cells to consistently promote bone formation in orthotopic defects in vivo.