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1.
Additive manufacturing of biodegradable metals: Current research status and future perspectives.
Qin, Y, Wen, P, Guo, H, Xia, D, Zheng, Y, Jauer, L, Poprawe, R, Voshage, M, Schleifenbaum, JH
Acta biomaterialia. 2019;:3-22
Abstract
The combination of biodegradable metals and additive manufacturing (AM) leads to a revolutionary change of metal implants in many aspects including materials, design, manufacturing, and clinical applications. The AM of nondegradable metals such as titanium and CoCr alloys has proven to be a tremendous success in clinical applications. The AM of biodegradable metals including magnesium (Mg), iron (Fe), and zinc (Zn) is still in its infancy, although much progress has been made in the research field. Element loss and porosity are common processing problems for AM of biodegradable metals like Zn and Mg, which are mainly caused by evaporation during melting under a high-energy beam. The resulting formation quality and properties are closely related to material, design, and processing, making AM of biodegradable metals a typical interdisciplinary subject involving biomaterials, mechanical engineering, and medicine. This work reviews the state of research and future perspective on AM of biodegradable metals from extensive viewpoints such as material, processing, formation quality, design, microstructure, and properties. Effects of powder properties and processing parameters on formation quality are characterized in detail. The microstructure and metallurgical defects encountered in the AM parts are described. Mechanical and biodegradable properties of AM samples are introduced. Design principles and potential applications of biodegradable metal implants produced by AM are discussed. Finally, current research status is summarized together with some proposed future perspectives for advancing knowledge about AM of biodegradable metals. STATEMENT OF SIGNIFICANCE Rapid development of research and applications on biodegradable metals and additive manufacturing (AM) has been made in recent years. Customized geometric shapes of medical metals with porous structure can be realized accurately and efficiently by laser powder bed fusion (L-PBF), which is beneficial to achieve reliable stress conduction and balanced properties. This review introduces the development history and current status of AM of biodegradable metals and then critically surveys L-PBF of Mg-, Fe-, and Zn-based metals from multiple viewpoints including materials, processing, formation quality, structural design, microstructure, and mechanical and biological properties. The present findings are summarized together with some proposed future challenges for advancing AM of biodegradable metals into real clinical applications.
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2.
Revisiting the insights and applications of protein engineered hydrogels.
J, B, Chanda, K, M M, B
Materials science & engineering. C, Materials for biological applications. 2019;:312-327
Abstract
Utilization of protein-protein interactions or protein-peptide interactions has led to new crosslinking chemistries, resulting into protein hydrogels. Enzyme catalyzed crosslinking of specific amino acids has also been used to generate crosslinked protein hydrogels. Weak, temporary, reversible or non-covalently crosslinked protein gels as well as strong, permanent, irreversible or covalently crosslinked protein gels with mechanical strengths of varying degrees are generated by means of various crosslinking strategies. These protein hydrogels are tailored by means of protein engineering and recombinant DNA technology, depending on its end use as scaffolds for specific tissue engineering, drug delivery, wound dressings etc. This review aims to cover the advancements in the use of protein engineering along with different crosslinking techniques to create novel protein hydrogels that finds various applications in biomedical industries.
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3.
Ureteral Obstruction After Endoscopic Treatment of Vesicoureteral Reflux: Does the Type of Injected Bulking Agent Matter?
Friedmacher, F, Puri, P
Current urology reports. 2019;(9):49
Abstract
PURPOSE OF REVIEW Endoscopic injection of bulking agents for the treatment of vesicoureteral reflux (VUR) has become a therapeutic alternative to antibiotic prophylaxis and ureteral reimplantation. Although considered as a safe and efficient procedure, several studies have reported cases of ureteral obstruction (UO) after endoscopic correction of VUR. This review article evaluates the present VUR literature to estimate the incidence of UO following endoscopic injection of different substances, while also discussing the impact of injection technique and implant volume. RECENT FINDINGS Twenty-five publications were identified that provided detailed information on 64 females and 32 males (age range, 7 months-48 years) that developed UO after endoscopic treatment of VUR using dextranomer/hyaluronic acid (Dx/HA), polyacrylate polyalcohol (PP), polydimethylsiloxane (PDMS), calcium hydroxyapatite (CaHA), polytetrafluoroethylene (PTFE), or collagen. There was some variation in the reported incidence of UO among these materials: Dx/HA (0.5-6.1%), PP (1.1-1.6%), PDMS (2.5-10.0%), CaHA (1.0%), and PTFE (0.3%). Postoperative UO was described following subureteric transurethral injection (STING), intraureteric hydrodistension implantation technique (HIT), combined HIT/STING and double HIT. The injected volume ranged widely, also depending on the type of bulking agent: Dx/HA (0.3-3.0 mL), PP (0.3-1.2 mL), PDMS (1.0-2.2 mL), CaHA (0.4-0.6 mL), and PTFE (1.5-2.0 mL). The timing of UO varied from immediately after the procedure to 63 months. Over half of patients showed asymptomatic hydroureteronephrosis on follow-up imaging, whereas the remaining presented with symptoms of acute UO or fever. UO remains a rare complication after endoscopic correction of VUR, generally reported in less than 1% of treated cases, which appears to be independent of the injected substance, volume, and technique. However, long-term follow-up is recommended as asymptomatic or delayed UO can occur, potentially leading to deterioration of renal function.
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4.
Protein-Engineered Functional Materials.
Wang, Y, Katyal, P, Montclare, JK
Advanced healthcare materials. 2019;(11):e1801374
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Abstract
Proteins are versatile macromolecules that can perform a variety of functions. In the past three decades, they have been commonly used as building blocks to generate a range of biomaterials. Owing to their flexibility, proteins can either be used alone or in combination with other functional molecules. Advances in synthetic and chemical biology have enabled new protein fusions as well as the integration of new functional groups leading to biomaterials with emergent properties. This review discusses protein-engineered materials from the perspectives of domain-based designs as well as physical and chemical approaches for crosslinked materials, with special emphasis on the creation of hydrogels. Engineered proteins that organize or template metal ions, bear noncanonical amino acids (NCAAs), and their potential applications, are also reviewed.
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5.
Demineralized Bone Matrix Carriers and their Clinical Applications: An Overview.
Zhang, H, Yang, L, Yang, XG, Wang, F, Feng, JT, Hua, KC, Li, Q, Hu, YC
Orthopaedic surgery. 2019;(5):725-737
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Abstract
Reconstruction of massive bone defects is challenging for orthopaedic clinicians, especially in cases of severe trauma and resection of tumors in various locales. Autologous iliac crest bone graft (ICBG) is the "gold standard" for bone grafting. However, the limited availability and complications at donor sites resulted in seeking other options like allografts and bone graft substitutes. Demineralized bone matrix (DBM) is a form of allograft using acidic solution to remove mineral components, while leaving much of the proteinaceous components native to bone, with small amounts of calcium-based solids, inorganic phosphates, and some trace cell debris. It is an osteoconductive and osteoinductive biomaterial and is approved as a medical device for use in bone defects and spinal fusion. To pack consistently into the defect sites and stay firmly in the filling parts, DBM products have various forms combined with biocompatible viscous carriers, including sponges, strips, injectable putty, paste, and paste infused with chips. The present review aims to summarize the properties of various kind of viscous carriers and their clinical use combined with DBM in commercially available products. Given DBM'mercially available products. Given DBM;s long clinical track record and commercial accessibility in standard forms, opportunities to further develop and validate DBM as a versatile bone biomaterial in orthopaedic repair and regenerative medicine contexts are attractive.
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Magnesium matrix nanocomposites for orthopedic applications: A review from mechanical, corrosion, and biological perspectives.
Shahin, M, Munir, K, Wen, C, Li, Y
Acta biomaterialia. 2019;:1-19
Abstract
Magnesium (Mg) and some of its alloys have attracted extensive interests for biomedical applications as they exhibit biodegradability and low elastic modulus that is closer to natural bones than the currently used metallic implant materials such as titanium (Ti) and its alloys, stainless steels, and cobalt-chromium (Co-Cr) alloys. However, the rapid degradation of Mg alloys and loss of their mechanical integrity before sufficient bone healing impede their clinical application. Our literature review shows that magnesium matrix nanocomposites (MMNCs) reinforced with nanoparticles possess enhanced strength, high corrosion resistance, and good biocompatibility. This article provides a detailed analysis of the effects of nanoparticle reinforcements on the mechanical properties, corrosion behavior, and biocompatibility of MMNCs as promising biodegradable implant materials. The governing equations to quantitatively predict the mechanical properties and underlying synergistic strengthening mechanisms in MMNCs are elucidated. The potential, recent advances, challenges and future research directions in relation to nanoparticles reinforced MMNCs are highlighted. STATEMENT OF SIGNIFICANCE Critically reviewing magnesium metal matrix nanocomposites (MMNCs) for the biomedical application. Clear definitions of strengthening mechanisms using reinforcement particle in the magnesium matrix, as there were controversial in governing equations of strengthening parameters. Providing better understanding of the effect of particle size, volume fraction, interfacial bonding, and uniform dispersion of reinforcement particles on MMNCs.
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Regenerative Materials for Surgical Reconstruction: Current Spectrum of Materials and a Proposed Method for Classification.
Sharma, A, Faubion, WA, Dietz, AB
Mayo Clinic proceedings. 2019;(10):2099-2116
Abstract
Chronic wound management is an enormous economic strain and quality-of-life issue for patients. Current treatments are ineffective or expensive and invasive. Materials (native and artificial) can act as the basis to enhance wound repair but often fall short of complete healing. The therapeutic index of materials have often been enhanced by combining them with drug or biologic elution technologies. Combination of materials with living drugs (cells) presents a new paradigm for enhancing therapy. Cell material interaction and therapeutic output will depend on variables ascribed to the living drug as well as variables ascribed to the underlying matrix. In this article, we review medical matrices currently approved by the US Food and Drug Administration (FDA) that would likely be the first generation of materials to be used in this manner. Currently there are hundreds of different materials on the market. Identification of the right combinations would benefit from a classification scheme to group materials with similar composition or derivation. We provide a classification scheme and FDA documentation references that should provide researchers and clinicians a starting point for testing these materials in the laboratory and rapidly transitioning cell therapies to the bedside.
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Stochasticity of Biological Soft Matter: Emerging Concepts in Intrinsically Disordered Proteins and Biological Phase Separation.
Turoverov, KK, Kuznetsova, IM, Fonin, AV, Darling, AL, Zaslavsky, BY, Uversky, VN
Trends in biochemical sciences. 2019;(8):716-728
Abstract
At the turn of this century, cardinal changes took place in the perceptions of the structure and function of proteins, as well as in the organizational principles of membrane-less organelles. As a result, the model of the organization of living matter is changing to one described by highly dynamic biological soft matter positioned at the edge of chaos. Intrinsically disordered proteins (IDPs) and membrane-less organelles are key examples of this new outlook and may represent a critical foundation of life, defining its complexity and the evolution of living things.
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Mesoporous bioactive glasses: Promising platforms for antibacterial strategies.
Kargozar, S, Montazerian, M, Hamzehlou, S, Kim, HW, Baino, F
Acta biomaterialia. 2018;:1-19
Abstract
The control of bacterial infections is of particular importance in the field of tissue engineering. Recently, much attention has been addressed toward the use of mesoporous bioactive glasses (MBGs) for antibacterial strategies, primarily because of their capability of acting as carriers for the local release of antimicrobial agents. The incorporation of antibacterial metallic ions including silver (Ag+), zinc (Zn2+), copper (Cu+ and Cu2+), cerium (Ce3+ and Ce4+), and gallium (Ga3+) cations into the MBG structure and their controlled release is proposed as one of the most attractive strategies for inhibiting bacterial growth and reproduction. Moreover, the possibility of loading and delivering various antibacterial biomolecules (e.g., antibiotics) through the porous structure of MBGs makes them as ideal candidates for antibacterial applications. In this review, we aim to present a comprehensive evaluation of MBG potential regarding antibacterial activities. For this purpose, different types of antibacterial ion-doped and drug-loaded MBGs are introduced and discussed in the light of existing knowledge, along with the significant challenges ahead. STATEMENT OF SIGNIFICANCE Prevention and treatment of infections is one of the today's greatest challenges in medical sciences, also considering the well-known issues related to increased bacterial resistance to antibiotics. The advent of mesoporous glasses led to the birth of a new class of multifunctional biomaterials acting as bioactive platforms for the local release of organic or inorganic agents eliciting an antimicrobial effect. This reviews summarizes the state of the art of MBGs in this field, highlighting the latest evolutions and the specific role played by metallic antimicrobial ions that can be incorporated in the glass composition and then properly released. Perspective for tissue engineering applications are also discussed to provide an up-to-date contribution that is useful to both experienced scientists and early-stage researchers.
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Mg-Zn alloys, most suitable for biomedical applications.
Bîrcă, AC, Neacşu, IA, Vasile, OR, Ciucă, I, Vasile, IM, Fayeq, MA, Vasile, BŞ
Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie. 2018;(1):49-54
Abstract
In this review are highlighted the corrosion and biocompatibility of biodegradable Mg alloys for their use in orthopedic applications. It was revealed that mixing with alloying elements, such as Mn and Zn, provides improved corrosion resistance to Mg alloys; this pursuit is built on the fact that Mg and its alloys are degradable through their time in the human body. Furthermore, Mg alloys afford a characteristic profile that is very close or even almost identical to that of human bone. Minimizing the rate of corrosion of Mg is the most adequate method, because a low corrosion rate of an Mg implant involves a decrease in the extent of hydrogen evolution and alkalization, which allow the human body to gradually absorb or consume the corrosion products.