Preparative methods of phosphorylated chitin and chitosan--an overview

Biomaterials such as chitin, chitosan and their derivatives have a significant and rapid development in recent years. Chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However, the applications of chitin and chitosan are limited due to its insolubility in most of the solvents. The chemical modification of chitin and chitosan are keen interest because of these modifications would not change the fundamental skeleton of chitin and chitosan but would keep the original physicochemical and biochemical properties. They would also bring new or improved properties. The chemical modification of chitin and chitosan by phosphorylation is expected to be biocompatible and is able to promote tissue regeneration. In view of rapidly growing interest in chitin and chitosan and their chemical modified derivatives, we are here focusing the recent developments on preparation of phosphorylated chitin and chitosan in different methods.     

Recent developments in the synthesis of poly(hydroxybutyrate) based biocomposites

Poly(hydroxybutyrate) (PHB) has become an attractive biomaterial in research and development for past few years. It is natural bio-based aliphatic polyester produced by many types of bacteria. Due to its biodegradable, biocompatible, and eco-friendly nature, PHB can be used in line with bioactive species. However, high production cost, thermal instability, and poor mechanical properties limit its desirable applications. So there is need to incorporate PHB with other materials or biopolymers for the development of some novel PHB based biocomposites for value addition. Many attempts have been employed to incorporate PHB with other biomaterials (or biopolymers) to develop sustainable biocomposites. In this review, some recent developments in the synthesis of PHB based biocomposites and their biomedical, packaging and tissue engineering applications have been focused. The development of biodegradable PHB based biocomposites with improved mechanical properties could be used to overcome its native limitations hence to open new possibilities for industrial applications.     

Polylactic acid: synthesis and biomedical applications

Social and economic development has driven considerable scientific and engineering efforts on the discovery, development and utilization of polymers. Polylactic acid (PLA) is one of the most promising biopolymers as it can be produced from nontoxic renewable feedstock. PLA has emerged as an important polymeric material for biomedical applications on account of its properties such as biocompatibility, biodegradability, mechanical strength and process ability. Lactic acid (LA) can be obtained by fermentation of sugars derived from renewable resources such as corn and sugarcane. PLA is thus an eco-friendly nontoxic polymer with features that permit use in the human body. Although PLA has a wide spectrum of applications, there are certain limitations such as slow degradation rate, hydrophobicity and low impact toughness associated with its use. Blending PLA with other polymers offers convenient options to improve associated properties or to generate novel PLA polymers/blends for target applications. A variety of PLA blends have been explored for various biomedical applications such as drug delivery, implants, sutures and tissue engineering. PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues due to their excellent biocompatibility and mechanical properties. The relationship between PLA material properties, manufacturing processes and development of products with desirable characteristics is described in this article. LA production, PLA synthesis and their applications in the biomedical field are also discussed.     

Bio-piezoelectricity: fundamentals and applications in tissue engineering and regenerative medicine

In recent years, smart materials have piqued the interest of scientists and physicians in the biomedical community owing to their ability to modify their properties in response to an external stimulation or changes in their surroundings. Biocompatible piezoelectric materials are an interesting group of smart materials due to their ability to produce electrical charges without an external power source. Electric signals produced by piezoelectric scaffolds can renew and regenerate tissues through special pathways like that found in the extracellular matrix. This review summarizes the piezoelectric phenomenon, piezoelectric effects generated within biological tissues, piezoelectric biomaterials, and their applications in tissue engineering and their use as biosensors.     

生产聚羟基脂肪酸酯的微生物细胞工厂

聚羟基脂肪酸酯(PHA)是一类由微生物合成的、生物可再生、生物可降解、具有多种材料学性能的高分子聚合物,在很多领域有着广泛的应用前景。以下从辅酶工程、代谢工程、微氧生产等方面综述了微生物法生产PHA的研究进展,并对利用PHA合成基因提高基因工程菌的代谢潜能进行了讨论。     

Carbon nanotubes in cancer diagnosis and therapy

During the past years, great progress has been made in the field of nanomaterials given their great potential in biomedical applications. Carbon nanotubes (CNTs), due to their unique physicochemical properties, have become a popular tool in cancer diagnosis and therapy. They are considered one of the most promising nanomaterials with the capability of both detecting the cancerous cells and delivering drugs or small therapeutic molecules to these cells. Over the last several years, CNTs have been explored in almost every single cancer treatment modality, including drug delivery, lymphatic targeted chemotherapy, thermal therapy, photodynamic therapy, and gene therapy. In this review, we will show how they have been introduced into the diagnosis and treatment of cancer. Novel SWNT-based tumor-targeted drug delivery systems (DDS) will be highlighted. Furthermore, the in vitro and in vivo toxicity of CNTs reported in recent years will be summarized.     

PHA synthase engineering toward superbiocatalysts for custom-made biopolymers

Poly-3-hydroxyalkanoates [P(3HA)s] are biologically produced polyesters that have attracted much attention as biodegradable polymers that can be produced from biorenewable resources. These polymers have many attractive properties for use as bulk commodity plastics, fishing lines, and medical uses that are dependent on the repeating unit structures. Despite the readily apparent benefits of using P(3HA)s as replacements for petrochemical-derived plastics, the use and distribution of P(3HA)s have been limited by their cost of production. This problem is currently being addressed by the engineering of enzymes involved in the production of P(3HA)s. Polyhydroxyalkanoate (PHA) synthase (PhaC) enzymes, which catalyze the polymerization of 3-hydroxyacyl-CoA monomers to P(3HA)s, were subjected to various forms of protein engineering to improve the enzyme activity or substrate specificity. This review covers the recent history of PHA synthase engineering and also summarizes studies that have utilized engineered PHA synthases.     

Prospective of guar gum and its derivatives as controlled drug delivery systems

Guar gum is a non-ionic polysaccharide that is found abundantly in nature and has many properties desirable for drug delivery applications. However, due to its high swelling characteristics in aqueous solution, the use of guar gum as delivery carriers is limited. Guar gum can be modified by derivatization, grafting and network formation to improve its property profile for a wide spectrum of biomedical applications. This review article is aimed at focusing the recent efforts and developments on guar gum and its derivatives as colon-specific, antihypertensive, protein and transdermal drug delivery systems. Based on the literatures reviewed, it is concluded that guar gum and its derivatives in the various forms such as coatings, matrix tablets, hydrogels and nano/microparticles can be exploited as potential carriers for targeted drug delivery.     

Bacillus subtilis as potential producer for polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by microbes to overcome environmental stress. Commercial production of PHAs is limited by the high cost of production compared to conventional plastics. Another hindrance is the brittle nature and low strength of polyhydroxybutyrate (PHB), the most widely studied PHA. The needs are to produce PHAs, which have better elastomeric properties suitable for biomedical applications, preferably from inexpensive renewable sources to reduce cost. Certain unique properties of Bacillus subtilis such as lack of the toxic lipo-polysaccharides, expression of self-lysing genes on completion of PHA biosynthetic process – for easy and timely recovery, usage of biowastes as feed enable it to compete as potential candidate for commercial production of PHA.     

Nanoparticles applied to cancer immunoregulation

AimIn recent years, we have seen a considerable increase in the relevance of nanostructures for the safe delivery of therapeutic agents and their capacity as an immunomodulatory tool.Materials and methodsPotential clinical applications related to their unique structural properties have been described in the evolving landscape of immunotherapy.ResultsThis review briefly summarizes the evidence for the role of nanoparticles in regulating the immune response.ConclusionsTheir main features to highlight how to provide an innovative means of biomedical application to oncology research.     

Biocompatibility of alumina-based biomaterials–A review

In today's medicine world, alumina-based biomaterials owing to their excellent biomechanical, and biocompatibility properties play a key role in biomedical engineering. However, the literature still suffers from not having a valid database regarding the protein adsorption and subsequently cell responses to these surfaces. Proteins by adsorption on biomaterials surfaces start interpreting the construction and also arranging the biomaterials surfaces into a biological language. Hence, the main concentration of this review is on the protein adsorption and subsequently cell responses to alumina’s surface, which has a wide range biomedical applications, especially in dentistry and orthopedic applications. In the presented review article, the general principles of foreign body response mechanisms, and also the role of adsorbed proteins as key players in starting interactions between cells and alumina-based biomaterials will be discussed in detail. In addition, the essential physicochemical, and mechanical properties of alumina surfaces which significantly impact on proteins and cells responses as well as the recent studies that have focused on the biocompatibility of alumina will be given. An in depth understanding of how the immune system interacts with the surface of alumina could prove the pivotal importance of the biocompatibility of alumina on its success in tissue engineering after implantation in body.     

Expression of 3-ketoacyl-acyl carrier protein reductase (fabG) genes enhances production of polyhydroxyalkanoate copolymer from glucose in recombinant Escherichia coli JM109

Polyhydroxyalkanoates (PHAs) are biologically produced polyesters that have potential application as biodegradable plastics. Especially important are the short-chain-length-medium-chain-length (SCL-MCL) PHA copolymers, which have properties ranging from thermoplastic to elastomeric, depending on the ratio of SCL to MCL monomers incorporated into the copolymer. Because of the potential wide range of applications for SCL-MCL PHA copolymers, it is important to develop and characterize metabolic pathways for SCL-MCL PHA production. In previous studies, coexpression of PHA synthase genes and the 3-ketoacyl-acyl carrier protein reductase gene (fabG) in recombinant Escherichia coli has been shown to enhance PHA production from related carbon sources such as fatty acids. In this study, a new fabG gene from Pseudomonas sp. 61-3 was cloned and its gene product characterized. Results indicate that the Pseudomonas sp. 61-3 and E. coli FabG proteins have different substrate specificities in vitro. The current study also presents the first evidence that coexpression of fabG genes from either E. coli or Pseudomonas sp. 61-3 with fabH(F87T) and PHA synthase genes can enhance the production of SCL-MCL PHA copolymers from nonrelated carbon sources. Differences in the substrate specificities of the FabG proteins were reflected in the monomer composition of the polymers produced by recombinant E. coli. SCL-MCL PHA copolymer isolated from a recombinant E. coli strain had improved physical properties compared to the SCL homopolymer poly-3-hydroxybutyrate. This study defines a pathway to produce SCL-MCL PHA copolymer from the fatty acid biosynthesis that may impact on PHA production in recombinant organisms.     

Poly-lactic acid synthesis for application in biomedical devices - a review

Bioabsorbable polymers are considered a suitable alternative to the improvement and development of numerous applications in medicine. Poly-lactic acid (PLA,) is one of the most promising biopolymers due to the fact that the monomers may produced from non toxic renewable feedstock as well as is naturally occurring organic acid. Lactic acid can be made by fermentation of sugars obtained from renewable resources as such sugarcane. Therefore, PLA is an eco-friendly product with better features for use in the human body (nontoxicity). Lactic acid polymers can be synthesized by different processes so as to obtain products with an ample variety of chemical and mechanical properties. Due to their excellent biocompatibility and mechanical properties, PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues. In order to maximize the benefits of its use, it is necessary to understand the relationship between PLA material properties, the manufacturing process and the final product with desired characteristics. In this paper, the lactic acid production by fermentation and the polymer synthesis such biomaterial are reviewed. The paper intends to contribute to the critical knowledge and development of suitable use of PLA for biomedical applications.     

基因工程功能化丝蛋白生物材料及其在生物医学中的应用

丝蛋白生物材料具有优异的力学性能、良好的生物相容性及可降解性,在生物医学领域具有巨大的应用潜力。现有丝蛋白生物材料在结构和功能方面的相关知识,为设计合成新型丝蛋白生物材料提供了理论基础。此外,利用基因工程技术可将编码新肽或结构域的基因序列添加到编码丝蛋白的基因序列中,以获得具有新功能的丝蛋白生物材料,并更好地满足现代生物医学的需求。文中总结了基因工程功能化的丝蛋白生物材料在生物医学领域中的应用现状和发展前景。     

Novel chitin and chitosan nanofibers in biomedical applications

Chitin and its deacetylated derivative, chitosan, are non-toxic, antibacterial, biodegradable and biocompatible biopolymers. Due to these properties, they are widely used for biomedical applications such as tissue engineering scaffolds, drug delivery, wound dressings, separation membranes and antibacterial coatings, stent coatings, and sensors. In the recent years, electrospinning has been found to be a novel technique to produce chitin and chitosan nanofibers. These nanofibers find novel applications in biomedical fields due to their high surface area and porosity. This article reviews the recent reports on the preparation, properties and biomedical applications of chitin and chitosan based nanofibers in detail.     

ZnO nanomaterials target mitochondrial apoptosis and mitochondrial autophagy pathways in cancer cells

In recent years, the application of engineering nanomaterials has significantly contributed to the development of various biomedical fields. Zinc oxide nanomaterials (ZnO NMts) have gained wide popularity due to their biocompatibility, unique physical and chemical properties, stability, and cost-effectiveness for large-scale production. They have emerged as potential materials for anticancer applications. This article provides a comprehensive review of the synthesis methods of ZnO NMts and highlights the advantages of combining ZnO NMts with anticancer drugs as a nano platform for cancer treatment. Additionally, the article briefly explains the mechanism of action of ZnO NMts in tumor cells, focusing on the mitochondrial pathways that target cell apoptosis and autophagy. It is observed that these pathways are primarily influenced by reactive oxygen species generated through oxidative stress. The article discusses the promising prospects of ZnO NMts combined with anticancer drugs in the field of cancer medicine and emphasizes the need for further in-depth research on the mitochondrial apoptosis and mitochondrial autophagy pathways.     

Advanced bacterial polyhydroxyalkanoates: Towards a versatile and sustainable platform for unnatural tailor-made polyesters

Polyhydroxyalkanoates (PHAs) are biopolyesters that generally consist of 3-, 4-, 5-, and 6-hydroxycarboxylic acids, which are accumulated as carbon and energy storage materials in many bacteria in limited growth conditions with excess carbon sources. Due to the diverse substrate specificities of PHA synthases, the key enzymes for PHA biosynthesis, PHAs with different material properties have been synthesized by incorporating different monomer components with differing compositions. Also, engineering PHA synthases using in vitro-directed evolution and site-directed mutagenesis facilitates the synthesis of PHA copolymers with novel material properties by broadening the spectrum of monomers available for PHA biosynthesis. Based on the understanding of metabolism of PHA biosynthesis, recombinant bacteria have been engineered to produce different types of PHAs by expressing heterologous PHA biosynthesis genes, and by creating and enhancing the metabolic pathways to efficiently generate precursors for PHA monomers. Recently, the PHA biosynthesis system has been expanded to produce unnatural biopolyesters containing 2-hydroxyacid monomers such as glycolate, lactate, and 2-hydroxybutyrate by employing natural and engineered PHA synthases. Using this system, polylactic acid (PLA), one of the major commercially-available bioplastics, can be synthesized from renewable resources by direct fermentation of recombinant bacteria. In this review, we discuss recent advances in the development of the PHA biosynthesis system as a platform for tailor-made polyesters with novel material properties.     

Expression of 3-Ketoacyl-Acyl Carrier Protein Reductase (fabG) Genes Enhances Production of Polyhydroxyalkanoate Copolymer from Glucose in Recombinant Escherichia coli JM109

Polyhydroxyalkanoates (PHAs) are biologically produced polyesters that have potential application as biodegradable plastics. Especially important are the short-chain-length-medium-chain-length (SCL-MCL) PHA copolymers, which have properties ranging from thermoplastic to elastomeric, depending on the ratio of SCL to MCL monomers incorporated into the copolymer. Because of the potential wide range of applications for SCL-MCL PHA copolymers, it is important to develop and characterize metabolic pathways for SCL-MCL PHA production. In previous studies, coexpression of PHA synthase genes and the 3-ketoacyl-acyl carrier protein reductase gene (fabG) in recombinant Escherichia coli has been shown to enhance PHA production from related carbon sources such as fatty acids. In this study, a new fabG gene from Pseudomonas sp. 61-3 was cloned and its gene product characterized. Results indicate that the Pseudomonas sp. 61-3 and E. coli FabG proteins have different substrate specificities in vitro. The current study also presents the first evidence that coexpression of fabG genes from either E. coli or Pseudomonas sp. 61-3 with fabH(F87T) and PHA synthase genes can enhance the production of SCL-MCL PHA copolymers from nonrelated carbon sources. Differences in the substrate specificities of the FabG proteins were reflected in the monomer composition of the polymers produced by recombinant E. coli. SCL-MCL PHA copolymer isolated from a recombinant E. coli strain had improved physical properties compared to the SCL homopolymer poly-3-hydroxybutyrate. This study defines a pathway to produce SCL-MCL PHA copolymer from the fatty acid biosynthesis that may impact on PHA production in recombinant organisms.     

Microbial biosurfactants production, applications and future potential

Microorganisms synthesise a wide range of surface-active compounds (SAC), generally called biosurfactants. These compounds are mainly classified according to their molecular weight, physico-chemical properties and mode of action. The low-molecular-weight SACs or biosurfactants reduce the surface tension at the air/water interfaces and the interfacial tension at oil/water interfaces, whereas the high-molecular-weight SACs, also called bioemulsifiers, are more effective in stabilising oil-in-water emulsions. Biosurfactants are attracting much interest due to their potential advantages over their synthetic counterparts in many fields spanning environmental, food, biomedical, and other industrial applications. Their large-scale application and production, however, are currently limited by the high cost of production and by limited understanding of their interactions with cells and with the abiotic environment. In this paper, we review the current knowledge and the latest advances in biosurfactant applications and the biotechnological strategies being developed for improving production processes and future potential.     

FabG mediates polyhydroxyalkanoate production from both related and nonrelated carbon sources in recombinant Escherichia coli LS5218

Polyhydroxyalkanoates (PHAs) composed of a mixture of short-chain-length-medium-chain-length (SCL-MCL) hydroxyacyl monomers are biologically produced polyesters that have properties ranging from thermoplastic to elastomeric, dependent on the molar ratio of SCL to MCL monomers incorporated into the copolymer. Because of the potential wide range of properties and applications for SCL-MCL PHA copolymers, it is important to develop and characterize novel metabolic pathways for SCL-MCL PHA production. The current study shows that coexpression of fabG genes from either E. coli or Pseudomonas sp. 61-3 with fabH(F87T) and PHA synthase genes enhances the production of SCL-MCL PHA copolymer from both related and nonrelated carbon sources in Escherichia coli LS5218, indicating the flexibility of FabG as a monomer-supplying enzyme for biological PHA production.