Thermodynamics of metal interactions with chitin-related biopolymers by isothermal titration calorimetry and production of 2-keto-3-deoxy-D-manno-octulosonic acid from D-glucose in vivo

Chitin, a polymer of N-acetyl-D-glucosamine (GlcNAc), is used as a biomaterial and for the removal of metals in water purification. Given the role of metal binding to carbohydrates in both biological and industrial settings, isothermal titration calorimetry (ITC) was used to determine the thermodynamics of binding between chitin-related carbohydrate substrates and metal ions. The binding interactions between chitin and common water contaminants mercury, copper, iron, nickel, chromium, lead, zinc, cadmium, silver and cobalt have been studied. The strongest binding has been found towards mercury and the weakest to cobalt with a Kb of 1.16*105 M-1 and 3.96*103M-1, respectively. The formal charge of the heavy metal changed the binding strength in an inverse fashion. The chitin-heavy metal cation interactions were all determined to occur in an enthalpically driven manner. The degree of binding of a series of small chitin fragments to divalent copper ion using ITC have also been tested. The binding strength of GlcNAc has been found to be the weakest among the substrates tested with a Kb of 3.8*103 M-1. Penta-N-acetylchitopentaose (GlcNAc)5 has provided the strongest metal interactions with a Kb of 22.1*103 M-1. All experiments afforded enthalpically driven and favorable interactions. Gibbs free energy of reaction values were all measured to be negative, which is indicative of spontaneous reactions. These results demonstrated that increasing numbers of GlcNAc units enhance the binding strength for divalent copper cation, but the magnitude of the effect points to statistical binding rather than chelation-based multivalency. KDO (2-keto-3-deoxy-D-manno-octulosonic acid) is an 8-carbon sugar that is essential for the growth of Gram-negative bacteria. The production of reasonable quantities of KDO would allow studies to understand the chemistry and biology of this key sugar with the potential to develop anti-infective therapeutics against Gram-negative bacteria. The first synthesis of 2-keto-3-deoxy-D-manno-octulosonic acid (KDO) using glucose through pathway engineering of Escherichia coli was designed as a low cost strategy to obtain KDO. Although a transporter protein for the sugar is unknown, KDO could be isolated from the fermentation broth. An optimum yield of 334 mg KDO per liter of cultured cells was obtained using glucose as a carbon source

Origami-Inspired Approaches for Biomedical Applications

Modern day biomedical applications require progressions that combine advanced technology with the conformability of naturally occurring, complex biosystems. These advancements yield conformational interactions between the biomedical devices and the biological organisms\u27 structures. Biomedical applications that adapt origami-inspired approaches have accrued aspired advances. Along with application-specific advantages, the most pertinent advances provided by origami-inspired strategies include voluminous structures with the ability to conform to biosystems, shape-shifting from two-dimensional (2D) to three-dimensional (3D) structures, and biocompatibility. Throughout this paper, the exploration of new studies, primarily within the past decade, with origami-based applications of biomedical devices, including their theories, experimental results, and plans for future testing are reviewed. This mini-review contains examples that aid the advancement of biomedical applications and hold promising future discoveries. The origami-inspired applications discussed within this paper are tissue scaffolds, drug delivery approaches, stents and catheters, implants, microfluidic devices, biosensors, and origami usage in surgery

Thermodynamics of binding of divalent magnesium and manganese to uridine phosphates: implications for diabetes-related hypomagnesaemia and carbohydrate biocatalysis

<p>Abstract</p> <p>Background</p> <p>Although the necessity of divalent magnesium and manganese for full activity of sugar nucleotidyltransferases and glycosyltransferases is well known, the role of these metal cations in binding the substrates (uridine 5'-triphosphate, glucose-1-phosphate, <it>N</it>-acetylglucosamine-1-phosphate, and uridine 5'-diphosphate glucose), products (uridine 5'-diphosphate glucose, uridine 5'-diphosphate <it>N</it>-acetylglucosamine, pyrophosphate, and uridine 5'-diphosphate), and/or enzyme is not clearly understood.</p> <p>Results</p> <p>Using isothermal titration calorimetry we have studied the binding relationship between the divalent metals, magnesium and manganese, and uridine 5'-phosphates to determine the role these metals play in carbohydrate biosynthesis. It was determined from the isothermal titration calorimetry (ITC) data that Mg⁺²and Mn⁺²are most tightly bound to PP_<it>i</it>, K_b= 41,000 ± 2000 M^-1and 28,000 ± 50,000 M^-1respectively, and UTP, K_b= 14,300 ± 700 M^-1and 13,000 ± 2,000 M^-1respectively.</p> <p>Conclusion</p> <p>Our results indicate that the formal charge state of the phosphate containing substrates determine the binding strength. Divalent metal cations magnesium and manganese showed similar trends in binding to the sugar substrates. Enthalpy of binding values were all determined to be endothermic except for the PP_{<it>i </it>}case. In addition, entropy of binding values were all found to be positive. From this data, we discuss the role of magnesium and manganese in both sugar nucleotidyltransferase and glycosyltransferase reactions, the differences in metal-bound substrates expected under normal physiological metal concentrations and those of hypomagnesaemia, and the implications for drug design.</p

Editorial for Gels 6th Anniversary Special Issue

Note: In lieu of an abstract, this is an excerpt from the first page. This Special Issue celebrates many outstanding quality papers published in Gels over the past six years since its first issue was published in 2015 [...

Mineralization of Biomaterials for Bone Tissue Engineering

Mineralized biomaterials have been demonstrated to enhance bone regeneration compared to their non-mineralized analogs. As non-mineralized scaffolds do not perform as well as mineralized scaffolds in terms of their mechanical and surface properties, osteoconductivity and osteoinductivity, mineralization strategies are promising methods in the development of functional biomimetic bone scaffolds. In particular, the mineralization of three-dimensional (3D) scaffolds has become a promising approach for guided bone regeneration. In this paper, we review the major approaches used for mineralizing tissue engineering constructs. The resulting scaffolds provide minerals chemically similar to the inorganic component of natural bone, carbonated apatite, Ca5(PO4,CO3)3(OH). In addition, we discuss the characterization techniques that are used to characterize the mineralized scaffolds, such as the degree of mineralization, surface characteristics, mechanical properties of the scaffolds, and the chemical composition of the deposited minerals. In vitro cell culture studies show that the mineralized scaffolds are highly osteoinductive. We also summarize, based on literature examples, the applications of 3D mineralized constructs, as well as the rationale behind their use. The mineralized scaffolds have improved bone regeneration in animal models due to the enhanced mechanical properties and cell recruitment capability making them a preferable option for bone tissue engineering over non-mineralized scaffolds

PGS:Gelatin nanofibrous scaffolds with tunable mechanical and structural properties for engineering cardiac tissues.

A significant challenge in cardiac tissue engineering is the development of biomimetic grafts that can potentially promote myocardial repair and regeneration. A number of approaches have used engineered scaffolds to mimic the architecture of the native myocardium tissue and precisely regulate cardiac cell functions. However, previous attempts have not been able to simultaneously recapitulate chemical, mechanical, and structural properties of the myocardial extracellular matrix (ECM). In this study, we utilized an electrospinning approach to fabricate elastomeric biodegradable poly(glycerol sebacate) (PGS):gelatin nanofibrous scaffolds with a wide range of chemical composition, stiffness and anisotropy. Our findings demonstrated that through incorporation of PGS, it is possible to create nanofibrous scaffolds with well-defined anisotropy that mimic the left ventricular myocardium architecture. Furthermore, we studied attachment, proliferation, differentiation and alignment of neonatal rat cardiac fibroblast cells (CFs) as well as protein expression, alignment, and contractile function of cardiomyocyte (CMs) on PGS:gelatin scaffolds with variable amount of PGS. Notably, aligned nanofibrous scaffold, consisting of 33 wt. % PGS, induced optimal synchronous contractions of CMs while significantly enhanced cellular alignment. Overall, our study suggests that the aligned nanofibrous PGS:gelatin scaffold support cardiac cell organization, phenotype and contraction and could potentially be used to develop clinically relevant constructs for cardiac tissue engineering

A contactless electrical stimulator: application to fabricate functional skeletal muscle tissue

Engineered skeletal muscle tissues are ideal candidates for applications in drug screening systems, bio-actuators, and as implantable constructs in tissue engineering. Electrical field stimulation considerably improves the differentiation of muscle cells to muscle myofibers. Currently used electrical stimulators often use direct contact of electrodes with tissue constructs or their culture medium, which may cause hydrolysis of the culture medium, joule heating of the medium, contamination of the culture medium due to products of electrodes corrosion, and surface fouling of electrodes. Here, we used an interdigitated array of electrodes combined with an isolator coverslip as a contactless platform to electrically stimulate engineered muscle tissue, which eliminates the aforementioned problems. The effective stimulation of muscle myofibers using this device was demonstrated in terms of contractile activity and higher maturation as compared to muscle tissues without applying the electrical field. Due to the wide array of potential applications of electrical stimulation to two- and three-dimensional (2D and 3D) cell and tissue constructs, this device could be of great interest for a variety of biological applications as a tool to create noninvasive, safe, and highly reproducible electric fields.World Premier International Research Center Initiative (WPI