Advances in Science and Technology Vol. 53

Abstract: Success in surgical joint replacements has resulted in a huge demand amongst patients. Coupled with the lowered average age of patients requiring hip replacements, younger patients are demanding longer life expectancy from such devices. The increasing need and demand for more durable implants have led to new formulations of high performance nanomaterials (materials with basic structural units of 1-100 nm). Nanotubes in particular have shown great promise because they: 1) have sizes that approach biological structures and 2) possess efficient channels for displaying chemistries relevant to living systems at high densities and well-controlled spatial distribution. Helical rosette nanotubes (HRN) are a new class of soft organic nanomaterials composed of a guanine-cytosine building block that self-assembles in aqueous environments into stable nanotubular structures with an inner diameter of ~1.1 nm. HRN can be decorated with biologically active chemical functionalities such as cell attracting peptide fragments. Previously, we have showed that HRN coated Ti can enhance OB attachment. In addition, proteins were seen to interact favorably with HRN networks in a manner favorable toward OB attachment. Furthermore, in the absence of proteins, HRN were seen to play the role of proteins in promoting OB attachment. The studies herein, attempt to understand the role of the lysine clusters on HRN toward OB attachment. Results show that OB do respond to lysine and molecular orientation considerations were shown to be important. Detailed structural considerations from molecular modeling further present the possibility of topographical influences (nanotube network architecture) towards OB attachment.

Abstract: To solve the shortage of the donor cornea in Japan, we are developing a poly(vinyl alcohol) hydrogel based keratoprosthesis. Minimum requirements for a keratoprosthesis include light transparency, non-toxicity, and nutrition and fluid permeability. Earlier clinical trials had frequently failed because corneal epithelial down growth occurred between the host cornea and the materials, and the materials were finally rejected from the host cornea. The major cause of this rejection is the weak adhesion between the host cornea and the prosthesis. In order to achieve the firm fixation of the artificial cornea to host cornea, composites of collagen-immobilized poly(vinyl alcohol) hydrogel with hydroxyapatite(PVA-HAp nano composites) were synthesized. The preparation method, characterization, and the results of corneal cell adhesion and proliferation on the composite materials were studied. The PVA-HAp nano composites were successfully synthesized. Chick embryonic keratocyto-like cells were well attached and proliferated on the PVA-HAp composites. This material showed potential for keratoprosthesis.

Abstract: Self-assembled niobium oxide microcones produced by potentiostatic anodization with varied NaF content (between 100 and 250 mg) in an HF electrolyte are shown to nucleate mineral when immersed in supersaturated solutions emulating mineral content in saliva and blood. The most extensive mineral coverage in 100 mL of 2.5 wt. % HF electrolyte occurs when NaF content is about 100 mg with substantial mineral formation occurring within 24 hours. Higher salt content apparently alters the conditions favoring mineral nucleation by generating smaller nucleation centers that ultimately diminish the extent of mineral coverage. Additionally, nucleation kinetics and morphological contrasts between mineral formed from saliva and blood is briefly discussed in terms of the relative degree of supersaturation with respect to hydroxyapatite. Finally, we show that the integrity of the microcone shape is not critical for mineral nucleation, an observation that builds on our prior hypothesis by promoting the importance of self-assembly and crystal formation. Based on these results, we demonstrate the influence of NaF and stress the role of the self-organization process in producing effective mineral nucleation sites.

Abstract: Membrane channel proteins play crucial roles in governing the transport of material and energy across every cellular membrane. Accordingly, they are the subjects of interest for science and medicine as well as major targets of drug discovery efforts. Recent work has also shown their potential as highly rapid and sensitive single molecule sensors. However, techniques conventionally used to measure the electrical transport through these proteins can be problematic to form and are extremely fragile, limiting the range and scope of possible studies. We have developed two new technologies which alleviate these shortcomings: in situ encapsulation of lipid membranes in hydrogels and automated microfluidic formation. The hydrogel encapsulated membranes are mechanically robust and long-lived as a result of the intimate contact between the hydrogel and the membrane, enabling measurements of single channel currents for a week or longer. The automated microfluidic formation apparatus enables the creation and manipulation of lipid membranes and the incorporation and measurement of channel proteins in these membranes through an entirely computer controlled process. We are working to apply these technologies toward DNA sequencing, drug discovery, and single molecule biophysics.

Abstract: Sodium salt carboxymethyl cellulose (CMC) was used to prepare HAp-CMC composites through co-precipitation process. HAp nanorods with well controlled particle size were welll aligned along the c axis in the final composites. TEM, XRD, FTIR analysis were used to characterized the samples. It was found that the carboxyl groups in cellulose might be the main guiding site for the precipitation and growth of HAp and the formation of the resulting composites.

Abstract: DP-bioglass is one of biodegradable glasses, which can be used as bioactive material in soft tissue and bone. It was often used in orthopedy and plastic surgery. Recently, bioglass was also used as a carrier for drug and gene delivery systems. Additionally, ferrimagnetic DP-bioglass can be potential candidates for magnetic induction hyperthermia, by using a magnetic field. The aim of this work is the preparation and characterization of surface-modified ferrimagnetic DP-bioglass. First DP-bioglass has to be surface-modified with polyethylene glycol (PEG) and folic acid (FA) to improve its intracellular uptake and ability to target specific cells. PEG-FA complex was synthesized using carbodiimide (DCC) to link PEG with FA. Then PEG-FA complex were immobilized on the surface of DP-bioglass by using amino-silane (AEAPS) as a coupling agent. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA) was used to demonstrate this immobilization process. In biological study showed that immobilized ferromagnetic DP-bioglass with PEG-FA was non-cytotoxicity and significantly enhanced the intracellular uptake of DP-bioglass by target cells.