Rivka Zusman

Biochemically active sol-gel glasses: The trapping of enzymes ☆

Abstract We describe the preparation and properties of a biochemically active sol-gel glass, obtained by trapping the enzyme alkaline phosphatase (ALP) in a polymerizing tetramethoxysilane. The immobilized purified ALP from bovine intestinal mucosa had a 30% activity yield and an improved stability to thermal deactivation compared to a solution. The composite bioactive glass was preserved in water at room temperature for two months without loosing activity. A non-Michaelis-Menten kinetics was observed. The concept of preparing bioactive materials by the sol-gel method seems to be general. Thus, other enzymes (chitinase, aspartase, β-glucosidase) were successfully trapped.

Doped sol-gel glasses as chemical sensors☆

Abstract It is reported that by trapping suitable analytical reagents, porous sol-gel glasses can be used for the preparation of a wide variety of chemical-sensing materials. The key to the successful preparation of these materials is based on the observation that a substantial fraction of the trapped molecules is exposed to the liquid or gaseous intra-pore volume. The glass matrix thus serves as a solid support for analytical reagents which interact with analyzates present in the adjacent phase. The phenomenon is quite general, and has been demonstrated for a variety of color tests for metal cations, proton (pH indication), anions, and organic molecules.

The spectroscopic behaviour of rhodamine 6G in polar and non-polar solvents and in thin glass and PMMA films

Abstract Absorption, fluorescence, quantum yields and lifetimes of rhodamine 6G in water, methanol, dichloroethane and chloroform were measured. From a comparison of these quantities with those for thin glass and plastic films conclusions are drawn about dimer formation and the stability of rhodamine 6G in these materials. The stability in the films is increased as compared with the solutions.

Doped sol-gel glasses as pH sensors

Abstract A series of pH indicators were trapped in sol-gel porous glasses by polymerization of tetramethoxysilane in the presence of a surface active agent. The properties of these novel sensing materials including spectral shifts, shifts in the pH-sensing range, cycle repeatability, leachability, rates of response and isosbestic points are described. A prototype of a pH meter based on a pH-sensing glass was constructed.

Luminescent solar concentrators based on thin films of polymethylmethacrylate on a polymethylmethacrylate support

Abstract Optical efficiencies for luminescence solar concentrators based on thin films of polymethylmethacrylate doped with luminescent dye BASF-241 deposited on PMMA transparent plates are measured and calculated. The influence of the refractive index of optical matching material on LSC performance is analyzed. A method for estimation of the refractive index of the thin film is devised and tested. Experimental data for the thin films doped with the dyes are consistent with the calculations.

Design and Properties of Enzymes Immobilized in Sol-Gel Glass Matrices

Technical convenience and the urge to lower costs are driving industrial interest, and thus applied research, toward ever-increasing effort to prepare successfully immobilized enzymes. Immobilization allows re-use of enzymes, protects them from harsh external conditions, from microbial contamination, and prolongs their useful lifetime. There are probably as many immobilization methods as there are enzymes. This proliferation of techniques reflects the complexity of the biological material and the variety of its uses. Simple inexpensive general techniques, resulting in stable and active enzyme catalysts are yet in demand (Kennedy and White, 1985a).

Comparative study of the role of serum levels of p53 antigen and its tumor cell concentration in colon cancer detection

The role of serum levels of p53 antigen in detection of colon cancer was studied in different groups of cancer and noncancer patients and was compared with the results of immunohistochemical analyses. The p53 antigen was isolated from the human serum as a cytoplasmic fraction using the recently described new type of columns for affinity chromatography, gel fiberglass columns (Zusman and Zusman, 1995). Its concentration was detected by high performance liquid chromatography. The serum level of the p53 antigen significantly increased in cancer patients (3.6 mg ml(-1)) as compared to its concentration in patients with benign tumors (1.7 mg ml(-1)) or in patients with noncancer disorders (0.49 mg ml(-1)), and this was found to be a result of higher concentration of p53 protein in tumor cells. Coefficient of correlation between cellular concentration of p53 protein and its serum level was 0.44 in noncancer lesions and 0.48 in cancer patients. Serum levels of p53 antigen was shown to be highly active either in patients with noncancer lesions or in patients with cancer (r = 0.46 and 0.51 respectively), whereas the cell determination of p53 protein was effective only among noncancer patients (r = 0.61) but not in cancer patients (r = 0.22). The findings suggests that serum determination of p53 antigen can perhaps reveal this oncoprotein already in the early stages of cancer or even predict the putative development of cancer. The possibility to use the serum-levels of p53 antigen in the follow up patients with chronic diseases and to detect transformation of these diseases into cancer, or monitoring former cancer patients in order to detect as early as possible the incidence of recurrent cancer is discussed.

Expression of p53 protein in rat colon cancer cell lines transfected with Rous sarcoma virus-33.

Expression of the cytoplasmic soluble form of p53 protein in the different rat colon cancer cell lines transfected and non-transfected with Rous sarcoma virus-33 was studied. Concentrations of the p53 protein were detected by commonly used immunochemical methods after its isolation by affinity chromatography columns with the gel fiberglass membranes. The main component of tumor-associated antigens (TAA) eluted from virus-transfected cells was the 53 kDa protein in its cytoplasmic soluble fraction. The non-virogenic colon cancer cells contain a few proteins and concentration of 53 kDa protein was low. Western immunoblotting revealed that the 53 kDa protein isolated from the cell lyzates studied was distinctly recognized by the p53 MAb. ELISA showed that its concentration was markedly higher in the lyzate obtained from the highly virogenic and tumorigenic R9 cell line compared with the non-virogenic cell line RT1. We concluded that the expression of the p53 protein is related to the viral transfection of cancerous cells. The possible role of this phenomenon in the etiology of cancer is discussed.

Luminescent Solar Concentrators Based On Dyes Incorporated In Thin Polymer Films

Optical efficiencies for Luminescent Solar Concentrators (LSC) based on thin films of Polymethylmethacrylate (PMMA) doped by luminescent dye BASF-241 deposited on PMMA transparent plates are measured and calculated. The influence of refractive index of optical matching material on LSC performance is analyzed. A comparison of emission anisotropy with quantum yield and self-absorption leads to optimalization of thickness and optical density of the thin doped films. Enhancement of luminescence of Rhodamine 6G (Rh6G) in the presence of silver aggregates is reported.