Timur A. Mukhametzyanov

Cellular imaging by green luminescence of Tb(III)-doped aminomodified silica nanoparticles

The work introduces Tb(III)-centered luminescence of amino-modified silica nanoparticles doped with Tb(III) complexes for cellular imaging. For these purposes water-in-oil procedure was optimized for synthesis of 20 and 35nm luminescent nanoparticles with amino-groups embedded on the surface. The obtained results indicate an impact of the nanoparticle size in decoration, aggregation behavior and luminescent properties of the nanoparticles in protein-based buffer solutions. Formation of a protein-based corona on the nanoparticles surface was revealed through the effect of the nanoparticles on helical superstructure of BSA. This effect is evident from CD spectral data, while no any size impact on the adsorption of BSA onto aminomodified silica surface was observed. Cellular uptake of the nanoparticles studied by confocal and TEM microscopy methods indicates greater cellular uptake for the smaller nanoparticles. Cytotoxicity of the nanoparticles was found to agree well with their cellular uptake behavior, which in turn was found to be greater for the smaller nanoparticles.

Influence of the Cross-Link Density on the Rate of Crystallization of Poly(ε-Caprolactone)

Cross-linked poly(ε-caprolactone) (PCL) is a smart biocompatible polymer exhibiting two-way shape memory effect. PCL samples with different cross-link density were synthesized by heating the polymer with various amounts of radical initiator benzoyl peroxide (BPO). Non-isothermal crystallization kinetics was characterized by means of conventional differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC). The latter technique was used to obtain the dependence of the degree of crystallinity on the preceding cooling rate by following the enthalpies of melting for each sample. It is shown that the cooling rate required to keep the cooled sample amorphous decreases with increasing cross-link density, i.e., crystallization process slows down monotonically. Covalent bonds between polymer chains impede the crystallization process. Consequently, FSC can be used as a rather quick and low sample consuming method to estimate the degree of cross-linking of PCL samples.

Fast scanning calorimetry of lysozyme unfolding at scanning rates from 5 K/min to 500,000 K/min

BACKGROUND Protein denaturation is often studied using differential scanning calorimetry (DSC). However, conventional instruments are limited in the temperature scanning rate available. Fast scanning calorimetry (FSC) provides an ability to study processes at much higher rates while using extremely small sample masses [ng]. This makes it a very interesting technique for protein investigation. METHODS A combination of conventional DSC and fast scanning calorimeters was used to study denaturation of lysozyme dissolved in glycerol. Glycerol was chosen as a solvent to prevent evaporation from the micro-sized samples of the fast scanning calorimeter. RESULTS The lysozyme denaturation temperatures in the range of scanning rates from 5 K/min to ca. 500,000 K/min follow the Arrhenius law. The experimental results for FSC and conventional DSC fall into two distinct clusters in a Kissinger plot, which are well approximated by two parallel straight lines. CONCLUSIONS The transition temperatures for the unfolding process measured on fast scanning calorimetry sensor are significantly lower than what could be expected from the results of conventional DSC using extrapolation to high scanning rates. Evidence for the influence of the relative surface area on the unfolding temperature was found. GENERAL SIGNIFICANCE For the first time, fast scanning calorimetry was employed to study protein denaturation with a range of temperature scanning rates of 5 orders of magnitude. Decreased thermal stability of the micro-sized samples on the fast scanning calorimeter raise caution over using bulk solution thermal stability data of proteins for applications where micro-sized dispersed protein solutions are used, e.g., spray drying.

A study of the formation of magnetically active solid dispersions of phenacetin using atomic and magnetic force microscopy

A lot of pharmaceutical substances have a poor solubility that limits their absorption and distribution to the targeted sites to elicit the desired action without causing untoward effects on healthy cells or tissues. For such drugs, new modes of delivery have to be developed for efficient and effective delivery of the drug to the target site. Formation of magnetically active solid dispersion of such drugs could be a useful approach to addressing this problem because they combine targeted delivery and good solubility. In this work, the distribution of superparamagnetic nanoparticles in the solid dispersion of polyethylene glycol with average molecular weight 950-1050 g/mol and phenacetin was studied using atomic force and magnetic force microscopy. The distribution of nanoparticles was found to be uniform in studied composites. Magnetically active solid dispersions may find application in the production of the capsulated drug delivery systems with enhanced solubility parameters.