The particle size is one of critical parameters influencing the biodistribution of detonation nanodiamonds (DND) after their administration into the body. As DNDs are prone to aggregation, the difference between their sizes in aqueous and physiological solutions has to be taken into account. Radioactive I125-BSA molecules were covalently immobilized on DNDs divided in three fractions of different average size. The DND-BSAI125 conjugates were intravenously administrated into adult mice and the particle allocation in the animal's organs and blood was evaluated based on the radioactivity distribution. We conclude that most of the conjugates were taken from the bloodstream and trapped in the liver and spleen. The short-term distribution pattern for all DNDs was similar regardless of size and practically unchanged with time. No significant clearance of the particles was observed for 4 h, but the presence of DNDs was detected in the blood. It was found that the largest particles tend to accumulate more into the liver as compared to the smaller ones. However, the size effect was not well pronounced for the studied size range.

Model test-systems for biochemical determination of glucose and cholesterol are designed by covalent coupling of enzymes to the surface of modified nanodiamonds (MND). In both cases after immobilization on MND the enzymes exhibit activity and catalyze the formation of a colored product in the chain of successive enzymatic reactions of oxidative azocoupling (Н₂О₂—4-aminoantipyrine—phenol). Produced MND-enzymes complexes: function in DI water and various buffers, over a wide range of temperature and pH, provide for the linear product yield over a broad concentration range of analyzed substances, make possible to test cholesterol and glucose in vitro many times, exhibit functional activity after long storage at + 4°C.

This paper demonstrates the effectiveness of using detonation nanodiamonds (DNDs) for detecting phenol in aqueous medium. The study has shown that the catalytic effect of DNDs in the oxidative azo coupling reaction (phenol-4-aminoantipyrine-hydrogen peroxide) is produced by trace amounts of iron and copper ions adsorbed on the surface of nanoparticles. The effectiveness of DNDs as a catalyst is determined by the amounts of these adsorbates and can be enhanced by a factor of two by additional adsorption of these ions onto the nanoparticles. A rise in the temperature of the DND-catalyzed azo coupling reaction leads to a considerable (4.5-fold) increase in the reaction product yield. DNDs used to detect phenol in aqueous medium enable a linear increase in the yield of the product of the azo coupling reaction at concentrations of the analyte of between 0.05 and 10 μg/ml. The study demonstrates that DNDs can be reused to detect phenol in water samples.

The catalytic efficiency of modified nanodiamonds (MND) in reactions of interaction between organic compounds was demonstrated on the example of azocoupling reaction (hydrogen peroxide-4-aminoantipyrine-phenol). It was found that catalytic action of MND was caused by redox active metal ions of Fe and Cu located on the MND surface. The neutralization of the ions significantly decreased catalytic properties of MND.