Nano-TiO2 stability in medium and size as important factors of toxicity in macrophage-like cells.

TiO2 along with nano-TiO2 are commonly found in consumer products. In vivo studies have observed an accumulation of nano-TiO2 in macrophages. However, characteristics of nano-TiO2 determining toxicity remain unclear. In our study, the cytotoxic effects of 14 diverse nano-TiO2 on THP-1 macrophage-like cells were measured by 3 cytotoxicity assays (MTS, WST-1 and LDH). Total averaged cytotoxicity was calculated using principal component analysis. Characteristics of all 14 nano-TiO2 included hydrodynamic diameter, zeta potential, shape, polydispersity index (PDI) and concentration; moreover, crystal form, specific surface area and crystallite size were measured for 10 nano-TiO2.The variables affecting cytotoxicity were chosen using LASSO (least absolute shrinkage and selection operator). Except for concentration, PDI in media measured within 1 h after preparation of the nanomaterial dispersion was selected as a variable affecting cytotoxicity: stable dispersion resulted in higher cytotoxic effects. Crystallite size has been shown to have nonlinear effects (particles of sizes between 20 and 60 nm were cytotoxic while smaller and larger ones were not) and thus it has been excluded from LASSO. The shape (particles/fibre) and crystal form did not affect the cytotoxicity. PDI and the nonlinear effect of size could be an explanation for the inconsistencies of the cytotoxicity of nano-TiO2 in various studies.

Remarks on small sample size taken from reference population for examination of factor VIII.

Investigation of plasma factor VIII activities in 20 reference (normal) individuals (N = 20) is frequently used to evaluate the reference distribution parameters by means of simple statistical method. Two examples demonstrate the inaccuracy of conclusions of such a small sample of data. The first one shows the comparison of estimate of F.VIII:C reference limits obtained from examination of 6 different groups randomly chosen (N = 20 each) with a group of N = 120 reference individuals. The second example presents the balance of haemophilia A carrier detection rate performed in 30 obligatory carriers and 42 normal women by examination of F.VIII:C and VWF-Ag using universal discriminant. The correction figures typical for specific conditions of our laboratory are obtained from examination of N = 20 and N = 80 individuals and using heuristic optimalization.

[Lyophilized plasmas for the control of thromboplastin time values and calibration of thromboplastins]. / Lyophilisierte Plasmen zur Kontrolle der Thromboplastinzeit-Werte und zur Kalibrierung der Thromboplastine.

The paper deals with the production of normal and pathological plasmas for the calibration of thromboplastin. Calibration is performed according to WHO principles. We compared single charges of thromboplastin (Sevac, CSSR, human brain) with each other and a selected reference charge with British thromboplastin. Lyophilised reference plasmas produced (20-50 healthy blood donors) and plasmas taken from patients treated with coumarin derivates (single and mixtures) could replace their fresh equivalents which was confirmed by testing 4 different batches. The stability of these plasmas (for a time of at least 12 months) was proved by repeated checks. These plasmas also served as controls in other laboratories in Czechoslovakia.

Lyophilised plasmas for one-stage determination of factor VIII.

Two batches of lyophilized normal pooled HEPES-stabilized plasma according to ZUCKER [11] and LOELIGER [7] were prepared. The F VIII activity established by the activated partial thromboplastin test (APTT-VIII) was identical in both plasmas and amounted to 0.99 U/ml (95% confidence limits 0.87 to 1.17 U/ml). It did not change within 11 months in plasmas according to ZUCKER, and 6 months in those according to LOELIGER (further on not followed). We prepared four batches of lyophilized HERPES-stabilized substrate plasma (severe form of hemophilia A) according to ZUCKER. They were employed for 5 to 13 months in APTT-VIII along with the frozen 3.2% sodium citrate substrate plasmas. The results showed a satisfactory agreement. The lyophilized plasmas did not influence even the dose-response-line. On the ground of these results we consider the reported lyophilized plasmas to be suitable reagents in APTT-VIII technique.