A microchip developed for detecting antibodies against plaque-derived antigens

Currently available Russia-made preparations intended for serological plague diagnostics are usually aimed at detecting antibodies to single bacterial antigens in the blood serum. To improve reliability of the data obtained, it is rational to use test systems to simultaneously quantify antibodies to several immunodominant Y. pestis antigens. An opportunity of using biochip technology for quantifying specific antibodies to Yersinia pestis antigens was investigated. To do this, 5 commercially available sera, 35 blood sera obtained from individuals vaccinated with live plague vaccine collected 1, 4, 5, 18 months after immunization, as well as 5 sera obtained from healthy donors were analyzed. The objective of this work was to develop a biological microchip (immunochip) for detecting antibodies specific to Y. pestis-derived antigens. In particular, amino-modified slides were sensitized by immunodominant Yersinia pestis-derived antigens: capsule antigen F1, lipopolysaccharide (LPS), main somatic antigen (MSA), fibrinolysin, and pestin PP. Diagnostic specificity and sensitivity of the immunochip were assessed by using the approved homoand heterologous immune-biological preparations and experimental animal sera. It was found that the immunochip demonstrated a 100% diagnostic efficiency. An opportunity of applying this immunochip to determine specific antibody profile in individuals vaccinated with live plague vaccine was estimated. A commercially available ELISA-AB-F1 of Yersinia pestis kit was used for comparison that allowed to detect antibodies to Y. pestis F1 antigen in 77.1% of vaccinated individuals within the examined time period covering between 1 to 18 months post-vaccination, at titer 1:160–1:2560. In contrast, using the immunochip resulted in detecting F1 antigen-specific antibodies in 91.4% of samples post-vaccination at titer 1:320–1:2560. Moreover, such immunochip additionally allowed to detect antibodies specific to the remainder of Y. pestis-derived LPS, MSA, pestin PP in 54.3%, 20%, 42% of vaccinated individuals, respectively. The percentage of positive seroconversion in individuals vaccinated with live plague vaccine was 77.1% based on the ELISA data, 91.4% — to the F1 antigen according to the immunochip data, and 94.3% — by analyzing an extended antigen panel. Combining multiple antigenic markers in our immunochip allowed to identify greater seroconversion among vaccinated people compared to a standard ELISA. Thus, the data obtained suggest that the proposed immunochip technology might be promising in assessing developing humoral immunity.

Molecular and epidemiological characterization of rpoB mutations in rifampicin-resistant Mycobacterium tuberculosis in Kyrgyz Republic

The nature and frequency of mutations in the rpoB gene of M. tuberculosis (MBT) vary considerably in various geographical locations. There is no information on the prevalence of specific mutations in the rpoB gene of MBT isolated from patients in Kyrgyz Republic. In this work, we analyzed a distribution of the rpoB gene mutations in Kyrgyz Republic. A total of 380 rifampicin-sensitive and 225 rifampicin-resistant MBT cultures were analyzed to identify and to characterize mutations in the rpoB gene using a biological microchip assay. The biochip test determined 18 different mutation types in 8 codons of the rifampicin-resistant samples. The majority of mutations (180 of 225, or 80 %) were in the codons 531 and 526, mainly in the codon 531 (137 of 225, 60.8 %). The Ser531>Leu mutation (134 of 225, 59.4 %) was by far the most common. Another group of mutations were in the codon 526 (43 of 225, 19.1 %). Five different types of mutations were found in the codon 526 which were: His526®Tyr (4.9 %), His 526®Asp (4.9 %), His526®Arg (4.0 %), His526®Leu (3.5 %), and His526®Pro (1.8 %). The third group of common mutations were Leu511®Pro (6.3 %) and Asp516®Tyr (4.4 %). Other mutations found in the codons 533, 522, 513, and 512 were less frequent and had a very low rate comprising about 1.8 % of the total mutation number among 225 rifampicinresistant samples.

Optimization of Si/SiGe Microrefrigerators for Hybrid Solid-State/Liquid Cooling

Monolithic Solid-state microrefrigerators have attracted a lot of attention during the last ten years since they have the potential to solve some of the problems related to localized heat generation and temperature stabilization in optoelectronic, microelectronics or even biological microchip applications. Combination of the solid-state cooling with other conventional techniques like liquid cooling, offers an additional degree of freedom to control both the overall temperature of the chip and to remove hot spots. We present a new approach based on Thermal Quadrupoles Method to model the behavior of a single stage Si/SiGe microrefrigerator in the DC operating regime. The sensitivity and precision of this method come from its analytical expressions, which are based on the solution of Fourier’s heat diffusion equation in the Laplace domain. The microrefrigerator top surface temperature is calculated by taking into account all possible mechanisms of heat generation and conduction within the entire device. The 3D heat and current spreading in the substrate is taken into account. The parasitic heat leakage to the cold junction due to heat generation and heat conduction within the metal lead is also considered. The theoretical results are then compared with experimental ones for several microrefrigerator sizes. A good agreement is found between them. Based on the simulations, the structure of the microrefrigerator is optimized for lowering the overall chip temperature and removing high power density hot spots in several applications in conjunction with liquid cooling techniques.