We present a high-precision technique for determination of the refractive index (RI) of liquids and gases. The technique is based on standard critical-angle refractometry, sensitivity of which is ...enhanced by deposition of an additional periodic multilayer stack on the interface between a prism and the medium under investigation. We show that this multilayer stack may be designed so that a reflectance change near the critical angle becomes much sharper than the one in the standard refractometers. Test measurements of set of glucose concentrations in the water are presented and baseline noise of 9
×
10
−8
RIU/Hz
1/2 is attained.
Introduction. Diarrheal syndrome is the most characteristic symptom of HIV infection, which occurs in 70% of patients and is often fatal. The severity of diarrheal syndrome, irrespective of immune ...status, is usually determined by specific microorganisms colonising the gastrointestinal tract. The objective of this study is to assess the prevalence of classical pathogens of acute intestinal infections in diarrheal syndrome in HIV-infected residents of the Chechen Republic (Grozny). Materials and methods. Stool samples (n = 191) of HIV-infected patients with a history of diarrheal syndrome were studied by real-time PCR with two kits of reagents: "AmpliSens OKI screen-FL" for the detection of DNA/RNA of Shigella spp./EIEC, Salmonella spp., Campylobacter spp., Adenovirus, Rotavirus, Norovirus and Astrovirus; "AmpliSens Escherichiosis-FL" for the detection of diarrheagenic E. coli (DEC) DNA of five pathogroups: EPEC, EHEC, ETEC, EIEC, EAgEC. Results. Genetic markers of the acute intestinal infection pathogens were detected in 20.9% of the examined individuals. In patients aged 0–7 years and 18–24 years, DNA/RNA of the tested pathogens were not detected. DNA of bacterial pathogens accounted for 93.9%, RNA of viral pathogens — 6.1%. The etiological structure of bacterial infections was represented by a significant predominance of DEC (84.8%) compared to 10.9% of Campylobacter spp. and 4.4% of Salmonella spp. The structure of viral infections included 66.7% Rotavirus and 33.3% Norovirus. Genetic markers of Adenovirus and Astrovirus have not been identified. In 77.5% of HIV-infected patients, diarrheal syndrome was caused by one pathogen (mono-infection), but in nine examined patients (22.5%) it had a combined etiology. Conclusion. The etiology of acute intestinal infections in HIV-infected patients of the Chechen Republic includes bacterial and viral pathogens, in every fifth the cause of diarrheal disease was DEC. Due to diarrhea in HIV-infected people being a polyetiological disease, it is necessary to introduce a comprehensive, fast, reliable, and affordable method for identifying a wide range of pathogens that cause secondary infections.
Optical biosensors have played a key role in the selective recognition of target biomolecules and in biomolecular interaction analysis, providing kinetic data about biological binding events in real ...time without labeling. The advantages of the label-free concept are the elimination of detrimental effects from labels that may interfere with fundamental interaction and the absence of a time-consuming pretreatment. The disadvantages of all label-free techniques–including the most mature one, surface plasmon resonance (SPR) technique, are a deficient sensitivity to a specific signal and undesirable susceptibilities to non-specific signals, e.g., to the volume effect of refraction index variations. These variations arise from temperature fluctuations and drifts and they are the limiting factor for many state-of-the-art optical biosensors. Here we describe a new optical biosensor technique based on the registration of dual optical s-polarized waves on a photonic crystal surface. The simultaneous registration of two different optical modes from the same surface spot permits the segregation of the volume and the surface signals, while the absence of metal damping permits an increase in the propagation length of the optical surface waves and the sensitivity of the biosensor. The technique was tested with the binding of biotin molecules to a streptavidin monolayer that has been detected with a signal/noise ratio of about 15 at 1 s signal accumulation time. The detection limit is about 20 fg of the analyte on the probed spot of the surface.
Data on inefficiency in some cases or temporary positive effect of commercial probiotics led to the development of the concept of autoprobiotic therapy. According to this, the correction of disturbed ...microbiocenoses is carried out using autostrains of indigenous normal flora (bifidobacteria, lactobacilli and enterococci). However, publications about effectiveness of autoprobiotic therapy are few and contradictory.
The aim
of the study was to investigate the biological properties and probiotic potential of intestinal lactobacilli, as well as the effectiveness of autoprobiotic therapy, based on Lactobacillus spp.
Methods.
Biological properties (antibiotic resistance, hemolytic, adhesive and antagonistic activity) were studied in 159 strains of intestinal lactobacilli. Autoprobiotic therapy with sour-milk ferments based on lactobacilli autostrains was carried out in 78 patients of the of the North Caucasus Federal District (NCFD) hospitals to correct the microbiocenosis of the large intestine due to antibiotic therapy.
Results.
The indigene strains of the intestinal lactobacilli of patients of NCFD hospitals are characterized by a wide spectrum of antibiotic sensitivity, lack of hemolysin production, medium adhesiveness and a high degree of antagonistic activity. Autoprobiotic therapy using Lactobacillus spp. significantly increases the amount of lactobacilli of the large intestine of patients in hospitals of the North Caucasian Federal District.
Conclusion.
A high probiotic potential of the indigenous intestinal lactobacilli is identified, which makes it possible to use them as effective autoprobiotics. The effectiveness of autoprobiotics with fermented milk starters with Lactobacillus spp. has been proven to restore the normal amount of intestinal lactobacilli patients after the use of broad-spectrum antibiotics.
The present study was conducted to evaluate the effect of biologically active substances from Medusomyces gisevii zoogloea (MG zoogloeas) on intestine microbiocenosis of white rats during the ...experimental antibioticassociated dysbiosis. The intestinal dysbiosis of rats was induced by gentamicin sulfate in dose of 10 mg/ rat twice a day for 10 days for all the rats. Animals in the control group received a standard diet recommended by the Institute of Nutrition, the animals of the experimental group received 120 mg of active substance of MG zoogloea/rat every day during the experiment, in addition to the usual diet. After the termination of the oral administration of gentamicin the animals of the second sub-group (experimental 2) received 120 mg of active substance of MG zoogloea every day during the experiment, in addition to the basic diet. The animals in the control group showed a dysbiosis symptoms, observed a significant decrease in the total bacterial counts, as well as the decrease of Bifidobacterium spp, Lactobacillus spp, Escherichia coli level starting from the fourth until 10th day of the experiment, the number of Candida spp. increased. Animals of the experimental group avoided the symptoms of dysbiosis, reduce of the test groups of bacteria occurred only on the eighth day, and Candida level did not rise. After discontinuation of gentamicin administration rats treated with MG showed rapid disappearance of dysbiosis symptoms, the number of microflora started to improve significantly already in the fourth day, while the control sub-group animals showed small increase occurred only on the eighth day. Results indicated that using biologically active substances from Medusomyces gisevii zoogloea has positive effects on intestine microbiocenosis of rats during the experimental antibiotic-associated dysbiosis.
Background. Despite on the general trend towards decreasing the incidence of newly diagnosed active forms of tuberculosis, the situation with spreading of this disease in Russian Federation remains ...extremely tense. At the same time, the diagnosis is carried out according to the standard scheme, which takes about a month; another month takes test formulation for drug sensitivity. Thus, the development of new methods for diagnostics and typing of mycobacteria, as well as practice implementation of these developments is an urgent direction. Modern developments in the field of microfluidic technologies open up great opportunities in this direction. Aim. Development of a method for identification and typing of Mycobacterium tuberculosis using a label-free biosensor on surface waves in a one-dimensional photonic crystal (PC SM biosensor). Methods. Oligonucleotide probes were selected and synthesized as DNA targets for M. tuberculosis typing. The photonic crystal surface was modified with aqueous solutions of (3-aminopropyl)triethoxysilane, Leuconostoc mesenteroides dextrans and bovine serum albumin. Experiments were carried out using a PC SM biosensor. Results. Sequences of detecting oligonucleotide probes were selected for spoligotyping of M. tuberculosis on the PC SM biosensor. Modification of their 3'-ends was carried out in order to create extended single-stranded regions that are not subject to the formation of secondary structures and facilitate hybridization with a single-stranded DNA target. Several series of experimental modifications of the PC surface were carried out by using L. mesenteroides dextrans with different functional groups (including detection of the modification results real time) with simultaneous registration of the increment layer size and volume refractive index of the mixture, which excludes the use of a reference cell. Other experiments were carried out to detect the specific binding of biotinylated oligonucleotide probes to the modified PC surface. Conclusions. A technique for the design of probes was developed and a model system of oligonucleotides for the detection of single-stranded DNA using a PC biosensor was proposed. The developed technique of modification of the PC surface with dextrans from L. mesenteroides, which allows to increase the sensitivity of detection of oligonucleotides using the PC SM biosensor. This approach will further expand the panel of diagnostic probes, including identification of resistance markers.
A photonic crystal surface mode imaging (PCSMi) technique is implemented for the simultaneous detection of antibody binding with specific antigens in arrays containing 96- and 384-spots. Like the ...surface plasmon resonance imaging (SPRi) technique, the presented approach is label-free and permits interrogating an analyte by hundreds of different ligands immobilized in small spots. The adsorption kinetics is recorded with a sub-picogram resolution at every spot simultaneously. Possible implementations of this technique for multiplexed and high-throughput biosensing are discussed.
•The simultaneous detection of biochemical reactions at 96 and 384 spots by a photonic crystal surface mode (PC SM) biosensor is presented.•The spectral shift of the PC SM resonance peak is detected by a standard color camera at each point of the PC chip surface.•Experimental data showed that the PC SMi biosensor can surpass its plasmonic counterpart (SPRi) both in signal-to-noise ratio and in dynamic range.
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