Technology for Formation of Hybrid Microfluidic Biosensor Systems for Label-Free Fluorimetric Express Detection of Protein Structures based on Molecular Recognition

The development and comparative study of technologies for manufacturing elements of hybrid biosensor systems intended for express biomedical analysis has been carried out. The technological process included the formation of the relief of microfluidic channels, chemical modification of their working surface, deposition of solid-state phosphor layers, sealing of the system, installation of inlet ports and packaging.

Development of a microfluidic biosensor for the diagnostics and typing of Mycobacterium Tuberculosis

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.

Analysis of Temperature-Jump Boundary Conditions on Heat Transfer for Heterogeneous Microfluidic Immunosensors

The objective of the current study is to analyze numerically the effect of the temperature-jump boundary condition on heterogeneous microfluidic immunosensors under electrothermal force. A three-dimensional simulation using the finite element method on the binding reaction kinetics of C-reactive protein (CRP) was performed. The kinetic reaction rate was calculated with coupled Laplace, Navier−Stokes, energy, and mass diffusion equations. Two types of reaction surfaces were studied: one in the form of a disc surrounded by two electrodes and the other in the form of a circular ring, one electrode is located inside the ring and the other outside. The numerical results reveal that the performance of a microfluidic biosensor is enhanced by using the second design of the sensing area (circular ring) coupled with the electrothermal force. The improvement factor under the applied ac field 15 Vrms was about 1.2 for the first geometry and 3.6 for the second geometry. Furthermore, the effect of temperature jump on heat transfer rise and response time was studied. The effect of two crucial parameters, viz. Knudsen number (Kn) and thermal accommodation coefficient (σT) with and without electrothermal effect, were analyzed for the two configurations.