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Rationale: Colorectal cancer (CRC) is one of the most prevalent oncological diseases with high mortality. Invasive optical (endoscopic) colono- scopy has been recognized as a golden standard for the CRC diagnostics. A promising area is the development of non-invasive tools for CRC diagnosis with circular RNA (circRNA). One of the most sensitive non-invasive tools for detection of cancer RNA markers is considered to be the biosensor methods with the use of nanowire chips with oDNA probes (fragments of DNA oligonucleotides) immobilized on their surface. It has been previously shown that circRNA hsa_circ_0136666_CBC1, hsa_circ_0031263_CBC1, and hsa_circ_0072715_CBC1 are associated with CRC. Aim: To determine the lower limit of concentration sensitivity of detection of CRC-associated circRNA with nanowire chips with immobilized oDNA probes, to demonstrate the usability of these chips for non-invasive detection of circRNA in plasma in the CRC diagnostics, and to establish the potential for the use of nanowire chips for the early CRC diagnosis. Methods: To ensure biospecific binding of the circRNA hsa_circ_0136666_CBC1, hsa_circ_0031263_CBC1, and hsa_circ_0072715_CBC1 (the CRC markers), oDNA probes with the nucleotide sequences complementary to the target circRNA have been immobilized on the nanowire surface. At the study step 1, we detected the lower concentration limit for detection of the target molecules with the use of their analogues, i.e. synthetic model oDNA with the nucleotide sequences complementary to oDNA probes. At the study step 2, we used the nanowire chips with immobilized oDNA probes to detect the circRNA in plasma of the patients with confirmed CRC. Plasma samples from non-cancer patients were used as controls. Results: The lower concentration limit for the detection of DNA analogues of the circRNA hsa_circ_0136666_CBC1, hsa_circ_0031263_CBC1, and hsa_circ_0072715_CBC1 with nanowire chips with oDNA probes was 10-16 М. The analysis of total RNA isolated from plasma of the CRC patients showed a significant increase in the signal from the sensory elements of the nanowire chip. The analysis of plasma samples from the non-cancer patients, the nanowire signal changes were non-significant indicating the absence of detectable concentrations of the circRNA in plasma of the non-cancer patients. Conclusion: We have identified the minimal detectable concentration of the circRNA hsa_circ_0136666_CBC1, hsa_circ_0031263_CBC1, and hsa_circ_0072715_CBC1, associated to the development of CRC, with nanowire chips with immobilized oDNA probes: it was 10-16 М. The experiment showed the usability of such nanowire chips for non-invasive detection of the given circRNA markers in total RNA samples isolated from plasma of CRC patients.

Prostate cancer (PC) is one of the major causes of death among elderly men. PC is often diagnosed later in progression due to asymptomatic early stages. Early detection of PC is thus crucial for effective PC treatment. The aim of this study is the simultaneous highly sensitive detection of a palette of PC-associated microRNAs (miRNAs) in human plasma samples. With this aim, a nanoribbon biosensor system based on “silicon-on-insulator” structures (SOI-NR biosensor) has been employed. In order to provide biospecific detection of the target miRNAs, the surface of individual nanoribbons has been sensitized with DNA oligonucleotide probes (oDNA probes) complementary to the target miRNAs. The lowest concentration of nucleic acids, detectable with our biosensor, has been found to be 1.1 × 10−17 M. The successful detection of target miRNAs, isolated from real plasma samples of PC patients, has also been demonstrated. We believe that the development of highly sensitive nanotechnology-based biosensors for the detection of PC markers is a step towards personalized medicine.

Ovarian cancer is a gynecological cancer characterized by a high mortality rate and tumor heterogeneity. Its early detection and primary prophylaxis are difficult to perform. Detecting biomarkers for ovarian cancer plays a pivotal role in therapy effectiveness and affects patients’ survival. This study demonstrates the detection of microRNAs (miRNAs), which were reported to be associated with ovarian cancer tumorigenesis, with a nanowire biosensor based on silicon-on-insulator structures (SOI-NW biosensor). The advantages of the method proposed for miRNA detection using the SOI-NW biosensor are as follows: (1) no need for additional labeling or amplification reaction during sample preparation, and (2) real-time detection of target biomolecules. The detecting component of the biosensor is a chip with an array of 3 µm wide, 10 µm long silicon nanowires on its surface. The SOI-NW chip was fabricated using the “top-down” method, which is compatible with large-scale CMOS technology. Oligonucleotide probes (oDNA probes) carrying sequences complementary to the target miRNAs were covalently immobilized on the nanowire surface to ensure high-sensitivity biospecific sensing of the target biomolecules. The study involved two experimental series. Detection of model DNA oligonucleotides being synthetic analogs of the target miRNAs was carried out to assess the method’s sensitivity. The lowest concentration of the target oligonucleotides detectable in buffer solution was 1.1 × 10−16 M. In the second experimental series, detection of miRNAs (miRNA-21, miRNA-141, and miRNA-200a) isolated from blood plasma samples collected from patients having a verified diagnosis of ovarian cancer was performed. The results of our present study represent a step towards the development of novel highly sensitive diagnostic systems for the early revelation of ovarian cancer in women.

Multipulse laser processing of materials is promising because of the additional possibilities to control the thickness of the treated and the heat-affected zones and the energy efficiency. To study the physics of mutual interaction of pulses at high repetition rate, a model is proposed where heat transfer in the target and gas-dynamics of vapor and ambient gas are coupled by the gas-dynamic boundary conditions of evaporation/condensation. Numerical calculations are accomplished for a substrate of an austenitic steel subjected to a 300 ns single pulse of CO2 laser and a sequence of the similar pulses with lower intensity and 10 μs inter-pulse separation assuring approximately the same thermal impact on the target. It is revealed that the pulses of the sequence interact due to heat accumulation in the target but they cannot interact through the gas phase. Evaporation is considerably more intensive at the single-pulse processing. The vapor is slightly ionized and absorbs the infrared laser radiation by inverse bremsstrahlung. The estimated absorption coefficient and the optical thickness of the vapor domain are considerably greater for the single-pulse regime. The absorption initiates optical breakdown and the ignition of plasma shielding the target from laser radiation. The multipulse laser processing can be applied to avoid plasma ignition.