No abstract

Early stage detection of cancer is essential for the improved long-term survival of patients. Currently, costly, extensively complex and invasive procedures, such as surgical tissue biopsies, are used for cancer screening. Thus, over the past few decades, advancements in microfluidics and lab-on-a-chip approaches have been made to develop minimally invasive and miniaturized platforms to identify and segregate circulating cancer biomarkers such as exosomes, circulating tumor cells (CTCs) and cell-free DNA (cfDNA) from body fluids. Our study presents a comprehensive overview of all such microfluidics based approaches for point-of-care cancer diagnostics, which have proven to require significantly reduced sample volumes with cost effective and minimally invasive criteria. We have also discussed the need for integrated and more efficient devices to further advance these technologies to be suitable for liquid biopsy in the clinical settings.

MicroRNAs (miRs) are small noncoding RNAs that play a critical role in gene regulation. Recently, traces of cancer-related miRs have been identified in body fluids, which make them remarkable noninvasive biomarkers. In this study, a new nanopore-based detection scheme utilizing a borosilicate micropipette and an assay of complementary γ-peptide nucleic acid (γ-PNA) probes conjugated to polystyrene beads have been reported for the detection of miR-204 and miR-210 related to the clear cell Renal Cell Carcinoma (ccRCC). Electroosmotic flow (EOF) is induced as the driving force to transport PNA-beads harboring target miRs to the tip of the pore (sensing zone), which results in pore blockades with unique and easily distinguishable serrated shape electrical signals. The concentration detection limit is investigated to be 1 and 10 fM for miR-204 and miR-210, respectively. The EOF transport mechanism enables highly sensitive detection of molecules with low surface charge density with 97.6% detection accuracy compared to the conventional electrophoretically driven methods. Furthermore, resistive-pulse experiments are conducted to study the correlation of the particles' surface charge density with their translocation time and verify the detection principle.

The Coulombic interaction in the oriented attachment growth of one-dimensional nanotubes is evaluated via a newly-derived analytical expression of the Coulombic interactions between a spherical attaching nanoparticle and a growing nanotube. The correlation between the interaction and the important growth parameters, including nanoparticle/nanotube size, aspect ratio, and nanoparticle-nanotube separation has been analyzed. Our work provides, for the first time, an efficient platform to investigate the growth kinetics and mechanisms of oriented attachment growth of nanotubes.