An integrated microfluidic system for diagnosis of the resistance of Helicobacter pylori to quinolone-based antibiotics.

Helicobacter pylori (H. pylori) is a species of bacteria that can colonize the human stomach mucosa. It is closely associated with gastric diseases such as ulcer and inflammation. Recently, some H. pylori strains were found to express resistance to a family of antibiotics known as quinolones due to single-point mutations. Although traditional polymerase chain reaction (PCR) and molecular diagnostic-based approaches can be used to determine the presence and abundance of antibiotic-resistant H. pylori strains, such processes are relatively expensive, labor-intensive, and require bulky and costly equipment. This study therefore reports an advanced diagnostic assay performed on an integrated microfluidic system for rapid detection of antibiotic resistance in H. pylori. The assay features three components: (1) nucleic acid extraction by specific probe-conjugated magnetic beads, (2) amplification of the target deoxyribonucleic acid (DNA) fragments by using single-nucleotide-polymorphism polymerase chain reaction (SNP-PCR), and (3) optical detection of the PCR products. The device integrates several microfluidic components including micro-pumps, normally-closed micro-valves, and reaction chambers such that the entire diagnostic assay can be automatically executed on a single microfluidic system within one hour with detection limits of 10(0), 10(2), and 10(2) bacterial cells for H. pylori detection and two different SNP sites strains. Three PCR-based assays for determining presence of H. pylori infection and two DNA single-point mutation assays aimed at determining whether the infected strains were resistant to quinolone can be performed simultaneously on a single chip, suggesting that this microfluidic system could be a promising tool for rapid diagnosis of the presence of antibiotic-resistant H. pylori strains.

Cancer cell-specific oligopeptides selected by an integrated microfluidic system from a phage display library for ovarian cancer diagnosis.

Ovarian cancer is one of the leading causes of female mortality worldwide. Unfortunately, there are currently few high-specificity candidate oligopeptide targeting agents that can be used for early diagnosis of this cancer. It has been suggested that cancer-specific oligopeptides could be screened from a phage display library. However, conventional methods are tedious, labor-intensive, and time consuming. Therefore, a novel, integrated microfluidic system was developed to automate the entire screening process for ovarian cancer cell-specific oligopeptides. An oligopeptide screened with microfluidic chip-based technique was demonstrated to have high affinity to ovarian cancer cells and demonstrated relatively low binding to other cancer cells, indicating a high specificity. Furthermore, the developed method consumed relatively low volumes of samples and reagents; only 70 µL of reactant was used within the whole experimental process. Each panning process was also significantly shortened to only 7.5 hours. Therefore, the screened oligopeptide could be used to isolate ovarian cancer cells in a rapid manner, thus greatly expediting the diagnosis and its application as oligopeptide targeting agent for theranostics of this cancer.

An integrated microfluidic system for screening of phage-displayed peptides specific to colon cancer cells and colon cancer stem cells.

Affinity reagents recognizing biomarkers specifically are essential components of clinical diagnostics and target therapeutics. However, conventional methods for screening of these reagents often have drawbacks such as large reagent consumption, the labor-intensive or time-consuming procedures, and the involvement of bulky or expensive equipment. Alternatively, microfluidic platforms could potentially automate the screening process within a shorter period of time and reduce reagent and sample consumption dramatically. It has been demonstrated recently that a subpopulation of tumor cells known as cancer stem cells possess high drug resistance and proliferation potential and are regarded as the main cause of metastasis. Therefore, a peptide that recognizes cancer stem cells and differentiates them from other cancer cells will be extremely useful in early diagnosis and target therapy. This study utilized M13 phage display technology to identify peptides that bind, respectively, to colon cancer cells and colon cancer stem cells using an integrated microfluidic system. In addition to positive selection, a negative selection process was integrated on the chip to achieve the selection of peptides of high affinity and specificity. We successfully screened three peptides specific to colon cancer cells and colon cancer stem cells, namely, HOLC-1, HOLC-2, and COLC-1, respectively, and their specificity was measured by the capture rate between target, control, and other cell lines. The capture rates are 43.40 ± 7.23%, 45.16 ± 7.12%, and 49.79 ± 5.34% for colon cancer cells and colon cancer stem cells, respectively, showing a higher specificity on target cells than on control and other cell lines. The developed technique may be promising for early diagnosis of cancer cells and target therapeutics.

Screening of aptamers specific to colorectal cancer cells and stem cells by utilizing On-chip Cell-SELEX.

Colorectal cancer (CRC) is the most frequently diagnosed cancer around the world, causing about 700,000 deaths every year. It is clear now that a small fraction of CRC, named colorectal cancer stem cells (CSCs) exhibiting self-renewal and extensive proliferative activities, are hard to be eradicated. Unfortunately, highly specific biomarkers for colorectal CSC (CR-CSCs) are lacking that prohibits the development of effective therapeutic strategies. This study designed and manufactured a novel microfluidic system capable of performing a fully automated cell-based, systematic evolution of ligands by exponential enrichment (SELEX) process. Eight CR-CSC/CRC-specific aptamers were successfully selected using the microfluidic chip. Three of the aptamers showed high affinities towards their respective target cells with a dissociation constant of 27.4, 28.5 and 12.3 nM, which are comparable to that of antibodies.