Microdevice-based solid-phase polymerase chain reaction for rapid detection of pathogenic microorganisms

Detecting harmful algal blooms with nucleic acid amplification-based biotechnological tools

Harmful algal blooms (HABs) represent a growing threat to aquatic ecosystems and humans. Effective HAB management and mitigation efforts strongly rely on the availability of timely and in-situ tools for the detection of microalgae. In this sense, nucleic acid-based (molecular) methods are being considered for the unequivocal identification of microalgae as an attractive alternative to the currently used time-consuming and laboratory-based light microscopy techniques. This review provides an overview of the progress made on new molecular biotechnological tools for microalgal detection, particularly focusing on those that combine a nucleic acid (DNA or RNA) amplification step with detection. Different types of amplification processes (thermal and isothermal) and detection formats (e.g. microarrays, biosensors, lateral flows) are presented, and a comprehensive overview of their advantages and limitations is provided Although isothermal techniques are an attractive alternative to thermal amplification to reach in-situ analysis, further development is still required. Finally, current challenges, critical steps and future directions of the whole analysis process (from sample procurement to in-situ implementation) are described.

Fabrication of a polycarbonate microdevice and boronic acid-mediated surface modification for on-chip sample purification and amplification of foodborne pathogens

In this study, we integrated sample purification and genetic amplification in a seamless polycarbonate microdevice to facilitate foodborne pathogen detection. The sample purification process was realized based on the increased affinity of the boronic acid-modified surface toward the cis-diol group present on the bacterial outer membrane. The modification procedure was conducted at room temperature using disposable syringe. The visible color and fluorescence signals of alizarin red sodium were used to confirm the success of the surface modification process. Escherichia coli O157:H7 containing green fluorescence protein (GFP) and Staphylococcus aureus were chosen as the microbial models to demonstrate the nonspecific immobilization using the microdevice. Bacterial solutions of various concentrations were injected into the microdevice at three flow rates to optimize the operation conditions. This microdevice successfully amplified the 384-bp fragment of the eaeA gene of the captured E. coli O157:H7 within 1 h. Its detection limit for E. coli O157:H7 was determined to be 1 × 10³ colony-forming units per milliliter (CFU mL^-1). The proposed microdevice serves as a monolithic platform for facile and on-site identification of major foodborne pathogens.

Microfluidics for studying metastatic patterns of lung cancer

The incidence of lung cancer continues to rise worldwide. Because the aggressive metastasis of lung cancer cells is the major drawback of successful therapies, the crucial challenge of modern nanomedicine is to develop diagnostic tools to map the molecular mechanisms of metastasis in lung cancer patients. In recent years, microfluidic platforms have been given much attention as tools for novel point-of-care diagnostic, an important aspect being the reconstruction of the body organs and tissues mimicking the in vivo conditions in one simple microdevice. Herein, we present the first comprehensive overview of the microfluidic systems used as innovative tools in the studies of lung cancer metastasis including single cancer cell analysis, endothelial transmigration, distant niches migration and finally neoangiogenesis. The application of the microfluidic systems to study the intercellular crosstalk between lung cancer cells and surrounding tumor microenvironment and the connection with multiple molecular signals coming from the external cellular matrix are discussed. We also focus on recent breakthrough technologies regarding lab-on-chip devices that serve as tools for detecting circulating lung cancer cells. The superiority of microfluidic systems over traditional in vitro cell-based assays with regard to modern nanosafety studies and new cancer drug design and discovery is also addressed. Finally, the current progress and future challenges regarding printable and paper-based microfluidic devices for personalized nanomedicine are summarized.

Microdevice-based solid-phase polymerase chain reaction for rapid detection of pathogenic microorganisms

We demonstrate the integration of DNA amplification and detection functionalities developed on a lab-on-a-chip microdevice utilizing solid-phase polymerase chain reaction (SP-PCR) for point-of-need (PON) DNA analyses. First, the polycarbonate microdevice was fabricated by thermal bonding  to contain microchambers as reservoirs for performing SP-PCR. Next, the microchambers were subsequently modified with polyethyleneimine and glutaraldehyde for immobilizing amine-modified forward primers. During SP-PCR, the immobilized forward primers and freely diffusing fluorescence-labeled reverse primers cooperated to generate target amplicons, which remained covalently attached to the microchambers for the fluorescence detection. The SP-PCR microdevice was used for the direct identifications of two widely detected foodborne pathogens, namely Salmonella spp. and Staphylococcus aureus, and an alga causing harmful algal blooms annually in South Korea, Cochlodinium polykrikoides. The SP-PCR microdevice would be versatilely applied in PON testing as a universal platform for the fast identification of foodborne pathogens and environmentally threatening biogenic targets.