Since the increment of the threat to public health caused by foodborne pathogens, researches have been widely studied on developing the miniaturized detection system for the on-site pathogen detection. In the study, we focused on the development of portable, robust, and disposable film-based polymerase chain reaction (PCR) chip containing a multiplex chamber for simultaneous gene amplification. In order to simply fabricate and operate a film-based PCR chip, different kinds of PCR chambers were designed and fabricated using polyethylene terephthalate (PET) and polyvinyl chloride (PVC) adhesive film, in comparison with commercial PCR, which employs a stereotyped system at a bench-top scale. No reagent leakage was confirmed during the PCR thermal cycling using the film PCR chip, which indicates that the film PCR chip is structurally stable for rapid heat cycling for DNA amplification. Owing to use of the thin film to fabricate the PCR chip, we are able to realize fast thermal transfer from the heat block that leads to short PCR amplification time. Moreover, using the film PCR chip, we could even amplify the target pathogen with 10 CFU mL⁻¹. The artificially infected milk with various concentration of Bacillus cereus was successfully amplified on a single film PCR chip. On the basis of the reliable results, the developed film PCR chip could be a useful tool as a POCT device to detect foodborne pathogens via genetic analysis.

To overcome the time and space constraints in disease diagnosis via the biosensing approach, we developed a new signal-transducing strategy that can be applied to colorimetric optical biosensors. Our study is focused on implementation of a signal transduction technology that can directly translate the color intensity signals—that require complicated optical equipment for the analysis—into signals that can be easily counted with the naked eye. Based on the selective light absorption and wavelength-filtering principles, our new optical signaling transducer was built from a common computer monitor and a smartphone. In this signal transducer, the liquid crystal display (LCD) panel of the computer monitor served as a light source and a signal guide generator. In addition, the smartphone was used as an optical receiver and signal display. As a biorecognition layer, a transparent and soft material-based biosensing channel was employed generating blue output via a target-specific bienzymatic chromogenic reaction. Using graphics editor software, we displayed the optical signal guide patterns containing multiple polygons (a triangle, circle, pentagon, heptagon, and 3/4 circle, each associated with a specified color ratio) on the LCD monitor panel. During observation of signal guide patterns displayed on the LCD monitor panel using a smartphone camera via the target analyte-loaded biosensing channel as a color-filtering layer, the number of observed polygons changed according to the concentration of the target analyte via the spectral correlation between absorbance changes in a solution of the biosensing channel and color emission properties of each type of polygon. By simple counting of the changes in the number of polygons registered by the smartphone camera, we could efficiently measure the concentration of a target analyte in a sample without complicated and expensive optical instruments. In a demonstration test on glucose as a model analyte, we could easily measure the concentration of glucose in the range from 0 to 10 mM.

Effective and reliable antibacterial surfaces are in high demand in modern society. Although recent works have shown excellent antibacterial performance by combining unique hierarchical nanotopological structures with functional polymer coating, determining the antibacterial performance arising from morphological changes is necessary. In this work, three-dimensional (3D) hierarchical polyaniline–gold (PANI/Au) hybrid nanopillars were successfully fabricated via chemical polymerization (i.e., dilute method). The morphology and structures of the PANI/Au nanopillars were controlled by the reaction time (10 min to 60 h) and the molar concentrations of the monomer (0.01, 0.1, and 1 M aniline), oxidant (0.002, 0.0067, 0.01, and 0.02 M ammonium persulfate), and acid (0.01, 0.1, 1, and 2 M perchloric acid). These complex combinations allow controlling the hierarchical micro- to nanostructure of PANI on a nanopillar array (NPA). Furthermore, the surface of the 3D PANI/Au hierarchical nanostructure can be chemically treated while maintaining the structure using initiated chemical vapor deposition. Moreover, the excellent antibacterial performance of the 3D PANI/Au hierarchical nanostructure (HNS) exceeds 99% after functional polymer coating. The excellent antibacterial performance of the obtained 3D PANI/Au HNS is mainly because of the complex topological and physicochemical surface modification. Thus, these 3D PANI/Au hierarchical nanostructures are promising high-performance antibacterial materials.

A novel modular chip-based bacterial DNA extraction device was developed to overcome limitations associated with conventional DNA extraction processes that involve lab-scale instrument systems. The DNA extraction modular chip consists of a core chamber, a magnetic jig, and a vibration jig. The vibration jig allows the precise blending of solutions such as a lysis buffer and target bacterial samples. The magnetic jig houses magnetic particles, which are modified with amine-family chemicals, to specifically immobilize bacterial DNA. Bacterial lysis and DNA extraction were shown to be simply performed by physically connecting the core chamber to both of the jigs. The performance of the developed modular chip was verified by real-time polymerase chain reaction (PCR) with post gel electrophoresis, and Escherichia coli O157:H7 was selected as a target bacterial species for testing. As a result, 1.0 × 10¹ colony forming unit (CFU) E. coli O157:H7 was effectively extracted using the modular chip. This confirmed that the developed DNA extraction chip may be simple and effective enough to use in the field. The developed chip shows high potential for functional expandability to ultimately be used in the molecular diagnosis of various pathogens.

Interfacial chemicals for metal surface functionalization were developed for applications of high water dispersibility and environmental stability. Metal nanomaterials, i.e., gold nanoparticles (AuNPs), were synthesized by introducing various interfacial chemicals, to improve the hydrophilicity of biosensors, such as those used in fluorescence resonance energy transfer (FRET) and lateral flow assay (LFA), respectively. Previously, thiolated AuNPs (SH-AuNPs) exhibited colloidal instability by forming irreversible aggregates in extreme environmental conditions; this phenomenon led to limitations such as poor sensitivity and reproducibility, in terms of biosensor application fields. Therefore, the development of novel interfacial chemicals remained a challenge for AuNP-based biosensor applications. Here, we first synthesized and demonstrated an ultra-stable AuNP functionalization by introducing N-heterocyclic carbene (NHC) compounds with a polyethylene glycol chain and azide terminal groups (NHC-AuNPs). The high binding energy of NHC-AuNPs compared with SH-AuNPs was demonstrated by density functional theory simulation, with NHC-AuNPs showing an unprecedented stability in extreme environmental conditions with varying ranges of pH, salts, and temperature; in particular, ultra-stability was observed in condition by freezing/thawing over 120 times. NHC-AuNPs were applied FRET and LFA biosensors and showed excellent sensing performances. Based on the results, NHC-AuNPs can be introduced for performance improvement in the development of diagnostic platforms to utilize in extreme environmental conditions.