Portable Colorimetric Hydrogel Beads for Point-of-Care Antimicrobial Susceptibility Testing.

Sepsis is a life-threatening condition with systemic inflammatory responses caused by bacterial infections. Considering the emergence of antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), sepsis is a great threat to public health. The gold standard methods for antimicrobial susceptibility testing (AST), however, take at least approximately 3 days to implement the entire blood culture, pure culture, and AST processes. To overcome the time-consuming nature of conventional AST, a method employing a chromatic biosensor composed of poly(diacetylene), alginate, and LB broth (PAL) is introduced in this study. Compared to the gold standards, AST with PAL biosensors can be completed within a time frame as short as 16 h. Such a significant reduction in time is possible because the consecutive cultures and AST are carried out simultaneously by encapsulating the bacterial nutrients and detection molecules into a single component. The bead-like hydrogel sensors were used in their freeze-dried form, which endows them with portability and stability, thus making them adequate for point-of-care testing. The PAL biosensor yields minimum inhibitory concentrations comparable to those from the Clinical and Laboratory Standards Institute, and the applicability of the biosensor is further shown in MRSA-infected mice.

Aptamer-Conjugated Polydiacetylene Colorimetric Paper Chip for the Detection of Bacillus thuringiensis Spores.

A colorimetric polydiacetylene (PDA) paper strip sensor that can specifically recognize Bacillus thuringiensis (BT) HD-73 spores is described in this work. The target-specific aptamer was combined with PDA, and the aptamer-conjugated PDA vesicles were then coated on polyvinylidene fluoride (PVDF) paper strips by a simple solvent evaporation method. The PDA-aptamer paper strips can be used to detect the target without any pre-treatment. Using the paper strip, the presence of BT spores is directly observable by the naked eye based on the unique blue-to-red color transition of the PDA. Quantitative studies using the paper strip were also carried out by analyzing the color transitions of the PDA. The specificity of this PDA sensor was verified with a high concentration of Escherichia coli, and no discernable change was observed. The observable color change in the paper strip occurs in less than 1 h, and the limit of detection is 3 × 107 CFU/mL, much below the level harmful to humans. The PDA-based paper sensor, developed in this work, does not require a separate power or detection device, making the sensor strip highly transportable and suitable for spore analysis anytime and anywhere. Moreover, this paper sensor platform is easily fabricated, can be adapted to other targets, is highly portable, and is highly specific for the detection of BT spores.

Biomimetic Membranes with Transmembrane Proteins: State-of-the-Art in Transmembrane Protein Applications.

In biological cells, membrane proteins are the most crucial component for the maintenance of cell physiology and processes, including ion transportation, cell signaling, cell adhesion, and recognition of signal molecules. Therefore, researchers have proposed a number of membrane platforms to mimic the biological cell environment for transmembrane protein incorporation. The performance and selectivity of these transmembrane proteins based biomimetic platforms are far superior to those of traditional material platforms, but their lack of stability and scalability rule out their commercial presence. This review highlights the development of transmembrane protein-based biomimetic platforms for four major applications, which are biosensors, molecular interaction studies, energy harvesting, and water purification. We summarize the fundamental principles and recent progress in transmembrane protein biomimetic platforms for each application, discuss their limitations, and present future outlooks for industrial implementation.

Chromatic biosensor for detection of phosphinothricin acetyltransferase by use of polydiacetylene vesicles encapsulated within automatically generated immunohydrogel beads.

We developed a simple and sensitive colorimetric biosensor in the form of microparticles by using polydiacetylene (PDA) vesicles encapsulated within a hydrogel matrix for the detection of phosphinothricin acetyltransferase (PAT) protein, which is one of the most important marker proteins in genetically modified (GM) crops. Although PDA is commonly used as a sensing material due to its unique colorimetric properties, existing PDA biosensors are ineffective due to their low sensitivity as well as their lack of robustness. To overcome these disadvantages, we devised immunohydrogel beads made of anti-PAT-conjugated PDA vesicles embedded at high density within a poly(ethylene glycol) diacrylate (PEG-DA) hydrogel matrix. In addition, the construction of immunohydrogel beads was automated by use of a microfluidic device. In the immunoreaction, the sensitivity of antibody-conjugated PDA vesicles was significantly amplified, as monitored by the unaided eye. The limit of detection for target molecules reached as low as 20 nM, which is sufficiently low enough to detect target materials in GM organisms. Collectively, the results show that immunohydrogel beads constitute a promising colorimetric sensing platform for onsite testing in a number of fields, such as the food and medical industries, as well as warfare situations.

Automated formation of multicomponent-encapuslating vesosomes using continuous flow microcentrifugation.

Vesosomes - hierarchical assemblies consisting of membrane-bound vesicles of various scales - are potentially powerful models of cellular compartmentalization. Current methods of vesosome fabrication are labor intensive, and offer little control over the size and uniformity of the final product. In this article, we report the development of an automated vesosome formation platform using a microfluidic device and a continuous flow microcentrifuge. In the microfluidic device, water-in-oil droplets containing nanoscale vesicles in the water phase were formed using T-junction geometry, in which a lipid monolayer is formed at the oil/water interface. These water-in-oil droplets were then immediately transferred to the continuous flow microcentrifuge. When a water-in-oil droplet passed through a second lipid monolayer formed in the continuous flow microcentrifuge, a bilayer-encapsulated vesosome was created, which contained all of the contents of the aqueous phase encapsulated within the vesosome. Encapsulation of nanoscale liposomes within the outer vesosome membrane was confirmed by fluorescence microscopy. Laser diffraction analysis showed that the vesosomes we fabricated were uniform (coefficient of variation of 0.029). The yield of the continuous flow microcentrifuge is high, with over 60% of impinging water droplets being converted to vesosomes. Our system provides a fully automatable route for the generation of vesosomes encapsulating arbitrary contents. The method employed in this work is simple and can be readily applied to a variety of systems, providing a facile platform for fabricating multicomponent carriers and model cells.