Reconfigurable Carbon Nanotube Multiplexed Sensing Devices

Here we report on the fabrication of reconfigurable and solution processable nanoscale biosensors with multisensing capability, based on single-walled carbon nanotubes (SWCNTs). Distinct DNA-wrapped (hence water-soluble) CNTs were immobilized from solution onto different prepatterned electrodes on the same chip, via a low-cost dielectrophoresis (DEP) methodology. The CNTs were functionalized with specific, and different, aptamer sequences that were employed as selective recognition elements for biomarkers indicative of stress and neuro-trauma conditions. Multiplexed detection of three different biomarkers was successfully performed, and real-time detection was achieved in serum down to physiologically relevant concentrations of 50 nM, 10 nM, and 500 pM for cortisol, dehydroepiandrosterone-sulfate (DHEAS), and neuropeptide Y (NPY), respectively. Additionally, the fabricated nanoscale devices were shown to be reconfigurable and reusable via a simple cleaning procedure. The general applicability of the strategy presented, and the facile device fabrication from aqueous solution, hold great potential for the development of the next generation of low power consumption portable diagnostic assays for the simultaneous monitoring of different health parameters

Cross-Reactive Plasmonic Aptasensors for Controlled Substance Identification

In this work, we developed an assay to determine if an arbitrary white powder is a controlled substance, given the plasmonic response of aptamer-gold nanoparticle conjugates (Apt-AuNPs). Toward this end, we designed Apt-AuNPs with specific a response to common controlled substances without cross reactivity to chemicals typically used as fillers in street formulations. Plasmonic sensor variation was shown to produce unique data fingerprints for each chemical analyzed, supporting the application of multivariate statistical techniques to annotate unknown samples by chemical similarity. Importantly, the assay takes less than fifteen minutes to run, and requires only a few micrograms of the material, making the proposed assay easily deployable in field operations

Bacterial Sunscreen: Layer-by-Layer Deposition of UV-Absorbing Polymers on Whole-Cell Biosensors

UV-protective coatings on live bacterial cells were created from the assembly of cationic and UV-absorbing anionic polyelectrolytes using layer-by-layer (LbL) methodology. A cationic polymer (polyallylamine) and three different anionic polymers with varying absorbance in the UV range (poly­(vinyl sulfate), poly­(4-styrenesulfonic acid), and humic acid) were used to encapsulate Escherichia coli cells with two different green fluorescent protein (GFP) expression systems: constitutive expression of a UV-excitable GFP (GFPuv) and regulated expression of the intensely fluorescent GFP from amphioxus (GFPa1) through a theophylline-inducible riboswitch. Riboswitches activate protein expression after specific ligand–RNA binding events. Hence, they operate as a cellular biosensor that will activate reporter protein synthesis after exposure to a ligand target. E. coli cells coated with UV-absorbing polymers demonstrated enhanced protection of GFP stability, metabolic activity, and viability after prolonged exposure to radiation from a germicidal lamp. The results show the effectiveness of LbL coatings to provide UV protection to living cells for biotechnological applications