One of the main challenges for implantable biomedical sensing schemes is obtaining a reliable signal while maintaining biocompatibility. In this work, we demonstrate that a combination of medical ultrasound imaging and smart hydrogel micromechanical resonators can be employed for continuous monitoring of analyte concentrations. The sensing principle is based on the shift of the mechanical resonance frequencies of smart hydrogel structures induced by their volume-phase transition in response to changing analyte levels. This shift can then be measured as a contrast change in the ultrasound images due to resonance absorption of ultrasound waves. This concept eliminates the need for implanting complex electronics or employing transcutaneous connections for sensing biomedical analytes in vivo. Here, we present proof-of-principle experiments that monitor in vitro changes in ionic strength and glucose concentrations to demonstrate the capabilities and potential of this versatile sensing platform technology.

There is a strong commercial need for inexpensive point-of-use sensors for monitoring disease biomarkers or environmental contaminants in drinking water. Point-of-use sensors that employ smart polymer hydrogels as recognition elements can be tailored to detect almost any target analyte, but often suffer from long response times. Hence, we describe here a fabrication process that can be used to manufacture low-cost point-of-use hydrogel-based microfluidics sensors with short response times. In this process, mask-templated UV photopolymerization is used to produce arrays of smart hydrogel pillars inside sub-millimeter channels located upon microfluidics devices. When these pillars contact aqueous solutions containing a target analyte, they swell or shrink, thereby changing the resistance of the microfluidic channel to ionic current flow when a small bias voltage is applied to the system. Hence resistance measurements can be used to transduce hydrogel swelling changes into electrical signals. The only instrumentation required is a simple portable potentiostat that can be operated using a smartphone or a laptop, thus making the system suitable for point of use. Rapid hydrogel response rate is achieved by fabricating arrays of smart hydrogels that have large surface area-to-volume ratios.

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Two phospholipases were found in the venom of Bungarus fasciatus, one in fraction III, the other in fraction X of the chromatographic separation. A neutral PLA2(III) purified from fraction III was subjected to amino acid sequencing by means of an automated sequenator applied to the intact RCM‐PLA2 (III) and the individual peptides obtained from HPLC separation of the three types of enzymatic peptides. PLA(III) was shown to consist of 118 amino acid residues with 14 half‐cystines. It is 65% homologous to the basic PLA2 obtained from fraction X.