Electrochemical Sensing of the Peptide Drug Exendin-4 Using a Versatile Nucleic Acid Nanostructure.

Although endogenous peptides and peptide-based therapeutics are both highly relevant to human health, there are few approaches for sensitive biosensing of this class of molecules with minimized workflow. In this work, we have further expanded on the generalizability of our recently developed DNA nanostructure architecture by applying it to electrochemical (EC) peptide quantification. While DNA-small molecule conjugates were used in a prior work to make sensors for small molecule and protein analytes, here DNA-peptide conjugates were incorporated into the nanostructure at the electrode surfaces, and antibody displacement permitted rapid peptide sensing. Interestingly, multivalent DNA-peptide conjugates were found to be detrimental to the assay readout, yet these effects could be minimized by solution-phase bioconjugation. The final biosensor was validated for quantifying exendin-4 (4.2 kDa)─a human glucagon-like peptide-1 receptor agonist important in diabetes therapy─for the first time using EC methods with minimal workflow. The sensor was functional in 98% human serum, and the low nanomolar assay range lies between the injected dose concentration and the therapeutic range, boding well for future applications in therapeutic drug monitoring.

A Comparative Study Between Septal Quilting Sutures Without Nasal Packing and Only Nasal Packing Post-septal Correction.

Septal correction is the commonest surgery by rhinologists worldwide. We aimed at studying the comfort level of the patient with standard postoperative nasal packing with Merocel and placing quilting sutures in septum leaving the nose unpacked in the postoperative period. We conducted the study in the tertiary care centre enrolling 82 patients in a quasi-randomised method of odd and even numbers placing them in the nasal packing group and the quilting group respectively. We used analogue scoring method for subjective assessment of comfort level in the postoperative period and the surgeon objectively assessed the patient on follow up. The results were tabulated and analysed. Postoperative pain, headache and sleep disturbance was significantly more in the nasal packing group. We found that the crusting is commonly seen in patients in the nasal packing group. Quilting the nasal septum and leaving the nasal cavity unpacked increases the comfort level of the patient in the postoperative period. The resultant pain, headache and sleep disturbance caused by nasal packing can be significantly avoided by using quilting the septum without nasal packing. We also observed that by avoiding nasal packing postoperatively, the patients were more comfortable and compliant with the treatment regimen and follow-up.

A reusable electrochemical proximity assay for highly selective, real-time protein quantitation in biological matrices.

Rapid and specific quantitation of a variety of proteins over a wide concentration range is highly desirable for biosensing at the point-of-care, in clinical laboratories, and in research settings. Our recently developed electrochemical proximity assay (ECPA) is a target-flexible, DNA-directed, direct-readout protein quantitation method with detection limits in the low femtomolar range, making it particularly amenable to point-of-care detection. However, consistent quantitation in more complex matrices is required at the point-of-care, and improvements in measurement speed are needed for clinical and research settings. Here, we address these concerns with a reusable ECPA, where a gentle regeneration of the surface DNA monolayer (used to capture the proximity complex) is achieved enzymatically through a novel combination of molecular biology and electrochemistry. Strategically placed uracils in the DNA sequence trigger selective cleavage of the backbone, releasing the assembled proximity complex. This allows repeated protein quantitation by square-wave voltammetry (SWV)-as quickly as 3 min between runs. The process can be repeated up to 19 times on a single electrode without loss of assay sensitivity, and currents are shown to be highly repeatable with similar calibrations using seven different electrodes. The utility of reusable ECPA is demonstrated through two important applications in complex matrices: (1) direct, quantitative monitoring of hormone secretion in real time from as few as five murine pancreatic islets and (2) standard addition experiments in unspiked serum for direct quantitation of insulin at clinically relevant levels. Results from both applications distinguish ECPA as an exceptional tool in protein quantitation.