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bioRxiv2021

Synthetic Natural Product-Inspired Peptides

Natural products (NPs) are a bountiful source of bioactive molecules. Unfortunately, discovery of novel bioactive NPs is challenging due to cryptic biosynthetic gene clusters (BGCs), low titers, and arduous purifications. Herein, we describe SNaPP (Synthetic Natural Product Inspired Peptides), a method for identifying NP-inspired bioactive molecules. SNaPP expedites bioactive molecule discovery by combining bioinformatics predictions of non-ribosomal peptide synthetases (NRPS) with chemical synthesis of the predicted NPs (pNPs). SNaPP utilizes a recently discovered cyclase, the penicillin binding protein (PBP)-like cyclase, as the lynchpin for the development of a library of cyclic peptide pNPs. Analysis of 500 BGCs allowed for identification of 131 novel pNPs. 51 diverse pNPs were synthesized using solid phase peptide synthesis and in-solution cyclization. Antibacterial testing revealed 14 pNPs with antibiotic activity, including activity against multidrug-resistant Gram-negative bacteria. Overall, SNaPP demonstrates the power of combining bioinformatics predictions with chemical synthesis to accelerate the discovery of bioactive molecules.

microbiology↗

bioRxiv2021

High-Stability Polyimide-based Flexible Electrodes with IrOx to Interface the Mouse Vagus Nerve

ObjectiveWe developed robust and cost-effective cuff Flex electrodes to facilitate bioelectronic medicine research in mouse models. They utilize polyimide (PI) as a dielectric insulation and iridium oxide (IrOx) for the electrodes, and are designed to interface small autonomic and somatic nerves (e.g. mouse vagus nerve). ApproachFlex electrodes were made using micro-fabrication technology, and innovative integration processes were developed to enable reliable acute and chronic vagus nerve interfaces. The electrochemical properties of Flex electrodes were characterized. Moreover, accelerated aging at 57 {degrees}C and stimulation-stability (Stim-Stab) testing (109 pulses at [~] 1.59 mC/cm2/phase) were performed to evaluate the lifetime of the PI encapsulation and IrOx electrodes, respectively. Flex electrodes efficacy was demonstrated by stimulating the mouse vagus nerve ([~]100 {micro}m) and measuring heart and respiratory rate changes as biomarkers. ResultsCost effective and robust lead and connector integration strategies were demonstrated, including small helical leads that improved the lead elongation by > 7x. PI encapsulation had stable impedance spectra for at least 336 days for interdigitated electrodes. Stim-Stab testing using an aggressive paradigm and rigorous optical and electrical characterization, revealed that half of electrodes showed less than minor damage at the endpoints. A trend of decreasing respiratory rate with stimulation current reached statistical significance at 500 {micro}A, demonstrating efficacy for Flex electrodes. SignificanceFlex electrodes offer demonstrated efficacy, low impedance (443 {+/-} 32 {Omega} at 103 Hz), excellent bench test stability, and cost-effective fabrication. Acute devices are easy to integrate, and mechanically robust chronic devices will be investigated in vivo in future studies. These characteristics make the electrodes well-positioned to advance bioelectronics medicine research by 1) enabling reliable studies with statistically relevant populations of acute mouse models, and 2) offering the potential for a technology that can be used in chronic studies, which scales to very small nerves.

bioengineering↗