Recording of Electrically Evoked Neural Activity and Bladder Pressure Responses in Awake Rats Chronically Implanted With a Pelvic Nerve Array.

Bioelectronic medical devices are well established and widely used in the treatment of urological dysfunction. Approved targets include the sacral S3 spinal root and posterior tibial nerve, but an alternate target is the group of pelvic splanchnic nerves, as these contain sacral visceral sensory and autonomic motor pathways that coordinate storage and voiding functions of the bladder. Here, we developed a device suitable for long-term use in an awake rat model to study electrical neuromodulation of the pelvic nerve (homolog of the human pelvic splanchnic nerves). In male Sprague-Dawley rats, custom planar four-electrode arrays were implanted over the distal end of the pelvic nerve, close to the major pelvic ganglion. Electrically evoked compound action potentials (ECAPs) were reliably detected under anesthesia and in chronically implanted, awake rats up to 8 weeks post-surgery. ECAP waveforms showed three peaks, with latencies that suggested electrical stimulation activated several subpopulations of myelinated A-fiber and unmyelinated C-fiber axons. Chronic implantation of the array did not impact on voiding evoked in awake rats by continuous cystometry, where void parameters were comparable to those published in naïve rats. Electrical stimulation with chronically implanted arrays also induced two classes of bladder pressure responses detected by continuous flow cystometry in awake rats: voiding contractions and non-voiding contractions. No evidence of tissue pathology produced by chronically implanted arrays was detected by immunohistochemical visualization of markers for neuronal injury or noxious spinal cord activation. These results demonstrate a rat pelvic nerve electrode array that can be used for preclinical development of closed loop neuromodulation devices targeting the pelvic nerve as a therapy for neuro-urological dysfunction.

Detection of atomic spin labels in a lipid bilayer using a single-spin nanodiamond probe.

Magnetic field fluctuations arising from fundamental spins are ubiquitous in nanoscale biology, and are a rich source of information about the processes that generate them. However, the ability to detect the few spins involved without averaging over large ensembles has remained elusive. Here, we demonstrate the detection of gadolinium spin labels in an artificial cell membrane under ambient conditions using a single-spin nanodiamond sensor. Changes in the spin relaxation time of the sensor located in the lipid bilayer were optically detected and found to be sensitive to near-individual (4 ± 2) proximal gadolinium atomic labels. The detection of such small numbers of spins in a model biological setting, with projected detection times of 1 s [corresponding to a sensitivity of ∼5 Gd spins per Hz(1/2)], opens a pathway for in situ nanoscale detection of dynamical processes in biology.

Poly(vinyl alcohol) physical hydrogels: noncryogenic stabilization allows nano- and microscale materials design.

Physical hydrogels based on poly(vinyl alcohol), PVA, have an excellent safety profile and a successful history of biomedical applications. However, highly inhomogeneous and macroporous internal organization of these hydrogels as well as scant opportunities in bioconjugation with PVA have largely ruled out micro- and nanoscale control and precision in materials design and their use in (nano)biomedicine. To address these shortcomings, herein we report on the assembly of PVA physical hydrogels via "salting-out", a noncryogenic method. To facilitate sample visualization and analysis, we employ surface-adhered structured hydrogels created via microtransfer molding. The developed approach allows us to assemble physical hydrogels with dimensions across the length scales, from ∼100 nm to hundreds of micrometers and centimeter sized structures. We determine the effect of the PVA molecular weight, concentration, and "salting out" times on the hydrogel properties, i.e., stability in PBS, swelling, and Young's modulus using exemplary microstructures. We further report on RAFT-synthesized PVA and the functionalization of polymer terminal groups with RITC, a model fluorescent low molecular weight cargo. This conjugated PVA-RITC was then loaded into the PVA hydrogels and the cargo concentration was successfully varied across at least 3 orders of magnitude. The reported design of PVA physical hydrogels delivers methods of production of functionalized hydrogel materials toward diverse applications, specifically surface mediated drug delivery.