Control of polymers' amorphous-crystalline transition enables miniaturization and multifunctional integration for hydrogel bioelectronics.

Soft bioelectronic devices exhibit motion-adaptive properties for neural interfaces to investigate complex neural circuits. Here, we develop a fabrication approach through the control of metamorphic polymers' amorphous-crystalline transition to miniaturize and integrate multiple components into hydrogel bioelectronics. We attain an about 80% diameter reduction in chemically cross-linked polyvinyl alcohol hydrogel fibers in a fully hydrated state. This strategy allows regulation of hydrogel properties, including refractive index (1.37-1.40 at 480 nm), light transmission (>96%), stretchability (139-169%), bending stiffness (4.6 ± 1.4 N/m), and elastic modulus (2.8-9.3 MPa). To exploit the applications, we apply step-index hydrogel optical probes in the mouse ventral tegmental area, coupled with fiber photometry recordings and social behavioral assays. Additionally, we fabricate carbon nanotubes-PVA hydrogel microelectrodes by incorporating conductive nanomaterials in hydrogel for spontaneous neural activities recording. We enable simultaneous optogenetic stimulation and electrophysiological recordings of light-triggered neural activities in Channelrhodopsin-2 transgenic mice.

Biologically Driven In Vivo Occlusion Design Provides a Reliable Experimental Glaucoma Model.

Fluid flow transport through the trabecular meshwork tissues is a major regulator of intraocular pressure (IOP) modulation in healthy and glaucomatous individuals. Microbead occlusion models of ocular hypertension regulate aqueous humor drainage to induce high IOP to allow for in vivo study of pressure-related glaucomatous pathology. However, the reliability and application of current injectable microbeads are hindered by inadequate design of the beads-tissue interfaces to maintain a stable IOP elevation over the long term. Considering the graded, porous architecture and fluid transport of the trabecular meshwork, we developed a tailored, injectable "viscobeads" technique, which induced a sustained elevation of IOP for at least 8 weeks. These composite viscobeads contain a non-degradable polystyrene (PS) core for structural support and a biodegradable polylactic-co-glycolic acid (PLGA) viscoelastic surface. This approach enhances the obstruction of aqueous humor drainage through heterogeneous sizes of trabecular meshwork fenestrations and reliably modulates the magnitude and duration of ocular hypertension. In a mouse model, a single viscobeads injection resulted in sustained IOP elevation (average 21.4±1.39 mm Hg), leading to a 34% retinal ganglion cell (RGC) loss by 56 days. In an earlier stage of glaucoma progression, we conducted non-invasive electroretinography (ERG) recording and revealed glaucomatous progression by analyzing high-frequency oscillatory potentials. To further explore the application of the viscobeads glaucoma models, we assayed a series of genes through adeno-associated virus (AAV)-mediated screening in mice and assessed the impact of genetic manipulation on RGC survivals. CRISPR mediated disruption of the genes, PTEN, ATF3 and CHOP enhanced RGC survival while LIN 28 disruption negatively impacted RGC survival. This biologically driven viscobeads design provides an accessible approach to investigate chronic intraocular hypertension and glaucoma-like neurodegeneration and ultimately tenders the opportunity to evaluate genetic and pharmacological therapeutics.

Artificial cell synthesis using biocatalytic polymerization-induced self-assembly.

Artificial cells are biomimetic microstructures that mimic functions of natural cells, can be applied as building blocks for molecular systems engineering, and host synthetic biology pathways. Here we report enzymatically synthesized polymer-based artificial cells with the ability to express proteins. Artificial cells were synthesized using biocatalytic atom transfer radical polymerization-induced self-assembly, in which myoglobin synthesizes amphiphilic block co-polymers that self-assemble into structures such as micelles, worm-like micelles, polymersomes and giant unilamellar vesicles (GUVs). The GUVs encapsulate cargo during the polymerization, including enzymes, nanoparticles, microparticles, plasmids and cell lysate. The resulting artificial cells act as microreactors for enzymatic reactions and for osteoblast-inspired biomineralization. Moreover, they can express proteins such as a fluorescent protein and actin when fed with amino acids. Actin polymerizes in the vesicles and alters the artificial cells' internal structure by creating internal compartments. Thus, biocatalytic atom transfer radical polymerization-induced self-assembly-derived GUVs can mimic bacteria as they are composed of a microscopic reaction compartment that contains genetic information for protein expression upon induction.

Control of Polymers' Amorphous-crystalline Transition for Hydrogel Bioelectronics Miniaturization and Multifunctional Integration.

Bioelectronic devices made of soft elastic materials exhibit motion-adaptive properties suitable for brain-machine interfaces and for investigating complex neural circuits. While two-dimensional microfabrication strategies enable miniaturizing devices to access delicate nerve structures, creating 3D architecture for expansive implementation requires more accessible and scalable manufacturing approaches. Here we present a fabrication strategy through the control of metamorphic polymers' amorphous-crystalline transition (COMPACT), for hydrogel bioelectronics with miniaturized fiber shape and multifunctional interrogation of neural circuits. By introducing multiple cross-linkers, acidification treatment, and oriented polymeric crystalline growth under deformation, we observed about an 80% diameter decrease in chemically cross-linked polyvinyl alcohol (PVA) hydrogel fibers, stably maintained in a fully hydrated state. We revealed that the addition of cross-linkers and acidification facilitated the oriented polymetric crystalline growth under mechanical stretching, which contributed to the desired hydrogel fiber diameter decrease. Our approach enabled the control of hydrogels' properties, including refractive index (RI 1.37-1.40 at 480 nm), light transmission (> 96%), stretchability (95% - 111%), and elastic modulus (10-63 MPa). To exploit these properties, we fabricated step-index hydrogel optical probes with contrasting RIs and applied them in optogenetics and photometric recordings in the mouse brain region of the ventral tegmental area (VTA) with concurrent social behavioral assessment. To extend COMPACT hydrogel multifunctional scaffolds to assimilate conductive nanomaterials and integrate multiple components of optical waveguide and electrodes, we developed carbon nanotubes (CNTs)-PVA hydrogel microelectrodes for hindlimb muscle electromyographic and brain electrophysiological recordings of light-triggered neural activities in transgenic mice expressing Channelrhodopsin-2 (ChR2).

Non-Invasive Electroretinogram Recording with Simultaneous Optogenetics to Dissect Retinal Ganglion Cells Electrophysiological Dynamics.

Electroretinography (ERG) is a non-invasive electrophysiological recording technique that detects the electrical signaling of neuronal cells in the visual system. In conventional ERG recordings, the signals are considered a collective electrical response from various neuronal cell populations, including rods, cones, bipolar cells, and retinal ganglion cells (RGCs). However, due to the limited ability to control electrophysiological responses from different types of cells, the detailed information underlying ERG signals has not been analyzed and interpreted. Linking the features of ERG signals to the specific neuronal response will advance the understanding of neuronal electrophysiological dynamics and provide more evidence to elucidate pathological mechanisms, such as RGC loss during the progression of glaucoma. Herein, we developed an advanced ERG recording system integrated with a programmable, non-invasive optogenetic stimulation method in mice. In this system, we applied an automatic and unbiased ERG data analysis approach to differentiate a, b wave, negative response, and oscillatory potentials. To differentiate the electrophysiological response of RGCs in ERG recordings, we sensitized mouse RGCs with red-light opsin, ChRmine, through adeno-associated virus (AAV) intravitreal injection. Features of RGC dynamics under red-light stimulation were identified in the ERG readout. This non-invasive ERG recording system, associated with the programmable optogenetics stimulation method, provides a new methodology to dissect neural dynamics under variable physiological and pathological conditions in vivo. With the merits of non-invasiveness, improved sensitivity, and specificity, we envision this system can be further applied for early-stage detection of RGC degeneration and functional progression in neural degenerative diseases, such as glaucoma.

Single neurons may encode simultaneous stimuli by switching between activity patterns.

How the brain preserves information about multiple simultaneous items is poorly understood. We report that single neurons can represent multiple stimuli by interleaving signals across time. We record single units in an auditory region, the inferior colliculus, while monkeys localize 1 or 2 simultaneous sounds. During dual-sound trials, we find that some neurons fluctuate between firing rates observed for each single sound, either on a whole-trial or on a sub-trial timescale. These fluctuations are correlated in pairs of neurons, can be predicted by the state of local field potentials prior to sound onset, and, in one monkey, can predict which sound will be reported first. We find corroborating evidence of fluctuating activity patterns in a separate dataset involving responses of inferotemporal cortex neurons to multiple visual stimuli. Alternation between activity patterns corresponding to each of multiple items may therefore be a general strategy to enhance the brain processing capacity, potentially linking such disparate phenomena as variable neural firing, neural oscillations, and limits in attentional/memory capacity.

Does electroconvulsive therapy (ECT) have any role in the management of intractable thalamic pain?

Three patients with intractable thalamic pain unresponsive to a range of previous treatments received a course of six bilateral electroconvulsive therapy (ECT) treatments over 2 weeks. There was no evidence of any improvement in the intensity of the pain, pain relief or mood as measured on visual analogue scales and with standard measures. Propofol was used as the anaesthetic induction agent. Two patients showed wide changes in blood pressure during ECT but all three patients showed prompt recovery. In the light of the negative findings of this study and those of a previous study of the use of unilateral ECT in similar patients it is concluded that ECT is not an effective treatment for post-stroke thalamic pain.

Dextromethorphan for the treatment of neuropathic pain: a double-blind randomised controlled crossover trial with integral n-of-1 design.

The aim was to compare the analgesic effectiveness and adverse effect incidence of oral dextromethorphan (DM) with placebo in patients with neuropathic pain. The first 10-day treatment period was a multiple-dose double-blind randomised controlled cross-over comparison of 13.5 mg of DM 3 times a day (t.d.s.) with placebo t.d.s.: 5 treatment pairs, each pair 1 day DM and 1 day placebo. The second 10-day treatment period used 27 mg of DM t.d.s. vs. placebo, with the same design. The study incorporated a 5 pair n-of-1 design for each of the 2 doses of DM. Patients took the study medication in addition to any pre-existing analgesic regime. Patients who reported benefit could continue with DM after the study. Nineteen patients with chronic neuropathic pain were studied over two 10-day treatment periods. Outcome measures were pain intensity, pain relief, adverse effects, mood, sleep and global rating of treatment. These were recorded by daily patient diaries and by clinic assessments before and after each treatment period. There were no significant differences between DM and placebo on any of the clinic assessment outcome measures. Two patients had significantly better analgesia on more than one outcome measure on within-patient testing. One had better analgesia with DM. The other had better analgesia with placebo. Ten patients had no adverse effects on either dose of DM. Two patients withdrew during the first treatment period because of adverse effects (which included increased pain intensity), and 5 during the second period. Five patients continued with DM after the study for 1-3 months. No long-term clinical benefit was apparent in those who continued with open DM. Dextromethorphan at either 40.5 or 81 mg daily did not relieve neuropathic pain.

Iontophoresis of vincristine versus saline in post-herpetic neuralgia. A controlled trial.

Twenty patients with post-herpetic neuralgia (median duration 28.5 months) were randomly allocated to receive transdermal iontophoresis of either vincristine or saline. Although significant improvement in pain by word score and visual analogue scale (P = 0.05) was reported by 6 out of 10 of the vincristine group, none of the patients considered themselves 'cured.' There was no significant change in the saline group. No adverse haematological or neurological side effects were seen, but skin irritation and painless electrical burns were common in both groups. The dramatic relief of pain in patients with post-herpetic neuralgia of 3 months or less reported elsewhere was not seen in our group who had pain of a longer duration. This present trial does not confirm the value of vincristine iontophoresis in the treatment of post-herpetic neuralgia of over 6 months duration.

Clinical pharmacokinetics applied to patients with intractable pain: studies with pethidine.

The minimum effective analgetic blood concentration (MEAC) of pethidine following intravenous administration was identified in 3 patients with intractable pain. In two patients this value remained the same whether the pethidine was given intravenously, orally or rectally. In the third patient, whose eneral bioavailability was only 20%, the MEAC was not obtained. However, intramuscular administration reliably achieved the MEAC and was useful clinically. During the study period of 3-12 months, the individual patient's MEAC remained similar. Two patients developed dependence on, and tolerance to, pethidine but neither the dependence nor the tolerance appeared to be related to the MEAC. These studies confirm the importance of clinical pharmacokinetic measurements in the investigation and treatment of patients with intractable pain.

Ventilatory response to intractable pain.

Fifty-two patients, admitted to a pain relief unit, had a cannula placed in the radial artery to measure the paO2, paCO2 and pH of arterial blood every 2 h, for periods ranging from 12 to 24 h. The patients were divided into 3 groups: 14 had low back pain, 21 patients had pain from cancer, and 17 had pain from other causes. Twenty were male and 32 were female with a mean age of 53 years (range 16-82 years). The mean paO2 of these groups was within normal limits. The mean paCO2 and pH for the 3 groups were, low back pain paCO2 4.1 kpa, pH 7.42, others, paCO2 4.2 kpa, pH 7.42. The finding of a normal pH associated with a low paCO2 suggests that patients were "reset" to a low paCO2. Treatment, which was most commonly nerve blocks, resulted in marked pain relief in 30 patients. Ten of these patients were available for follow-up at least 1 week later (4 from the low back pain group, 6 from the cancer group), and in every patient, after pain relief, there was a rise in paCO2 which was statistically significant (P less than 0.001) and was not accompanied by a fall in pH. This suggests that intractable pain is accompanied by chronic hyperventilation and that the relief of pain is accompanied by a decrease in ventilation.