Modifications of Parylene by Microstructures and Selenium Nanoparticles: Evaluation of Bacterial and Mesenchymal Stem Cell Viability

Parylene-based implants or coatings introduce surfaces suffering from bacteria colonization. Here, we synthesized polyvinylpyrrolidone-stabilized selenium nanoparticles (SeNPs) as the antibacterial agent, and various approaches are studied for their reproducible adsorption, and thus the modification of parylene-C–coated glass substrate. The nanoparticle deposition process is optimized in the nanoparticle concentration to obtain evenly distributed NPs on the flat parylene-C surface. Moreover, the array of parylene-C micropillars is fabricated by the plasma etching of parylene-C on a silicon wafer, and the surface is modified with SeNPs. All designed surfaces are tested against two bacterial pathogens, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The results show no antibacterial effect toward S. aureus, while some bacteriostatic effect is observed for E. coli on the flat and microstructured parylene. However, SeNPs did not enhance the antibacterial effect against both bacteria. Additionally, all designed surfaces show cytotoxic effects toward mesenchymal stem cells at high SeNP deposition. These results provide valuable information about the potential antibacterial treatment of widely used parylene-C in biomedicine.

An ultrafast-response and flexible humidity sensor for human respiration monitoring and noncontact safety warning

The humidity sensor is an essential sensing node in medical diagnosis and industrial processing control. To date, most of the reported relative humidity sensors have a long response time of several seconds or even hundreds of seconds, which would limit their real application for certain critical areas with fast-varying signals. In this paper, we propose a flexible and low-cost humidity sensor using vertically aligned carbon nanotubes (VACNTs) as electrodes, a PDMS-Parylene C double layer as the flexible substrate, and graphene oxide as the sensing material. The humidity sensor has an ultrafast response of ~20 ms, which is more than two orders faster than most of the previously reported flexible humidity sensors. Moreover, the sensor has a high sensitivity (16.7 pF/% RH), low hysteresis (<0.44%), high repeatability (2.7%), good long-term stability, and outstanding flexibility. Benefiting from these advantages, especially the fast response, the device has been demonstrated in precise human respiration monitoring (fast breathing, normal breathing, deep breathing, asthma, choking, and apnea), noncontact electrical safety warning for bare hand and wet gloves, and noncontact pipe leakage detection. In addition, the facile fabrication of the flexible platform with the PDMS-Parylene C double layer can be easily integrated with multisensing functions such as pH sensing, ammonium ion sensing, and temperature sensing, all of which are useful for more pattern recognition of human activity.

Biocompatibility and feasibility of VisiPlate, a novel ultrathin, multichannel glaucoma drainage device

Background Glaucoma is the leading cause of blindness worldwide. Glaucoma drainage devices and minimally invasive glaucoma surgeries (MIGS) often present with tradeoffs in safety and durability of efficacy. Using a rabbit model, we examined the biocompatibility and feasibility of VisiPlate, a novel, ultrathin, tubeless subconjunctival shunt comprised of a network of microchannels. Methods Six naive female New Zealand White rabbits received implants (three only in the right eye with contralateral eye untreated and three in both eyes) composed of a 400-nm-thick aluminum oxide core coated with 2 µm of parylene-C, manufactured with microelectromechanical systems (MEMS) techniques. Tonometry, slit lamp exam, clinical exam, fluorescein patency testing, and histopathology were performed. Results VisiPlate demonstrated IOP-lowering of 20–40% compared to baseline at each time point over the course of 3 months in the nine implanted eyes. All eyes developed blebs over the implant, and fluorescein testing demonstrated fluid patency at 22 days post-implantation. Slit lamp and clinical observations showed that VisiPlate was well tolerated, with low levels of conjunctival congestion, conjunctival swelling, aqueous flare, hyphema, and iris involvement from surgery that resolved over time. At sacrifice time points of 93 days and 180 days, the only notable observations were mild levels of conjunctival congestion in implanted eyes. Histopathology showed minimal tissue response and no obvious inflammation, fibrosis, or necrosis around the implant. Conclusions The results of this in vivo study demonstrate the biocompatibility and IOP-lowering effect of a multichannel, ultrathin subconjunctival shunt in a rabbit model. The data suggest that VisiPlate may safely enhance aqueous outflow and significantly reduce intraocular pressure.

Assessing the Blockage of Toxicity of Stereolithographically 3D-Printed Parts Coated with Parylene C

Comparing to fused deposition modeling (FDM), the stereolithography (SLA) 3D printing method can provide higher fabrication speed and much better resolution, which is demanded by biomedical usage. However, the additives migrating from SLA printed plastic are toxic to creatures, and the method to reduce the toxicity by soaking and exposure to ultraviolet is inadequate, while current biocompatible photo-polymerizing resins are rare and expensive. Here, we provide a method to nearly block all toxicity by coating the fabrication with parylene C. We use early life zebrafish to assess the toxicity of the SLA printed petri dishes whether or not coated with parylene C. The result shows nearly no influence of the coated petri dishes cultured early life zebrafish development compared to control groups, while the fertilized embryos of uncoated groups get killed in 24 hours. The method provides a cheap and easy way to produce customized biocompatible fabrication, which contributes to the popularization of 3D printed products, either in daily life or in research.

Assessing the Blockage of Toxicity of Stereolithographically 3D-Printed Parts Coated with Parylene C

Comparing to fused deposition modeling (FDM), the stereolithography (SLA) 3D printing method can provide higher fabrication speed and much better resolution, which is demanded by biomedical usage. However, the additives migrating from SLA printed plastic are toxic to creatures, and the method to reduce the toxicity by soaking and exposure to ultraviolet is inadequate, while current biocompatible photo-polymerizing resins are rare and expensive. Here, we provide a method to nearly block all toxicity by coating the fabrication with parylene C. We use early life zebrafish to assess the toxicity of the SLA printed petri dishes whether or not coated with parylene C. The result shows nearly no influence of the coated petri dishes cultured early life zebrafish development compared to control groups, while the fertilized embryos of uncoated groups get killed in 24 hours. The method provides a cheap and easy way to produce customized biocompatible fabrication, which contributes to the popularization of 3D printed products, either in daily life or in research.