Fabrication and Analysis of Polydimethylsiloxane (PDMS) Microchannels for Biomedical Application

Unprecedented Approach of Fabrication and Analysis of a Bioactive PDMS/Hydroxyapatite/Graphene Nanocomposite Scaffold with a Vascular Channel to Combat Carcinogenesis

In the present investigation, natural bone-derived hydroxyapatite (HA, 2 wt %) and/or exfoliated graphene (Gr, 0.1 wt %)-embedded polydimethylsiloxane (PDMS) elastomeric films were prepared using a vascular method. The morphology, mechanical properties, crystallinity, and chemical structure of the composite films were evaluated. The in vitro biodegradation kinetics of the films indicates their adequate physiological stability. Most of the results favored PDMS/HA/Gr as a best composite scaffold having more than 703% elongation. A simulation study of the microfluidic vascular channel of the PDMS/HA/Gr scaffold suggests that the pressure drop at the outlet became greater (from 1.19 to 0.067 Pa) unlike velocity output (from 0.071 to 0.089 m/s), suggesting a turbulence-free laminar flow. Our bioactive scaffold material, PDMS/HA/Gr, showed highest cytotoxicity toward the lung cancer and breast cancer cells through Runx3 protein-mediated cytotoxic T lymphocyte (CTL) generation. Our data and predicted mechanism also suggested that the PDMS/HA/Gr-supported peripheral blood mononuclear cells (PBMCs) not only increased the generation of CTL but also upregulated the expression of RUNX3. Since the PDMS/HA/Gr scaffold-supported Runx3 induced CTL generation caused maximum cell cytotoxicity of breast cancer (MCF-7) and lung cancer (A549) cells, PDMS/HA/Gr can be treated as an excellent potential candidate for CTL-mediated cancer therapy.

Polydimethylsiloxane Surface Modification of Microfluidic Devices for Blood Plasma Separation

Over the last decade, researchers have developed a variety of new analytical and clinical diagnostic devices. These devices are predominantly based on microfluidic technologies, where biological samples can be processed and manipulated for the collection and detection of important biomolecules. Polydimethylsiloxane (PDMS) is the most commonly used material in the fabrication of these microfluidic devices. However, it has a hydrophobic nature (contact angle with water of 110°), leading to poor wetting behavior and issues related to the mixing of fluids, difficulties in obtaining uniform coatings, and reduced efficiency in processes such as plasma separation and molecule detection (protein adsorption). This work aimed to consider the fabrication aspects of PDMS microfluidic devices for biological applications, such as surface modification methods. Therefore, we studied and characterized two methods for obtaining hydrophilic PDMS surfaces: surface modification by bulk mixture and the surface immersion method. To modify the PDMS surface properties, three different surfactants were used in both methods (Pluronic® F127, polyethylene glycol (PEG), and polyethylene oxide (PEO)) at different percentages. Water contact angle (WCA) measurements were performed to evaluate the surface wettability. Additionally, capillary flow studies were performed with microchannel molds, which were produced using stereolithography combined with PDMS double casting and replica molding procedures. A PDMS microfluidic device for blood plasma separation was also fabricated by soft lithography with PDMS modified by PEO surfactant at 2.5% (v/v), which proved to be the best method for making the PDMS hydrophilic, as the WCA was lower than 50° for several days without compromising the PDMS's optical properties. Thus, this study indicates that PDMS surface modification shows great potential for enhancing blood plasma separation efficiency in microfluidic devices, as it facilitates fluid flow, reduces cell aggregations and the trapping of air bubbles, and achieves higher levels of sample purity.

Two-dimensional biocompatible plasmonic contact lenses for color blindness correction

Color blindness, or color vision deficiency (CVD), is an ocular disease that suppresses the recognition of different colors. Recently, tinted glasses and lenses have been studied as hopeful devices for color blindness correction. In this study, 2D biocompatible and flexible plasmonic contact lenses were fabricated using polydimethylsiloxane (PDMS) and a low-cost, and simple design based on the soft nano-lithography method and investigated for correction of red-green (deuteranomaly) color blindness. In addition, the stability test of the fabricated plasmonic contact lenses was investigated into the phosphate buffered saline (PBS) solution and the proposed lens offers an excellent stability into the PBS solution. The plasmonic contact lens proposed herein is based on the plasmonic surface lattice resonance (SLR) phenomenon and offers a good color filter for color blindness correction. The biocompatibility, low cost, stability, and simple fabrication of these contact lenses can offer new insights for applications of color blindness correction.

Micellar Carriers of Active Substances Based on Amphiphilic PEG/PDMS Heterograft Copolymers: Synthesis and Biological Evaluation of Safe Use on Skin

Amphiphilic copolymers containing polydimethylsiloxane (PDMS) and polyethylene glycol methyl ether (MPEG) were obtained via an azide-alkyne cycloaddition reaction between alkyne-functionalized copolymer of MPEG methacrylate and azide-functionalized PDMS. “Click” reactions were carried out with an efficiency of 33–47% increasing grafting degrees. The grafted copolymers were able to carry out the micellization and encapsulation of active substances, such as vitamin C (VitC), ferulic acid (FA) and arginine (ARG) with drug loading content (DLC) in the range of 2–68% (VitC), and 51–89% (FA or ARG). In vitro release studies (phosphate buffer saline, PBS; pH = 7.4 or 5.5) demonstrated that the maximum release of active substances was mainly after 1–2 h. The permeability of released active substances through membrane mimicking skin evaluated by transdermal tests in Franz diffusion cells indicated slight diffusion into the solution (2–16%) and their remaining in the membrane. Studies on the selected carrier with FA showed no negative effect on cell viability, proliferation capacity or senescence, as well as cell apoptosis/necrosis differences or cell cycle interruption in comparison with control cells. These results indicated that the presented micellar systems are good candidates for carriers of cosmetic substances according to physicochemical characterization and biological studies.