Thermoresponsive Poly(vinyl methyl ether) (PVME) Retained by 3-Aminopropyltriethoxysilane (APTES) Network

Abstract

Thermoresponsive polymers (TRP)­s have been widely used for various applications from controlling membrane fouling in separation to cell/cell sheet harvesting in regenerative medicine. While poly­(N-isopropylacrylamide) (pNIPAAm) is the most commonly used TRP, less expensive and easily processed poly­(vinyl methyl ether) (PVME) also shows a hydrophilic to hydrophobic transition at 32–35 °C, near physiological conditions. In this study, we investigated the processing conditions for retaining a stable layer of PVME thin film on silica surfaces via entrapment in a 3-aminopropyltriethoxysilane (APTES) network. In addition, the thermoresponsive behaviors (TRB) of the retained PVME films were evaluated. Blend thin films of PVME/APTES with 90:10 and 50:50 mass ratios were spin-coated from their solutions in ethanol under ambient conditions and then annealed in a vacuum oven at 40, 60, 80, or 120 °C for 1, 2, or 3 days. The annealed films were then thoroughly rinsed with room temperature water and then soaked in water for 3 days. Our results showed that annealing at a temperature of ≥40 °C was necessary for retaining a PVME film on the surface. The higher annealing temperature led to greater film retention, probably due to the formation of a tighter APTES network. Regardless of processing conditions, all retained PVME films showed TRB, determined by water contact angles below and above the transition temperature of PVME. Additionally, particle attachment and protein adsorption on retained PVME films showed lower attachment or adsorption at room temperature as compared to that at 37 °C, and a greater difference was observed for the 90:10 blend where more PVME was consisted. Furthermore, human mesenchymal stem cells attached and proliferated on the retained PVME surfaces at 37 °C and rapidly detached at room temperature. These results illustrated the potential applications of PVME surfaces as thermoresponsive supports for low-fouling applications and noninvasive cell harvesting.

Transparent tempo oxidized cellulose nanofibril (TOCNF) composites with increased toughness and thickness by lamination

“…While it can be expected that TOCNF may be somewhat different than CNFs due to the conversion of some of the OH groups to COONa, it will still retain a similar hydrophilic behavior thanks to the large amount of unconverted OH groups on the surface. Further, while many expect the amine surface to of APTES to be relatively hydrophilic, APTES tends to interact with hydrogen bonding groups underneath (such as alcohol or silanol) and push the propyl segment towards the top, giving a relatively hydrophobic surface (please refer to Figure 4.11 for the molecular structure of APTES) 90 . Overall, a higher adhesion at the interface was achieved by the introduction of APTES as can be seen in the lap shear results exhibit on Table 4.2, where for both neat TOCNF and TOCNF composite films with epoxy A the results did not show a statistical difference.…”

Investigating Mechanisms of Subcutaneous Preconditioning Incubation for Neural Stem Cell Embedded Hydrogels

“…Central nervous system (CNS) injury, including spinal cord injury (SCI), and disease often results in long-term physical impediment ranging from sensory deficiencies to quadriplegia. − Multiple strategies have been developed to achieve regeneration following CNS injury including treatment with anti-inflammatories, modulation of chondroitin sulfate proteoglycans (CSPGs)/nerve growth cone interactions, and the delivery of stem cells. − Neural stem cells (NSCs) can replace neurons damaged or lost to CNS injury, but survival at the site is poor because of the hostile host environment that triggers apoptotic signaling in the transplanted cells. − Preconditioning NSCs to express pro-survival genes prior to application to CNS injury supports integration at the injury site by conferring to the cells the ability to tolerate the physiological stress they will experience . Stem cells are responsive to inflammatory mediators, leading to altered gene expression and signaling. , For instance, mesenchymal stem cells (MSCs) preconditioned with cytokines showed increased survival following transplantation to injury site through upregulated phosphorylation of protein kinase B (PKB), also known as AKT, extracellular signal-regulated kinases (ERK), and c-Jun N-terminal kinase (JNK) and an increased superoxide dismutase 2 (SOD2) level. , We have also recently shown that exposure of NSC to interferon gamma (IFN-γ) in vitro led to alterations in AKT/ERK/JNK signaling to support neurogenesis. , Preconditioning cells in an in vitro environment that recapitulates the eventual targeted injury site has also been shown to alter cell survival.…”

Multi-responsive γ-methylene-γ-butyrolactone/N-vinyl caprolactam copolymers involving pH-dependent reversible lactonization

“…6 Thermo-responsive polymers characterized by a lower critical solution temperature (LCST) are certainly among the most studied stimuli responsive systems. [7][8][9][10][11] In particular, those characterized by a LCST close to the physiological temperature, [12][13][14][15][16][17][18][19][20][21] such as poly (N-vinylcaprolactam) (PNVCL), [16][17][18][19] have attracted a lot of attention especially for biomedical applications. PNVCL is a very popular thermosensitive sequence which exhibits a Type I phase change and a classical Flory-Huggins thermo-responsive phase diagram with a continuous phase transition from about 30 °C to 50 °C, depending on the molar mass and concentration.…”