Hydrogels are water-swollen, typically soft networks
useful as
biomaterials and in other fields of biotechnology. Hydrogel networks
capable of sensing and responding to external perturbations, such
as light, temperature, pH, or force, are useful across a wide range
of applications requiring on-demand cross-linking or dynamic changes.
Thus far, although mechanophores have been described as strain-sensitive
reactive groups, embedding this type of force-responsiveness into
hydrogels is unproven. Here, we synthesized multifunctional polymers
that combine a hydrophilic zwitterion with permanently cross-linking
alkenes, and dynamically cross-linking disulfides. From these polymers,
we created hydrogels that contain irreversible and strong thiol–ene
cross-links and reversible disulfide cross-links, and they stiffened
in response to strain, increasing hundreds of kPa in modulus under
compression. We examined variations in polymer composition and used
a constitutive model to determine how to balance the number of thiol–ene
vs disulfide cross-links to create maximally force-responsive networks.
These strain-stiffening hydrogels represent potential biomaterials
that benefit from the mechanoresponsive behavior needed for emerging
applications in areas such as tissue engineering.
Noncovalent approaches to achieve smart ion-transport regulation in artificial nanochannels have garnered significant interest in the recent years because of their advantages over conventional covalent routes. Herein, we demonstrate a simple and generic approach to control the surface charge in mesoporous silica nanochannels by employing π-electron-rich charged motifs (pyranine-based donors) to interact with the surface of mesoporous silica modified with π-electron-deficient motifs (viologen-based acceptors) through a range of noncovalent forces, namely, charge-transfer, electrostatic, and hydrophobic interactions. The extent of each of these interactions was independently controlled by molecular design and pH, while employing them in a synergistic or antagonistic fashion to modulate the binding affinity of the charged motifs. This enabled the precise control of the surface charge of the nanochannels to achieve multiple ion-transport states.
Green synthesis of nanoparticles (NPs) involves the use of diverse extracts of biological origin as substrates to synthesize nanoparticles and can overcome the hazards associated with chemical 2 methods. Coconut inflorescence sap, which is unfermented phloem sap obtained by tapping of coconut inflorescence, is a rich source of sugars and secondary metabolites. In this study, coconut inflorescence sap was used to synthesize silver nanoparticles (AgNPs). We have initially undertaken metabolomic profiling of coconut inflorescence sap from West Coast Tall cultivar to delineate its individual components. Secondary metabolites constituted the major portion of the inflorescence sap along with sugars, lipids and, peptides. The concentration of silver nitrate, inflorescence sap and incubation temperature for synthesis of AgNPs were optimized. Incubating the reaction mixture at 40ºC was found to enhance AgNP synthesis. The AgNPs synthesized were characterized using UV-Visible spectrophotometry, X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Antimicrobial property of AgNP was tested in tissue culture of arecanut (Areca catechu L.) where bacterial contamination (Bacillus pumilus) was a frequent occurrence. Significant reduction in the contamination was observed when plantlets were treated with aqueous solutions of 0.01, 0.02 and 0.03% of AgNPs for one hour. Notably, treatment with AgNPs did not affect growth and development of the arecanut plantlets. Cytotoxicity of AgNPs was quantified in HeLa cells. Viability (%) of HeLa cells declined significantly at 10 ppm concentration of AgNP and complete mortality was observed at 60 ppm. Antimicrobial properties of AgNPs synthesized from inflorescence sap were also evaluated and confirmed in human pathogenic bacteria viz., Salmonella sp., Vibrio parahaemolyticus, and Escherichia coli. The study concludes that unfermented inflorescence sap, with above neutral pH, serves as an excellent reducing agent to synthesize AgNPs from Ag+.3
Mesoporous silica-based charge reversal systems have gained significant attention in recent years due to a variety of applications such as drug delivery, dye adsorption, catalysis, chromatography, etc. Such systems often use covalent strategies to immobilize functional groups on the silica scaffold. However, lack of dynamism, modularity, and postsynthetic flexibility associated with covalent routes limit their wider applicability. Alternatively, supramolecular routes are gaining increased attention owing to their ability to overcome these limitations. Here, we introduce a simple and facile noncovalent design for a highly reversible assembly of charged amphiphiles within mesopores. Hexyl pendant groups were covalently attached to the surface to provide hydrophobic anchoring for charged amphiphiles to enable facile switching of surface charge of the mesoporous silica. These charge-switchable surfaces were used for fast and selective adsorption of dyes from aqueous solutions.
Polyaniline films are under extensive consideration for applications in sensors, memory devices, displays, biomedicals, etc., owing to their unique optical and electronic functional states that are switchable in response to external stimuli. The application arena of these materials could be enhanced by creating active, adaptive, and autonomous systems with preprogramable spatiotemporal control over the functional states. Here, we present a simple approach to achieve autonomous temporal regulation of polyaniline films’ optical and electrical states by integrating enzyme-catalyzed biochemical reaction. The enzymatic reaction produces a feedback-induced transient pH profile, and correspondingly, the functional states of polyaniline films give rise to a similar switching profile, whose lifetime could be preprogrammed via enzyme concentration. This autonomous, temporally regulated polymer film system represents an advancement to the existing switchable materials that operate at equilibrium.
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