Herein,
we report a novel approach that involves Pickering stabilization
of micometer-sized liquid crystal (LC) droplets with biocompatible
soft materials such as a whey protein microgel (WPM) to facilitate
the analysis of analyte-induced configurational transition of the
LC droplets. The WPM particles were able to irreversibly adsorb at
the LC–water interface, and the resulting WPM-stabilized LC
droplets possessed a remarkable stability against coalescence over
time. Although the LC droplets were successfully protected by a continuous
network of the WPM layer, the LC–water interface was still
accessible for small molecules such as sodium dodecyl sulfate (SDS)
that could diffuse through the meshes of the adsorbed WPM network
or through the interfacial pores and induce an LC response. This approach
was exploited to investigate the dynamic range of the WPM-stabilized
LC droplet response to SDS. Nevertheless, the presence of the unadsorbed
WPM in the aqueous medium reduced the access of SDS molecules to the
LC droplets, thus suppressing the configuration transition. An improved
LC response to SDS with a lower detection limit was achieved after
washing off the unadsorbed WPM. Interestingly, the LC exhibited a
detection limit as low as ∼0.85 mM for SDS within the initial
WPM concentration ranging from 0.005 to 0.1 wt %. Furthermore, we
demonstrate that the dose–response behavior was strongly influenced
by the number of droplets exposed to the aqueous analytes and the
type of surfactants such as anionic SDS, cationic dodecyltrimethylammonium
bromide (DTAB), and nonionic tetra(ethylene glycol)monododecyl ether
(C12E4). Thus, our results address key issues
associated with the quantification of aqueous analytes and provide
a promising colloidal platform toward the development of new classes
of biocompatible LC droplet-based optical sensors.
Herein, we report controlled protein adsorption and delivery of thermo- and pH-responsive poly(N-isopropylacrylamide-co-methacrylic acid) (PNIPAM-co-MAA) microgels at different temperatures, pH values and ionic strengths by employing bovine serum albumin (BSA)...
We
report a promising strategy based on chitosan (CS) hydrogels
and dual temperature- and pH-responsive poly(N-isopropylacrylamide-co-methacrylic acid) (PNIPAM-co-MAA) microgels
to facilitate release of a model drug, moxifloxacin (MFX). In this
protocol, first, the microgels were prepared using a free radical
copolymerization method, and subsequently, these carboxyl-group-rich
soft particles were incorporated inside the hydrogel matrix using
an EDC-NHS amidation method. Interestingly, the resulting microgel-embedded
hydrogel composites (MG-HG) acting as a double barrier system largely
reduced the drug release rate and prolonged the delivery time for
up to 68 h, which was significantly longer than that obtained using
microgels or hydrogels alone (20 h). On account of the dual-responsive
features of the embedded microgels and the variation of water-solubility
of drug molecules as a function of pH, MFX could be released in a
controllable manner by regulating the temperature and pH of the delivery
medium. The release kinetics followed a Korsmeyer-Peppas model, and
the drug delivery mechanism was described by Fickian diffusion. Both
the gel precursors and the hydrogel composites exhibited low cytotoxicity
against mammalian cell lines (HeLa and HEK-293) and no deleterious
hemolytic activity up to a certain higher concentration, indicating
excellent biocompatibility of the materials. Thus, the unprecedented
combination of modularity of physical properties caused by soft particle
entrapment, unique macromolecular architecture, biocompatibility,
and the general utility of the stimuli-responsive polymers offers
a great promise to use these composite materials in drug delivery
applications.
Herein, we demonstrate for the first time the synthesis of ultra-stable, spherical, nematic LC droplets of narrow size polydispersity coated by sustainable, biodegradable, plant-based materials that trigger a typical bipolar-to-radial...
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