Self-assembled poloxamer-legumin/vicilin nanoparticles for the nanoencapsulation and controlled release of folic acid.

Plant-based food proteins are a promising choice for the preparation of nanoparticles (NPs) due to their high digestibility, low cost, and ability to interact with various compounds and nutrients. Moreover, nanoencapsulation offers a potential solution for protecting nutrients during processing and enhancing their bioavailability. This study aimed to develop and evaluate nanoparticles (NPs) based on legumin/vicilin (LV) proteins extracted from fava beans, with the goal of encapsulating and delivering a model nutraceutical compound, folic acid (FA). Specifically, NPs were self-assembled from LV proteins extracted from commercially available frozen fava beans using a pH-coacervation method with poloxamer 188 (P188) and chemically cross-linked with glutaraldehyde. Microscopy and spectroscopy studies were carried out on the empty and FA-loaded NPs in order to evaluate the particle morphology, size, size distribution, composition, mechanism of formation, impact of FA loading and release behavior. In vitro studies with Caco-2 cells also confirmed that the empty and FA-loaded nanoparticles were non-toxic. Thus, the LV-NPs are good candidates as food additives for the delivery and stabilization of nutrients as well as in drug delivery for the controlled release of therapeutics.

Probing the response of poly (N-isopropylacrylamide) microgels to solutions of various salts using etalons.

The Hofmeister series is a qualitative ordering of ions according to their ability to precipitate proteins in aqueous solution and is extremely important to consider when trying to understand materials and biomolecular structure and function. Herein, we utilized optical devices (etalons) composed of poly(N-isopropylacrylamide) (pNIPAm)-co-10% acrylic acid (AAc) or pNIPAm-based microgels to investigate how various salts in the Hofmeister series influenced the microgel hydration state. Etalons were exposed to a series of salts solutions at different concentrations and the position of the peaks in the reflectance spectra monitored using reflectance spectroscopy. As expected, pNIPAm-co-10%AAc microgel-based etalons responded to the presence of ions, although in this case the response to cations deviated from the Hofmeister series. However, when using etalons prepared with pNIPAm-based microgels, the responses followed the Hofmeister series for both cation and anions. Finally, we observed that the sensitivity of etalons prepared with pNIPAm microgels was significantly higher than the response obtained from etalons composed of pNIPAm-co-10%AAc microgels. This was explained by considering the charge on the pNIPAm-co-10%AAc microgels that influences how osmotic and Hofmeister effects impacts hydration state.

Microgel-Based Stretchable Reservoir Devices for Elongation Enhanced Small Molecule Release Rate.

Stretchable poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-10% AAc) microgel-based reservoir devices were fabricated and used to control the release rate of the small molecule model drug tris(4-(dimethylamino)phenyl)methylium chloride (crystal violet, CV) to solution by varying the Au layer thickness coating the microgels and device elongation. Specifically, we showed that CV could be loaded into the microgel layer of the devices via electrostatic interactions at pH 6.5, and the release could be triggered upon exposure to a pH 3.0 solution, which breaks the microgel-CV electrostatic interactions. We demonstrated that the rate of release could be increased by decreasing the Au layer thickness coating microgels and by stretching, that is, thin Au and high elongation promoted the relatively fast release of CV from the device. We found that the Au overlayer thickness (and porosity) dominated the observed release rate profiles when the device was not stretched (or at low elongation), while elongation-induced cracks dominated the release rate at high elongation. We also showed that the CV release kinetics could transition from low ("off") to high ("on"), which enhanced when the devices are stretched. This behavior could be exploited in the future for autonomous release systems that release small molecules when stretched by natural processes, for example, movement of joints and muscles.

Stimuli-responsive microgels for controlled deposition of gold nanoparticles on surfaces.

A variety of gold nanoparticle (AuNP) core/poly(N-isopropylacrylamide) (pNIPAm) shell microgels (Au@pNIPAm) were generated using seed-mediated polymerization. The shell thickness and AuNP core diameter were easily tunable at the time of synthesis. The resultant Au@pNIPAm microgels were characterized via photon-correlation spectroscopy, transmission electron microscopy and ultraviolet-visible spectroscopy. AuNP arrays were generated by "painting" the microgels on a surface, using the shell thickness to define the distance between the AuNPs, followed by shell removal via plasma etching. We found that when the pNIPAm shell thickness decreased (via its tuning at the time of synthesis or deposition at elevated temperature at which the shell is collapsed) the AuNPs were closer to one another. We also showed that via sequential deposition Au@pNIPAm microgels with different AuNP core sizes could be deposited on a single surface. The presented "painting protocol" offers a facile way to coat large area surfaces quickly which is not easily achievable using other approaches. We envision that this approach is extremely versatile, allowing a number of different nanomaterials embedded in pNIPAm shells to be deposited/patterned on surfaces. With the control over the deposition on the surface that we show here, we hope that the Au@pNIPAm microgels will find use in lithography/surface patterning applications.

Enzyme-assisted polymer film degradation-enabled biomolecule sensing with poly (N-isopropylacrylamide)-based optical devices.

A biosensor for mouse Immunoglobulin G (IgG) was generated from responsive polymer-based interference filters (etalons). To accomplish this, an excess amount of alkaline phosphatase-modified goat anti-mouse IgG (AP-GAM, F(ab')2 fragment specific to mouse IgG) was added to mouse IgG, and allowed to react for some time. After a given reaction time, the bound AP-GAM could be isolated from the unbound, excess AP-GAM by addition of goat anti-mouse IgG (Fc fragment specific)-modified magnetic microspheres (GAM-M) that bind the mouse IgG bound to AP-GAM. After application of a magnetic field, the free, unbound AP-GAM was isolated from the mixture and exposed to an etalon that has its upper Au surface modified with phosphate-containing polymer that can be degraded by AP-GAM. By the phosphate-containing polymer being degraded by the excess AP-GAM, the cleaved phosphate groups can diffuse into the interference filter's active polymer layer that yields a change in the optical properties that can be related to the amount of IgG in the sample. This concept is extremely straightforward to implement, and can be modified to detect a variety of other analytes of interest.