Thermoresponsive nanoparticle agglomeration/aggregation in salt solutions: Dependence on graft density

Preparation, structural characterization, and functional properties of wheat gluten amyloid fibrils-chitosan double network hydrogel as delivery carriers for ferulic acid

It has been demonstrated that ferulic acid (FA) can be effectively encapsulated using wheat gluten amyloid fibrils (AF) and chitosan (CS) in a double network hydrogel (DN) form, with cross-linking mediated by Genipin (GP). Within this system, the DN comprising gluten AF-FA and CS-FA exhibited optimal loading metrics at a formulation designated as DN8, achieving a load efficiency of 88.5 % and a load capacity of 0.78 %. Analysis through fluorescence quenching confirmed that DN8 harbored the highest quantity of FA. Fourier-transform infrared spectroscopy (FTIR) further verified a significant increase in β-sheet content post-hydrogel formation, enhancing the binding capacity for FA. Rheological assessments indicated a transition from solution to gel, delineating the phase state of the DN. Comprehensive in vitro digestion studies revealed that DN8 provided superior sustained release properties, exhibited the highest total antioxidant capacity, and displayed potent inhibitory activities against angiotensin I converting enzyme (ACE) and acetylcholinesterase (Ach-E). Additionally, the DN significantly bolstered the stability of FA against photothermal degradation. Collectively, these findings lay foundational insights for the advancement of the wheat gluten protein AF-based delivery system for bioactive compounds and provided a theoretical basis for the development of functional foods.

Arabic gum grafted with phenolic acid as a novel functional stabilizer for improving the oxidation stability of oil-in-water emulsion

Three kinds of phenolic acids: ferulic acid (FA), caffeic acid (CA), and gallic acid (GA) with different chemical structures were individually grafted onto Arabic gum (AG) via a laccase mediated method, and their roles in stabilizing o/w emulsions were evaluated. The total phenolic content in modified AG increased from 2.7 ± 0.2 to 18.7 ± 0.2, 19.8 ± 0.6, 22.4 ± 0.8 mg/g after 4 h of laccase catalysis, respectively. FTIR spectra of modified AGs exhibited additional phenolic characteristics, revealing the successful grafting of phenolic acids to AG structure. Compared with natural AG, modified AGs showed remarkably enhanced thermal stability, as well as antioxidant capacity in an order of gallic acid > caffeic acid > ferulic acid. The incorporation of phenolic acids into AG dramatically improved its emulsification performance. Herein, gallic acid-modified AG evinced up to 17.6 % and 12.6 % increments in emulsifying activity and emulsion stability relative to natural AG, respectively. Moreover, the oxidative stability of AG emulsions was pronouncedly meliorated by the introduced phenolic acids, especially gallic acid, as manifested by the suppressed production of primary and secondary oxidation products.

Assembling PNIPAM-Capped Gold Nanoparticles in Aqueous Solutions

Employing small-angle X-ray scattering (SAXS), we explore the conditions under which assembly of gold nanoparticles (AuNPs) grafted with the thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAM) emerges. We find that short-range order assembly emerges by combining the addition of electrolytes or polyelectrolytes with raising the temperature of the suspensions above the lower-critical solution temperature (LCST) of PNIPAM. Our results show that the longer the PNIPAM chain is, the better organization in the assembled clusters. Interestingly, without added electrolytes, there is no evidence of AuNPs assembly as a function of temperature, although untethered PNIPAM is known to undergo a coil-to-globule transition above its LCST. This study demonstrates another approach to assembling potential thermosensitive nanostructures for devices by leveraging the unique properties of PNIPAM.

Directional Self-Assembly of Nanoparticles Coated with Thermoresponsive Block Copolymers and Charged Small Molecules

Herein, we report the directional stimuli-responsive self-assembly of gold nanoparticles (AuNPs) coated with a thermoresponsive block copolymer (BCP), poly(ethylene glycol)-b-poly(N-isopropylacrylamide) (PEG-b-PNIPAM) and charged small molecules. AuNPs modified with PEG-b-PNIPAM possessing a AuNP/PNIPAM/PEG core/active/shell structure undergo temperature-induced self-assembly into one-dimensional (1D) or two-dimensional (2D) structures in salt solutions, with the morphology varying with the ionic strength of the medium. Salt-free self-assembly is also realized by modulating the surface charge by the codeposition of positively charged small molecules; 1D or 2D assemblies are formed depending on the ratio between the small molecule and PEG-b-PNIPAM, consistent with the trend observed with the bulk salt concentration. A series of charge-controlled self-assembly at various conditions revealed that the temperature-induced BCP-mediated self-assembly reported here provides an effective means for on-demand directional self-assembly of nanoparticles (NPs) with controlled morphology, interparticle distance, and optical properties, and the fixation of high-temperature structures.

Development of Thermally Responsive PolyNIPAm Microcarrier for Application of Cell Culturing-Part I: A Feasibility Study

Poly(N-isopropylacrylamide) (polyNIPAm) microspheres were synthesized via the suspension polymerization technique. Thermal and redox initiators were compared for the polymerization, in order to study the effect of initiator type on the surface charge and particle size of polyNIPAm microspheres. The successful polymerization of NIPAm was confirmed by FTIR analysis. Microspheres of diameter >50 µm were synthesized when a pair of ammonium persulfate (APS) and N,N,N',N'-tetramethylene-diamine (TEMED) redox initiators was used, whilst relatively small microspheres of ~1 µm diameter were produced using an Azobis-isobutyronitrile (AIBN) thermal initiator. Hence, suspension polymerization using a redox initiator pair was found to be more appropriate for the synthesis of polyNIPAm microspheres of a size suitable for human embryonic kidney (HEK) cell culturing. However, the zeta potential of polyNIPAm microspheres prepared using an APS/TEMED redox initiator was significantly more negative than AIBN thermal initiator prepared microspheres and acted to inhibit cell attachment. Conversely, strong cell attachment was observed in the case of polyNIPAm microspheres of diameter ~90 µm, prepared using an APS/TEMED redox initiator in the presence of a cetyl trimethyl ammonium bromide (CTAB) cationic surfactant; demonstrating that surface charge modified polyNIPAm microspheres have great potential for use in cell culturing.

Delivery, Fate, and Mobility of Silver Nanoparticles in Citrus Trees

Crop disease control is crucial for the sustainable development of agriculture, with recent advances in nanotechnology offering a promising solution to this pressing problem. However, the efficacy of nanoparticle (NP) delivery methods has not been fully explored, and knowledge regarding the fate and mobility of NPs within trees is still largely unknown. In this study, we evaluate the efficiency of NP delivery methods and investigate the mobility and distribution of NPs with different surface coatings (citrate (Ct), polyvinylpyrrolidone (PVP), and gum Arabic (GA)) within Mexican lime citrus trees. In contrast to the limited delivery efficiency reported for foliar and root delivery methods, petiole feeding and trunk injection are able to deliver a large amount of NPs into trees, although petiole feeding takes much longer time than trunk injection (7 days vs 2 h in citrus trees). Once NPs enter plants, steric repulsive interactions between NPs and conducting tube surfaces are predicted to facilitate NP transport throughout the plant. Compared to PVP and Ct, GA is highly effective in inhibiting the aggregation of NPs in synthetic sap and enhancing the mobility of NPs in trees. Over a 7 day experimental period, the majority of the Ag recovered from trees (10 mL, 10 ppm GA-AgNP suspension) remain throughout the trunk (81.0% on average), with a considerable amount in the roots (11.7% on average), some in branches (4.4% on average), and a limited amount in leaves (2.9% on average). Furthermore, NP concentrations during injection and tree incubation time postinjection are found to impact the distribution of Ag in tree. We also present evidence for a transport pathway that allows NPs to move from the xylem to the phloem, which disperses the NPs throughout the plant architecture, including to the roots.

Facile design and development of photoluminescent graphene quantum dots grafted dextran/glycol-polymeric hydrogel for thermoresponsive triggered delivery of buprenorphine on pain management in tissue implantation

A novel nano-formulations of biocompatible, biodegradable and thermo-responsive graphene quantum dots (GQDs) loaded dextran/poly(N-isopropylacrylamide) (Dex/PNIPAM) copolymeric matrix was synthesized and analyzed the materials characterization, sustained drug delivery system, tissue feasibility in the tissue implantation site. This research report was aimed to grafting and functionalizing thermo-responsive (Dex/PNIPAM) copolymeric composite with presence of graphene quantum dots to achieve thermal responsive drug delivery (TrDD) with no harm effect in the implantation site. The synthesized GQD by using ionic liquid were evaluated by spectroscopic (DLS, PL, XRD and Raman spectroscopy) and Transmission electron microscopic analysis (TEM). The ultra-small GQDs loaded Dex/PNIPAM and was appeared to be asymmetric and open uniform porous structure, which can be significantly favorable for cell uptake and greatly influenced to be an effective drug carrier into the cellular compartment with good fluid flow. The PNIPAM polymeric composite were exhibited sustained and enhanced drug release percentages with increasing temperature at above low critical solution temperature (LCST) is 39 °C comparable to the cumulative drug release profile of below LCST (32 °C), which demonstrated that thermo-responsive polymer was played a significant role in the delivery system. The treated group of GQDs-Dex/PNIPAM was observed that no inflammation and shows noteworthy stromal cell infiltration, demonstrating that the synthesized drug carriers did not harm to the nerves and tissues and only was responsible for the pain management.

Implementation of physiological fluids to provide insight into the characterization, fate, and biological interactions of silver nanoparticles

Silver nanoparticles (AgNPs) are being increasingly utilized in consumer and medical applications. However, there remains conflicting reports on their safety, which are evaluated through a combination of in vitro and in vivo exposure models. These discrepancies may arise, in part, due to the inherent differences between cell-based and animal systems. It is well established that nanotoxicological effects are highly dependent on the unique physicochemical properties and behavior of the particle set, including size, surface chemistry, agglomeration, and ionic dissolution. However, recent studies have identified that these properties vary as a function of exposure environment; providing a rationale for the contradictory results between in vitro and in vivo assessments. Artificial physiological fluids are emerging as a powerful tool as they allow for the characterization of NPs in an environment which they would likely encounter in vivo, in addition to having the experimental advantages of flexibility and consistency. Here, we demonstrated that the utilization of artificial fluids provided a mechanism to assess AgNP behavior and induced bioresponses in environments that they would likely encounter in vivo. AgNPs were introduced within an alveolar-based exposure model, which included alveolar epithelial (A549) cells incubated within artificial alveolar fluid (AF). Additionally, the particles underwent extensive characterization within both AF and lysosomal fluid, which the AgNPs would encounter following cellular internalization. Following incubation in physiological environments AgNP properties were significantly modified versus a traditional media environment, including alterations to both extent of agglomeration and rate of ionic dissolution. Moreover, when A549s were exposed to AgNPs in AF, the cells displayed lower cytotoxicity and stress rates, corresponding to a fluid-dependent drop in silver ion production. This work highlights the need for enhanced in vitro models that more closely mimic in vivo exposure environments in order to capture true NP behaviors and cellular interactions.

Protein Polymer-Based Nanoparticles: Fabrication and Medical Applications

Nanoparticles are particles that range in size from about 1⁻1000 nanometers in diameter, about one thousand times smaller than the average cell in a human body. Their small size, flexible fabrication, and high surface-area-to-volume ratio make them ideal systems for drug delivery. Nanoparticles can be made from a variety of materials including metals, polysaccharides, and proteins. Biological protein-based nanoparticles such as silk, keratin, collagen, elastin, corn zein, and soy protein-based nanoparticles are advantageous in having biodegradability, bioavailability, and relatively low cost. Many protein nanoparticles are easy to process and can be modified to achieve desired specifications such as size, morphology, and weight. Protein nanoparticles are used in a variety of settings and are replacing many materials that are not biocompatible and have a negative impact on the environment. Here we attempt to review the literature pertaining to protein-based nanoparticles with a focus on their application in drug delivery and biomedical fields. Additional detail on governing nanoparticle parameters, specific protein nanoparticle applications, and fabrication methods are also provided.

The Role of Chain Molecular Weight and Hofmeister Series Ions in Thermal Aggregation of Poly(2-Isopropyl-2-Oxazoline) Grafted Nanoparticles

Thermoresponsive nanoparticles are promising smart materials for many applications. However, a rational design for applications requires a deeper understanding and experimental verification of the various parameters that influence the thermoresponsiveness of the spherical polymer brushes that define most of such nanomaterials. Therefore, we investigate superparamagnetic iron oxide nanoparticles (SPION) grafted with poly(2-isopropyl-2-oxazoline) (6–33 kg mol⁻¹) by temperature-cycled dynamic light scattering and differential scanning calorimetry. The grafting of dense spherical polymer brushes leads to lower aggregation temperatures and transition enthalpies when compared with the free polymer. The transition enthalpy and temperature depend on the polymer shell size and structure. The addition of kosmotropic salts decreases the aggregation temperature following the Hofmeister series.