pH- and Thermo-sensitive Hydrogel Nanoparticles

The Synergic Effect of Gut-Derived Probiotic Bacillus cereus SL1 And Ocimum sanctum on Growth, Intestinal Histopathology, Innate Immunity, and Expression of Enzymatic Antioxidant Genes in Fish, Cirrhinus mrigala (Hamilton, 1822)

An effective alternative approach to combat aquaculture challenges is the strategic application of bioresources, which not only mitigate disease ailment but also optimize fish growth. Hence, current research was undertaken to highlight the synergic role of bioresources such as plant immunostimulant Ocimum sanctum along with potent gut-derived probiotic Bacillus cereus strain SL1 (Gen Bank Accession Number: FJ627945.1) on mrigal (Cirrhinus mrigala) growth, antioxidant status, gut histopathology, and immune response. For 90 days, fingerlings (average weight 6.8 ± 0.5 g) were fed on diets having varying concentrations of O. sanctum and B. cereus. After the completion of the feeding trial, various growth, immunity, and histological and antioxidant metrics were evaluated according to standard procedures. In comparison to the control and other treatment groups, T3 group showed a significant (P < 0.05) increase in growth parameters, antioxidant enzymatic activity, and hematological and immunological parameters. In addition to it, supplementation of both B. cereus and O. sanctum also upregulated the antioxidant-related gene expressions, such as hepatic catalase gene by 1.89-3.00 folds, hepatic SOD-1 by 4.46-7.52 folds, and GPx-1of the liver by 1.56-1.95 folds. For 10 days, fingerlings were challenged with the pathogenic bacterium Aeromonas hydrophila (MTCC-1739), and maximum survival rate (77.77%) was reported in fingerlings of T3 treatment. Further histopathological studies of gut tissues affirm that O. sanctum and B. cereus play a synergic role in the protection of digestive organs from the pathogenic bacterium A. hydrophila. These results suggest that O. sanctum and B. cereus synergically improved the growth performance, immunity, antioxidant status, and gut histology of C. mrigala leading to its sustainable culture.

MicroRNA-targeting nanomedicines for the treatment of intervertebral disc degeneration

Low back pain stands as a pervasive global health concern, afflicting almost 80% of adults at some point in their lives with nearly 40% attributable to intervertebral disc degeneration (IVDD). As only symptomatic relief can be offered to patients there is a dire need for innovative treatments.Given the accumulating evidence that multiple microRNAs (miRs) are dysregulated during IVDD, they could have a huge potential against this debilitating condition. The way miRs can profoundly modulate signaling pathways and influence several cellular processes at once is particularly exciting to tackle this multifaceted disorder. However, miR delivery encounters extracellular and intracellular biological barriers. A promising technology to address this challenge is the vectorization of miRs within nanoparticles, providing both protection and enhancing their uptake within the scarce target cells of the degenerated IVD. This comprehensive review presents the diverse spectrum of miRs' connection with IVDD and demonstrates their therapeutic potential when vectorized in nanomedicines.

Dissipative Particle Dynamics Simulation of Nanoparticle Diffusion in a Crosslinked Polymer Network

Dissipative particle dynamics simulation is conducted to investigate the diffusion of a nanoparticle in a crosslinked polymer network based on a bead-spring model. Focusing on cases where the particle is comparable in size to the network mesh, we find from rigid networks that the excluded-volume and hydrodynamic interaction effects associated with solvent beads lead to lubricity, which assists the particle to slip through an opening into the adjacent cell. For flexible networks, the hopping mechanism for particle escape becomes less pronounced with higher network flexibility due to either a smaller spring constant or slacker strands, each consisting of more beads. This behavior could be explained by the larger cell size fluctuation and its slower relaxation, whereby large enough openings temporarily formed are longer-lived, increasing the chance for particle hopping.

Photoinduced synthesis of fluorescent hydrogels without fluorescent monomers

A fluorescent monomer-free one-step strategy is developed for the synthesis of fluorescent acrylamide gels, using inexpensive and commercially available rhodamine B as the hydrogen donor in type II photoinitiation system....

Transport of probe particles in a polymer network: effects of probe size, network rigidity and probe-polymer interaction

Fundamental understanding of the effect of microscopic parameters on the dynamics of probe particles in different complex environments has wide implications. Examples include diffusion of proteins in biological hydrogels, porous media, polymer matrix, etc. Here, we use extensive molecular dynamics simulations to investigate the dynamics of the probe particle in a polymer network on a diamond lattice, which provides substantial crowding to mimic the cellular environment. Our simulations show that the dynamics of the probe increasingly becomes restricted, non-Gaussian and subdiffusive on increasing the network rigidity, binding affinity and probe size. In addition, the velocity autocorrelation functions show negative dips owing to the viscoelasticity and caging due to the surrounding network. These observations go with the general experimental findings. Importantly, for a probe particle of size comparable to the mesh size, unrestricted motion engulfing large length scales has been observed. This happens with a more flexible polymer network, which is easily pushed by the bigger probe. On increasing the rigidity of the network, the bigger probe can not efficiently push the network and as a result the long tail disappears. Our study gives a general qualitative picture of the transport of probes in a gel-like medium, as encountered in different contexts.

Effects of precursor and cross-linking parameters on the properties of dextran-allyl isocyanate-ethylamine/poly(ethylene glycol diacrylate) biodegradable hydrogels and their release of ovalbumin

In this paper, we studied the effects of molecular weight of poly(ethylene glycol diacrylate) (PEGDA) precursor, the degree of substitution (DS) of both allyl isocyanate (AI) and amine groups in dextran-based precursor (Dex-AE), and photoinitiator concentration on Dex-AE/PEGDA hydrogel formation and its ovalbumin (OVA) release. FT-IR spectra showed chemical bond interaction between amine and urethane groups of the hydrogel carriers with OVA. The increase in PEGDA molecular weight led to a faster OVA release because of a more open gel network structure. The study on the DS of AI in Dex-AE precursor showed that an increase in AI did not result in a prominent gel network structure difference. However, the urethane groups in Dex-AE precursor showed some interactions with OVA and, thus, resulted in a slower release rate. The incorporation of amine group into Dex-AE precursor did not affect the gel network structure, but reduced the OVA release rate, and the level of reduction increased with an increasing amine group substitution into the Dex-AE precursor. This reduction could be attributed to the interaction between the amine groups in the gel carrier and OVA. An increase in the photoinitiator concentration showed no effect on the gel network structure or OVA release.

Brownian dynamics simulation of tracer diffusion in a cross-linked network

Brownian dynamics simulation is employed to study the self-diffusion of tracer particles in a cross-linked gel network based on a coarse-grained bead-spring lattice model. Several effects are investigated including the network porosity, flexibility, degree of cross linking, and electrostatic interaction. For uncharged systems, the tracer long-time diffusivity is found to decrease with deceasing porosity and flexibility, but with increasing degree of cross linking. For charged systems, the diffusion is further hindered by the electrostatic interaction, regardless of whether the tracer particle and the network are oppositely or similarly charged. However, there exists a difference in the hindrance mechanism between the two cases. For the former, a substantial decrease in the diffusivity can occur at high network porosities due to electrostatic entrapment.

Hydrogel nanoparticles in drug delivery

Hydrogel nanoparticles have gained considerable attention in recent years as one of the most promising nanoparticulate drug delivery systems owing to their unique potentials via combining the characteristics of a hydrogel system (e.g., hydrophilicity and extremely high water content) with a nanoparticle (e.g., very small size). Several polymeric hydrogel nanoparticulate systems have been prepared and characterized in recent years, based on both natural and synthetic polymers, each with its own advantages and drawbacks. Among the natural polymers, chitosan and alginate have been studied extensively for preparation of hydrogel nanoparticles and from synthetic group, hydrogel nanoparticles based on poly (vinyl alcohol), poly (ethylene oxide), poly (ethyleneimine), poly (vinyl pyrrolidone), and poly-N-isopropylacrylamide have been reported with different characteristics and features with respect to drug delivery. Regardless of the type of polymer used, the release mechanism of the loaded agent from hydrogel nanoparticles is complex, while resulting from three main vectors, i.e., drug diffusion, hydrogel matrix swelling, and chemical reactivity of the drug/matrix. Several crosslinking methods have been used in the way to form the hydrogel matix structures, which can be classified in two major groups of chemically- and physically-induced crosslinking.

Grid pattern of nanothick microgel network

A novel grid pattern of two kinds of nanothick microgels was developed by alternate patterning using photolithography. At first, 100-microm-wide nanothick PAAm microgel stripes were grafted on a polystyrene surface by UV irradiation of the photoreactive azidobenzoyl-derivatized polyallylamine-coated surface through a photomask with 100-microm-wide stripes. Then, a second set of 100-microm-wide nanothick PAAc microgel stripes were grafted across the PAAm-grated polystyrene surface by UV irradiation of the photoreactive azidophenyl-derivatized poly(acrylic acid)-coated surface through a photomask placed perpendicularly to the first set of PAAm microgel stripes. The PAAc microgel stripe pattern was formed over the PAAm microgel stripe pattern. The cross angle of the two microgel stripes could be controlled by adjusting the position of the photomask when the second microgel pattern was prepared. Swelling and shrinking of the microgels were investigated by scanning probe microscopy (SPM) in an aqueous solution. SPM observation indicated that the thickness of the gel network was 100 to 500 nm. The regions containing PAAm, PAAc, and the PAAc-PAAm overlapping microgels showed different swelling and shrinking properties when the pH was changed. The PAAm microgel swelled at low pH and shrank at high pH whereas the PAAc microgel swelled at high pH and shrank at low pH. However, the PAAc-PAAm overlapping microgel did not change as significantly as did the two microgels, indicating that the swelling and shrinking of the two gels was partially offset. The pH-induced structural change was repeatedly reversible. The novel grid pattern of nanothick microgels will find applications in various fields such as smart actuators, artificial muscles, sensors, and drug delivery systems as well as in tissue engineering and so forth.

Immobilization of derivatized dextran nanoparticles on konjac glucomannan/chitosan film as a novel wound dressing

The aim of this study was to prepare konjac glucomannan (KGM)/chitosan (CS) film containing glycidyl methacrylate derivatized dextran (dex-GMA)/acrylic acid(AAc) nanoparticles loaded with antibacterial agent. In this study, An optimized procedure chosen from three methods was used to prepare Erythromycin (EM)-loaded poly(dex-GMA/AAc) nanoparticles and obtained nanoparticles ranged from 50-200 nm. Film was found to have equilibrium water content (EWC) 99.3% which could prevent exudates on wound bed from accumulating and also have excellent water adsorption 2362.3 +/- 55.2%; the water vapor transmission rate (WVTR) was 2335 +/- 36 gm(-2) day(-1) and evaporative water loss from the film (EWL) was approximately 10% after 1 h and within 6 h it increased to 90%. Drug release of film containing nanoparticles or absent was determined, within 22 h accumulative release was 40.3%, 72.5% respectively. In conclusion, KGM/CS film containing nanoparticles could not only maintain a moist environment over wound bed in moderate to heavily exuding wound but also provide a continuous and sustained release of the antibacterial agent on the wound surface, which could be potential wound dressing.

Self-assembled supramolecular hydrogels formed by biodegradable PEO–PHB–PEO triblock copolymers and α-cyclodextrin for controlled drug delivery

A materials design of a new supramolecular hydrogel self-assembled between alpha-cyclodextrin and a biodegradable poly(ethylene oxide)-poly[(r)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer was demonstrated. The cooperation effect of complexation of PEO segments with alpha-cyclodextrin and the hydrophobic interaction between PHB blocks resulted in the formation of the supramolecular hydrogel with a strong macromolecular network. The in vitro release kinetics studies of fluorescein isothiocyanate labeled dextran (dextran-FITC) model drug from the hydrogel showed that the hydrogel was suitable for relatively long-term sustained controlled release of macromolecular drugs, which many simple triblock copolymer hydrogel systems could not achieve. The hydrogel was found to be thixotropic and reversible, and can be applied as a promising injectable drug delivery system.

The use of colloidal microgels as a (trans)dermal drug delivery system

A co-polymer of poly(N-isopropylacrylamide) (85%) co-butyl acrylate (10%) co-methacrylic acid (5%) (NIPAM/BA/MAA) (85/10/5) microgel was synthesised and investigated as a potential pH and temperature sensitive transdermal delivery device. Three compounds having different octanol/water partition coefficients and solubilities were incorporated into the microgel, namely: salicylamide (SA), methyl paraben (MP) and propyl paraben (PP). Physico-chemical characterisation of these microgel-drug complexes showed that microgels incorporating MP and SA have smaller volumes after changing environmental pH or temperature when compared with the co-polymer NIPAM/BA/MAA (85/10/5) alone. This reduction in volume could be attributed to the incorporation of the compounds into the microgel particles, having a shielding effect on the charged groups present within the network. Diffusion studies, across human skin, were performed at 305K in the range of pH 3-7 for saturated solutions of SA, MP and PP, and for microgel particles incorporating the three compounds. The transport rate for these microgels incorporating MP was reduced by 2/3-fold compared to the saturated solution, by one order of magnitude for PP, meanwhile the transport rate for these microgels incorporating SA is the same order of magnitude as that for the corresponding saturated solutions. Transdermal release studies of the saturated colloidal dispersions indicated that pH control of the drug release was marginal. The incorporation of compounds into the pH/temperature sensitive co-polymer NIPAM/BA/MAA (85/10/5) and the subsequent release depends on the octanol/water partition coefficient and solubility of the respective compound.

Vinylpyrrolidone-co-(meth)acrylic acid inserts for ocular drug delivery: Synthesis and evaluation

Copolymeric hydrogels constituting of vinylpyrrolidone and methacrylic or acrylic acid repeat units have been prepared and investigated for their ability to act as controlled release vehicles in ophthalmic drug delivery. The materials were synthesized by radical-induced polymerization in the presence of N,N'-methylenebisacrylamide crosslinker, and the influences of network composition and drug solubility upon the swelling properties, adhesion behavior, and drug release characteristics were studied. In vitro release experiments showed that some of these materials could be useful vehicles for the delivery of drugs such as pilocarpine or chloramphenicol, while in vivo studies, using the rabbit model, confirmed their high potential for the controlled ocular delivery of pilocarpine hydrochloride.

Dual-stimuli-responsive hydrogels based on poly(N-isopropylacrylamide)/chitosan semi-interpenetrating networks

The synthesis and characterisation of semi-interpenetrating polymeric networks obtained by the radical-induced polymerisation of N-isopropylacrylamide in the presence of chitosan using tetraethyleneglycoldiacrylate as the crosslinker is described. The influence of the degree of crosslinking and that of the ratio of chitosan to poly(N-isopropylacrylamide) on the "pH/temperature induced" phase transition behaviour and swelling characteristics of the hydrogel system are investigated. The ability of the same system to act as a controlled release vehicle for pilocarpine hydrochloride is evaluated.

Biodistribution of fluoresceinated dextran using novel nanoparticles evading reticuloendothelial system

The rapid clearance of circulating nanoparticles from the blood stream coupled with their high uptake by liver and spleen has thus far been overcome by reducing the particle size, and by making the particle surface hydrophilic with poloxamers and poloxamines. We have prepared hydrogel nanoparticles of polyvinylpyrrolidone of a size less than 100 nm diameter with precise size distribution. Since the inner cores of these particles are also hydrophilic, these particles are capable of encapsulating water-soluble compounds. Biodistribution of these particles shows practically negligible (<1%) uptake by the macrophages in liver and spleen, and approximately 5-10% of these particles remain in circulation even 8 h after i.v. injection. Increasing the surface hydrophobicity as well as particle size can increase the RES uptake of these particles. Because of longer residence in blood, the hydrogel nanoparticles have potential therapeutic applications particularly in cancer: the water-soluble cytotoxic agents encapsulated in these particles can be targeted to tumors while minimizing the likelihood of toxicity to reticuloendothelial system (RES).