Polyacrylate/polyacrylate-PEG biomaterials obtained by high internal phase emulsions (HIPEs) with tailorable drug release and effective mechanical and biological properties

The paper focuses on the preparation of polyacrylate based biomaterials designed as patches for dermal/transdermal drug delivery using materials obtained by the high internal phase emulsion (HIPE) technique. In particular, butyl acrylate and glycidyl methacrylate were selected, respectively, as backbone and functional monomer while two different crosslinkers, bifunctional or trifunctional, were used to form the covalent network. The influence of PEG on the main properties of the materials was also investigated. The obtained materials show a characteristic and interconnected internal structure as confirmed by SEM studies. By an industrial point of view, an interesting feature of this system is that it can be shaped as needed, in any form and thickness. The physiochemically characterized materials showed a tailorable curcumin (model of hydrophobic drugs) drug release, effective mechanical properties and cell viability and resulted neither pro nor anti-angiogenic as demonstrated in vivo by the chick embryo choriallantoic membrane (CAM) assay. Based on these results, the obtained polyHIPEs could be proposed as devices for dermal/transdermal drug delivery and/or for the direct application on wounded skin.

Thermosensitive Display of Carbohydrate Ligands on Microgels for Switchable Binding of Proteins and Bacteria

The synthesis of carbohydrate-functionalized thermosensitive poly(N-isopropylacrylamide) microgels and their ability to bind carbohydrate-binding pathogens upon temperature switch are reported. It is found that the microgels' binding affinity is increased above their lower critical solution temperature (LCST), enabling thermo-triggerable capture of pathogens. Here, a series of microgels with comparatively low mannose functionalization degrees below 1 mol % is achieved by a single polymerization step. Upon increase in mannose density, the microgel size increases, and the LCST decreases to 26 °C. Clustering with concanavalin A indicated that binding affinity is enhanced by a higher mannose content and by raising the temperature above the LCST. Binding studies with Escherichia coli confirm stronger specific interactions above the LCST and formation of mechanically stable aggregates enabling efficient separation of E. coli by filtration. For small incubation times above the LCST, the microgels' potential to release pathogens again below the LCST is confirmed also. Compared to existing switchable scaffolds, microgels nearly entirely composed of a thermosensitive material undergo a large change in volume, which allows them to drastically vary the density of ligands to switch between capture and release. This straightforward yet novel approach is likely compatible with a broad range of bioactive ligands. Therefore, thermosensitive microgels represent a promising platform for the specific capture or release of cells or pathogens.

Paramagnetic Clusters of Mn3(O2CCH3)6(Bpy)2 in Polyacrylamide Nanobeads as a New Design Approach to a T1- T2 Multimodal Magnetic Resonance Imaging Contrast Agent

There is an increasing need for gadolinium-free magnetic resonance imaging (MRI) contrast agents, particularly for patients suffering from chronic kidney disease. Using a cluster-nanocarrier combination, we have identified a novel approach to the design of biomedical nanomaterials and report here the criteria for the cluster and the nanocarrier and the advantages of this combination. We have investigated the relaxivity of the following manganese oxo clusters: the parent cluster Mn₃(O₂CCH₃)₆(Bpy)₂ (1) where Bpy = 2,2'-bipyridine and three new analogs, Mn₃(O₂CC₆H₄CH═CH₂)₆(Bpy)₂ (2), Mn₃(O₂CC(CH₃)═CH₂)₆(Bpy)₂ (3), and Mn₃O(O₂CCH₃)₆(Pyr)₂ (4) where Pyr = pyridine. The parent cluster, Mn₃(O₂CCH₃)₆(Bpy)₂ (1), had impressive relaxivity ( r₁ = 6.9 mM^-1 s^-1, r₂ = 125 mM^-1 s^-1) and was found to be the most amenable for the synthesis of cluster-nanocarrier nanobeads. Using the inverse miniemulsion polymerization technique (1) in combination with the hydrophilic monomer acrylamide, we synthesized nanobeads (∼125 nm diameter) with homogeneously dispersed clusters within the polyacrylamide matrix (termed Mn₃Bpy-PAm). The nanobeads were surface-modified by co-polymerization with an amine-functionalized monomer. This enabled various postsynthetic modifications, for example, to attach a near-IR dye, Cyanine7, as well as a targeting agent. When evaluated as a potential multimodal MRI contrast agent, high relaxivity and contrast were observed with r₁ = 54.4 mM^-1 s^-1 and r₂ = 144 mM^-1 s^-1, surpassing T₁ relaxivity of clinically used Gd-DTPA chelates as well as comparable T₂ relaxivity to iron oxide microspheres. Physicochemical properties, cellular uptake, and impacts on cell viability were also investigated.

Material stiffness influences the polarization state, function and migration mode of macrophages

Biomaterial implantation is followed by an inflammatory cascade dominated by macrophages, which determine implant acceptance or rejection through pro- and anti-inflammatory polarization states (Anderson et al., 2008; Brown and Badylak, 2013). It is known that chemical signals such as bacterial endotoxins and cytokines (IL4) can direct macrophage polarization (Mantovani et al., 2004); however, recent evidence implicates biophysical cues in this process (McWhorter et al., 2015; Patel et al., 2012). Here we report that THP-1 derived macrophages cultured on collagen-coated polyacrylamide gels of varying stiffness adapt their polarization state, functional roles and migration mode according to the stiffness of the underlying substrate. Through gene expression and protein secretion analysis, we show that stiff polyacrylamide gels (323 kPa) prime macrophages towards a pro-inflammatory phenotype with impaired phagocytosis in macrophages, while soft (11 kPa) and medium (88 kPa) stiffness gels prime cells towards an anti-inflammatory, highly phagocytic phenotype. Furthermore, we show that stiffness dictates the migration mode of macrophages; on soft and medium stiffness gels, cells display Rho-A kinase (ROCK)-dependent, podosome-independent fast amoeboid migration and on stiff gels they adopt a ROCK-independent, podosome-dependent slow mesenchymal migration mode. We also provide a mechanistic insight into this process by showing that the anti-inflammatory property of macrophages on soft and medium gels is ROCK-dependent and independent of the ligand presented to them. Together, our results demonstrate that macrophages adapt their polarization, function and migration mode in response to the stiffness of the underlying substrate and suggest that biomaterial stiffness is capable of directing macrophage behaviour independent of the biochemical cues being presented to them. The results from this study establish an important role for substrate stiffness in directing macrophage behaviour, and will lead to the design of immuno-informed biomaterials that are capable of modulating the macrophage response after implantation. STATEMENT OF SIGNIFICANCE: Biomaterial implantation is followed by an inflammatory cascade dominated by macrophages, which determine implant acceptance or rejection through pro- and anti-inflammatory polarization states. It is known that chemical signals can direct macrophage polarization; however, recent evidence implicates biophysical cues in this process. Here we report that macrophages cultured on gels of varying stiffness adapt their polarization state, functional roles and migration mode according to the stiffness of the underlying substrate. The results from this study establish an important role for substrate stiffness in directing macrophage behaviour, and will lead to the design of immuno-informed biomaterials that are capable of modulating the macrophage response after implantation.

Hypoxia impacts human MSC response to substrate stiffness during chondrogenic differentiation

Tissue engineering strategies often aim to direct tissue formation by mimicking conditions progenitor cells experience within native tissues. For example, to create cartilage in vitro, researchers often aim to replicate the biochemical and mechanical milieu cells experience during cartilage formation in the developing limb bud. This includes stimulating progenitors with TGF-β1/3, culturing under hypoxic conditions, and regulating mechanosensory pathways using biomaterials that control substrate stiffness and/or cell shape. However, as progenitors differentiate down the chondrogenic lineage, the pathways that regulate their responses to mechanotransduction, hypoxia and TGF-β may not act independently, but rather also impact one another, influencing overall cell response. Here, to better understand hypoxia's influence on mechanoregulatory-mediated chondrogenesis, we cultured human marrow stromal/mesenchymal stem cells (hMSC) on soft (0.167 kPa) or stiff (49.6 kPa) polyacrylamide hydrogels in chondrogenic medium containing TGF-β3. We then compared cell morphology, phosphorylated myosin light chain 2 staining, and chondrogenic gene expression under normoxic and hypoxic conditions, in the presence and absence of pharmacological inhibition of cytoskeletal tension. We show that on soft compared to stiff substrates, hypoxia prompts hMSC to adopt more spread morphologies, assemble in compact mesenchymal condensation-like colonies, and upregulate NCAM expression, and that inhibition of cytoskeletal tension negates hypoxia-mediated upregulation of molecular markers of chondrogenesis, including COL2A1 and SOX9. Taken together, our findings support a role for hypoxia in regulating hMSC morphology, cytoskeletal tension and chondrogenesis, and that hypoxia's effects are modulated, at least in part, by mechanosensitive pathways. Our insights into how hypoxia impacts mechanoregulation of chondrogenesis in hMSC may improve strategies to develop tissue engineered cartilage. STATEMENT OF SIGNIFICANCE: Cartilage tissue engineering strategies often aim to drive progenitor cell differentiation by replicating the local environment of the native tissue, including by regulating oxygen concentration and mechanical stiffness. However, the pathways that regulate cellular responses to mechanotransduction and hypoxia may not act independently, but rather also impact one another. Here, we show that on soft, but not stiff surfaces, hypoxia impacts human MSC (hMSC) morphology and colony formation, and inhibition of cytoskeletal tension negates the hypoxia-mediated upregulation of molecular markers of chondrogenesis. These observations suggest that hypoxia's effects during hMSC chondrogenesis are modulated, at least in part, by mechanosensitive pathways, and may impact strategies to develop scaffolds for cartilage tissue engineering, as hypoxia's chondrogenic effects may be enhanced on soft materials.

Two-in-One Platform for High-Efficiency Intracellular Delivery and Cell Harvest: When a Photothermal Agent Meets a Thermoresponsive Polymer

Efficient intracellular delivery of exogenous macromolecules is a key operation in biological research and for clinical applications. Moreover, under particular in vitro or ex vivo conditions, harvesting the engineered cells that maintain good viability is also important. However, none of the methods currently available is truly satisfactory in all respects. Herein, a "two-in-one" platform based on a polydopamine/poly( N-isopropylacrylamide) (PDA/PNIPAAm) hybrid film is developed, showing high efficiency in both cargo delivery and cell harvest without compromising cell viability. Due to the strong photothermal effect of PDA in response to near-infrared irradiation, this film can deliver diverse molecules to a number of cell types (including three hard-to-transfect cells) with an efficiency of ∼99% via membrane-disruption mechanism. Moreover, due to the thermoresponsive properties of PNIPAAm, the cells are harvested from the film without compromising viability by simply decreasing the temperature. A proof-of-concept experiment demonstrates that, using this platform, "recalcitrant" endothelial cells can be transfected by the functional ZNF580 gene and the harvested transfected cells can be recultured with high retention of viability and improved migration. In general, this "two-in-one" platform provides a reliable, universally applicable approach for both intracellular delivery and cell harvest in a highly efficient and nondestructive way, with great potential for use in a wide range of biomedical applications.

A strong, tough, and osteoconductive hydroxyapatite mineralized polyacrylamide/dextran hydrogel for bone tissue regeneration

The design of hydrogels with adequate mechanical properties and excellent bioactivity, osteoconductivity, and capacity for osseointegration is essential to bone repair and regeneration. However, it is challenging to integrate all these properties into one bone scaffold. Herein, we developed a strong, tough, osteoconductive hydrogel by a facile one-step micellar copolymerization of acrylamide and urethacrylate dextran (Dex-U), followed by the in situ mineralization of hydroxyapatite (HAp) nanocrystals. We show that the soft, flexible, and hydrophobically associated polyacrylamide (PAAm) network is strengthened by the stiff crosslinked Dex-U phase, and that the mineralized HAp simultaneously improves the mechanical properties and osteoconductivity. The obtained HAp mineralized PAAm/Dex-U hydrogel (HAp-PADH) has extremely high compressive strength (6.5 MPa) and enhanced fracture resistance (over 2300 J m^-2), as compared with pure PAAm hydrogels. In vitro, we show that the mineralized HAp layer promotes the adhesion and proliferation of osteoblasts, and effectively stimulates osteogenic differentiation. Through the in vivo evaluation of hydrogels in a femoral condyle defect rabbit model, we show regeneration of a highly mineralized bone tissue and direct bonding to the HAp-PADH interface. These findings confirm the excellent osteoconductivity and osseointegration ability of fabricated HAp-PADH. The present HAp-PADH, with its superior mechanical properties and excellent osteoconductivity, should have great potential for bone repair and regeneration. STATEMENT OF SIGNIFICANCE: We developed a strong, tough, and osteoconductive hydrogel by a facile one-step micellar copolymerization of acrylamide and urethane methacrylate dextran (Dex-U), followed by the in situ mineralization of hydroxyapatite (HAp) nanocrystals. The hydrophobic micellar copolymerization and introduction of the stiff crosslinked Dex-U phase endowed the soft polyacrylamide (PAAm) network with enhanced strength and toughness. The in situ mineralized HAp nanocrystals on the hydrogels further improved the mechanical properties of the hydrogels and promoted osteogenic differentiation of cells. Mechanical tests together with in vitro and in vivo evaluations confirmed that the HAp mineralized PAAm/Dex-U hydrogel (HAp-PADH) achieved a combination of superior mechanical properties and excellent osseointegration, and thus may offer a promising candidate for bone repair and regeneration.

Effect of Polyacrylamide/Attapulgite Composite on Foraging Behaviors of Formosan Subterranean Termites (Blattodea: Rhinotermitidae)

Moisture conditions of food and soil are essential for the survival and foraging activities of subterranean termites. Polyacrylamide/attapulgite composite is a water-retaining agent that has been applied to increase moisture of agricultural soils. We hypothesize that polyacrylamide/attapulgite composite may increase the moisture of bait matrixes and soil surrounding baiting containers and therefore attract termites and increase their foraging activities. In the present study, aggregation and feeding preferences, survivorship, body water percentage, and wood consumption of Formosan subterranean termites, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), were investigated when responding to polyacrylamide/attapulgite composite that was buried within soil (substrate) or filled in the void volume of baiting containers. Two-choice tests showed that termites consumed significantly more wood when polyacrylamide/attapulgite composite was buried within dry soil (27%-moisture) than the controls (no polyacrylamide/attapulgite composite was provided). However, polyacrylamide/attapulgite composite buried within wet soil (54%-moisture) did not significantly affect foraging behaviors of termites. Multiple-choice tests showed no aggregation or feeding preference of termites in the baiting containers filled with polyacrylamide/attapulgite composite compared with the soil-filled or unfilled ones, whenever the substrate was dry or wet. No-choice tests showed that the presence of polyacrylamide/attapulgite composite (buried within soil or filled in baiting containers) significantly increased wood consumption and body water percentage of termites as well as wood moisture under dry-substrate conditions. Our studies suggest that burying polyacrylamide/attapulgite composite within dry soil may enhance foraging activities of termites, but filling the bait stations with polyacrylamide/attapulgite composite may not effectively attract termites.

Soft Hydrogel Zwitterionic Coatings Minimize Fibroblast and Macrophage Adhesion on Polyimide Substrates

Minimizing the foreign body reaction to polyimide-based implanted devices plays a pivotal role in several biomedical applications. In this work, we propose materials exhibiting nonbiofouling properties and a Young's modulus reflecting that of soft human tissues. We describe the synthesis, characterization, and in vitro validation of poly(carboxybetaine) hydrogel coatings covalently attached to polyimide substrates via a photolabile 4-azidophenyl group, incorporated in poly(carboxybetaine) chains at two concentrations of 1.6 and 3.1 mol %. The presence of coatings was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy. White light interferometry was used to evaluate the coating continuity and thickness (between 3 and 6 μm under dry conditions). Confocal laser scanning microscopy allowed us to quantify the thickness of the swollen hydrogel coatings that ranged between 13 and 32 μm. The different hydrogel formulations resulted in stiffness values ranging from 2 to 19 kPa and led to different fibroblast and macrophage responses in vitro. Both cell types showed a minimum adhesion on the softest hydrogel type. In addition, both the overall macrophage activation and cytotoxicity were observed to be negligible for all of the tested material formulations. These results are a promising starting point toward future advanced implantable systems. In particular, such technology paves the way for novel neural interfaces able to minimize the fibrotic reaction, once implanted in vivo, and to maximize their long-term stability and functionality.

Poly(N-isopropylacrylamide)/polydopamine/clay nanocomposite hydrogels with stretchability, conductivity, and dual light- and thermo- responsive bending and adhesive properties

Conducting hydrogels have attracted attention as a special functional class of smart soft materials and have found applications in various advanced fields. However, acquiring all the characteristics such as conductivity, adequate adhesiveness, self-healing ability, stretchability, biocompatibility, and stimulating deformation responsiveness still remains a challenge. Inspired by the mechanism of bioadhesion in marine mussels, a multifunctional nanocomposite hydrogel with excellent adhesiveness to a broad range of substrates including human skin was developed with the help of synergistic multiple coordination bonds between clay, poly(N-isopropylacrylamide) (PNIPAM), and polydopamine nanoparticles (PDA-NPs). The prepared hydrogel showed controllable near-infrared (NIR) responsive deformation after incorporation of PDA-NPs as highly effective photothermal agents in the thermo-sensitive PNIPAM network. Meanwhile, the fabricated nanocomposite hydrogels showed excellent stretchability and conductivity, which make them attractive material candidates for application in various fields, such as electronic skin, wearable devices, and so on.

Inhibiting Bacterial Adhesion by Mechanically Modulated Microgel Coatings

Bacterial infection is a severe problem especially when associated with biomedical applications. This study effectively demonstrates that poly- N-isopropylmethacrylamide based microgel coatings prevent bacterial adhesion. The coating preparation via a spraying approach proved to be simple and both cost and time efficient creating a homogeneous dense microgel monolayer. In particular, the influence of cross-linking density, microgel size, and coating thickness was investigated on the initial bacterial adhesion. Adhesion of Staphylococcus aureus ATCC 12600 was imaged using a parallel plate flow chamber setup, which gave insights in the number of the total bacteria adhering per unit area onto the surface and the initial bacterial deposition rates. All microgel coatings successfully yielded more than 98% reduction in bacterial adhesion. Bacterial adhesion depends both on the cross-linking density/stiffness of the microgels and on the thickness of the microgel coating. Bacterial adhesion decreased when a lower cross-linking density was used at equal coating thickness and at equal cross-linking density with a thicker microgel coating. The highest reduction in the number of bacterial adhesion was achieved with the microgel that produced the thickest coating ( h = 602 nm) and had the lowest cross-linking density. The results provided in this paper indicate that microgel coatings serve as an interesting and easy applicable approach and that it can be fine-tuned by manipulating the microgel layer thickness and stiffness.

Biodegradable Thermomagnetically Responsive Soft Untethered Grippers

Soft-robotic devices such as polymeric microgrippers offer the possibility for pick and place of fragile biological cargo in hard-to-reach conduits with potential applications in drug delivery, minimally invasive surgery, and biomedical engineering. Previously, millimeter-sized self-folding thermomagnetically responsive soft grippers have been designed, fabricated, and utilized for pick-and-place applications but there is a concern that such devices could get lost or left behind after their utilization in practical clinical applications in the human body. Consequently, strategies need to be developed to ensure that these soft-robotic devices are biodegradable so that they would disintegrate if left behind in the body. In this paper, we describe the photopatterning of bilayer gels composed of a thermally responsive high-swelling poly(oligoethylene glycol methyl ether methacrylate ( M_n = 500)-bis(2-methacryloyl)oxyethyl disulfide), P(OEGMA-DSDMA), and a low-swelling poly(acrylamide- N, N'-bis(acyloyl)cystamine) hydrogel, in the shape of untethered grippers. These grippers can change shape in response to thermal cues and open and close due to the temperature-induced swelling of the P(OEGMA-DSDMA) layer. We demonstrate that the grippers can be doped with magnetic nanoparticles so that they can be moved using magnetic fields or loaded with chemicals for potential applications as drug-eluting theragrippers. Importantly, they are also biodegradable at physiological body temperature (∼37 °C) on the basis of cleavage of disulfide bonds by reduction. This approach that combines thermoresponsive shape change, magnetic guidance, and biodegradability represents a significant advance to the safe implementation of untethered shape-changing biomedical devices and soft robots for medical and surgical applications.

Zwitterionic Skins with a Wide Scope of Customizable Functionalities

With growing interest in the fields of wearable devices, it is crucial yet rather challenging to develop skinlike soft conductive materials with customizable functionalities and human tissue-compatible mechanical properties. Previously reported electronic skins struggle to meet the demands for transparence, mechanical adaptability, and stable conductivity during deformation. The recent rise of ionic skins with inorganic salts or ionic liquids doping provides the intrinsic stretchability, however, dilemmas remain for their limited functionalities such as a monotonous appearance and a narrow scope of mechanical and sensory properties. Herein, we design a type of zwitterionic hydrogels from the perspective of molecular interactions, which successfully combines ultrastretchability (>10000% strain), high strength (∼300 kPa), self-healability (at room temperature within 12 h), 3D printability, distinct stimuli-responsibility, biocompatibility, and antibacterial activity. The wide spectrum of such excellent properties has been rarely reported before and along with the ability to fabricate bioinspired intelligent skins recreating multiple sensations and mechanical properties of human skin, covering a broad range of sensitivity, and displaying tunable visual effect. We believe this work will inspire the programming of stimuli-responsive skinlike materials and contribute to the smart devices for information transformation between natural and artificial interfaces.

Reduced Graphene-Oxide-Embedded Polymeric Nanofiber Mats: An "On-Demand" Photothermally Triggered Antibiotic Release Platform

The steady increase of antimicrobial resistance of different pathogens requires the development of alternative treatment strategies next to the oral delivery of antibiotics. A photothermally activated platform based on reduced graphene oxide (rGO)-embedded polymeric nanofiber mats for on-demand release of antibiotics upon irradiation in the near-infrared is fabricated. Cross-linked hydrophilic nanofibers, obtained by electrospinning a mixture of poly(acrylic acid) (PAA) and rGO, show excellent stability in aqueous media. Importantly, these PAA@ rGO nanofiber mats exhibit controlled photothermal heating upon irradiation at 980 nm. Nanofiber mats are efficiently loaded with antibiotics through simple immersion into corresponding antibiotics solutions. Whereas passive diffusion based release at room temperature is extremely low, photothermal activation results in increased release within few minutes, with release rates tunable through power density of the applied irradiation. The large difference over passive and active release, as well as the controlled turn-on of release allow regulation of the dosage of the antibiotics, as evidenced by the inhibition of planktonic bacteria growth. Treatment of superficial skin infections with the antibiotic-loaded nanofiber mats shows efficient wound healing of the infected site. Facile fabrication and implementation of these photothermally active nanofiber mats makes this novel platform adaptable for on-demand delivery of various therapeutic agents.

Ions released from a S-PRG filler induces oxidative stress in Candida albicans inhibiting its growth and pathogenicity

Candida albicans causes opportunistic fungal infections usually hidden among more dominant bacteria and does not exhibit high pathogenicity in vivo. Among the elderly, due to reduced host resistance to pathogens attributable to immunoscenesence, oral candidiasis is more likely to develop often leading to systemic candidiasis. Surface pre-reacted glass ionomer filler (S-PRG filler) is an ion-releasing functional bioactive glass that can release and recharge six ions which in turn strengthens tooth structure, inhibits demineralization arising from dental caries, and suppresses dental plaque accumulation. However, its effects on C. albicans have never been elucidated. Here, we evaluated the effects of ion released from S-PRG filler on C. albicans. Results show that extraction liquids containing released ions (ELIS) decreased the amount of hydrogen peroxide and catalase activity in C. albicans. Moreover, ELIS presence was found to affect C. albicans: (1) suppression of fungal growth and biofilm formation, (2) prevent adherence to denture base resin, (3) inhibit dimorphism conversion, and (4) hinder the capability to produce secreted aspartyl proteinase. Taken together, our findings suggest that ELIS induces oxidative stress in C. albicans and suppresses its growth and pathogenicity. In this regard, we propose that ELIS has the potential to be clinically used to help prevent the onset and inhibition of oral candidiasis among the elderly population.

Temperature-Controlled Reversible Exposure and Hiding of Antimicrobial Peptides on an Implant for Killing Bacteria at Room Temperature and Improving Biocompatibility in Vivo

Modification of implants by antimicrobial peptides (AMPs) can improve the antimicrobial activity of the implants. However, AMPs have some cytotoxicity in vivo when they are exposed at body temperature. To tackle this challenge, we propose to develop a new approach to generating a smart antimicrobial surface through exposure of AMPs on the surface. A polydopamine film was first formed on the substrates, followed by the conjugation of a temperature-sensitive polymer, poly( N-isopropylacrylamide) (pNIPAM), to the film through atom transfer radical polymerization (ATRP). Then, AMPs were conjugated to the NIPAM on the resultant pNIPAM-modified surface through a click chemistry reaction. Because of the temperature-sensitive property of pNIPAM, the AMPs motif was more exposed to the external environment at room temperature (25 °C) than at body temperature (37 °C), making the surface present a higher antimicrobial activity at room temperature than at body temperature. More importantly, such a smart behavior is accompanied with the increased biocompatibility of the surface at body temperature when compared to the substrates unmodified or modified by AMPs or pNIPAM alone. Our in vivo study further verified that pNIPAM-AMP dual modified bone implants showed increased biocompatibility even when they were challenged with the bacteria at room temperature before implantation. These results indicate that the implants are antibacterial at room temperature and can be safely employed during surgery, resulting in no infection after implantations. Our work represents a new promising strategy to fully explore the antimicrobial property of AMPs, while improving their biocompatibility in vivo. The higher exposure of AMPs at room temperature (the temperature for storing the implants before surgery) will help decrease the risk of bacterial infection, and the lower exposure of AMPs at body temperature (the temperature after the implants are placed into the body by surgery) will improve the biocompatibility of AMPs.

Quantifying the effect of polyacrylamide dosage, Na+ and Ca2+ concentrations, and clay particle size on the flocculation of mature fine tailings with robust statistical methods

Polymer-driven flocculation and dewatering of mature fine tailings (MFT) is critical to improve their consolidation. MFT flocculation and dewatering depends on the size of the suspended clay particles, and on the composition and properties of the liquid in which they are dispersed. The effect of water chemistry on the polymer-particle dynamics is nontrivial, particularly for non-spherical, polydisperse particles such as natural clays. In this study, we used a response surface methodology to systematically assess the impact of Na⁺ and Ca²⁺ concentration and anionic polyacrylamide dosage in the flocculation and dewatering of MFT. We observed a beneficial synergistic effect between Ca²⁺ concentration and polyacrylamide dosage, although excess of Ca²⁺ may reduce polyacrylamide activity. In addition, we investigated the impact of clay particle size on MFT flocculation. Polyacrylamide did not flocculate MFT fractions where the fine clay particles (<2 μm) represented most of the population. Good settling, however, was observed when fine silt particles (from 2 to 44 μm) were present, indicating that the presence and accumulation of larger/heavier particles on the polymer-induced flocs is crucial to form aggregates that readily settle under gravity. The insights gained from this study can contribute to more efficient use of flocculants, more effective use of cations, and better understanding of the impact of particles size in MFT flocculation.

Thermoreversible Hyaluronic Acid-PNIPAAm Hydrogel Systems for 3D Stem Cell Culture

Human pluripotent stem cells (hPSCs) offer considerable potential for biomedical applications including drug screening and cell replacement therapies. Clinical translation of hPSCs requires large quantities of high quality cells, so scalable methods for cell culture are needed. However, current methods are limited by scalability, the use of animal-derived components, and/or low expansion rates. A thermoresponsive 3D hydrogel for scalable hPSC expansion and differentiation into several defined lineages is recently reported. This system would benefit from increased control over material properties to further tune hPSC behavior, and here a scalable 3D biomaterial with the capacity to tune both the chemical and the mechanical properties is demonstrated to promote hPSC expansion under defined conditions. This 3D biomaterial, comprised of hyaluronic acid and poly(N-isopropolyacrylamide), has thermoresponsive properties that readily enable mixing with cells at low temperatures, physical encapsulation within the hydrogel upon elevation at 37 °C, and cell recovery upon cooling and reliquefaction. After optimization, the resulting biomaterial supports hPSC expansion over long cell culture periods while maintaining cell pluripotency. The capacity to modulate the mechanical and chemical properties of the hydrogel provides a new avenue to expand hPSCs for future therapeutic application.

In vitro nuclear receptor inhibition and cytotoxicity of hydraulic fracturing chemicals and their binary mixtures

The widespread use of hydraulic fracturing (HF) in oil and gas extraction operations has led to concern over environmental risks posed by chemicals used in HF fluids. Here we employed a suite of stable luciferase reporter gene assays to investigate the potential for selected HF chemicals or geogenics to activate or antagonise nuclear receptor signalling. We screened three biocides (bronopol [BP], glutaraldehyde [GA], and tetrakis(hydroxymethyl)phosphonium sulfate [THPS]), a surfactant (2-butoxyethanol), a friction reducer (polyacrylamide), and a coal seam geogenic (o-cresol) for their potential to act as agonists or antagonists of the estrogen receptor, androgen receptor, progesterone receptor (PR), glucocorticoid receptor or peroxisome proliferator-activated receptor gamma (PPARγ). None of the chemicals induced luciferase activity in any of assays used in the study. In antagonistic mode, BP, GA and THPS caused reductions in luciferase activity in the reporter assays at higher concentrations (50-100 μM), while at low concentrations (2-10 μM) GA and THPS enhanced luciferase activity in some assays relative to controls. None of the other tested chemicals exhibited antagonism in the selected assays. In most cases, altered receptor signalling only occurred at concentrations exhibiting cytotoxicity. However, PPARγ activity, and to a lesser extent PR activity, were inhibited by THPS at sub-cytotoxic concentrations. The majority of binary combinations tested exhibited significantly less-than-additive cytotoxicity, and none of the combinations exhibited synergistic cytotoxicity. In summary, the results of the present study indicate that the selected chemicals are not likely to function as direct agonists of the nuclear receptors tested, and only one chemical, THPS was an apparent partial antagonist of two nuclear receptors.

THE IMPACT OF THE ACRYLIC MONOMER ON THE MORPHOLOGICAL STRUCTURE OF RAT LINGUAL MUCOSA

The analysis of publications shows that diverse multiple factors can induce changes in taste sensitivity and the main irritants are the chemicals of different types. However, the study of the effect of the components of dental structural materials on the state of lingual mucosa, in particular, taste sensors, has not been fully elucidated to date. The purpose of the paper was the study of the effect of monomer of the "Ftoraks" base acrylic resin on the state of the rats' lingual mucosa within 2-4 weeks after its impact. The previous paper [5] presents the findings of the study on the impact of the monomer of the "Ftoraks" base acrylic resin on the state of the rats' lingual mucosa in the early period (1 to 7 days) and its subsequent regeneration. The studies have found that the greatest changes in the lingual mucosa occur on day 3 and 7 after the application of monomer, and are of erosive-inflammatory origin. Regeneration of the lingual epithelium is delayed. The studies confirm that the monomer of acrylic resin causes a number of pathological changes in the mucous membrane and muscles of the rat tongue, the nature of which varies depending on the duration of its impact. On day 14 in the lingual mucosa the destructive processes are significantly delayed, substituting for the sclerotic processes in the proper plate and atrophic processes, observed, first of all, in the papillae of the tongue. It is appropriate to assume that such changes in the papillae will lead to violation of the taste reception, first of all, in the areas of lateral surfaces of the body of the tongue and in the root area. At the same time, it should be noted that at the end of the experimental period (on day 28 of the contact of the monomer with the lingual mucosa), in the mucous membrane of the tongue, along with atrophic and sclerotic processes, the destructive changes and inflammatory reaction are evident. We hypothesize that this may indicate about partial recovery of taste sensitivity due to the decrease in the number of gustatory buds, taste papillae of different types and the increase in the period of their regeneration.

Water-soluble factors eluated from surface pre-reacted glass-ionomer filler promote osteoblastic differentiation of human mesenchymal stem cells

Surface pre-reacted glass‑ionomer (S‑PRG)-containing dental materials, including composite and coating resins have been used for the restoration and/or prevention of dental cavities. S‑PRG is known to have the ability to release aluminum, boron, fluorine, silicon, and strontium ions. Aluminum ions are known to be inhibitors whereas boron, fluorine, silicon, and strontium ions are known to be promoters of mineralization, via osteoblasts. However, it remains to be clarified how an aqueous eluate obtained from S‑PRG containing these ions affects the ability of mesenchymal stem cells (MSCs), which are known to be present in dental pulp and bone marrow, to differentiate into osteogenic cell types. The present study demonstrated that 200‑ to 1,000‑fold‑diluted aqueous eluates obtained from S‑PRG significantly upregulated the mRNA expression level of the osteogenic differentiation marker alkaline phosphatase in human MSCs (hMSCs) without exhibiting the cytotoxic effect. In addition, the 500‑ to 1,000‑fold‑diluted aqueous eluates obtained from S‑PRG significantly and clearly promoted mineralization of the extracellular matrix of hMSCs. It was additionally demonstrated that hMSCs cultured on the cured resin composites containing S‑PRG fillers exhibited osteogenic differentiation in direct correlation with the weight percent of S‑PRG fillers. These results strongly suggested that aqueous eluates of S‑PRG fillers promoted hard tissue formation by hMSCs, implicating that resins containing S‑PRG may act as a useful biomaterial to cover accidental exposure of dental pulp.

Preparative Purification of Polyphenols from Aronia melanocarpa (Chokeberry) with Cellular Antioxidant and Antiproliferative Activity

The aim of this study was the purification process of polyphenols from Aronia melanocarpa (chokeberry), and the purification parameters were optimised by adsorption and desorption tests. By comparing adsorption and desorption ability of polyphenols from chokeberry on six kinds of macroporous resin, XAD-7 resin was selected. Experiments prove that the best purification parameters of static adsorption and desorption were sample pH = 4.0 with 4 h of adsorption; and desorption solvent is 95% ethanol (pH = 7.0) with 2 h of desorption. The best dynamic parameters were 9.3 bed volume (BV) of sample loading amount at a feeding flow rate of 2 BV/h, and washing the column with 5.8 BV of water, followed by subsequent elution with an eluent volume of 5.0 mL at an elution flow rate of 2 BV/h. Next the antioxidant and antiproliferative activity of polyphenols from chokeberry, blueberries, haskap berries was studied on HepG2 human liver cancer cells. The results show that polyphenol from chokeberry has a strong antioxidant effect. Taking into account the content of polyphenols in fruit, polyphenols from chokeberry represent a very valuable natural antioxidant source with antiproliferative products.

Reducing Facial Wrinkle Size and Increasing Skin Firmness Using Skin Care Polymers

Many cosmetic polymers shrink on drying, producing a tensile force if coated on a substrate. This tensile force can be used to smoothen wrinkles and pores in facial skin. In this study, we evaluated two polymers, a polyvinylpyrrolidone (PVP) and a polyacrylate, for skin tightening properties. We conducted a double-blinded, placebo-controlled and randomized clinical study with 32 female volunteers aged 35-65 years who perceived themselves to have a loss of skin elasticity. Both polymers were formulated in a model cosmetic emulsion with hydrogenated polyisobutene as the oil phase. We measured skin firmness and tightening parameters at baseline and after each product application. Also, facial images were recorded with a fringe projection instrument. The firming measurements indicated that both polymers instantly tightened facial skin, whereas the placebo product offered no significant tightening benefit. However, in clinical evaluation, only the polyacrylate polymer produced statistically significant improvements in wrinkle size and skin firmness on the face without significant consumer use complaints such as tackiness. We concluded that skin care products using PVP and polyacrylates have the potential to offer immediate and visible benefits to consumers with aged skin.

Cellular uptake and intracellular localization of poly (acrylic acid) nanoparticles in a rainbow trout (Oncorhynchus mykiss) gill epithelial cell line, RTgill-W1

The ever-growing production of engineered nanoparticles (NPs) for use in many agricultural, commercial, consumer, and industrial applications will lead to their accidental or intentional release into the environment. Potential routes of environmental exposure include manufacturing or transport spills, disposal of NP-containing products down the drain and/or in landfills, as well as direct usage on agricultural land. Therefore, NPs will inevitably contaminate aquatic environments and interact with resident organisms. However, there is limited information regarding the mechanisms that regulate NP transport into fish from the environment. Thus, our primary objective was to elucidate the mechanism(s) underlying cellular uptake and intracellular fate of 3-9nm poly (acrylic acid) NPs loaded with the fluorescent dye Nile red using a rainbow trout (Oncorhynchus mykiss) gill epithelial cell line (RTgill-W1). In vitro measurements with NP-treated RTgill-W1 cells were carried out using a combination of laser scanning confocal microscopy, flow cytometry, fluorescent biomarkers (transferrin, cholera toxin B subunit, and dextran), endocytosis inhibitors (chlorpromazine, genistein, and wortmannin), and stains (4', 6-diamidino-2-phenylindole, Hoechst 33342, CellMask Deep Red, and LysoTracker Yellow). Clathrin-mediated endocytosis (CME), caveolae-mediated endocytosis and macropinocytosis pathways were active in RTgill-W1 cells, and these pathways were exploited by the non-cytotoxic NPs to enter these cells. We have demonstrated that NP uptake by RTgill-W1 cells was impeded when clathrin-coated pit formation was blocked by chlorpromazine. Furthermore, colocalization analysis revealed a moderate positive relationship between NPs and LysoTracker Yellow-positive lysosomal compartments indicating that CME was the dominant operative mechanism involved in NP internalization by RTgill-W1 cells. Overall, our results clearly show that fish gill epithelial cells internalized NPs via energy-dependent endocytotic processes. This study enhances our understanding of complex NP-cell interactions and the results obtained in vitro imply a potential risk to aquatic organisms.

Impact of chitosan and polyacrylamide on formation of carbonaceous and nitrogenous disinfection by-products

Coagulation is one of the most commonly used practices in water treatment to remove natural organic matter, which can serve as precursors for disinfection by-products (DBPs). Furthermore, some coagulant aids, particularly amine-based polymers, could foster the formation of both carbonaceous and nitrogenous DBPs (C-DBPs and N-DBPs, respectively). In this study, we evaluated the formation potentials of 11 C-DBPs and N-DBPs during chloramination when two coagulant aids, chitosan and polyacrylamide (PAM), were used under typical water treatment conditions. Our results suggest that both chitosan and PAM promote the formation of N-DBPs, while neither affects the formation of C-DBPs. We further investigated a potential method to mitigate the formation of N-DBPs. Methyl iodide (MeI), an alkylating agent, was effective at reducing the formation of N-DBPs by converting amine to quaternary ammonium groups in chitosan. ¹H-NMR results confirmed that the quaternarization reaction did take place. This study reports that chitosan, a natural coagulant, and PAM contribute to the formation of toxic DBPs. More importantly, it provides a preventative strategy for curbing the formation of DBPs through chemical structural modification.