Comparing pH-responsive nanogel swelling in dispersion and inside a polyacrylamide gel using photoluminescence spectroscopy and small-angle neutron scattering

Nanosized probes that report their changes in dimensions within networks in response to environmental stimuli are potentially important for applications such as drug delivery, load-supporting hydrogels and soft robotics. Recently, we developed a fluorescent pH-responsive nanogel (NG) that used Förster-resonance energy transfer (FRET) to report changes in the probe separation and NG swelling within hydrogels using photoluminescence (PL) spectroscopy. However, FRET cannot measure nanoparticle dimensions and is subject to artefacts. Here, we report the use of small-angle neutron scattering (SANS) to study both the NGs in dispersion and in polyacrylamide (PAAm) gels as a function of pH. We compare the PL and SANS data for both systems and as a function of pH. The SANS data for the dispersed NGs indicate that they have a core-shell structure with a swollen mesh size of ∼1.0 nm. We hypothesized that the NGs inside the PAAm gel would show the same general changes in scattering as the pH is increased, as observed for the dispersed NGs, and this is confirmed by the data. In summary, the data confirm that PL is a suitable (accessible) method for reporting internal environmental changes within gels using NG probes.

Optimizing treatment of alcohol vinasse using a combination of advanced oxidation with porous α-Fe2O3 nanoparticles and coagulation-flocculation

This study utilizes a novel method, namely the combination of advanced oxidation processes with synthesized highly porous α-Fe2O3 nanoparticles and coagulation-flocculation with polyacrylamide, to investigate the effects on COD removal in alcohol vinasse. Highly porous α-Fe2O3 nanoparticles were prepared via a chemical precipitation technique. The characteristic of the synthesized α-Fe2O3 nanoparticles were determined by FT-IR, Raman spectroscopy, XRD, SEM, and N2 adsorption-desorption isotherms. The effect of different α-Fe2O3 nanoparticles loading for chemical oxygen demand (COD) removal efficiency was investigated. The results revealed that at α-Fe2O3 nanoparticle dose of 3000 ppm had the highest COD removal for vinasse. Then, central composite design (CCD) was used to optimize the operating variables such as pH, time, oxidant dosage, and coagulant dosage, and their optimum values were determined to be pH:7.36, 90 min, 17.89 wt% oxidant dosage, and 1.6 wt% coagulant dosage, to achieve a high COD removal efficiency in 70 ℃ for alcohol vinasse (98.64%). Based on optimal conditions, the porous α-Fe2O3 nanoparticles possess superior catalytic activity in the advanced oxidation process compared to other treating methods. Also, the mechanism of the catalytic oxidation reaction is evaluated.

Immobilization of Bacillus amyloliquefaciens SP1 and its alkaline protease in various matrices for effective hydrolysis of casein

An extracellular alkaline protease producing B. amyloliquefaciens SP1 was isolated from apple rhizosphere having multifarious plant growth-promoting activities. B. amyloliquefaciens SP1 protease was immobilized using various concentrations of calcium alginate, agar and polyacrylamide to determine the optimum concentration for formation of the beads. Enzyme activity before immobilization (at 60 °C, pH 8.0 for 5 min) was 3580 µg/ml/min. The results of immobilization with various matrices revealed that 3 % calcium alginate (2829.92 µg/ml/min), 2 % agar (2600 µg/ml/min) and 10 % polyacrylamide (5698.99 µg/ml/min) were optimum concentrations for stable bead formation. Immobilized enzyme reusability results indicated that calcium alginate, agar and polyacrylamide beads retained 25.63, 22.05 and 34.04 % activity in their fifth repeated cycle, respectively. In cell immobilization technique, the free movement of microorganisms is restricted in the process, and a semi-continuous system of fermentation can be used. In the present work, this technique has been used for alkaline protease production using different matrices. Polyacrylamide (10 %) was found with the highest total alkaline protease titer, i.e., 24,847 µg/ml/min semi-continuously for 18 days as compared to agar (total enzyme titer: 5800 in 10 days) and calcium alginate (total enzyme titer: 13,010 in 15 days). This present study reported that polyacrylamide (10 %) among different matrices has maximum potential of immobilization of B. amyloliquefaciens SP1 and its detergent stable alkaline protease with effective application in bloodstain removal.

Electrochemical examination of ability of dsDNA/PAM composites for storing and releasing of doxorubicin

Composites consisting of ss- and ds-DNA strands and polyacrylamide (PAM) hydrogel have been synthesized. DNA was entrapped non-covalently. The obtained DNA biomaterial exhibited a strong increase in guanine and adenine anodic currents when temperature reached the physiological level. This increase was related to the unique oligonucleotide structural changes in the composite. The structural alterations in the PAM lattices were employed for the release of the drug accumulated in the composite. Doxorubicin (Dox) was selected as the drug; it was accumulated by intercalation to dsDNA and was slowly released from the dsDNA/PAM system by using a minor temperature increase (up to 40÷45 °C) as it is routinely done in hyperthermia. The applied release temperature was either constant or oscillating. The binding strength, the rate of Dox release and the properties of the composite were examined using voltammetry, SEM and ICP-MS.

Soft hydrogel promotes dorsal root ganglion by upregulating gene expression of Ntn4 and Unc5B

Mechanical property is an important factor of cellular microenvironment for neural tissue regeneration. In this study, polyacrylamide (PAM) hydrogels with systematically varying elastic modulus were prepared using in situ radical polymerization. We found that the hydrogel was biocompatible, and the length of dorsal root ganglion (DRG)'s axon and cell density were optimal on the hydrogels with elastic modulus of 5.1 kPa (among hydrogels with elastic modulus between 3.6 kPa and 16.5 kPa). These DRGs also exhibited highest gene and protein expression of proliferation marker Epha4, Ntn4, Sema3D and differentiation marker Unc5B. Our study revealed the mechanism of how material stiffness affects DRG proliferation and differentiation. It will also provide theoretical basis and evidence for the design and development of nerve graft with better repair performance.

Photoresponsive Hydrogels with Photoswitchable Stiffness: Emerging Platforms to Study Temporal Aspects of Mesenchymal Stem Cell Responses to Extracellular Stiffness Regulation

An extensive number of cell-matrix interaction studies have identified matrix stiffness as a potent regulator of cellular properties and behaviours. Perhaps most notably, matrix stiffness has been demonstrated to regulate mesenchymal stem cell (MSC) phenotype and lineage commitment. Given the therapeutic potential for MSCs in regenerative medicine, significant efforts have been made to understand the molecular mechanisms involved in stiffness regulation. These efforts have predominantly focused on using stiffness-defined polyacrylamide (PA) hydrogels to culture cells in 2D and have enabled elucidation of a number of mechano-sensitive signalling pathways. However, despite proving to be a valuable tool, these stiffness-defined hydrogels do not reflect the dynamic nature of living tissues, which are subject to continuous remodelling during processes such as development, ageing, disease and regeneration. Therefore, in order to study temporal aspects of stiffness regulation, researchers have developed and exploited novel hydrogel substrates with in situ tuneable stiffness. In particular, photoresponsive hydrogels with photoswitchable stiffness are emerging as exciting platforms to study MSC stiffness regulation. This chapter provides an introduction to the use of PA hydrogel substrates, the molecular mechanisms of mechanotransduction currently under investigation and the development of these emerging photoresponsive hydrogel platforms.

Protein electrophoretic migration data from custom and commercial gradient gels

This paper presents data related to the article “A method for easily customizable gradient gel electrophoresis” (A.J. Miller, B. Roman, E.M. Norstrom, 2016) [1]. Data is presented on the rate of electrophoretic migration of proteins in both hand-poured and commercially acquired acrylamide gradient gels. For each gel, migration of 9 polypeptides of various masses was measured upon completion of gel electrophoresis. Data are presented on the migration of proteins within separate lanes of the same gel as well as migration rates from multiple gels.

Mechanical Deformation of Cultured Cells with Hydrogels

Polyacrylamide hydrogels can be used to culture cells in a range of stiffness that can closer mimic physiological environments. Changes in environmental stiffness have been documented in conditions such as fibrosis, cancer, and aging. In this chapter, we describe a method in which we pour gels directly into multiwell plates using a plastic support that covalently binds to the polymerizing hydrogel. The hydrogel is then crosslinked to calfskin collagen using a crosslinker. The result is a thick hydrogel, scalable to any size plate, which covers the entire surface of the well with no edge effects. The gels can be routinely assembled and are easily reproducible. These scaffolds are used as in vitro models to study fibroblast reaction to variation in environmental stiffness.

Crosslinked sulfonated polyacrylamide (Cross-PAA-SO3H) tethered to nano-Fe3O4 as a superior catalyst for the synthesis of 1,3-thiazoles

Crosslinked sulfonated polyacrylamide (Cross-PAA-SO₃H) attached to nano-Fe₃O₄ as a superior catalyst has been used for the synthesis of 3-alkyl-4-phenyl-1,3-thiazole-2(3H)-thione derivatives through a three-component reactions of phenacyl bromide or 4-methoxyphenacyl bromide, carbon disulfide and primary amine under reflux condition in ethanol. A proper, atom-economical, straightforward one-pot multicomponent synthetic route for the synthesis of 1,3-thiazoles in good yields has been devised using crosslinked sulfonated polyacrylamide (Cross-PAA-SO₃H) tethered to nano-Fe₃O₄. The catalyst has been characterized by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA) and vibrating-sample magnetometer (VSM).

Use of a 2.5% Cross-Linked Polyacrylamide Hydrogel in the Management of Joint Lameness in a Population of Flat Racing Thoroughbreds: A Pilot Study

Osteoarthritis is one of the most common disease processes effecting equine athletes, causing up to 60% of all lameness. This prospective longitudinal study reports on the effect of treatment of carpal and metacarpophalangeal joint lameness with 2.5% cross-linked polyacrylamide hydrogel (PAAG). A total of 49 flat-racing Thoroughbreds at a single training facility were included in the study. The results show a significant improvement in lameness grades at weeks 1 (P < .01), 4 (P < .001), 12 (P < .001), and 24 (P < .001) when compared to baseline lameness at week 0. This pilot study suggests that 2.5% cross-linked PAAG is a safe and effective joint treatment for managing joint lameness in Thoroughbred racehorses and warrants further blinded and controlled studies to fully evaluate the efficacy of the 2.5% cross-linked PAAG and its mode of action.

A Novel Method to Make Polyacrylamide Gels with Mechanical Properties Resembling those of Biological Tissues

Studies characterizing how cells respond to the mechanical properties of their environment have been enabled by the use of soft elastomers and hydrogels as substrates for cell culture. A limitation of most such substrates is that, although their elastic properties can be accurately controlled, their viscous properties cannot, and cells respond to both elasticity and viscosity in the extracellular material to which they bind. Some approaches to endow soft substrates with viscosity as well as elasticity are based on coupling static and dynamic crosslinks in series within polymer networks or forming gels with a combination of sparse chemical crosslinks and steric entanglements. These materials form viscoelastic fluids that have revealed significant effects of viscous dissipation on cell function; however, they do not completely capture the mechanical features of soft solid tissues. In this report, we describe a method to make viscoelastic solids that more closely mimic some soft tissues using a combination of crosslinked networks and entrapped linear polymers. Both the elastic and viscous moduli of these substrates can be altered separately, and methods to attach cells to either the elastic or the viscous part of the network are described. Graphic abstract: Polyacrylamide gels with independently controlled elasticity and viscosity.

Polyacrylamide stabilized alkenyl succinic anhydride emulsion as sizing agent for various cellulosic pulps and fillers

Cellulosic fiber is hydrophilic in nature and making it hydrophobic represents a process called sizing in papermaking. Alkenyl succinic anhydride (ASA) sizing is dominating over other sizing processes due to its high reactivity and economy. The shelf life of conventionally used cationic starch (CS) stabilized ASA emulsion is 20-25 min. In our previous study, the ASA emulsion was found to be stable up to 4 h using anionic polyacrylamide (APAM) as stabilizer. Present communication was aimed to utilize, the APAM stabilized ASA emulsion with most commonly utilized cellulosic pulps (mixed hardwood, bagasse and recycled) and fillers to assist its commercial utilization in papermaking. APAM stabilized ASA emulsion facilitated back water utilization with improved sizing degree unlike CS based ASA emulsion. Lower amount of ASA sizing was required in bagasse pulp compared to other pulps which might be attributed to low crystallinity ratios and hydrogen bond energy.

Microwave pretreatment of polyacrylamide flocculated waste activated sludge: Effect on anaerobic digestion and polyacrylamide degradation

Deterioration of anaerobic digestion can occur with the presence of polyacrylamide (PAM) in waste activated sludge, but the information on alleviating this deterioration is still limited. In this study, the simultaneous alleviation of negative effect of PAM and improvement of methane production during anaerobic digestion was accomplished by microwave pretreatment. Experimental results showed that with the microwave pretreatment times increased from 0 to 12 min, the biochemical methane potential of PAM-flocculated sludge (12 g PAM/kg total solids) asymptotically increased from 123.1 to 242.5 mL/g volatile solids, hydrolysis rate increased from 0.06 to 0.13 d^-1. Mechanism analysis indicated that the microwave pretreatment accelerated the release and hydrolysis of organic substrates from PAM-flocculated sludge, facilitated the breaking of large firm "PAM-sludge" floccules, and benefited the degradation of PAM, which alleviated the PAM inhibitory impacts on digestion and meanwhile provided better contact between the released organic substrates and anaerobic bacteria for methane production.

Biotransformation of cladribine by a nanostabilized extremophilic biocatalyst

Cladribine (2-chloro-2'-deoxy-β-d-adenosine) is a 2'-deoxyadenosine analogue, approved by the FDA for the treatment of hairy cell leukemia and more recently has been proved for therapeutic against many autoimmune diseases as multiple sclerosis. The biosynthesis of this compound using Thermomonospora alba CECT 3324 as biocatalyst is herein reported. This thermophilic microorganism was successfully entrapped in polyacrylamide gel supplemented with nanoclays such as bentonite. The immobilized biocatalyst (T. alba-Ac-Bent 1.00 %), was able to biosynthesize cladribine with a conversion of 89 % in 1 h of reaction and retains its activity for more than 270 reuses without significantly activity loss, showing better operational stability and mechanical properties than the natural matrix. A microscale assay using the developed system, could allow the production of at least 181 mg of cladribine in successive bioprocesses.

Coagulation behavior of kaolin-anionic surfactant simulative wastewater by polyaluminum chloride-polymer dual coagulants

In this study, polyaluminum chloride (PAC) and cationic polymers were used to treat kaolin suspension in the presence of sodium dodecyl benzene sulfonate (SDBS). Effects of PAC dosage, pH, and rotation rate on the coagulation efficiency and floc properties were studied. And the interaction of chemicals and kaolin-SDBS was discussed. Results showed that dual coagulants could decrease the influence of SDBS on the turbidity removal compared with PAC. PAC + polyacrylamide dual coagulant showed superior performance, and the maximal removal ratios of turbidity and dissolved organic carbon were 98.5 and 42.2%, respectively. Optimal coagulation performance was achieved at pH 5-7, where charge neutralization of Al hydrolysates and bridging of polyacrylamide were the primary mechanisms. And flocs with compact structure and small size were formed. Flocs coagulated by PAC were prone to be broken at the pH of raw water after introducing high rotation rate. After dosing polyacrylamide, floc size was enhanced under alkaline condition. Meanwhile, flocs showed stronger recoverability and an open structure because the regeneration mechanism was mainly the bridging effect of polyacrylamide.

Applying organic polymer flocculants in conditioning and advanced dewatering of landfill sludge as a substitution of ferric trichloride and lime: Mechanism, optimization and pilot-scale study

In this study, poly dimethyl diallyl ammonium chloride (PDADMAC) and polyacrylamide (PAM) were applied to substitute ferric trichloride (FeCl₃) and lime conditioning for advanced dewatering of landfill sludge (LS). Four response surface methodology (RSM) models were constructed for FeCl₃-lime, FeCl₃-PAM, PDADMAC-lime and PDADMAC-PAM, and identical dosages, namely 29.86, 57.91, 5.73 and 2.99 mg/g dry solids (DS) for FeCl₃, lime, PDADMAC and PAM, were obtained by solving the system of four RSM equations at water content of 60% to investigate conditioning mechanisms. Compared to FeCl₃-lime, PDADMAC-PAM conditioning had strong charge neutralization and bridging performance, and obtained conditioned LS with large flocs size, strong network structure and rapid dewatering rate. By integrating RSM with nonlinear programming for optimization, the total cost of PDADMAC-PAM route was saved by 7.9% and close to FeCl₃-lime, and the optimized condition with dosages of 1.93 and 3.47 kg/t DS was further confirmed by pilot-scale experiments. The results indicated that PDADMAC-PAM was a feasible substitute for FeCl₃-lime in sludge conditioning, and showed more advantage if dewatered sludge was further treated by incineration.

Influence of polyelectrolyte architecture on the electrokinetics and dewaterability of industrial membrane bioreactor activated sludge

Improvement of sludge dewaterability is greatly hindered by the presence of large amounts of interstitial water molecules trapped in the sludge as a result of strong hydrophilic characteristics. This study has investigated the influence of six different polyacrylamide (PAM) flocculants with different molecular architecture (linear, slightly and highly branched), charge density (CD) and molecular weight (MW) on the electro-kinetics and dewatering of highly stable industrial membrane bioreactor (MBR) sludge. The impact of PAM on flocculation is manifested in the supernatant turbidity, particle zeta potential, sludge capillary suction time (CST), floc size and settleability. Turbidity removal and reduction in zeta potential are used to identify the optimum polymer dose. An optimum dose of 70 mg.L^-1 has been determined for linear PAM of 40% CD. However, a highly-branched PAM, with the same CD, has shown an optimum value of 30 mg.L^-1. In all cases, a turbidity removal of more than 99% and CST reduction of 51-64% is attained; the linear PAMs have resulted in the highest CST reduction. Higher PAM doses have resulted in larger flocs and the maximum particle size is observed at the saturation point. The reduction in sludge volume relates with the floc size and PAM dose. For sludge conditioning and dewaterability, highly branched PAM with low MW has shown superior performance over linear high MW PAM. Enhancement of flocculation and dewatering is correlated with the surface charge neutralization and bridging mechanisms.

A multifunctional polyacrylamide/chitosan hydrogel for dyes adsorption and metal ions detection in water

Removing noxious dyes and detecting excessive metal ions in water are both effective means to prevent damage from contaminants and ensure water safety. The emphasis problems were addressed by preparation a polyacrylamide chitosan (PAAM/CS) hydrogel. Polyacrylamide (PAAM) provides overall mechanical strength to carry loads and facilitate circulation, chitosan (CS) provides adsorption positions with high adsorption capacity. Which made that PAMM/CS hydrogel efficiently performed sorption of xylenol orange (XO). As the functional dye, XO binds to PAAM/CS and confers colorimetric properties on PAAM/CS hydrogels. XO sorbed hydrogel realized fluorescence dual-signal detection of Fe3+ and Al3+ in water. The significant swelling and adsorption potency of the hydrogel, combined with the dual-signal detection capability of XO sorbed hydrogel, make this hydrogel a versatile material for environmental applications.

Effects of cellulose nanofibrils and starch compared with polyacrylamide on fundamental properties of pulp and paper

Bio-based additives received significant attention in pulp and paper properties improvement. For this, the most cited biochemical Cellulose Nano Fibrils (CNFs) and Cationic Starch (CS) were experimentally compared with the most declared synthetic chemical, Cationic Polyacrylamide (CPAM). SEM images showed better paper surface filling by the utilization of the chemicals. The three studied polymers, in solely or combination mechanism, improved mainly bagasse pulp and paper properties compared to the blank sample, except for pulp drainage, which decreased by CNFs to lower volumes presumably due to its intrinsic characteristics. Cationic polymers (CP) compared to CP/CNFs approaches increased pulp retention and drainage but decreased paper density and strengths. The best pulp retention and drainage achieved by CS followed by CPAM, while paper air persistency, density, and strength properties evaluated highest by CP/CNFs followed by CNFs. Generally, CS revealed a more significant improvement in pulp and paper properties than CPAM either with or without CNFs.

Lignin grafted hydroxyapatite entrapped in polyacrylamide: Characterization and adsorptive features for Th4+ and bovine serum albumin

Water-soluble sulfolignin (SL) was grafted onto hydroxyapatite (Hap) by using epichlorohydrin. SLgHap was then entrapped in cross-linked polyacrylamide by in situ polymerizations of acrylamide and N, N'-methylenebisacrylamide to obtain the composite of PSLgHap. The composite was characterized by FT-IR, BET- porosity, XRD, EDXRF, SEM-EDX, TGA-DTG, PZC, CEC, and swelling tests. The adsorptive features of PSLgHAP were investigated for Th⁴⁺ and BSA in view of its dependence on pH, ionic intensity, concentration, temperature, and time. The results of characterization tests confirmed the formation of PSLgHap. The grafting efficiency concerning sulfur contents of PSLgHap was 96% by EDXRF. The isotherms were best represented by the Sips model, Langmuir adsorption capacities were 369 and 390 mg g_SLgHap^-1 for BSA and Th⁴⁺. The enthalpy and entropy changes were positive whilst Gibbs energy was negative by entropy controlled. The adsorption kinetics of both species was obeyed to pseudo second-order model, whereas it was first-order for BSA and hybrid-order for Th⁴⁺ of Langmuir model.

3D Microwell Platforms for Control of Single Cell 3D Geometry and Intracellular Organization

Introduction

Cell structure and migration is impacted by the mechanical properties and geometry of the cell adhesive environment. Most studies to date investigating the effects of 3D environments on cells have not controlled geometry at the single-cell level, making it difficult to understand the influence of 3D environmental cues on single cells. Here, we developed microwell platforms to investigate the effects of 2D vs. 3D geometries on single-cell F-actin and nuclear organization.

Methods

We used microfabrication techniques to fabricate three polyacrylamide platforms: 3D microwells with a 3D adhesive environment (3D/3D), 3D microwells with 2D adhesive areas at the bottom only (3D/2D), and flat 2D gels with 2D patterned adhesive areas (2D/2D). We measured geometric swelling and Young's modulus of the platforms. We then cultured C2C12 myoblasts on each platform and evaluated the effects of the engineered microenvironments on F-actin structure and nuclear shape.

Results

We tuned the mechanical characteristics of the microfabricated platforms by manipulating the gel formulation. Crosslinker ratio strongly influenced geometric swelling whereas total polymer content primarily affected Young's modulus. When comparing cells in these platforms, we found significant effects on F-actin and nuclear structures. Our analysis showed that a 3D/3D environment was necessary to increase actin and nuclear height. A 3D/2D environment was sufficient to increase actin alignment and nuclear aspect ratio compared to a 2D/2D environment.

Conclusions

Using our novel polyacrylamide platforms, we were able to decouple the effects of 3D confinement and adhesive environment, finding that both influenced actin and nuclear structure.

Photoacoustic imaging phantoms for assessment of object detectability and boundary buildup artifacts

Standardized phantoms and test methods are needed to accelerate clinical translation of emerging photoacoustic imaging (PAI) devices. Evaluating object detectability in PAI is challenging due to variations in target morphology and artifacts including boundary buildup. Here we introduce breast fat and parenchyma tissue-mimicking materials based on emulsions of silicone oil and ethylene glycol in polyacrylamide hydrogel. 3D-printed molds were used to fabricate solid target inclusions that produced more filled-in appearance than traditional PAI phantoms. Phantoms were used to assess understudied image quality characteristics (IQCs) of three PAI systems. Object detectability was characterized vs. target diameter, absorption coefficient, and depth. Boundary buildup was quantified by target core/boundary ratio, which was higher in transducers with lower center frequency. Target diameter measurement accuracy was also size-dependent and improved with increasing transducer frequency. These phantoms enable evaluation of multiple key IQCs and may support development of comprehensive standardized test methods for PAI devices.

Experimental study on dynamic behavior of polyacrylamide-reinforced tailings

Earthquakes are a significant factor that contributes to tailings dam failure. Generally, the seismic stability of a tailings dam can be increased by improving the dynamic properties of tailings. The dynamic properties of tailings can be improved effectively using polymers. In this study, the dynamic properties of polyacrylamide-reinforced tailings were investigated via a sequence of dynamic triaxial tests. The content of polyacrylamide in the test sample was 0.3%. Test results show that the cyclic liquefaction resistance, initial dynamic shear modulus, dynamic shear modulus, and dynamic shear modulus ratio of polyacrylamide-reinforced tailings were slightly greater than those of unreinforced tailings. The damping ratio of polyacrylamide-reinforced tailings was lower than that of unreinforced tailings when the dynamic shear strain exceeded 0.038%. The increase in the dynamic pore water pressure of polyacrylamide-reinforced tailings during cyclic loading decelerated significantly compared with that of unreinforced tailings. The revised Zeng model can effectively described the changes in dynamic pore-water pressure of unreinforced and polyacrylamide-reinforced tailings. The polyacrylamide can improve the structural stability of the tailings specimen and also improve the dynamic properties of the tailings, thereby enhancing the seismic stability of the tailings dam.

Generation of Giant Unilamellar Vesicles (GUVs) Using Polyacrylamide Gels

Giant unilamellar vesicles (GUVs) are a widely used model system for a range of applications including membrane biophysics, drug delivery, and the study of actin dynamics. While several protocols have been developed for their generation in recent years, the use of these techniques involving charged lipid types and buffers of physiological ionic strength has not been widely adopted. This protocol describes the generation of large numbers of free-floating GUVs, even for charged lipid types and buffers of higher ionic strength, using a simple approach involving soft polyacrylamide (PAA) gels. This method entails glass cover slip functionalization with (3-Aminopropyl)trimethoxysilane (APTES) and glutaraldehyde to allow for covalent bonding of PAA onto the glass surface. After polymerization of the PAA, the gels are dried in vacuo. Subsequently, a lipid of choice is evenly dispersed on the dried gel surface, and buffers of varying ionic strength can be used to rehydrate the gels and form GUVs. This protocol is robust for the production of large numbers of free-floating GUVs composed of different lipid compositions under physiological conditions. It can conveniently be performed with commonly utilized laboratory reagents.

A Double-Blinded Positive Control Study Comparing the Relative Efficacy of 2.5% Polyacrylamide Hydrogel (PAAG) Against Triamcinolone Acetonide (TA) And Sodium Hyaluronate (HA) in the Management of Middle Carpal Joint Lameness in Racing Thoroughbreds

The purpose of this prospective double-blinded positive control study was to compare the efficacy of 2.5% polyacrylamide hydrogel (2.5% PAAG) in the management of middle carpal joint lameness in Thoroughbreds against treatments of triamcinolone acetonide (TA) or sodium hyaluronate (HA). A total of 31 flat-racing Thoroughbreds with lameness (grade 1-3/5) localized to the carpus by intra-articular analgesia were selected. Following a radiological assessment of the carpi confirming the absence of fragment/fracture, the horses were randomly assigned for intra-articular treatment with either 2 ml of 2.5% PAAG, 12 mg TA or 20 mg HA (followed by two further intravenous treatments of 40 mg, at weekly intervals in the HA group only), by a treating veterinarian. All horses were rested for 48 hours post-treatment and then re-entered an unaltered training regimen. Subsequent examinations at 2, 4, and 6 weeks were performed by a blinded examining veterinarian for all groups, while horses treated with 2.5% PAAG were monitored for 12 weeks for recurrence of lameness. Significantly more joints treated with 2.5% PAAG were lame free (83%) at 6 weeks compared to TA (27%; P = .007) and to HA (40%; P = .04). There was no significant difference between TA and HA groups at any time. All the joints treated within 2.5% PAAG that were lame free at 6 weeks (10/12) were still lame-free at 12 weeks. In conclusion, treatment with 2.5% PAAG led to statistically superior results compared to TA and HA in the management of selected middle carpal joint lameness in flat-racing Thoroughbreds, with therapeutic effects persisting up to 12 weeks.