Acrylic Acid Content Research Articles

Xanthan-Gum/Pluronic-F-127-Based-Drug-Loaded Polymeric Hydrogels Synthesized by Free Radical Polymerization Technique for Management of Attention-Deficit/Hyperactivity Disorder.

Smart and intelligent xanthan gum/pluronic F-127 hydrogels were fabricated for the controlled delivery of atomoxetine HCl. Different parameters such as DSC, TGA, FTIR, XRD, SEM, drug loading, porosity, swelling index, drug release, and kinetics modeling were appraised for the prepared matrices of hydrogels. FTIR confirmed the successful synthesis of the hydrogel, while TGA and DSC analysis indicated that the thermal stability of the reagents was improved after the polymerization technique. SEM revealed the hard surface of the hydrogel, while XRD indicated a reduction in crystallinity of the reagents. High gel fraction was achieved with high incorporated contents of the polymers and the monomer. An increase in porosity, drug loading, swelling, and drug release was observed with the increase in the concentrations of xanthan gum and acrylic acid, whereas Pluronic F-127 showed the opposite effect. A negligible swelling index was shown at pH 1.2 and 4.6 while greater swelling was observed at pH 7.4, indicating a pH-responsive nature of the designed hydrogels. Furthermore, a higher drug release was found at pH 7.4 compared to pH 1.2 and 4.6, respectively. The first kinetics order was followed by the prepared hydrogel formulations. Thus, it is signified from the discussion that smart xanthan gum/pluronic F-127 hydrogels have the potential to control the release of the atomoxetine HCl in the colon for an extended period of time.

A novel pH-responsive hydrogel system based on Prunus armeniaca gum and acrylic acid: Preparation and evaluation as a potential candidate for controlled drug delivery

pH-responsive hydrogels have become effective and attractive materials for the controlled release of drugs at pre-determined destinations. In the present study, a novel hydrogel system based on Prunus armeniaca gum (PAG) and acrylic acid (AA) was prepared by a free radical mechanism using N, N-methylene bisacrylamide (MBA) as cross-linker and potassium persulfate (KPS) as initiator. A series of hydrogels varying PAG, AA, and MBA concentration was developed to determine the impact of these components. Formulated hydrogels were characterized for pH-responsive swelling, drug release, gel content, and porosity. Structural analysis was performed by FTIR, XRD, and SEM analysis. TGA study was applied to assess thermal stability. Oral acute toxicity and in vivo drug release were performed in rabbits. Hydrogels exhibited pH-dependent swelling and drug release. Swelling, drug loading and release, and porosity increased by increasing PAG and AA concentration while decreased by increasing MBA. The gel content of formulations was increased by increasing all three components. FTIR studies confirmed the development of copolymeric networks and the loading of drug. XRD studies revealed that hydrogels were amorphous, and the crystalline drug was changed into an amorphous form during loading. TGA results indicated that hydrogels were stable up to 600 °C. Acute oral toxicity results confirm that hydrogels were nontoxic up to a dose of 2 g/kg body weight in rabbits. The pharmacokinetic evaluation revealed that hydrogels prolonged the availability of the drug and the peak plasma concentration of the drug was obtained in 6 h as compared to the oral solution of the drug. Tramadol hydrochloride (THC) was used as a model drug. Hence, pH-responsive swelling and release, nontoxic nature and improved pharmacokinetics support that PAG-based hydrogels may be considered as potential controlled-release polymeric carriers.

Facile fabrication of Artemisia sphaerocephala krasch gum hydrogels by radiation induced cross-linking polymerization and enhanced ultrahigh adsorption for methylene blue

Although Artemisia sphaerocephala krasch gum (ASKG) has attracted growing attention in the field of medical engineering and food industries, however, there are few studies on the gelation of ASKG. In this paper, acrylic acid modified ASKG hydrogels were prepared by radiation induced grafting, cross-linking and polymerization technique for the first time. The semi-IPN structure was prepared by the cross-linked ASKG network and poly-AAc dispersed within the network. The effects of the adsorbed dose on the swelling ratio and gel fraction were investigated. The different acrylic acid content modified ASKG hydrogels (ASKGAAc1 and ASKGAAc2) for methyl blue (MB) adsorption were investigated, and the ASKG hydrogels was also studied for comparison. The influence of pH, contact time, initial concentration, temperature, ion strength on MB adsorption were tested. The results showed that acrylic acid can promote the formation of hydrogel and greatly enhanced the adsorption of ASKG. The adsorption isotherms were well obeyed the Langmuir model, and the maximum adsorption capacity for MB of ASKG, ASKGAAc1 and ASKGAAc2 were 571.43, 1517.8 and 1654.9 mg/g, respectively. Moreover, the MB adsorption by ASKG based hydrogels was exothermic, spontaneous, and more favorable at lower temperature. Furthermore, the adsorption-desorption experiments demonstrated a good reusability of these hydrogels.

Impact of composition and salinity on swelling and gel strength of poly (acrylamide-co-acrylic acid) preformed particle gel

The effects of various material compositions and reservoir environments on the ultimate strength and swelling kinetics of a commercial preformed particle gel (PPG) have been investigated. This study used different ratios of acrylamide and acrylic acid copolymers with a specific crosslinker concentration. Results have indicated that increasing the acrylic acid proportion enhances the PPGs’ ability to swell but weakens their network structure. In contrast, increasing the crosslinker content decreases the swelling ratio and increases the gel strength. The highest equilibrium swelling capacity among the six preformed particle gel samples was obtained for PPG2, which has the highest acrylic acid amount and the lowest crosslinker content, with a swelling ratio of 2400 g/g in deionized water and 59.8 g/g in brine 1 (67535.8 mg/l). On the contrary, PPG5, with the lowest acrylic acid and highest crosslinker content, has a swelling capacity of 239 g/g and more than 17 g/g in distilled and brine 1, respectively. Yet, PPG5 has the highest swollen gel strength of 615.5 Pa in deionized water and 3344 Pa in brine 1. The PPGs’ swelling ratios showed stepwise improvements along with increasing temperature, notably after 50 °C, yet, the storage modulus (G′) was negatively affected. The PPGs revealed the highest swelling behavior in pH 6–8, decreasing dramatically in more acidic and basic conditions. The swelling ratios of the PPGs in brine 1 at 50 °C were between 12 and 32 g/g, having strengths in the range of 566–5508 Pa, depending on the crosslinker ratio. The PPGs also demonstrated the ability to compete with other commercial PPGs as they have shown physical and thermal stability when aging at 50 °C, specifically those with high crosslinker content (PPG5).

The potential of electropolymerized crosslinked PEGDMA coating on steel for further functionalization: Surface parameters and HMEC-1 cells attachment correlations

Recently we have proposed the electropolymerized coating for steel 316L obtained via our patented experimental set and here we provide the study concerning further functionalization of the coating with: 1) COOH groups resulting from acrylic acid in situ electropolymerization, and 2) grafting polymeric coating functionalized with COOH with adhesive peptide including REDV (arginine-glutamic acid-aspartic acid-valine) sequence. Bare steel and the materials with polymeric coating variants with and without REDV were then subjected to HMEC-1 (human dermal microvascular endothelial cells) culture.Surface of the materials were analysed in terms of roughness, wettability, and chemical composition with XPS. It was indicated that COOH content expectedly varied with concentration of acrylic acid used to the functionalization and that REDV grafting for each concentration was successful. We drawn correlations between adhered cells number and surface roughness parameters and contact angle values for each variant. Low contact angle representing hydrophilic character of the surface is beneficial for this type of materials. However, there is a synergistic effect of roughness, wettability, and chemical composition of the material on cells adhesion and one cannot be considered with omission of others. With increasing peptide concentration, wettability first decreases then increases so that optimal peptide content has to be determined.

Novel Natrosol/Pectin-co-poly (acrylate) based pH-responsive polymeric carrier system for controlled delivery of Tapentadol Hydrochloride

Background & ObjectivesThis study aimed to create a controlled delivery system for Tapentadol Hydrochloride by developing interpenetrating networks (IPNs) of Natrosol-Pectin copolymerized with Acrylic Acid and Methylene bisacrylamide, and to analyze the effects of various ingredients on the physical and chemical characteristics of the IPNs. MethodsNovel Tapentadol Hydrochloride-loaded Natrosol-Pectin based IPNs were formulated by using the free radical polymerization technique. Co-polymerization of Acrylic Acid (AA) with Natrosol and Pectin was performed by using Methylene bisacrylamide (MBA). Ammonium persulfate (APS) was used as the initiator of crosslinking process. The impact of ingredients i.e. Natrosol, Pectin, MBA, and Acrylic Acid on the gel fraction, porosity, swelling (%), drug loading, and drug release was investigated. FTIR, DSC, TGA, SEM and EDX studies were conducted to confirm the grafting of polymers and to evaluate the thermal stability and surface morphology of the developed IPNs. ResultsSwelling studies exhibited an increase in swelling percentage from 84.27 to 91.17% upon increasing polymer (Natrosol and Pectin) contents. An increase in MBA contents resulted in a decrease in swelling from 85 to 67.63%. Moreover, the swelling was also observed to increase with higher AA contents. Significant drug release was noted at higher pH instead of gastric pH value. Oral toxicological studies revealed the nontoxic and biocompatible nature of Natrosol-Pectin IPNs. Interpretation & ConclusionThe developed IPNs were found to be an excellent system for the controlled delivery of Tapentadol Hydrochloride.

Synthesis of pH-sensitive nanocarrier-based acrylic acid-grafted-flaxseed gum for quercetin delivery for anti-cancer application

This study deals with the fabrication and characterization of quercetin-loaded acrylic acid-grafted-flaxseed gum nanoparticles (QUR@AA-g-FGS) to delivers quercetin to the targeted colonic area and to enhances anti-cancer activity. The acrylic acid-grafted-flaxseed gum (AA-g-FGS) was synthesized using ceric ammonium nitrate (CAN) as a redox initiator via the conventional method. The synthesized acrylic acid-grafted-flaxseed (AA-g-FGS) gum was also optimized through varying grafting parameters such as acrylic acid and CAN concentration, time and temperature to obtain the maximum yield of acrylic acid-grafted-flaxseed gum. The quercetin release behavior of QUR@AA-g-FGS was studied at several biological pH and the highest drug release (95%) was observed at pH 7.4 and 8 h. The quercetin release kinetic data was following the first order (R2 = 0.9842) kinetic model. The cytotoxicity of QUR@AA-g-FGS was investigated on HCT-15 cell line (cancerous human cell line) and, QUR@AA-g-FGS demonstrated outstanding toxicity toward HCT-15 cell line. Thus, the present study procures a worthwhile, nominal and ecologically sound approach toward the synthesis of QUR@AA-g-FGS for colon targeted drug delivery system.

Intrinsic and Extrinsic Tunability of Double-Network Hydrogel Strength and Lubricity.

Double-network (DN) hydrogels are promising materials for tissue engineering due to their biocompatibility, high strength, and toughness, but understanding of their microstructure-property relationships still remains limited. This work investigates a DN hydrogel comprising a physically crosslinked agarose, as the first network, and a chemically crosslinked copolymer with a varying ratio of acrylamide and acrylic acid, as the second network. The charge, intrinsic to most DN hydrogels, introduces a responsive behavior to chemical and electrical stimuli. The DN strengthens agarose hydrogels, but the strengthening decreases with the swelling ratio resulting from increasing acrylic acid content or reducing salt concentration. Through careful imaging by atomic force microscopy, the heterogenous surface structure and properties arising from the DN are resolved, while the lubrication mechanisms are elucidated by studying the heterogeneous frictional response to extrinsic stimuli. This method reveals the action of the first (agarose) network (forming grain boundaries), copolymer-rich and poor regions (in grains), charge and swelling in providing lubrication. Friction arises from the shear of the polymeric network, whereas hydrodynamic lift and viscoelastic deformation become more significant at higher sliding velocities. We identify the copolymer-rich phase as the main source of the stimulus-responsive behavior. Salt concentration enhances effective charge density and reduces viscoelastic deformation, while electric bias swells the gel and improves lubrication. This work also demonstrates the dynamic control of interfacial properties like hydrogel friction and adhesion, which has implications for other areas of study like soft robotics and tissue replacements.

Design, Development and in vitro Evaluation of Hydrogels Prepared by Free Radical Polymerization of Acrylic Acid (AAc) Containing a Model Antidiabetic Drug

Abstract: Introduction: The controlled release of medicaments in the management of diabetes is desirable to have a better therapeutic activity of the drug. Objectives: In the present study hydrogels were prepared as a controlled drug delivery system taking Rosiglitazone as a model drug. Materials and Methods: Hydrogels were created using the Free Radical Polymerization approach, with the crosslinker N, N′-Methylene bisacrylamide serving as a binding agent for the polymerization. To create a polymeric network, ammonium persulphate has been used as a polymerization inducer for AAc to poly (acrylic acid) in the existence of polyvinyl alcohol (PVP). A maximum of fifteen formulations were created with various concentrations of polymers and crosslinking agents to test the swelling, diffusion coefficients, ESR, and in vitro drug release properties of the drugs tested. The FT-IR and DSC techniques were used to determine the drug's compatibility with the polymers. The XRD studies were carried out to understand the nature of the drug contained within the hydrogel formulation. The morphologies of the surface were determined using SEM. Results and Discussion: A greater swelling was observed in the basic pH range and a marginal swelling was observed in the acidic pH range according to the swelling studies. The ESR affirmed that the pH of the hydrogels was indeed a factor in the swelling of the gels. The results of the diffusion study revealed that the diffusion coefficient has risen as a result of the reduction in cross-linker concentration and the increase in acrylic acid concentration in the solution. The in vitro release of drug data revealed that the swelling has been increased as a result of the increased concentration of acrylic acid, which resulted in the increased release of the drug. However, when the concentrations of PVP and cross-linker were increased, it was discovered that the drug release was decreased. Conclusion: AAc-PVP based hydrogel was found to be a promising controlled drug delivery system for the treatment of Rosiglitazone, according to the findings of this study. Keywords: Hydrogels, PVP Acrylic acid, Free Radical Polymerization, Antidiabetic Drug.

New Self-Healing Metallosupramolecular Copolymers with a Complex of Cobalt Acrylate and 4′-Phenyl-2,2′:6′,2″-terpyridine

Currently, the chemistry of self-healing polymers is aimed not only at obtaining materials with high self-healing efficiency, but also at improving their mechanical performance. This paper reports on a successful attempt to obtain self-healing copolymers films of acrylic acid, acrylamide and a new metal-containing complex of cobalt acrylate with a 4'-phenyl-2,2':6',2″-terpyridine ligand. Samples of the formed copolymer films were characterized by ATR/FT-IR and UV-vis spectroscopy, elemental analysis, DSC and TGA, SAXS, WAXS and XRD studies. The incorporation of the metal-containing complex directly into the polymer chain results in an excellent tensile strength (122 MPa) and modulus of elasticity (4.3 GPa) of the obtained films. The resulting copolymers demonstrated self-healing properties both at acidic pH (assisted by HCl healing) with effective preservation of mechanical properties, and autonomously in a humid atmosphere at room temperature without the use of initiators. At the same time, with a decrease in the content of acrylamide, a decrease in the reducing properties was observed, possibly due to an insufficient amount of amide groups to form hydrogen bonds through the interface with terminal carboxyl groups, as well as a decrease in the stability of complexes in samples with a high content of acrylic acid.

Grafting of Poly (Acrylic Acid) onto Cassia fistula Seed Gum: Synthesis, Optimization, and Characterization

Aim: This study aimed to synthesize a natural polysaccharide-based semisynthetic mucoadhesive and sustained-release copolymer. 
 Background: Natural polysaccharides have been preferred as drug carriers because of their abundance, easy availability, low cost, biocompatibility, biodegradability, and physiochemical compatibility. But sometimes they need to be chemically functionalized in order to impart some physiochemical properties for the customization of drug delivery.
 Objective: The objective was to graft poly (sodium acrylate) onto Cassia fistula seed gum and the characterizations of the derived copolymer.
 Method: CFSG-grafted-poly (sodium acrylate) (CFSG-g-PSA) was synthesized by microwave-assisted free-radical initiation method using ceric ammonium nitrate (CAN) as a free-radical initiator. The concentration of acrylic acid (AA), ceric ammonium nitrate (CAN), and microwave-irradiation time (MW) were taken as independent synthetic variables. Synthesis was designed by 23 full factorial designs with two levels of each variable. %grafting, % grafting efficiency and % conversion was taken as response variables. ANOVA and numerical optimization were done using Design-Expert Software (version 11.0) to obtain the optimized synthetic condition. The copolymer was characterized by elemental analysis, FTIR, NMR, viscosity, DSC, TGA-DTA, PXRD, SEM, water-uptake, and biodegradation study.
 Results: Elemental analysis, FTIR, and NMR study ratified the formation of the copolymer. The highest % of grafting was found to be 790% in this study. The combination of microwave irradiation and CAN have shown a synergistic effect on % grafting and % grafting efficiency. Software-based numerical optimization finds the S1 batch as the best synthetic batch (790%G) with 10 g AA, 0.5 g CAN, and 1 min MW. The study also exhibits the biodegradation nature of the copolymer in a simulated colonic environment.
 Conclusion: The study demonstrates the synthesis of graft-copolymer by simple, easy, rapid, and one-pot method without the use of any sophisticated instrument and nitrogen environment.

Robust, Versatile Access to Quasi-Monodispersed Phase Change Sub-Microcapsules via Ab Initio Emulsion Polymerization

The phase change sub-microcapsules (PCMCs) with the particle size of 100 nm to 1 μm have a great application potential in the field of hybrid materials for solar energy storage, while the preparation of PCMCs remains challenging without ultrasonic treatment and high-speed (>1000 rpm) homogenization. Herein, PCMCs with readily tunable phase change properties are prepared via facile, robust ab initio emulsion polymerization. The PCMCs present the quasi-monodispersed particle morphologies with the tunable particle size from 159 to 383 nm depending on the loading content of acrylic acid and the free surfactant. The latent heat density and phase change temperature of the PCMCs can be tuned from 66.6 to 115.2 J/g and from 20.8 to 65.4 °C, respectively, depending on the loading content and the type of phase change cores. The PCMCs confirm the latent heat efficiency of about 1, the high thermal reliability, and the high shape stability. The PCMCs can be functionalized by polyaniline coatings with an efficient photothermal effect. The robust, versatile approach to functionalized PCMCs can provide an alternative opportunity for the development of the next-generation smart thermal energy materials.

High Water Resistance and Enhanced Mechanical Properties of Bio-Based Waterborne Polyurethane Enabled by in-situ Construction of Interpenetrating Polymer Network

In this study, acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization. The effects of the content of acrylic acid on the properties of the resulting waterborne polyurethane-poly (acrylic acid) (WPU-PAA) dispersion and the films were systematically investigated. The results showed that the cross-linking density of the interpenetrating network polymers was increased and the interlocking structure of the soft and hard phase dislocations in the molecular segments of the double networks was tailored with increasing the content of acrylic acid, leading to enhancement of the mechanical properties and water resistance of WPU-PAA films. Notably, with the increase in content of acrylic acid, the tensile strength, Young’s modulus, and toughness of the WPU-PAA-110 film increased by 3 times, and 8 times, and 2.4 times compared with WPU-PAA-80, respectively. The WPU-PAA-100 film showed the best water resistance, and the water absorption rate at 96 h was only 3.27%. This work provided a new design scheme for constructing bio-based WPU materials with excellent properties.

Synthesis of a graft copolymer of chloroprene rubber with acrylic acid as a shoe adhesive

Synthesized graft copolymers of chloroprene rubber with acrylic acid. A mixture of benzene and dimethylformamide was used as a solvent, and potassium persulfate was used as a polymerization initiator. Based on the dependence of the copolymerization rate on the concentrations of components and temperature, the order of the reaction rate in terms of the concentration of acrylic acid (2.0), potassium persulfate (1.2) and the activation energy of the process (24.4 kJ/mole) were determined. The degree of grafting of polyacrylic acid increases from 2% to 140% with increasing process time, monomer and initiator concentrations. Grafting efficiency is high (70-90%) in a wide range of time and component concentrations. The graft copolymer has high adhesion to the surface of the skin and tissue.

Production of dimethylsulfoniopropionate, dimethylsulfide and acrylic acid from marine microalgae

Production of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS), and acrylic acid (AA) from 22 marine microalgae representing six phyla were examined at different growth stages. The concentrations of DMSP, DMS, and AA per cell in the media showed significant changes during the whole growth period, and the highest concentrations were found at the stationary growth phase or the senescent phase. Different species had different concentration levels of DMSP, DMS, and AA, among which Pyrrhophyta, Bacillariophyte, and Chrysophyta had relatively large release. The highest concentrations of DMSP, DMS, and AA were 56.70, 0.86, and 44.60 fmol cell−1 in Scrippsiella trochoidea, Prymnesiacee, and Karenia mikimotoi, respectively. The ratios of DMS/DMSP and AA/(DMSP+AA) in the 22 marine microalgae differed dramatically over the growth cycle. The DMS/DMSP ratios were <25%, indicating that only a small fraction of DMSP was converted to DMS by enzymatic cleavage. Moreover, there was a higher ratio of enzymatic degradation of DMSP in the senescent growth stage. The AA/(DMSP+AA) ratio, representing the degradation ratio of DMSP, increased significantly at the beginning of growth period and then decreased. Hence, the changes in these ratios could approximately illustrate the degradation mechanism of DMSP among diverse species at different growth phases.

A novel hollow microsphere composite MnOx/PAA: effective catalyst for ozone decomposition at high humidity.

Ozone air pollution poses a serious threat to human health and ecological environment. Manganese oxide (MnOx) is a popular material for ozone decomposition with excellent catalytic performance. However, the catalytic activity may be reduced under high-humidity conditions because of oxygen vacancy of MnOx from the water evaporation. In this paper, a new type of MnOx/poly(acrylic acid-co-divinylbenzene) (PAA) catalyst with MnOx supported on hollow PAA was successfully prepared, which greatly improved the ozone decomposition efficiency under high humidity. It was shown that when the acrylic acid (AA) content was more than 50%, the PAA polymer layer was hydrophilic and the ozone decomposition efficiency would keep high activity for both the low- and high-humidity conditions. The best performance of ozone decomposition was identified for the methanol reduction and AA content of 60%, in which the efficiencies reached 94.5% and 85% at 50% and 90% humidity levels, respectively. It is the synergetic effect of the hydrophilic PAA support and hollow structure that retains and improves the decomposition activity, which can absorb the water vapor molecules and increase the ozone retention time. Therefore, the hollow microsphere catalyst prepared in this paper has great potential in solving the problem of ozone air pollution.

Optimization of Polyacrylic Acid Coating on Graphene Oxide-Functionalized Reverse-Osmosis Membrane Using UV Radiation through Response Surface Methodology.

Reverse osmosis (RO) is affected by multiple types of fouling such as biofouling, scaling, and organic fouling. Therefore, a multi-functional membrane capable of reducing more than one type of fouling is a need of the hour. The polyacrylic acid and graphene oxide (PAA-GO) nanocomposite functionalization of the RO membrane has shown its effectiveness against both mineral scaling and biofouling. In this research, the polyacrylic acid concentration and irradiation times were optimized for the PAA-GO-coated RO membrane using the response surface methodology (RSM) approach. The effect of these parameters on pure water permeability and salt rejection was investigated. The models were developed through the design of the experiment (DoE), which were further validated through the analysis of variance (ANOVA). The optimum conditions were found to be: 11.41 mg·L−1 (acrylic acid concentration) and 28.08 min (UV activation times) with the predicted results of 2.12 LMH·bar−1 and 98.5% NaCl rejection. The optimized membrane was prepared as per the model conditions, which showed an increase in both pure water permeability and salt rejection as compared to the control. The improvement in membrane surface smoothness and hydrophilicity for the optimized membrane also helped to inhibit mineral scaling by 98%.

Preparation, In Vitro Characterization, and Cytotoxicity Evaluation of Polymeric pH-Responsive Hydrogels for Controlled Drug Release.

The aim of the current investigation was based on the development of pH-responsive hydrogels of chondroitin sulfate, carbopol, and polyvinyl alcohol polymerized with acrylic acid in the presence of ammonium persulfate and ethylene glycol dimethylacrylate for controlled drug delivery. A free radical polymerization technique was used for the preparation of these pH-responsive hydrogels. The gel fraction of the prepared hydrogels was increased with the increase in the chondroitin sulfate, carbopol, polyvinyl alcohol, and acrylic acid content, while the sol-fraction was decreased. Swelling and drug release studies were performed in various pH conditions. Greater swelling and drug release were observed at high pH values (pH 4.6 and 7.4) as compared to low pH value (pH 1.2), representing the pH-responsive nature of the synthesized hydrogels. Porosity and drug loading were increased with the incorporation of high concentrations of hydrogel contents except polyvinyl alcohol, which showed reverse effects. Similarly, biodegradation study reported a slow degradation rate of the prepared hydrogels with the increase in hydrogel constituents. Cytotoxicity study proved the safe use of developed hydrogels as no toxic effect was shown on T84 human colon cancer cells. Similarly, various characterizations, including Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy, were performed for prepared hydrogels. Hence, we could demonstrate that the prepared hydrogels can be used as a promising drug carrier for the controlled delivery of drugs.

Designing and In Vitro Characterization of pH-Sensitive Aspartic Acid-Graft-Poly(Acrylic Acid) Hydrogels as Controlled Drug Carriers.

Acetaminophen is an odorless and white crystalline powder drug, used in the management of fever, pain, and headache. The half-life of acetaminophen is very short; thus, multiple intakes of acetaminophen are needed in a day to maintain a constant pharmacological action for an extended period of time. Certain severe adverse effects are produced due to the frequent intake of acetaminophen, especially hepatotoxicity and skin rashes. Therefore, a drug carrier system is needed which not only prolongs the release of acetaminophen, but also enhances the patient compliance. Therefore, the authors prepared novel aspartic acid-graft-poly(acrylic acid) hydrogels for the controlled release of acetaminophen. The novelty of the prepared hydrogels is based on the incorporation of pH-sensitive monomer acrylic acid with polymer aspartic acid in the presence of ethylene glycol dimethacrylate. Due to the pH-sensitive nature, the release of acetaminophen was prolonged for an extended period of time by the developed hydrogels. Hence, a series of studies was carried out for the formulated hydrogels including sol-gel fraction, FTIR, dynamic swelling, polymer volume analysis, thermal analysis, percent porosity, SEM, in vitro drug release studies, and PXRD analysis. FTIR analysis confirmed the grafting of acrylic acid onto the backbone of aspartic acid and revealed the development of hydrogels. The thermal studies revealed the high thermal stability of the fabricated hydrogels as compared to pure aspartic acid. An irregular surface with a few pores was indicated by SEM. PXRD revealed the amorphous state of the developed hydrogels and confirmed the reduction in the crystallinity of the unreacted aspartic acid by the formulated hydrogels. An increase in gel fraction was observed with the increasing concentration of aspartic acid, acrylic acid, and ethylene glycol dimethacrylate due to the availability of a high amount of free radicals. The porosity study was influenced by the various compositions of developed hydrogels. Porosity was increased due to the enhancement in the concentrations of aspartic acid and acrylic acid, whereas it decreased with the increase in ethylene glycol dimethacrylate concentration. Similarly, the pH-responsive properties of hydrogels were evaluated by dynamic swelling and in vitro drug release studies at two different pH levels (1.2 and 7.4), and a greater dynamic swelling and acetaminophen release were exhibited at pH 7.4 as compared to pH 1.2. An increase in swelling, drug loading, and drug release was seen with the increased incorporation of aspartic acid and acrylic acid, whereas a decrease was detected with the increase in the concentration of ethylene glycol dimethacrylate. Conclusively, the formulated aspartic acid-based hydrogels could be employed as a suitable nonactive pharmaceutical ingredient for the controlled delivery of acetaminophen.

Dimethylsulfoniopropionate, dimethylsulfide, and acrylic acid of a typical semi-enclosed bay in the western Yellow Sea: Spatiotemporal variations and influencing factors

As the degradation products of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS) and acrylic acid (AA) are crucial to the sulfur cycle in the ocean. However, the biogeochemical processes of DMSP, DMS, and AA remain unclear. A monthly investigation was conducted to determine the DMSP, DMS, and AA concentrations and related parameters in the surface water of Jiaozhou Bay, a semi-enclosed bay in the western Yellow Sea, from December 2010 to November 2011. The monthly mean concentrations of DMSP, DMS, and AA were in the ranges of 5.02–27.25 nmol L−1, 0.41–3.14 nmol L−1, and below the detection limit–301.75 nmol L−1, respectively, showing significant seasonal variations with higher concentrations in summer than in autumn. The results were attributed to a combination of biogenic factors, including phytoplankton, zooplankton, and bacteria, as well as environmental factors, such as temperature and nutrients. The DMSP, DMS, and AA concentrations were not significantly correlated with chlorophyll a and bacterial abundance because of the influence of the community structure and anthropogenic activities. DMS was mainly produced by the enzymatic cleavage of DMSP, whereas AA was affected primarily by terrigenous input. The monthly mean sea-to-air fluxes of DMS ranged from 0.74 (in Apr) to 6.55 (in Jan) μmol m−2 d−1 with an average of 2.80 μmol m−2 d−1.