High Polymer Concentrations Research Articles

Measurement of thermodynamic properties, including volumetric, sonic, and viscometrical properties, of aqueous solutions containing polyethylene glycol and erythromycin at 293.15, 303.15, and 313.15 K

Abstract In this study, the interactions in aqueous binary and ternary systems containing polyethylene glycol (6000) and erythromycin at different temperatures were investigated to utilize this information in the aqueous two-phase method for different purposes, including separation and purification. Through experimental methods, density, sound velocity, and viscosity at 293.15, 303.15, and 313.15 K were measured in aqueous solutions, including erythromycin and polyethylene glycol. From the experimental density data, apparent molar volume (ϕ V), limiting apparent molar volume (ϕ V 0) and transfer molar volume ( ∆ t r ϕ V 0 ) ${{\increment}}_{\mathrm{t}\mathrm{r}}{\phi }_{\mathrm{V}}^{0})$ have been calculated. Also, the experimental sound velocity data determined apparent molar isentropic compressibility (ϕ k), limiting apparent molar isentropic compressibility (ϕ k 0) and transfer isentropic compressibility ( ∆ tr ϕ k 0 ) ${{\increment}}_{\mathrm{tr}}{\phi }_{\mathrm{k}}^{0})$ values of polyethylene glycol (6000) from water to erythromycin solutions. Furthermore, experimental viscosity data and the Jones–Dole equation determined viscosity β ′-coefficient and transfer viscosity β ′-coefficient ( ∆ t r β ′ ) ${{\increment}}_{\mathrm{t}\mathrm{r}}{\beta }^{\prime })$ values. The obtained results investigated the polymer effect as kosmotropic or chaotropic on erythromycin drug and the interaction between polyethylene glycol and erythromycin (solute-solute interactions). The results show that the interaction between drug and polymer is more desirable in the high-concentration polymer. Finally, results indicate that polyethylene glycol (6000) has played a kosmotropic role in aqueous solutions of erythromycin.

Rheology of emulsions with polymer solutions as the continuous phase

We investigate the effect of the addition of polymers on the flow properties of emulsions. Surfactant-stabilised 80 v% oil-in-water emulsions, exhibiting a yield stress, with either xanthan gum (a stiff, rodlike polymer) or polyethylene oxide (PEO, a flexible, elastic polymer) in the continuous phase (concentrations between 0.005 wt% and 0.5 wt%) are prepared and investigated using shear rheology and confocal microscopy. The flow properties of the emulsions are very robust, and only at high concentrations of polymer (≥ 0.2 wt%), significant changes in the flow properties are observed. In the case of xanthan gum, higher shear stresses are measured. For high concentrations the yield stress is masked by the high zero shear viscosity and shear thinning behaviour of the xanthan gum giving rise to an apparent second power law regime. In the case of PEO, an increase in the shear thinning exponent is observed, together with a decrease in the yield stress. The interaction of PEO with the surfactant SDS (sodium dodecyl sulfate) at higher PEO concentrations strongly affects the emulsion rheology, perhaps by reducing the friction coefficient between the oil droplets.

PREPARATION AND CHARACTERIZATION OF SONNERATIA ALBA LEAF EXTRACT MICROCAPSULES BY SOLVENT EVAPORATION TECHNIQUE

Objective: Sonneratia alba leaves were used by the community for traditional medicine to cure muscle pain, back pain, antioxidants, rheumatism, malaria, wounds, tuberculosis (TB) and as a spermicide. S. alba leaves extract was easy to damage because of the light exposure, change of pH, weather and a long period of storage time. The problem can be solved by coating the extract with a microencapsulation technique. The purpose of this research was to formulate the microcapsules of S. alba leaves extract with solvent evaporation technique using Ethocel 10 cP and Eudragit E100 as a matrix. Methods: S. alba leaves were extracted using ethanol 96%. This extract was dried by a rotary evaporator. The microencapsulation process of S. alba leaves extract was done by solvent evaporation technique (O/W: oil in water). The formula of S. alba leaves extract microcapsules was designed into six formulas (Eudragit E100: EA1, EA2, EA3 and Ethocel 10 cP: EB1, EB2, EB3). Microcapsules of S. alba leaves extract were characterized for particle size in terms of surface morphology by scanning electron microscope (SEM) and encapsulation efficiency. Antioxidant activity of the formulation have been evaluated by DPPH method. Physical characterization on microparticles was performed by conducting entrapment efficiency and SEM picture. Results: In this research, the microparticles containing S. alba extract has been developed by using ethyl cellulose (Ethocel 10 cP) and eudragit (Eudragit E100) as the polymer matrix. The results showed that a high concentration of polymer (Ethocel 10 cP and Eudragit E100) used in microencapsulation resulted in better S. alba leaves extract microcapsules in terms of physical characteristics. Particle size of microcapsules containing S. alba leaves extract were in the range of 0.701 to 1.163 μm. Encapsulation efficiency (% EE) was categorized as poor because the value were ≤ 80% to which 74.386% (EB3) and 75.248% (EA1). SEM picture of EA1 (Eudragit E100) revealed that the surface of microcapsule were rough and porous. When Ethocel 10 cP was used as a polymer, a smoother surface and less visible pores of microcapsule were obtained. The antioxidant ability of S. alba leaves extract microcapsule showed that IC50 values were 53.26 ppm. Conclusion: It can be concluded that microcapsules of S. alba leaves extract can be prepared by solvent evaporation technique using Eudragit E100 and Ethocel 10 cP as polymer. S. alba leaves has potent antioxidant activity either as an extract or after being formulated into microcapsules.

Study of Pt Alloy Catalysts for Oxygen Reduction Reaction on Rde and in MEA for High-Temperature Pemfcs

High-temperature polymer electrolyte fuel cells (HT-PEMFCs) have advantages in enhanced fuel impurities tolerance, easier heat rejection, and simpler water management[1]. Low-temperature PEMFCs with perfluorosulfonic acid electrolytes (e.g., Nafion) could not provide sufficient proton conductivity in the absence of water when T > 120 °C, limiting the application when a higher temperature is desired. High-temperature (HT-) PEMFCs have been developed by using phosphoric acid (H3PO4)-doped polymer electrolyte (e.g., polybenzimidazole, quaternary ammonium biphosphate ion pair coordinated polyphenylene, etc.) [2-4], where H3PO4 can conduct proton at high temperature up to 200 °C. Such change of the reaction environment, however, also affects oxygen reduction reaction (ORR) kinetics. Despite of a facilitated reaction kinetics under high temperature, a high Pt loading is still demanded in state-of-the-art HT-PEMFCs. To enhance ORR activity and increase Pt utilization, here we employ a strategy to alloy Pt with another transition metal (M), which has been demonstrated to be effective in LT-PEMFCs. In this study, Pt and Pt-M catalysts were used to investigate the alloy effect on the adsorption strength of H3PO4 and ORR in both half-cell rotating disk electrode (RDE) and membrane electrode assembly (MEA). In RDE study, the competition adsorption of phosphoric acid has led to a suppression on ORR activity on all catalysts, with less impact on ORR at 160 °C using pure H3PO4 than RT using 1 M H3PO4. Since alloying not just affects the O binding energy, but also H3PO4 adsorption, a different trend of ORR on Pt-M alloy catalysts was resulted in the presence of H3PO4. The alloy effect was further studied in MEA at 160 °C, which also indicates the effectiveness of using HT-RDE setup for HT-ORR catalyst screening. Reference: [1] Gittleman, C. S.; Jia, H.; De Castro, E. S.; Chisholm, C. R. I.; Kim, Y. S. Proton Conductors for Heavy-Duty Vehicle Fuel Cells. Joule 2021, 5 (7), 1660–1677.[2] Pingitore, A. T.; Huang, F.; Qian, G.; Benicewicz, B. C. Durable High Polymer Content m/ p-Polybenzimidazole Membranes for Extended Lifetime Electrochemical Devices. ACS Appl. Energy Mater. 2019, 2 (3), 1720–1726.[3] Lee, K. S.; Spendelow, J. S.; Choe, Y. K.; Fujimoto, C.; Kim, Y. S. An Operationally Flexible Fuel Cell Based on Quaternary Ammonium-Biphosphate Ion Pairs. Nat. Energy 2016, 1 (9).[4] Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated Phosphonic Acid Electrodes for High Power Heavy-Duty Vehicle Fuel Cells. Nat. Energy 2022, 7 (3), 248–259.

Reduced Glutathione Antioxidant Stability in Polymer Solutions Toward Wound Bioactive Dressing Application

Reduced glutathione (GSH) is incorporated in polymeric wound dressings to prevent oxidative stress-induced cellular damage and the development of chronic wounds. The present study investigates the influence of polyvinyl alcohol (PVA), polyethylene oxide (PEO), and PVA/PEO blend polymeric solutions on the stability of GSH during the preparations or storage. The stability was studied in three concentrations which were 3%, 5% and 8%, after sometimes between 0 to 7 days. The level of GSH achieved the highest electron donor activity at day 7 in 8% PVA/PEO (95.42%) and 8% PVA (94.27%) solutions, whereas GSH activity decreased when incorporated with PEO solutions. Such a decrease in the GSH activity due to PEO being less water-resistant and hydrolytic degradation susceptibility could expose the GSH to an aqueous environment and lead to the loss of GSH activity. In conclusion, a higher concentration of polymer and less-water resistant polymers can shield the GSH from an aqueous environment and maintain its stability in the polymer solutions used in wound dressing applications.

Application of Twin-Screw Melt Granulation to Overcome the Poor Tabletability of a High Dose Drug.

Pharmaceutical tablet manufacturing has seen a paradigm shift toward continuous manufacturing and twin-screw granulation-based technologies have catalyzed this shift. Twin-screw granulator can simultaneously perform unit operations like mixing, granulation, and drying of the granules. The present study investigates the impact of polymer concentration and processing parameters of twin-screw melt granulation, on flow properties and compaction characteristics of a model drug having high dose and poor tabletability. Acetaminophen (AAP) and polyvinylpyrrolidone vinyl acetate (PVPVA) were used as a model drug (90-95% w/w) and polymeric binder (5-10%w/w), respectively, for the current study. Feed rate (~650-1150g/h), extruder screw speed (150-300rpm), and temperature (60-150°C) were used as processing variables. Results showed the reduction in particle size of drug in the extrudates (D90 of 15-25μm from ~80μm), irrespective of processing condition, while flow properties were a function of polymer concentration. Overall, good flowability of the products and their tablets with optimum tensile strength can be obtained through using high polymer concentration (i.e., 10% w/w), lower feed rate (~650g/h), lower extruder screw speed (150rpm), and higher processing temperatures (up to 120°C). The findings from the current study can be useful for continuous manufacturing of tablets of high dose drugs with minimal excipient loading in the final dosage form.

Matrix free polymer nanocomposites from amphiphilic hairy nanoparticles: Solvent selectivity and mechanical properties

Matrix free polymer nanocomposite of spherical nanoparticles with shells made of amphiphilic homopolymer was studied in molecular dynamics experiments. The amphiphilic homopolymer was presented as sequence of identical monomer units, each containing two beads having different affinity to solvent. The self-assembly in solution of such hairy nanoparticles was studied depending on solvent quality and selectivity for different polymer concentrations. Two of the most characteristic morphologies were identified and described. The first one is a structure resembling a mixture of sea hedgehogs. There is a nanoparticle in the core of a hedgehog, and the spines consist of several grafted chains. Hedgehogs float freely, do not aggregate with other nanoparticles, their solutions have a low moduli of elasticity and viscosity up to a fairly high polymer concentration. The second morphology is thin membrane lamellae assembled from amphiphilic homopolymers. In this case, the nanoparticles are joined into a single network-like aggregate at very low polymer concentrations. Such networks possess a unique porous structure and demonstrate high elasticity and viscosity moduli. These findings could be useful for molecular design of smart materials, that are able to reversibly assemble, disintegrate on request and repair damage by self-healing mechanism. • Nanoparticles, coated with amphiphilic homopolymers, are studied. • Such nanoparticles can self-assemble either into gels or into “hedgehogs” mixture. • Gels have membrane-like, porous structure, and demonstrate elastic and viscous response. • Core-shell filaments preserve aggregation and favor uniform distribution of “hedgehogs”. • Structure type is determined by solvent quality and selectivity.

Rheology and molecular interactions in polyacrylonitrile solutions: Role of a solvent

We examined the rheological properties of polyacrylonitrile (PAN) solutions in seven solvents over a wide range of shear rates. These solutions were characterized using the Hansen solubility parameter. The viscosity of these dilute solutions was primarily determined by this parameter. However, above the crossover point (at c[η] > 0.7) not only viscosity but also nature of the solvents was found to be an important factor. At high polymer concentrations, certain solutions showed gelation tendency.This study aims to determine a correlation between the rheological properties of the solutions and the affinity of the solvent with PAN. These correlations are present for an intrinsic viscosity (or the Huggins constant), a second virial coefficient, and solubility parameter. However, in certain cases, experimental points do not correspond to general dependence. This is also observed for these solutions when presenting the data of viscoelastic measurements in G′–G″ coordinates: certain points deviate from the general dependence.A detailed infrared spectroscopy analysis has been used for examining these experimental results. It has been shown the water presence in the solvents and polymer solutions even than anhydrous solvents were used. Water presence tend to a solvent–water associate formation in the solutions. The solubility of PAN in these solvents and the gelation tendency depends on the polymer concentration, in addition to the structure and stability of the polymer–water associates. The experimental results obtained and the reported correlation made it possible to develop a subsequence of solvents used as per their affinity with PAN. The charactristics of dilute solutions were compared with the rheological properties of moderately concentrated solution.

Polymer-Induced Drag Reduction in Dilute Newtonian and Semi-Dilute Non-Newtonian Fluids: An Assessment of the Double-Gap Concentric Cylinder Method.

Polymer-induced drag reduction (DR) in fluids was studied using a rotational rheometer with double-gap concentric cylinder geometry. Although both polymers (polyacrylamide (PAM) and 2-acrylamido-2-methylpropane sulfonic acid (SPAM)) had molecular weights of several MDa, the contrasting polymer charge, nonionic and anionic, led to different polymer overlap concentrations (c*), PAM ≫ SPAM, and fluid rheology, with PAM fluids mostly Newtonian and SPAM fluids non-Newtonian (shear-thinning). Based on these differences, it was important to account for the infinite shear viscosity and normalize the polymer concentration by the intrinsic concentration (cint) so that the DR performance of the two polymer fluids could be accurately compared. Both polymers induced DR, and the maximum DR by SPAM (DR% = 28) was slightly higher than that by PAM (DR% = 22) when Rep ∼ 1700. For PAM, the loss of DR with time diminished at higher polymer concentrations (≥100 ppm, at Rep = 3149) but was found to be sensitive to high Rep, with polymer chain scission the likely cause of the reduced performance. For the semi-dilute SPAM fluids, the shear stability contrasted that of PAM, showing negligible dependence on the polymer concentration and Rep. The apparent rapid loss of DR was predominantly attributed to a time-dependent effect and not polymer degradation. In pipe flow, the maximum DR for SPAM was higher than that measured by rheometry and was attributed to differences in the flow conditions. However, changes in the normalized DR/c with polymer concentration were found to be consistent between the two flow geometries. Furthermore, the high fluid stresses in pipe flow (at high Rep) led to drag reduction losses consistent with PAM, as the time-dependent effect was not seen.

Proton-conducting membranes based on CsH2PO4 and copolymer of tetrafluoroethylene with vinylidene fluoride

In this work, proton conductivity, morphology and mechanical properties of (1–x)CsH2PO4–xF-42 (x=0.05–0.3, weight ratio) membranes were investigated for the first time. Thin flexible membranes for x≥0.15 with the uniform distribution of the components were obtained by a tape casting method. Mechanical properties of the membranes were measured by Vickers microhardness tests for a low polymer content (x˂0.15), also the tensile strength for membranes with high polymer content x=0.2–0.3 were evaluated. Proton conductivity of the (1–x)CsH2PO4–xpF-42 composite polymer electrolytes decreases monotonically with increasing x due to the effect of a «conductor-insulator» percolation. The combination of conductivity, mechanical strength and hydrophobic properties of (1–x)CsH2PO4–xF-42 makes certain compositions of proton-conducting membranes (x~0.2–0.25) promising for their use in intermediate-temperature fuel cells, despite decreased conductivity.

A surfactant-free approach: Novel one-step ultrasonic nebulizer spray method to generate amphiphilic Janus particles

HypothesisA solvent evaporation-induced phase separation method, which is based on the preferential partitioning of two or more immiscible materials after solvent evaporation on providing heat, has been one of the main strategies for synthesis of Janus particles (JPs). Considering this approach, it should be possible to synthesize surfactant free-JPs in continuous flow by the ultrasonic nebulizer spray method. ExperimentsTwo polymers, polystyrene and polymethylmethacrylate, were dissolved in dichloromethane, and droplets of a precursor solution generated by an ultrasonic nebulizer were then conveyed through a borosilicate glass cylinder with two heating zones. The solvent evaporation-induced phase separation occurred in a single flow process, which resulted in the preferential partitioning of two incompatible polymers in the droplets, leading to the formation of the spherical bicompartmental JPs. FindingsThe successful fabrication of spherical JPs was observed at high polymer concentrations (1.5 and 2.0 wt%), and at elevated temperature (40–75 °C). The fluorescent compartmentalization of JPs was confirmed. Furthermore, the interfacial arrangement of JPs at oil–water interface was studied. A detailed explanation of theoretical prediction of interfacial configurations of JPs was provided. Lastly, the generated JPs were proved as Pickering stabilizers at the oil–water interface.

What determines the drop size in sprays of polymer solutions?

The effect of viscoelasticity on sprays produced from agricultural flat fan nozzles is investigated experimentally using dilute aqueous solutions of polyethylene oxide (PEO). Measurements of the droplet size distribution reveal that polymer addition to water results in the formation of overall bigger droplets with a broader size distribution. The median droplet size is found to increase linearly with the extensional relaxation time of the liquid and to be well captured by a simple empirical expression in terms of non-dimensional Weber and Deborah numbers. We show that the increase in droplet size with increasing viscoelasticity can be partly attributed to an increase of the wavelength of the flapping motion responsible for the sheet breakup, resulting in the formation of larger ligaments from which droplets are formed. We also show that droplet size distributions, rescaled by the average drop size, are well described by a compound gamma distribution with parameters n and m encoding for the ligament corrugation and the width of the ligament size distribution, respectively. These parameters are found to saturate to values n = 4 and m = 4 at sufficiently high polymer concentrations. • Viscoelasticity leads to larger droplets in sprays for agricultural flat fan nozzles. • Polymer additives can therefore be used to reduce airborne spray drift. • The median droplet size increases linearly with the extensional relaxation time. • Droplet sizes are Gamma distributed with broad drop and ligament sizes with polymers.

Formulation and Characterization of Piroxicam Emulgel for Topical Drug Delivery

The aim and objective of this research work was to formulate and evaluate Piroxicam Emugel for topical drug delivery. Various concentration of gelling agent were used for preparation of Piroxicam Emugel along with emulsifiers Tween-80 and Span-80 with glycerine as a humectants. The Clove oil and eucalyptus oil were used as permeation enhancer. The formulated Emulgel was characterized for their physical appearance, pH determination, spreadability, extrudability, drug content, in vitro drug release and stability studies. According to our results, the range of pH of the formulations was from 5.6±0.2 to 6.8±0.3 for final batches which is considered acceptable. Formulation F3, F4, F6 and F7 spreadability was found to be 32.03 ± 0.54 g.cm/sec, 30.79±0.2 g.cm/sec, 26.41±0.51 g.cm/sec and 30.44±0.6 g.cm/sec respectively. The Formulation F5 and F8 was prepared with higher concentration of carbopol i.e. 1.5 g were of in stiff category and the spreadabilty value found to be 18.14±0.36 g.cm/sec and 20.30±0.34 g.cm/sec respectively. The percentage swelling index was (F5, F6, F7 and F8) found to be 44.24 %, 27.35%, 31.98 % and 46.38 respectively. Extrudability of Formulation F5 and F8 was less i.e. 17.32± 0.5 gm/cm2 and 20.39±0.58 gm/cm2 respectively as containing higher concentration of polymer. Formulation F3, F4, F6, F7 having optimum concentration of polymer extrudability was good i.e. 30.47±0.52 gm/cm2, 27.39±0.6 gm/cm2, 29.49±0.56 gm/cm2 and 26.90±0.6 gm/cm2 respectively. Extrudability was decreased with an increase in concentration of Carbopol. Invitro drug release (98.45% in 8h) from the Emulgel, batch F7 was concluded as optimized batch. Drug release was in following order F5< F1< F3< F2< F4< F8 < F6 < F7. Presence of two Penetration enhancer’s Clove oil and Eucalyptus oil has resulted in better performance as compared to other formulations. All these developed emugel formulation have acceptable physical properties, hence F7 can be considered as the optimized formulation. From this research, the formulated Emulgel of Piroxicam would be an effective alternative to conventional delivery of Piroxicam for the management of pain and inflammation.

Bioinspired MXene/polyurethane plastic films with exceptional flexibility and toughness for electromagnetic interference shielding

Conductive materials with good mechanical performance are desired for electromagnetic interference (EMI) shielding. MXene (Ti3C2Tx), as a new 2D material, shows great potential due to its outstanding conductivity. The rigid nature and hydrophilic surface of MXene indicate its similarity to minerals, leading to the possibility of forming a conductive artificial nacre shell. Herein, highly flexible and tough MXene nanosheet/polyurethane composite films with a nacre-like structure are reported. The hydrogen bonding between MXene nanosheets and polyurethane chains endows an internal plasticization process and results in exceptional flexibility and toughness of 21.0 MJ m−3. Meanwhile, the MXene nanosheet/polyurethane composite film exhibits high electrical conductivity (126 S cm−1) and excellent specific EMI shielding efficiency (11312 dB cm2 g−1) at an ultra-small thickness (12.5 μm) and high polymer content (45.6 wt%). The nacre-inspired conductive composite film in this work offers a new strategy for the design and preparation of tough and flexible conductive materials.

The Depletion Mechanism Actuates Bacterial Aggregation by Exopolysaccharides and Determines Species Distribution & Composition in Bacterial Aggregates.

Bacteria in natural environments and infections are often found in cell aggregates suspended in polymer-rich solutions, and aggregation can promote bacterial survival and stress resistance. One aggregation mechanism, called depletion aggregation, is driven by physical forces between bacteria and high concentrations of polymers in the environment rather than bacterial activity per se. As such, bacteria aggregated by the depletion mechanism will disperse when polymer concentrations fall unless other adhesion mechanisms supervene. Here we investigated whether the depletion mechanism can actuate the aggregating effects of Pseudomonas aeruginosa exopolysaccharides for suspended (i.e. not surface attached) bacteria, and how depletion affects bacterial inter-species interactions. We found that cells overexpressing the exopolysaccharides Pel and Psl remained aggregated after short periods of depletion aggregation whereas wild-type and mucoid P. aeruginosa did not. In co-culture, depletion aggregation had contrasting effects on P. aeruginosa’s interactions with coccus- and rod-shaped bacteria. Depletion caused S. aureus (cocci) and P. aeruginosa (rods) to segregate from each other and S. aureus to resist secreted P. aeruginosa antimicrobial factors resulting in species co-existence. In contrast, depletion aggregation caused P. aeruginosa and Burkholderia sp. (both rods) to intermix, enhancing type VI secretion inhibition of Burkholderia by P. aeruginosa, leading to P. aeruginosa dominance. These results show that in addition to being a primary cause of aggregation in polymer-rich suspensions, physical forces inherent to the depletion mechanism can promote aggregation by some self-produced exopolysaccharides and determine species distribution and composition of bacterial communities.

Systematic Exploration of a Catalytic Metal–Organic Framework/Polyurethane Composite for Medical Device Applications: Effects of MOF Particle Size, MOF Loading, and Polymer Concentration on Composite Material Activity

The metal–organic framework (MOF) CuBTTri, H3[(Cu4Cl)3(BTTri)8] (where H3BTTri = 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene), is a promising catalyst for the development of antithrombotic medical device materials via localized nitric oxide (NO) generation from endogenous S-nitrosothiols. This work evaluates the effects of three key parameters of CuBTTri-embedded polyurethane composite materials—MOF preparation/particle size, MOF loading, and polymer concentration—on the rate of NO generation. We discovered that CuBTTri preparation and particle size have a significant impact on NO generation. Specifically, hand-ground MOF particles (0.3 ± 0.1 µm diameter) generate NO at greater rates compared to larger as-prepared, raw MOF particles (0.4 ± 0.2 µm diameter) and smaller, filtered MOF particles (0.2 ± 0.1 µm diameter) for composite materials. This finding contradicts previous research for CuBTTri powder which found that the smaller the particles, the greater the catalytic rate. In examining the effects of MOF loading and polymer concentration, our data show that increasing these parameters generally results in increased rates of NO generation; though thresholds appear to exist in which increasing these parameters results in diminishing returns and impedes NO generation capacity for certain composite formulations. We found that polymer concentration is the key determinant of water absorptivity and statistically significant decreases in water uptake accompany statistically significant increases in NO generation. It was also found that formulations with relatively high MOF loadings and low polymer concentrations or low MOF loadings and high polymer concentrations inhibit the rate of NO generation. In summary, this research provides a framework for more strategic selections of key parameters when fabricating composite materials for medical device applications.

3D bioprinting of gellan gum-based hydrogels tethered with laminin-derived peptides for improved cellular behavior.

The treatment of skeletal muscle defects is still a topic of noteworthy concern since surgical intervention is not capable of recovering muscle function. Herein, we propose myoblasts laden in laminin-inspired biofunctionalized gellan gum hydrogels as promising tissue-engineered skeletal muscle surrogates. Gellan gum-based hydrogels were developed by combining native gellan gum (GG) and GG tethered with laminin-derived peptides (CIKVAVS (V), KNRLTIELEVRTC (T) or RKRLQVQLSIRTC (Q)), using different polymer content (0.75%-1.875%). Hydrogels were characterized in terms of compressive modulus, molecules trafficking, and C2C12 adhesion. Hydrogels with higher polymeric content (1.125%-1.875%) showed higher stiffness whereas hydrogels with lower polymer content (0.75%-1.125%) showed higher fluorescein isothiocyanate-dextran molecules diffusion. Cell spreading was achieved regardless of the laminin-derived peptide but preferred in hydrogels with higher polymer content (1.125%-1.875%). Taken together, hydrogels with 1.125% of polymer content were selected for printability analysis. GG-based inks showed a non-newtonian, shear-thinning, and thixotropic behavior suitable for printing. Accordingly, all inks were printable, but inks tethered with T and Q peptides presented some signs of clogging. Cell viability was affected after printing but increased after 7 days of culture. After 7 days, cells were spreading but not showing significant signs of cell-cell communications. Therefore, cell density was increased, thus, myocytes loaded in V-tethered GG-based inks showed higher cell-cell communication, spreading morphology, and alignment 7, 14 days post-printing. Overall, myoblasts laden in laminin-inspired biofunctionalized GG-based hydrogels are a promising skeletal muscle surrogate with the potential to be used as in vitro model or explored for further in vivo applications.

Formulation and Evaluation of Atenolol Microspheres

Objective: The aim of present study is to formulate and evaluate atenolol microspheres using excipients like sodium alginate, calcium chloride and starch soluble. Method: The encapsulation efficiency was higher in formulations with higher polymer concentrations than in the other nine. In order to make microspheres, the ionotropic gelation method was used. High yielding and easy to produce, this technology represents a significant improvement over current procedures. Conclusion: A granulometric research, bulk and tapped density, mean particle size and angle of repose, drug entrapment efficiency and in-vitro dissolution study were all found to be within acceptable limits in terms of their results Keywords: Microspheres, Ionotropic gelation technique,sustained release.

Experimental Study of Polymer Injection on Oil Recovery Factor Enhancement Using Homogenous and Heterogenous Micromodel Porous Media

Polymer injection is one method of chemical enhanced oil recovery, which increase oil recovery by improving mobility when viscous fingering occurred in waterflooding operation. The result of polymer injection is better sweep efficiency, which is presented by more even distribution of the injected fluid. However, in common laboratory evaluation for polymer injection testing, it was no visual observation that presents directly for the fluid distribution. This experimental study was carried out to visually observe the polymer injection mechanism to displace oil by micromodel as porous media. The micromodel used in this study is transparent acrylic material which was etched by laser engraving technology to create grains that resemble reservoir rocks. The micromodel was saturated by brine water and light oil respectively as initial reservoir fluids. Then, the water was injected as waterflooding operation to displace oil in a micromodel. Hydrolyzed Polyacrylamide (HPAM) polymer with various concentrations were injected into the micromodel as the last scenario. Through this experiment, the movement and distribution of fluids in chemical enhanced oil recovery especially polymer injection was able to be recorded for further analysis. Observation for each scenario was done by Digital Image Analysis (DIA). The micromodel flooding results showed that the higher concentration of polymer would give higher oil recovery. The front stability and good distribution of polymer will result in better sweep efficiency, then higher oil recovery will be achieved. This experiment gives result visually how polymer enhance oil recovery. This experiment is expected to be leading innovation for Enhanced Oil Recovery (EOR) laboratory studies in Indonesia.

In vitro Evaluation of Floating Microspheres of Gabapentin by Solvent Evaporation Method

The present study involves the design and characterization of floating microspheres with gabapentin as model drug for prolongation of tonic clonic jerk time, microsphere of gabapentin, was developed to reduce the frequency of drug administration, ease of dose adjustment and improve patient compliance. In this study, the shape and surface morphology of microspheres were characterized by scanning electron microscopy. In vitro drug release studies were performed and drug release kinetics was evaluated using the linear regression method. Effects of polymer concentration, solvent composition, particle size, drug entrapment efficiency and drug release were also studied. The synthesized microspheres exhibited prolonged drug release (> 10 h) and remained buoyant for > 24 h. The drug entrapment efficiency was in the range 50-70 %. At higher polymer concentration, the average particle size was increased and the drug release rate decreased. In vitro studies revealed diffusion-controlled drug release from the microspheres. Among all the formulations (F1-F6), F3 is the optimized formulation of gabapentin was prepared by solvent evaporation techniques using Ethyl cellulose as polymer and particle size, microsphere efficiencies and in vitro release of the fabricated microsphere were evaluated. Particle sizes of the microspheres were influenced by the concentration of Ethyl cellulose and stirring speed. From the results of the in vitro study shows that the desired release rate is achieved by ethyl cellulose. The object of this study was to develop and evaluate stable microspheres of gabapentin drug an antiepileptic drug using combination of Eudragit and ethyl cellulose as polymer which delivers the drug at a controlled rate for a prolonged period of time. Ethyl cellulose used in this study and it is showing hard binding of microspheres.