Conventional Solvent Evaporation Research Articles

Dissolution of abietic acid in water by the solid dispersion method using methylcellulose analogs

Abstract Solid dispersion materials of abietic acid (ABA) were prepared with methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), and sodium carboxymethylcellulose (CMC-Na) using a conventional solvent evaporation method. In these materials, ABA was incorporated in an amorphous form. During dissolution tests, ABA from ABA/MC and ABA/HPMC solid dispersion materials initially rapidly dissolved, followed by a decrease in the dissolution rate before eventually plateauing. The dissolution of ABA from ABA/CMC-Na solid dispersion materials was similar, although it increased slightly with an increased shaking time over a long period. ABA from ABA/MC solid dispersion materials exhibited a higher dissolution rate compared with ABA from both ABA/HPMC and ABA/CMC-Na solid dispersion materials. The amount of undissolved material from ABA/cellulose derivative solid dispersion materials was lower compared with ABA/cellulose nanofiber and ABA/TEMPO-oxidized cellulose nanofiber solid dispersion materials. In addition, both ABA/MC and ABA/HPMC solid dispersion materials exhibited good growth-inhibitive effects against Trametes versicolor, a representative of white-rot fungus, compared with ABA/CMC-Na, ABA/cellulose nanofiber and ABA/TEMPO-oxidized cellulose nanofiber solid dispersion materials. Consequently, MC proved to be the most effective water-soluble carrier for ABA in water among the cellulose derivatives tested.

Solid-state properties and antibiotic potency of levofloxacin – dicarboxylate salts prepared by the green method

This research dealt with the green methods to react levofloxacin (LF) with dicarboxylate acids: oxalic acid (OX), succinic acid (SA), malonic acid (MN), and maleic acid (MA) and investigated its impact on the LF’s stability, solubility, and antimicrobial potency, which never been reported before. Solvent-dropped grinding (SDG) using ethanol 95 % was used to prepare the organic antibiotic salts, reducing the solvent usage significantly compared to the conventional solvent evaporation method, supported with solid-state characterization using electrothermal, differential scanning calorimetry and powder X-ray diffractometry. Next, Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance (1H-NMR) confirmed and determined the interaction structure between LF and the acids. Afterward, the benefits of the LF-dicarboxylate salts were investigated, including stability, solubility, and antibiotic potency. The results demonstrated that the SDG could produce LF-OX hydrate, LF-SA hydrate, and anhydrous LF-MN in a (1:1) molar ratio, with a diffractogram never yet explained. Meanwhile, the LF-MA (1:1) salt solid-state structure was identical to the reported one. Notably, these LF-dicarboxylates showed better solubility, stability, and potency than LF alone, suggesting potential for further dosage formulations.

Concurrently Improving both Mechanical and Electrochemical Performances of Quasi-Solid-State Electrical Double-Layer Capacitors by a Rational Design of Gel Polymer Electrolytes.

Aqueous poly(vinyl alcohol) (PVA) gel electrolyte-based quasi-solid-state electrical double-layer capacitors (QSEDLCs) have been extensively investigated in the past ten years, but challenges remain to fabricate the PVA gel electrolyte possessing both superior mechanical and outstanding electrochemical performances. Herein, we develop a strategy to address this issue by a rational design of PVA gel electrolytes, based on a combination of the freeze-thaw (FT) method and sodium perchlorate (NaClO4)-based water-in-salt (WIS) electrolyte. Our study demonstrates that either the FT method or the NaClO4-based WIS electrolyte can improve both the mechanical performance of the PVA gel electrolyte by increasing the crystallization of PVA chains and the electrochemical performance of the PVA gel electrolyte-based QSEDLC by different mechanisms. In comparison with the conventional solvent evaporation method, this work provides an effective strategy to concurrently improve both the mechanical and electrochemical performances of aqueous QSEDLCs.

Advancing towards practice: A novel LC-MS/MS method for detecting retinol in dried blood spots

BackgroundTo date, clinical laboratories face challenges in quantifying retinol from DBS samples. Disputes arise throughout the whole detection process, encompassing the storage condition, the release strategy as well as the selection of internal standards. MethodsWe incubated DBS with ascorbic acid solution. Then, retinol-d4 in acetonitrile was introduced to incorporate isotopic internal standard and promote protein precipitation. Afterward, sodium carbonate solution was added to ionize cytochromes (such as bilirubin), which amplified the difference of their hydrophobicity to retinol. Subsequently, cold-induced phase separation could be facilitated to separate retinol from the impurities. In the end, the upper layer was injected for LC-MS/MS analysis. ResultsBy comparing the detected retinol content in whole blood and DBS samples prepared from the same volume, we confirmed the established pretreatment was capable to extract most of retinol from DBS (recovery >90 %). Thereafter, we verified that within DBS, retinol possessed satisfying stability without antioxidation. Indoor-light exposure and storage duration would not cause obvious degradation (<10 %). Following systematic validation, the established method well met the criteria outlined in the relevant guidelines. After comparing with detected DBS results to the paired plasma samples, 54 out of 60 met the acceptance limit for cross-validation of ±20 %. ConclusionsWe realized precise quantification of retinol from one 3.2 mm DBS disc. By circumventing conventional antioxidation, liquid-liquid/solid-phase extraction and organic solvent evaporation, the pretreatment could be completed within 15 min consuming only minimal amounts of low-toxicity chemicals (ascorbic acid, acetonitrile, and sodium carbonate). We expect this contribution holds the potential to significantly facilitate the evaluation of patients' vitamin A status by using DBS samples in the future.

Synthesis, crystal growth and supramolecular chemistry of 4-dimethylaminopyridinium salts of benzoates and a phenolate ion

Abstract Seven novel molecular salts were synthesized from the commonly available 4-dimethylaminopyridine organic base and benzoic acid derivatives contain additional functional groups. Benzoic acids with additional hydroxyl, nitro, amino, and bromo functional groups, were successfully employed and investigated their role in non-covalent interactions within the supramolecular chemistry of heterosynthons solid-state architecture. The collection of all 4-dimethylamopyrinium salts of benzoates and phenolate was accomplished through the utilization of conventional solvent evaporation technique. The resulting molecular salts were afforded by deprotonation of the acidic moiety such as COOH, or OH to the ring N of 4-dimethylaminopyridine, establishing a strong charged-assisted hydrogen bond between the deprotonated group (benzoate or phenolate) and protonated ring N. The structure of compounds was fully elucidated by single X-ray diffraction, powder X-ray diffraction, 1H NMR, FT-IR, and thermogravimetric analysis. The crystal packing is interpreted by the strong charge-assisted N–H⋯O hydrogen bond between the NH+ and the corresponding deprotonated group and O–H⋯O, N–H⋯N hydrogen bonding. The analysis concluded that C–H⋯O, CH3⋯O, C–H⋯π, CH3⋯π, π–π, C–H⋯Br, and CH3⋯Br contacts contribute significantly to stabilizing and expanding the high-dimensionality (2D–3D framework) of the structures. The structures were thoroughly explored for their various bonding and nonbonding interactions, as well as their supramolecular chemistry in detail. The antimicrobial activities of all compounds were evaluated using the Oxford cup method.

Development and Evaluation of Antifungal Efficacy of Ketoconazole Pharmacosome

Pharmacosomes are neutral colloidal, lipid vesicular drug delivery system having both negative &amp; positive charge that enhance the bioavailability of drugs by enhacing their solubility both in aqueous as well as non-aqueous phase, additionally reduce gastrointestinal toxicity of drug. Ketoconazole is an imidazole derivative agent which is used both in the treatment of topical or systematic fungal infections with fungi static activity against dermatophytes, yeasts and other pathogenic fungi. Ketoconazole is Biopharmaceutical classification system (BCS) class II drugs that display pH dependent dissolution and absorption. In this present research work Pharmacosome of Ketoconazole was prepared in different ratios of Ketoconazole-PC complex (1:1, 1:1.5 and1:2) using conventional solvent evaporation method. FT-IR spectra showed no significant untoward interaction, Vesicles shape and morphology was carried out with Phase contrast microscopy (PCM) and Scanning electron microscopy (SEM), In-vitro permeation study and anti-fungal activity were duly examined. Drug content in the formulations (1:1) (1:1.5) and (1:2) were found 92.5%, 94.3% and 89.7% respectively. FT-IR conformed proper formation of drug- Pharmaosome complex. Particle size distribution were found to be regular and of spherical shape. In-vitro permeation study showed 78.03%, 89.05% and 55.27% drug release as per respectively formulations (KTP1, KTP2 and KTP3). Pharmacosomes of ketoconazole show improvement in antifungal activity than ketoconazole (Pure).

Injectable sustained-release poly(lactic-co-glycolic acid) (PLGA) microspheres of exenatide prepared by supercritical fluid extraction of emulsion process based on a design of experiment approach.

This study aimed to develop an improved sustained-release (SR) PLGA microsphere of exenatide using supercritical fluid extraction of emulsions (SFEE). As a translational research, we investigated the effect of various process parameters on the fabrication of exenatide-loaded PLGA microspheres by SFEE (ELPM_SFEE) using the Box-Behnken design (BBD), a design of experiment approach. Further, ELPM obtained under optimized conditions and satisfying all the response criteria were compared with PLGA microspheres prepared using the conventional solvent evaporation (ELPM_SE) method through various solid-state characterizations and in vitro and in vivo evaluations. The four process parameters selected as independent variables were pressure (X 1), temperature (X 2), stirring rate (X 3), and flow ratio (X 4). The effects of these independent variables on five responses, namely the particle size, its distribution (SPAN value), encapsulation efficiency (EE), initial drug burst release (IBR), and residual organic solvent, were evaluated using BBD. Based on the experimental results, a desirable range of combinations of various variables in the SFEE process was determined by graphical optimization. Solid-state characterization and in vitro evaluation revealed that ELPM_SFEE improved properties, including a smaller particle size and SPAN value, higher EE, lower IBR, and lower residual solvent. Furthermore, the pharmacokinetic and pharmacodynamic study results indicated better in vivo efficacy with desirable SR properties, including a reduction in blood glucose levels, weight gain, and food intake, for ELPM_SFEE than those generated using SE. Therefore, the potential drawback of conventional technologies such as the SE for the preparation of injectable SR PLGA microspheres could be improved by optimizing the SFEE process.

A COMPARATIVE STUDY OF SOLUBILITY ENHANCEMENT OF BICALUTAMIDE BY SOLID LIPID NANOPARTICLES AND SOLID DISPERSION TECHNIQUE

A comparative evaluation of solid lipid nanoparticles and solid dispersion of bicalutamide using PVP K30 and stearic acid was performed. Bicalutamide solid dispersions (BL- SD) were prepared with conventional solvent evaporation method and bicalutamide solid lipid nanoparticles (BL-SLN) were prepared by precipitation method. The formulations were assessed on the standard evaluation parameters. The study demonstrated that BL-SLN was performed better as compared to (BL- SD).

Design and Development of Pharmacosome Loaded with Piroxicam to Improve Oral Bioavailability

The design of the present investigation was to prepare Piroxicam bounded pharmacosomes to improve the water solubility, bioavailability and to minimize the gastrointestinal toxicity of Piroxicam. Pharmacosome is a potential approach in vesicular drug delivery systems which exhibits several advantages over conventional vesicular drug delivery systems. Pharmacosomes are phospholipid complexes with a potential to improve bioavailability of poorly water soluble as well as poorly lipophilic drugs. Piroxicam was complexed with soya phosphatidylcholine in various ratios using conventional solvent evaporation technique. In our study, Pharmacosomes thus prepared were subjected to drug solubility, drug content evaluation, surface morphology (by scanning electron microscopy), crystallinity (by X- ray powder diffraction), quality control tests for capsules and in-vitro dissolution study. Solubility profile of the prepared complexes was found to be much better than Piroxicam pure drug. This improvement in solubility of the prepared pharmacosomes may result in improved dissolution and lower gastrointestinal toxicity. Drug content was found to be 96.84%w /W for the optimized Piroxicam phospholipid complex, F1 (Piroxicam: lecithin ratio of 1:1). The pharmacosomes were found to be disc shaped in scanning electron microscopy. X-ray powder diffraction data confirmed the formation of phospholipid complexes. The formulation F1 showed 94.69% drug release while the free Piroxicam showed a total of only 60.42% at the end of 10-hour dissolution study. Thus the solubility and hence the bioavailability of Piroxicam can be increased to a greater extent by complexing it with soya phosphatidylcholine.

Preparation of PLGA Nanoparticles by Milling Spongelike PLGA Microspheres

Currently, emulsification-templated nanoencapsulation techniques (e.g., nanoprecipitation) have been most frequently used to prepare poly-d,l-lactide-co-glycolide (PLGA) nanoparticles. This study aimed to explore a new top-down process to produce PLGA nanoparticles. The fundamental strategy was to prepare spongelike PLGA microspheres with a highly porous texture and then crush them into submicron-sized particles via wet milling. Therefore, an ethyl formate-based ammonolysis method was developed to encapsulate progesterone into porous PLGA microspheres. Compared to a conventional solvent evaporation process, the ammonolysis technique helped reduce the tendency of drug crystallization and improved drug encapsulation efficiency accordingly (solvent evaporation, 27.6 ± 4.6%; ammonolysis, 65.1 ± 1.7%). Wet milling was performed on the highly porous microspheres with a D50 of 64.8 μm under various milling conditions. The size of the grinding medium was the most crucial factor for our wet milling. Milling using smaller zirconium oxide beads (0.3~1 mm) was simply ineffective. However, when larger beads with diameters of 3 and 5 mm were used, our porous microspheres were ground into submicron-sized particles. The quality of the resultant PLGA nanoparticles was demonstrated by size distribution measurement and field emission scanning electron microscopy. The present top-down process that contrasts with conventional bottom-up approaches might find application in manufacturing drug-loaded PLGA nanoparticles.

Acoustic levitation and high-resolution synchrotron X-ray powder diffraction: A fast screening approach of niclosamide amorphous solid dispersions

The levitation of samples in an acoustic field has been of interest in the preparation and study of amorphous solid dispersions (ASD). Here, niclosamide-polymer solutions were levitated in a multi-emitter single-axis acoustic levitator and analyzed for 10 min at a High-resolution synchrotron X-ray powder diffraction beamline. This assembly enabled high-quality and fast time-resolved measurements with microliter sample size and measurement of solvent evaporation and recrystallization of niclosamide (NCL). Polymers HPMCP-55S, HPMCP-50, HPMCP-55, Klucel®, and poloxamers were not able to form amorphous dispersions with NCL. Plasdone® and Soluplus® demonstrated excellent properties to form NCL amorphous dispersions, with the last showing superior solubility enhancement. Furthermore, this fast levitation polymer screening showed good agreement with results obtained by conventional solvent evaporation screening evaluated for five days in a stability study, carried out at 40 °C/75% RH. The study showed that acoustic levitation and high-resolution synchrotron combination opens up a new horizon with great potential for accelerating ASD formulation screening and analysis.

Crystallization of pure adipic acid from methanol solvent and their characterization studies: Intense NLO activity from Centrosymmetric crystal

The influence of methanol solvent in assisting the nucleation of adipic acid crystals has been investigated for the first time. The pH value and nucleation period was determined. The better- quality adipic acid single crystals having crystal size up to 10 × 7 x 6mm3 were grown successfully by conventional slow solvent evaporation experiment at room temperature and their solubility has been experimented with four different solvents namely methanol, ethanol, acetone and water at three different temperature 30°, 40° and 50° respectively. Crystallographic information, crystalline nature and characteristic h k l planes of adipic acid was revealed by single crystal XRD and powder XRD studies. The direct optical band gap energy, characteristic functional groups and other information like thermal decomposition temperature, melting point were studied from UV –Vis-NIR, Spectroscopic FTIR and TG-DTA instrument analysis. The measured powder SHG efficiency of adipic acid is found to be 2.14 times superior to the reference material potassium dihydrogen phosphate (KDP).

Autophagy-Inducing Inhalable Co-crystal Formulation of Niclosamide-Nicotinamide for Lung Cancer Therapy.

Niclosamide (NIC), an anthelminthic drug, is found to be promising in overcoming the problem of various types of drug-resistant cancer. In spite of strong anti-proliferative effect, NIC shows low aqueous solubility, leading to poor bioavailability. To overcome this limitation, and enhance its physicochemical properties and pharmacokinetic profile, we used co-crystallization technique as a promising strategy. In this work, we brought together the crystal and particle engineering at a time using spray drying to enhance physicochemical and aerodynamic properties of co-crystal particle for inhalation purpose. We investigated the formation and evaluation of pharmaceutical co-crystals of niclosamide-nicotinamide (NIC-NCT) prepared by rapid, continuous and scalable spray drying method and compared with conventional solvent evaporation technique. The newly formed co-crystal was evaluated by XRPD, FTIR, Raman spectroscopy and DSC, which showed an indication of formation of H bonds between drug (NIC) and co-former (NCT) as a major binding force in co-crystal development. The particle geometry of co-crystals including spherical shape, size 1-5μm and aerodynamic properties (ED, 97.1 ± 8.9%; MMAD, 3.61 ± 0.87μm; FPF, 71.74 ± 6.9% and GSD 1.46) attributes suitable for inhalation. For spray-dried co-crystal systems, an improvement in solubility characteristics (≥ 14.8-fold) was observed, relative to pure drug. To investigate the anti-proliferative activity, NIC-NCT co-crystals were investigated on A549 human lung adenomas cells, which showed a superior cytotoxic activity compared with pure drug. Mechanistically, NIC-NCT co-crystals enhanced autophagic flux in cancer cell which demonstrates autophagy-mediated cell death as shown by confocal microscopy. This technique could help in improving bioavailability of drug, hence reducing the need for high dosages and signifying a novel paradigm for future clinical applications.

Influence of l-Lysine-doped Tartaric Acid–Potassium Bromide single crystals: growth and characterization of photonic applications

The effect of l-lysine-doped tartaric acid–potassium bromide (LYTAPB) single crystals has been successfully crystallized by employing conventional slow solvent evaporation method. The lattice unit cell dimensions are valued by single environment crystal X-ray diffraction analysis. The functional groups and spectral properties of the LYTAPB crystal were accredited by FTIR spectral investigation. The linear optical characteristics of the LYTAPB crystal is observed by UV–Vis spectral studied. It has been observed that the load differs linearly through the hardness value. The mechanical stability is measured through the Vickers hardness. Through NLO analysis, the LYTAPB crystal is found to be a phase matchable single crystal and is good transmittance to approve the lower cutoff wavelength district. Second harmonic generation optical susceptibility of the LYTAPB crystal has been verified by Nd:YAG laser technique. Optical limiting achievement of the LYTAPB crystal is established significant wavelength of 1064 nm to possessing SHG efficiency of 1.3 times greater than that of KDP. Hence, it can use the potential material to the frequency–repetition effect of the grown crystals for solid-state photonic materials.

Exosome-modified PLGA Microspheres for Improved Internalization into Dendritic Cells and Macrophages

Considering the significance of effective antigen presentation for boosting immune responses, it is essential to develop delivery systems for antigen presenting cells (APCs; dendritic cells and macrophages). As a simple and facile way for improving delivery efficiency of PLGA microspheres (MS) into APCs, we fabricated exosome-conjugated PLGA MS via polydopamine coating in this study. Spherical micro-sized particles were first prepared by conventional water-in oil-in water (W1/O/W2) double emulsion and solvent evaporation methods and were observed by scanning electron microscopy (SEM). With increasing model protein (ovalbumin)/MS weight ratios, higher amounts of ovalbumin (OVA) were immobilized onto MS. After exosome (EXO) conjugation to MS via polydopamine coating, the amount of nitrogen was significantly increased on the surface of MS, indicating that EXO were successfully conjugated onto MS. EXO-coated dopamine MS (EXO-Dopa MS) exhibited significantly improved delivery into DC2.4 cells and RAW264.7 cells, compared with bare MS and Dopa MS. Therefore, EXO-Dopa MS could be used as effective carriers of immune stimulating biomolecules into APCs for cancer immunotherapy.

Optimizing optical traits of ammonium zinc sulphate hydrate crystal exploiting Nd3+ for photonic device applications

Current investigation explores the impact of Nd3+ ion on linear and nonlinear optical properties of ammonium zinc sulphate hydrate (AZSH) crystal for defining its suitability for photonic device applications. The Nd3+ ion influenced AZSH (Nd-AZSH) crystal has been grown by conventional slow solvent evaporation technique at room temperature. The energy dispersive spectroscopic (EDS) technique has been utilized to uncover the chemical constituents of the Nd-AZSH crystal. The powder X-ray diffraction technique has been employed to evaluate the structural parameters of Nd-AZSH crystal. The influence of Nd3+ on linear optical transmittance of AZSH crystal has been examined within the wavelength range of 200–1100 nm by means of UV–vis spectral analysis. The attributes of Nd3+ in promoting the second harmonic generation (SHG) efficiency of AZSH crystal has been explored by means of Kurtz-Perry powder test. The Nd-AZSH crystal has been tested by the He-Ne laser assisted Z-scan technique to investigate the third order nonlinear optical (TONLO) characteristics at wavelength 632.8 nm. The TONLO refractive index (n2), absorption coefficient (β) and susceptibility (χ3) has been evaluated using the Z-scan data.

Improvement of the dissolution rate and bioavailability of fenofibrate by the supercritical anti-solvent process

The purpose of this study was to improve solubility and oral bioavailability of fenofibrate via solid dispersion (SD) using a supercritical anti-solvent (SAS) process with amphipathic polymers P407 and TPGS. Solid dispersion techniques have been widely used to enhance the solubility and dissolution profiles of poorly soluble drugs. Fenofibrate is classified as a Biopharmaceutics Classification System class II compound because of its low solubility and high gastrointestinal permeability. Two copolymers were selected based on solubility and dissolution tests. Their physicochemical properties were compared with those prepared by conventional solvent evaporation (CSE). The SD formulations containing fenofibrate were successfully prepared using the SAS and CSE methods. The dissolution rate (%) of fenofibrate at 60 min was significantly improved compared with the solution of raw fenofibrate (19.5% ± 3.7%) by 95.1% ± 2.5% and 93.7% ± 4.1% using the SAS and the CSE process, respectively. This approximately four-fold increase in dissolution rate indicates that oral bioavailability can be enhanced. In addition, pharmacokinetic study was analyzed using the area under the curve (AUC) and Cmax values of SAS-SD and CSE-SD in rats. The AUC was 2.1 times higher and Cmax was 1.9 times higher in SAS-SD, indicating higher concentrations of fenofibrate in the blood. In a pharmacodynamic study to evaluate the efficacy of the drug in hyperlipidemic rat models, SAS-SD showed strong lipid-lowering effects including cholesterol (1.9-fold) and triglycerides (3.3-fold), than CSE-SD. Taken together, these results suggested that SAS-SD has excellent potential as a formulation for the poorly soluble drug fenofibrate.

Preparation of NiO nanoparticles in mesoporous silica via eutectic freezing and freeze-drying of aqueous precursor salts

Abstract Immobilization of small metal oxide particles on a solid support by impregnation with solutions of metal salts is a common route of catalyst preparation. Here we explore a modification of this route, based on eutectic freezing of the aqueous precursor salts in the pores of SBA-15, and removal of water/ice by freeze-drying. The two-solvents method was used to selectively fill the pore space of SBA-15 with precursor salts (nickel acetate or nitrate). A morphological and structural analysis of the nickel oxide formed in the pores after thermal decomposition of the salts was performed and compared to samples obtained via conventional solvent evaporation. Immobilized NiO nanocrystallites prepared via eutectic freezing appeared in two morphologies: (a) rodlike particles of ca 5 nm diameter, i.e., somewhat smaller than the pore diameter of SBA-15 (7 nm); (b) species detectable by powder XRD and energy-dispersive X-ray spectroscopy (EDXS), but not by TEM. Nitrogen adsorption isotherms are sensitive to the distribution of NiO in the pores: Pore blocking effects appear in the desorption branch for samples containing rodlike NiO particles, but not in samples in which no particles are detectable by TEM.

Biodegradable Poly(l-lactic acid) (PLLA) Coatings Fabricated from Nonsolvent Induced Phase Separation for Improving Corrosion Resistance of Magnesium Rods in Biological Fluids.

Magnesium (Mg)-based biometals are increasingly becoming a promising candidate of the next-generation implantable materials due to their unique properties, such as high biocompatibility, favorable mechanical strength, and good biodegradability in physiological conditions. However, the swift corrosion of Mg, resulting in early loss of structural support, has posed an enormous challenge in clinical application of Mg-based implants. To overcome these limitations, herein we developed a novel method, which combines the traditional dip-coating with nonsolvent induced phase separation (NIPS), to fabricate biodegradable PLLA coatings with controlled membrane morphology on pure Mg rods. Unlike the conventional dip-coating, where the polymer solution on the Mg substrates is left to evaporate directly under proper atmosphere, in NIPS, the polymer solution on the substrates is not left to dry but immersed in a nonsolvent of the PLLA, leading to the precipitation of polymer networks. Our results demonstrated that various polymer coatings with different morphologies and inner structures could be easily fabricated by a careful selection of nonsolvents. In comparison to dense PLLA coatings obtained from conventional solvent evaporation, PLLA coatings with a dense surface and porous inner structure were obtained when hexane and petroleum ether were used as the nonsolvents, while PLLA coatings with a completely porous structure were obtained when polar acetone and ethanol were chosen. The electrochemical corrosion tests and immersion tests further showed that all polymer coatings could significantly improve the corrosion resistance and suppress the corrosion rates of the substrates. However, PLLA films obtained via NIPS had much lower pH changes and slower Mg2+ release, implying better protective effects of the fabricated coatings. Based on results of all experiments, a new process for the corrosion mechanism of Mg implants during immersion has also been proposed in this work.

Dehydration/Rehydration Cycles for Mixing Phospholipids without the Use of Organic Solvents.

An environmentally friendly and straightforward dehydration/rehydration method for glycerophospholipid mixing that avoids the use of organic solvents, cosolvents, or additives was developed. We prepared binary mixtures of zwitterionic and anionic glycerophospholipids using only deionized water in the entire mixing process. The resulting lipid films were subsequently reconstituted in vesicular form and compared to controls using differential scanning calorimetry. The calorimetric scans revealed no significant differences between mixing methods for any of the studied cases. These findings suggest that the developed dehydration/rehydration procedure creates a sample with equivalent compositional uniformity than the conventional solvent evaporation technique.