Sol Form Research Articles

Increasing the performance properties of hydraulic concrete using ultra- and fine-dispersed additives

Taking into account the constantly growing requirements for the quality, reliability and durability of concrete structures for hydraulic structures, there is a need to develop hydraulic concrete compositions with improved performance properties. The aim of the study is to improve the physico-mechanical and deformative properties of hydraulic concrete using finely dispersed aluminosilicate rocks – perlites and colloidal additives in the form of silicic acid sol. The object of the study is modified hydraulic engineering concrete based on a composite binder using finely dispersed vitreous and crystallized perlite, silicic acid sol and a polycarboxylate-based superplasticizer «Polyplast». Results of the study: The choice of silica-containing additives is substantiated and it is shown that their use has a positive effect on the properties of hydraulic concrete. The effect of complex modification on the properties of hydraulic concrete was established by reducing the content of Portland cement and replacing it with finely dispersed glassy perlite, pre-crushed to a specific surface of 300-600 m2/kg, introducing silicic acid sol and the superplasticizer "Polyplast", which make it possible to improve the physical, mechanical, deformation and hydrophysical properties: compressive strength - 53.4 MPa; ultimate tensile strength in bending - 10.9 MPa; crack resistance coefficient - 0.20; prismatic strength - 46.3 MPa; modulus of elasticity 37.345 MPa × 103; Poisson's ratio - 0.199, water absorption - by weight - 2.43%; water resistance grade - W16. It has been proven that by adding finely dispersed perlite, silica sol and superplasticizer Polyplast to Portland cement, it is possible to obtain hydraulic concrete characterized by strength indicators not inferior in strength to the control composition, and with increased indicators of water resistance and crack resistance compared to traditional compositions.

Development of Gentamicin Bilosomes Laden In Situ Gel for Topical Ocular Delivery: Optimization, In Vitro Characterization, Toxicity, and Anti-microbial Evaluation.

The eye drops are the prominent preparation used to treat surface eye disease (bacterial conjunctivitis). However, they have some limitations i.e., short corneal residence, resulting in low ocular bioavailability and necessitating frequent dose administration. The present study developed gentamicin (GE) bilosomes (BM)- laden in situ gel to improve therapeutic activity. The in situ gel system is initially in sol form before administration and converted into gel form in physiological eye conditions. The GE-BM was developed using the thin film hydration technique and optimized by D-optimal design. GE-BM was characterized for vesicle size, entrapment efficiency, zeta potential, morphology, and Fourier transform electron microscope (FTIR). The optimized GE-BM (GE-BMopt) was incorporated into an in situ gel and assessed for physicochemical characteristics. GE-BMopt in situ gel was evaluated for in vitro release, ex vivo permeation, toxicity, and antimicrobial study. GE-BMopt has a vesicle size of 185.1±4.8nm, PDI of 0.254, zeta potential of 27.6 mV, entrapment efficiency of 81.86±1.29 %, and spherical morphology. The FTIR study presented no chemical interactions between GE and excipients. GE-BMopt in situ gel (GE-BMoptIG4) showed excellent viscosity, gelling strength, and ex-vivo bio-adhesion. GE-BMopt-IG4 showed significant high and sustained release of GE (78.08±4.73% in 12h). GE-BMopt-IG4 displayed 3.27-fold higher ex-vivo goat corneal permeation than a pure GE solution. GE-BMopt-IG4 showed good corneal tolerance without any damage or irritation. GE-BMopt-IG4 showed significantly (P<0.05) higher anti-bacterial activity (ZOI) against Staphylococcus aureus and Escherichia coli than pure GE solution. The study determined that the BM in situ gel system can serve as a substitute carrier for GE to enhance its therapeutic effectiveness, and further preclinical studies are required.

Coordinated regulation for α-Al2O3 and mullite structures in the alumina-mullite fiber based on the different adding form of Fe element

The coordinated regulation for α-Al2O3 and mullite structures in the alumina-mullite duplex fiber poses a challenging yet crucial task in achieving a fiber with exceptional high-temperature properties. In this study, Fe element was added into the alumina-mullite fibers in the form of iron sol and ferric nitrate solution, respectively, with the aim of obtaining a fiber consisting of fine mullite grains embedded with nano α-Al2O3 grains. The results revealed that the addition of Fe element significantly enhances the crystallization process of mullite in alumina-mullite fibers. Specifically, adding iron sol resulted in the reduce of α-Al2O3 formation temperature to 1300 °C, while introducing Ferric nitrate solution promoted the formation of mullite phase. Simultaneous introduction of 1.3 wt% iron sol and 1.3 wt% Ferric nitrate solution contributed to achieve alumina-mullite fiber with tensile strength of 2.06 GPa. In addition, the influence mechanism of Fe source on the phase transformation and microstructures of alumina-mullite fiber were discussed.

Effect of molar concentration and drying methodologies on monodispersed silica sol for synthesis of silica aerogels with temperature-resistant characteristics

A variety of hierarchical nanoporous silica aerogels with diversified particle distributions were synthesized from well-dispersed silica sols by a traditional sol–gel method. Among the six particle sizes of aerogels, the silica aerogel with 0.4 M TEOS/MTMS surface modification and supercritical drying attains 11.61 ± 2.96 nm constituent part with well slender size particle dissemination, high-temperature confrontation and low thermal conductivity. In association with the outmoded two-step acid-base dilution of silica sols, the well-diffused form of silica sols with surface alteration also provides a low thermal conductivity of 0.01865 W.m−1 K−1 with greater thermal resistance. In addition, the drying shrinkage can be minimized with surface modification by properly silylation with TMCS. The concentrations of well-diffused silica sol were adjusted to achieve higher surface area, low density, large pore size and structure, and temperature resilience with the help of controlling the sol–gel reaction. The resilient skeleton structure developed from the assembly of tiny particles can efficiently restrict the glutinous heat dissipation between aerogel networks without collapsing a porous network up to a higher temperature of 900 °C. However, this network retains a similar pattern up to 1000 °C with only 32 % volume contraction after 2hr of heat treatments. At an elevated temperature of 1100–1200 °C, the viscid heat flow between nanoparticles and the porous network cannot be meritoriously suppressed and starts to collapse after a shorter duration. The enormous results of silica aerogels will help design suitable thermal insulation with higher resilience and low thermal conductivity.

Preparation and characterisation of hydrotalcites colloid dispersions suitable for deacidification of paper information carriers

Hydrotalcite samples were prepared in the form of powder and/or sol under different conditions and characterised by various techniques. A suitable system of liquid carriers consisting of perfluoroheptane, isopropanol, and water (PFH-IPA-H2O) was chosen to apply HTlcs as deacidifying agents on paper. The areas of miscibility and immiscibility in the PFH-IPA-H2O system were determined at a temperature of 25 °C. The properties of HTlcs dispersed in the prepared solvent were measured. The size of the particles was determined by optical microscopy with image analysis. The average particle size ranges from 1 µm to 2 µm. The settling speed of particles in the prepared colloidal systems was monitored using turbidimetry. Sols in the mixture of solvents had uniformly dispersed particles that settled slowly. The effect of the prepared colloidal HTlcs dispersions on the properties of the paper, specifically the pH of its surface, was also tested. Hydrotalcites in the form of a sol with a ratio of magnesium to aluminium of 5:1 were found to be promising candidates for deacidification. The use of surfactant additives in the preparation of HTlcs did not positively affect the properties of the paper.

Lamotrigine-Loaded Poloxamer-Based Thermo-Responsive Sol-Gel: Formulation, In Vitro Assessment, Ex Vivo Permeation, and Toxicology Study.

The present study aimed to prepare, characterize, and evaluate a thermo-responsive sol-gel for intranasal delivery of lamotrigine (LTG), which was designed for sustained drug delivery to treat epilepsy. LTG sol-gel was prepared using the cold method by changing the concentrations of poloxamer 407 and poloxamer 188, which were used as thermo-reversible polymers. The optimized formulations of sol-gel were analyzed for clarity, pH, viscosity, gelation temperature, gelation time, spreadability, drug content, in vitro drug release studies, ex vivo permeation studies, and in vivo toxicological studies. FTIR, XRD, and DSC were performed to determine the thermal stability of the drug and polymers. The prepared formulations had a clear appearance in sol form; they were liquid at room temperature and became gel at temperatures between 31 °C and 36 °C. The pH was within the range of the nasal pH, between 6.2 and 6.4. The drug content was found to be between 92% and 94%. In vitro drug release studies indicated that the formulations released up to 92% of the drug within 24 h. The FTIR, DSC, and XRD analyses showed no interaction between the drug and the polymer. A short-term stability study indicated that the formulation was stable at room temperature and at 4-8 °C. There was a slight increase in viscosity at room temperature, which may be due to the evaporation of the vehicle. A histological study indicated that there were no signs of toxicity seen in vital organs, such as the brain, kidney, liver, heart, and spleen. It can be concluded from the above results that the prepared intranasal sol-gel for the delivery of LTG is safe for direct nose-to-brain delivery to overcome the first-pass effect and thus enhance bioavailability. It can be considered an effective alternative to conventional drug delivery for the treatment of epilepsy.

Novel Bioequivalent Tablet of Solifenacin Succinate Prepared Using Direct Compression Technique for Improved Chemical Stability.

We designed a bioequivalent tablet form of solifenacin succinate (SOL) with an improved storage stability using a direct compression (DC) technique. An optimal direct compressed tablet (DCT) containing an active substance (10 mg), lactose monohydrate, and silicified microcrystalline cellulose as diluents, crospovidone as a disintegrant, and hydrophilic fumed silica as an anti-coning agent was constructed by evaluating the drug content uniformity, mechanical properties, and in vitro dissolution. The physicochemical and mechanical properties of the DCT were as follows: drug content 100.1 ± 0.7%, disintegration time of 6.7 min, over 95% release within 30 min in dissolution media (pH 1.2, 4.0, 6.8, and distilled water), hardness > 107.8 N, and friability ~0.11%. The SOL-loaded tablet fabricated via DC showed an improved stability at 40 °C and RH 75%, exhibiting markedly reduced degradation products compared to those fabricated using ethanol or water-based wet granulation or a marketed product (Vesicare®, Astellas Pharma). Moreover, in a bioequivalence study in healthy subjects (n = 24), the optimized DCT offered a pharmacokinetic profile comparable to that of the marketed product, with no statistical differences in the pharmacokinetic parameters. The 90% CIs for the geometric mean ratios of the test to the reference formulation for the area under the curve and the maximum drug concentration in plasma were 0.98-1.05 and 0.98-1.07, respectively, and satisfied the FDA regulatory criteria for bioequivalence. Thus, we conclude that DCT is a beneficial oral dosage form of SOL with an improved chemical stability.

A self-healable and injectable hydrogel for pH-responsive doxorubicin drug delivery in vitro and in vivo for colon cancer treatment

Hydrogels are three-dimensional solid-like structures with a wide range of applications in drug transport, tissue engineering, wound dressing, etc. We developed herein a new hydrogel by mixing 5′-guanosine monophosphate (5′-GMP) disodium salt (16 mM) and 1,4,5,8-naphthalene tetracarboxylic acid tetra potassium salt (NAP) (4 mM) in 4:1 (GMP:NAP) stoichiometry in aqueous media (pH ∼4 at 25 °C). The mechanical properties of the resulting hydrogel were investigated by rheological studies, which showed that the hydrogel formed at pH 4 is the most stable [storage modulus (Gꞌ) of ∼4000 Pa] and has higher endurance for the oscillatory strain (20% strain). Spectroscopic investigations provided insights into the unique self-assembly of 5′-GMP and NAP. Further, the composite exhibited pH-responsive hydrogelation over the pH range of 3–6, and the gel was transformed into a sol form at pH > 5. This stimuli-sensitive nature of the hydrogel was then exploited for the encapsulation and efficacious delivery of an anticancer drug, doxorubicin (DOX), specifically toward the colorectal cancer. Microscopic studies revealed the presence of a regular entangled fibrillar network for the hydrogels, which allowed for its exceptionally high drug loading capacity. The controlled release of DOX from the hydrogel was then studied at the physiological pH of the gastrointestinal tract, i.e. pH ∼7.4. The DOX-loaded hydrogel (DOX-Gel) exhibited a ∼82% release of DOX over 100 h at pH ∼7.4. The enhanced cellular toxicity of DOX was observed in CT-26 murine colorectal carcinoma cell lines treated with the DOX-loaded hydrogel compared to DOX only as manifested from the fluorescence-activated cell sortinganalyses and fluorescence microscopic studies. The fluorescence-activated cell sorting analysis showed a ∼4.5-fold increase in the drug internalization for the DOX-Gel as compared to DOX only formulations. The co-localization of DOX into the cell nucleus was confirmed from confocal microscopy. The in vivo drug delivery efficacy of this pH-responsive hydrogel was further assessed on an animal tumor model, Balb/c mice (n = 9). A significant regression of ∼87.5% in the tumor volume was observed after 21 days of DOX-gel administration, in contrast to DOX only formulation, which showed only a ∼46.0% regression in the tumor volume. The blood reports of the non-treated control mice and the mice treated with DOX only indicated a metastatic behavior in comparison with the mice treated with the DOX-Gel. This, the present system, is a self-healable, injectable hydrogel, which makes it an ideal drug delivery vehicle with stimuli-responsive controlled drug release capabilities even in vivo.

Contribution of n-TiO2 Combining with PAM/PPG/NFS Ternary Additive to Improving the Capacity of Gel Lead Acid Battery

An additive mixture of nanoTiO2 (n-TiO2 in sol form), nano fumed SiO2 (nf-SiO2, NFS), propylene glycol (PPG) and polyacryl amide (PAM) was used for preparation of gelled electrolytes. They were characterized by some physicochemical and electrochemical methods to consider their effect on the capacity of lead acid battery during working process. The material property of samples was observed by scanning electron microscopy, thermal analysis, FTIR study, and X-ray diffraction. The resistance of electrolyte was considered by electrochemical impedance spectroscopy. The capacity of battery were observed by charge-discharge at constant current density (0.8 mA cm−2) and charge-discharge according to the international recognized standards (IEC 61056–1:2012; 2.35 V/6 h–0.25 C/1.7 V or 0.5 C/1.7 V) for anodized PbO2 cells and VRLA cells (Gel-VRLA cells, AGM Gel-VRLA cells, and AGM flooded-VRLA cells), respectively. The results showed that a suitable content of n-TiO2 should be 0.2 wt% combined with ternary additive (PAM/PPG/NFS, 0.2/0.1/0.6 wt%, respectively). The discharge capacity of the VRLA cells with 0.2 wt% n-TiO2 was higher than that without n-TiO2 at both discharge rates 0.25 and 0.5 C. In particular, their service life reaches more than 225 cycles at 0.25 C discharging thanks to the use of AGM separator, meeting the IEC 61056–1:2012 standard (200 cycles).

Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times.

Formulation and Evaluation of Floating in Situ Gel Based Gastro Retentive Drug Delivery of Cimetidine

In this study, we formulate and evaluate an in-situ gel of cimetidine using sodium alginate and pectin. CaCO3 was employed as a cross-linking agent, while sodium alginate and pectin were used as polymers. The polymeric formulations used in in-situ gelation drug delivery systems are in sol form before injection in the body but form a gel in the body. Drug release is maintained and regulated thanks to the composition of the gel depending on elements such as temperature modulation, pH variations, the presence of ions, and ultra-violet irradiation. This research aimed to create a unique in-situ gel system for continuous medication administration by using biodegradable polymers found in nature. Polymers that undergo a sol-to-gel phase transition when certain physicochemical conditions are altered are used in this system. At a pH appropriate for life, an in-situ gel developed. Spectrophotometric analysis of the total quantity of drug release was performed during in vitro release investigations in gastric fluid models. The formulation with 1.2% sodium alginate and 1.5% pectin was able to regulate the release of the medicine for a longer period of time, as shown in a well-planned series of studies. Viscosity, drug content, pH, in vitro gelling capacity, in vitro floating ability, water absorption capacity, and sustained drug release were all characteristics of the in-situ gel that were consistent with expectations. The in-situ gels use a fickian diffusion mechanism to release the drugs.

Micellization and gelation characteristics of Pluronic P123 and single ester-bonded cleavable cationic gemini surfactant: A potential system for solubilization and release of ibuprofen

We herein report the mixed micelle and monolayer formation of mixtures of a biocompatible and cleavable oxy-diester twin tailed (gemini) surfactant, 2,2′-[(oxybis(ethane-1,2-diyl))bis(oxy)]bis(N-hexadecyl-N,Ndimethyl-2-oxoethanaminium) dichloride (16-E1-16) with the triblock copolymer, P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H) using tensiometry, dynamic light scattering (DLS), and rheology. It was observed that P123 and 16-E1-16 have strong interaction and form small mixed micelles with similar micellar composition throughout the bulk mole fraction range with insignificant counterion binding. Besides, P123 and 16-E1-16 mixed surfactant system forms thermodynamically stable mixed monolayer that is rich in P123. Variation of viscosity with shear rate revealed better injectable property of the formulations of binary mixtures of P123 and 16-E1-16 compared to pure P123. Also, below α16-E1-16 = 0.3, all the mixtures were in the form of sol which transform into a weak gel at physiological temperatures making these formulations relevant as injectable delivery system. Solubilization capacity of these mixed micelles towards ibuprofen (IBU) showed that addition of 16-E1-16 to P123 micelles reduces its solubilization capacity but with the advantage of making the formulation injectable due to their favorable shear induced viscosity changes and thermogelation properties. Mixed micelles showed faster drug release rate predominantly following Fickian mechanism with negligible contribution of relaxation process in the release phenomena. There is no report showing interaction of biocompatible and cleavable gemini surfactant 16-E1-16 with P123 in mixed micelle and monolayer formation with detailed rheological, drug encapsulation and release studies even though this amphiphilic system has a potential to act as an injectable drug delivery system.

In Situ Gel Drug Delivery System: A Review

In situ gel forming polymeric formulations are drug delivery systems that are in sol form before being administered to the body, but gel in situ from which the medication is released in a sustained and controlled manner. Temperature modulation, pH alteration, ions present in the site and ultraviolet irradiation are factors that influence gel formation. Gellan gum, alginicacid, xyloglucan, pectin, chitosan, poly (DL-lactic acid), poly (DL-lactide co glycolide), and poly caprolactone are some of the polymers used to make in situ gels. Solvents such as water, dimethyl sulphoxide, N-methyl pyrrolidone, triacetin, and 2-pyrrolidone are utilized for these formulations, depending on the solubility of the polymer. Major routes of administration of In situ gels are oral, ocular, rectal, vaginal, injectable, and intraperitonial. In comparison to conventional drug delivery systems, in situ gel forming polymeric formulations provide various advantages, including sustained and prolonged action. From a manufacturing standpoint, such devices are less complex to produce, resulting in cheaper investment and manufacturing costs.

Addressing the Osteoporosis Problem-Multifunctional Injectable Hybrid Materials for Controlling Local Bone Tissue Remodeling.

Novel multifunctional biomimetic injectable hybrid systems were synthesized. The physicochemical as well as biological in vitro and in vivo tests demonstrated that they are promising candidates for bone tissue regeneration. The hybrids are composed of a biopolymeric collagen/chitosan/hyaluronic acid matrix and amine group-functionalized silica particles decorated with apatite to which the alendronate molecules were coordinated. The components of these systems were integrated and stabilized by cross-linking with genipin, a compound of natural origin. They can be precisely injected into the diseased tissue in the form of a viscous sol or a partially cross-linked hydrogel, where they can serve as scaffolds for locally controlled bone tissue regeneration/remodeling by supporting the osteoblast formation/proliferation and maintaining the optimal osteoclast level. These materials lack systemic toxicity. They can be particularly useful for the repair of small osteoporotic bone defects.

Low‐cost inkjet printing of thin‐film mullite structures

AbstractA commodity inkjet printer was modified to print layered ceramic structures on stiff glass substrates, using inks in the form of sols with mullite stoichiometry. The sol composition was optimized in terms of ink viscosity, surface tension, and evaporation properties. The ink was then fed into a multi‐nozzle commodity printer head and deposited by ink‐jetting. Thin lines without bulges with a thickness of ∼1.8 μm with concave profile and a line width of ∼100 μm were successfully printed on fused silica substrates. The presence of mullite was confirmed by Raman spectroscopy and XRD after sintering of printed structures.

Optimization and Evaluation of In situ Nasal Gel of Donepezil Hydrochloride

Introduction: The nasal route has been explored as a route of administration, due to the benefits it offers. The formulation in the form of in situ gel has been utilized for the local and systemic effect. This type of formulation first exists in sol form, but once they are administered, it undergoes gelation to form gel, and this approach can be used for successful drug delivery system. Methods: Thus, in the present study, formulation of in situ gel for nasal administration for donepezil hydrochloride (HCL), by the use of 32 factorial designs, to improve its nasal bioavailability, was developed by increasing its nasal retention time and arrive at an optimized formulation. The formulation was developed by the use of cold method, by incorporation of thermoreversible polymer poloxamer 407 and mucoadhesive agent tragacanth. The in situ gel was later evaluated for different parameters such as pH, gelation time gelation temperature, gel strength, drug content, mucoadhesion, viscosity, in vitro drug diffusion, and stability. Results: Based on results obtained, F5 formulation was found to be optimum. The concentration of 22.5% Poloxamer 407 with 0.07% tragacanth showed promising nasal drug delivery system for donepezil HCl, with enhanced residence time due to increase in viscosity and mucoadhesion characteristics. Conclusion: The use of in situ gel formulation thus can effectively and safely improve the nasal residence time and absorption of donepezil HCl.

Application of selenium and silicon to alleviate short-term drought stress in French marigold (Tagetes patula L.) as a model plant species

AbstractSelenium (Se) and silicon (Si) are the beneficial elements that may significantly modify plants’ tolerance to various types of biotic and abiotic stress. They may be particularly important due to the current climate changes. The aim of model experiments was to assess how selenium and silicon could alleviate short-term drought stress in French marigold (Tagetes patula L. “Pascal”). Tagetes plant species are economically important annual plants and are also very popular decorative flowering species in city parks due to its beautiful colored flowers and resistance on drought stress. Silicon was applied in the form of silica sol and choline-stabilized orthosilicic acid (ch-OSA). Selenium was applied in the form of sodium selenate (Na2SeO4). They were tested at the following concentrations (mg dm−3 of NS): silica sol – level I (23.25), level II (31.0); ch-OSA – level I (0.21), level II (0.63); and Se – level I (0.4), level II (0.8). The experiment showed that silicon had stimulating effect on the biometric parameters of control plants cultivated under an optimal water regime. When the plants treated with selenium were exposed to stress, the values of their biometric parameters were generally higher than in the plants treated with silicon. Both silicon and selenium significantly modified the gas exchange parameters. During the growing season, the net photosynthesis activity (PN), stomatal conductance (gs), and transpiration rate (E) tended to decrease, but they increased significantly when selenium and silicon were applied. In general, the factors significantly modified the plants’ content of macro- and micronutrients as well as the proportions between them. Both selenium and silicon alleviated the short-term drought stress in French marigolds as a model plant, but when silicon was applied, the positive effect was modified by the source and its concentration.

Paving way for fabrication of silica-based single -frequency seed laser: Ultrahighly Yb-doped optical fibers via sol-gel method combined with silica tube inner wall coating and fusion-tapering technique

A method based on sol-gel preparation combined with silica tube inner wall coating and fusion-tapering technique for fabrication of ultrahighly rare-earth-doped fibers without fluorescent quenching is provided. Ultrahighly Yb-doped high SiO2 content glass fiber is developed and is easily spliced to commercial fiber-components. A ~ 1.03 μm laser with 70 dB-SNR and 0.2 nm-linewidth is achieved. The problem of low dissolution rate to rare-earth ions in silica fibers and the splicing problem between soft glass fibers and commercial fiber components have been overcome, indicating the method has potential in fabrication of short-cavity high-gain silica fiber which is applicable to single-frequency seed source. The method is worth exploring in that the core can extend to any heavily rare-earth-doped system as long as it can be realized in the sol form with good dispersion, therefore paving way for fabrication of silica-based single-frequency seed laser.

OPTIMIZATION AND CHARACTERIZATION OF ION ACTIVATED OCULAR IN-SITU GEL FORMULATION FOR BACTERIAL CONJUNCTIVITIS

Objective: The present research work aims at describing the formulation, optimization and evaluation of ion activated ocular in-situ gel of gatifloxacin for treatment of bacterial conjunctivitis so as to overcome patient inconvenience, precorneal drug elimination, variation in efficacy, vision blurring and frequent instillation associated with conventional eye drops and ointments.&#x0D; Methods: In-situ gel was prepared using gellan gum as an ion activated phase transition polymer and HPMC K100M as release retardant. Gatifloxacin was characterized by spectrophotometry. Crystalline state of the drug was determined using X Ray Diffraction study. The developed formulation exhibited instantaneous gel formation in simulated lacrimal fluid (pH 7.4), which was further evaluated for its rheology, irritancy parameters, in vitro release, trans-corneal permeation and antimicrobial activity.&#x0D; Results: Gatifloxacin exhibited λmax 286 nm obeying Beer Lambert’s law and pH-dependent solubility at a pH range of 2 to 4. 0.6% gellan gum and 0.4% HPMC K100M were optimized in the formulation which exhibited a viscosity of 55 cps in sol form and 325 cps in gel form with pseudoplastic behavior and prolonged in vitro release. Permeation of formulation was 75.8% in 7 h with log P of drug 0.59. Developed isotonic and non-irritant formulation had a lower apparent permeability coefficient of 8.15 x 10-5 cm/sec as compared to marketed formulation.&#x0D; Conclusion: A Formulation can be viewed as an efficacious medicine by virtue of its higher zone of inhibition, ability to enhance precorneal residence time and consequently ocular bioavailability with lesser frequency of administration attributed to slow and prolonged diffusion of the drug from the polymeric solutions.

Employment of Alginate Floating In Situ Gel for Controlled Delivery of Celecoxib: Solubilization and Formulation Studies.

Celecoxib (CXB) is a COX-2-selective nonsteroidal anti-inflammatory drug used to control pain and various inflammatory conditions. CXB has limited oral bioavailability and a slow dissociation rate due to its poor water solubility. In order to enhance the oral bioavailability of CXB and reduce the frequency of administration, the present study was aimed at enhancing the aqueous solubility of CXB by a cosolvency technique and then at formulating and evaluating a CXB in situ floating gelling system for sustained oral delivery. Three cosolvents, namely, PEG 600, propylene glycol, and glycerin, at different concentrations, were used to solubilize CXB. Particle size analysis was performed to confirm the solubility of CXB in the solutions. The floating in situ gel formulations were then prepared by the incorporation of the CXB solution into sodium alginate solutions (0.25, 0.5, and 1% w/v). Formulations, in sol form, were then in vitro characterized for their physical appearance, pH, and rheological behaviors, while formulations in gel form were evaluated for their floating behavior and in vitro drug release studies. FTIR spectroscopy was performed to examine drug-polymer interaction. The selected formula was evaluated biologically for its anti-inflammatory and analgesic activities. Results revealed that the less-polar solvent PEG 600 at 80% v/v had the highest solubilization potential, and it was used to optimize the in situ gel formulation. The candidate formula (F3) was found to have the highest sodium alginate concentration (1% w/v) and showed the optimum sustained release profile with the Higuchi model release kinetics. The results from the FTIR spectroscopy analysis showed noticeable drug-polymer molecular interaction. Moreover, F3 exhibited a significantly higher percentage of paw edema inhibition at 8 h compared with the reference drug (p < 0.05). Also, it showed a sustained duration of analgesia that persisted for the entire experimental time.