Gelation behavior of in situ forming gels based on HPMC and biphasic calcium phosphate nanoparticles

A comparative evaluation of aluminum chloride hexahydrate gel iontophoresis versus tap water iontophoresis in people with primary palmar hyperhidrosis: A randomised clinical trial

Background Primary palmar hyperhidrosis causes a lot of problems for patients and negatively affects their quality of life. Currently, iontophoresis with tap water and aluminum chloride hexahydrate is used for primary palmar hyperhidrosis. Yet, little evidence exists about iontophoresis with aluminum chloride hexahydrate in the form of gel. This study investigated the effect of aluminum chloride hexahydrate gel iontophoresis compared to tap water iontophoresis on primary palmar hyperhidrosis. Methods In this randomised controlled trial study, 32 patients with primary palmar hyperhidrosis were divided randomly into two groups (n = 16). Participants received 7 sessions of iontophoresis with aluminum chloride hexahydrate gel or tap water every other day on the dominant hand. The sweating rate was measured by gravimetry and iodine-starch tests before and after the last treatment session. Results Following the iontophoresis, the rate of sweating in both hands in the two groups was significantly reduced (P < 0.001). However, the sweating rate in the treated hand and the non-treated hand showed no significant difference. There was no significant difference observed in sweating rate reduction between both groups over time, but the larger effect size values observed in the aluminum chloride hexahydrate gel iontophoresis group may suggest the superiority of this gel over tap water in reducing the rate of sweating. Limitations Further investigations with longer follow-up are needed to confirm the hypothesis regarding the effectiveness of aluminum chloride hexahydrate gel iontophoresis over other types of iontophoresis. In addition, contraindications of iontophoresis such as pregnancy, pacemakers, and epilepsy should be considered. Conclusion The present study provides preliminary evidence suggesting that aluminum chloride hexahydrate gel iontophoresis is an effective alternative treatment to decrease sweating rate in extended areas with fewer side effects in patients with primary palmar hyperhidrosis.

Biomass-based single- and double-network hydrogels derived from cellulose microfiber and chitosan for potential application as plant growing substrate

A series of hydrogels were synthesized from renewable and low-cost micro-sized cellulose fiber. The single-network hydrogel was composed of cellulose fiber and a small amount of another polysaccharide, chitosan, which 'glued' individual cellulose fiber pieces together through Schiff-base bonding. The double-network hydrogel was constructed by adding a secondary network, the covalently crosslinked polyacrylamide, into the single-network hydrogel, which was synthesized by conducting Schiff-base reaction and free radical polymerization at the same time in a facile one-pot process. In both single- and double-network hydrogels, cellulose fiber constituted the dominant component. Both types of hydrogels exhibited good swelling properties. The double-network hydrogel showed much improved stability against soaking in water and higher salt tolerance. Germination experiment with choy sum seeds sowed on hydrogel surface showed that the seeds were able to germinate and further develop roots, shoots, and true leaves, demonstrating the potential of the biomass-derived hydrogels for soilless plant growing applications.

Incorporating the Antioxidant Fullerenol into Calcium Phosphate Bone Cements Increases Cellular Osteogenesis without Compromising Physical Cement Characteristics

Herein, fullerenol (Ful), a highly water-soluble derivative of C60 fullerene with demonstrated antioxidant activity, is incorporated into calcium phosphate cements (CPCs) to enhance their osteogenic ability. CPCs with added carboxymethyl cellulose/gelatin (CMC/Gel) are doped with biocompatible Ful particles at concentrations of 0.02, 0.04, and 0.1 wt v%-1 and evaluated for Ful-mediated mechanical performance, antioxidant activity, and in vitro cellular osteogenesis. CMC/gel cements with the highest Ful concentration decrease setting times due to increased hydrogen bonding from Ful's hydroxyl groups. In vitro studies of reactive oxygen species (ROS) scavenging with CMC/gel cements demonstrate potent antioxidant activity with Ful incorporation and cement scavenging capacity is highest for 0.02 and 0.04 wt v%-1 Ful. In vitro cytotoxicity studies reveal that 0.02 and 0.04 wt v%-1 Ful cements also protect cellular viability. Finally, increase of alkaline phosphatase (ALP) activity and expression of runt-related transcription factor 2 (Runx2) in MC3T3-E1 pre-osteoblast cells treated with low-dose Ful cements demonstrate Ful-mediated osteogenic differentiation. These results strongly indicate that the osteogenic abilities of Ful-loaded cements are correlated with their antioxidant activity levels. Overall, this study demonstrates exciting potential of Fullerenol as an antioxidant and proosteogenic additive for improving the performance of calcium phosphate cements in bone reconstruction procedures.

Synthesis, characterization, photo-polymerization, hydrolytic stability, and etching behavior of new self-etch adhesive monomers

Considering the poor hydrolytic stability of the most methacrylate-based functional monomers of self-etch dental adhesives in acidic and aqueous conditions, in this study allyl-based photo-polymerizable self-etch monomers was synthesized in order to improve the hydrolytic stability. The new self-etch monomers based on phosphonic acid functional groups were synthesized through a two-step procedure. First, phosphoric anhydride, poly-phosphoric acid, and polyethylene glycol were reacted to produce phosphate ester precursor (P-PEG-P). Next, allyl 2, 3-epoxypropyl ether was reacted with P-PEG-P to synthesize allyl self-etch monomer. Glycidyl methacrylate was also reacted with P-PEG-P to synthesize a methacrylate self-etch analogue monomer. The monomers were characterized using FTIR and 1H-NMR spectroscopy. The viscosities of monomers were measured using a rheometer. The degree photopolymerization conversion of monomers was measured using FTIR spectroscopy. The pH assay was performed by a digital pH-meter. The etching behavior of the monomers on human teeth was studied using scanning electron microscopy (SEM). Thermo-gravimetric analysis (TGA) was performed to evaluate the possible interaction of the monomers with tricalcium phosphate (TCP). The solubility of synthesized monomers was examined in ethanol, acetone, and water. The hydrolytic stability of cured resins in artificial saliva during 4 months was also surveyed. The synthesis of new self-etching monomers was successfully confirmed by spectroscopy analyses. The results represented appropriate viscosity of self-etching monomers around 1 (Pa s). The resin containing methacrylate monomer exhibited its degree of conversion is more than that of allyl monomer (p < 0.05). The allyl and methacrylate self-etch monomers exhibited pH values of 1.2 and 1.3, respectively. SEM micrograph verified that the synthesized monomers were able to suitable etching of the enamel human premolar teeth. The data obtained from TGA tests revealed that thermal stability of (TCP) containing monomers is enhanced. Also, the monomers exhibited an excellent solubility in polar solvents, but when they are mixed with TCP, they are not, anymore, dissolved in these solvents. Furthermore, the allyl monomer showed higher hydrolytic stability than the methacrylate monomer. The new photo-polymerizable acidic monomer based on allyl functionality showed enhanced hydrolytic stability compared to methacrylate-based monomer. It may be considered as a promising monomer for self-etch dental adhesives.

Hydrogel and Effects of Crosslinking Agent on Cellulose-Based Hydrogels: A Review

Hydrogels are hydrophilic polymer materials that can swell but are insoluble in water. Hydrogels can be synthesized with synthetic or natural polymers, but natural polymers are preferred because they are similar to natural tissues, which can absorb a high water content, are biocompatible, and are biodegradable. The three-dimensional structure of the hydrogel affects its water insolubility and ability to maintain its shape. Cellulose hydrogels are preferred over other polymers because they are highly biocompatible, easily accessible, and affordable. Carboxymethyl cellulose sodium (CMCNa) is an example of a water-soluble cellulose derivative that can be synthesized using natural materials. A crosslinking agent is used to strengthen the properties of the hydrogel. Chemical crosslinking agent is used more often than physical crosslinking agent. In this review, article, different types of crosslinking agents are discussed based on synthetic and natural crosslinking agents. Hydrogels that utilize synthetic crosslinking agent have advantages, such as adjustable mechanical properties and easy control of the chemical composition. However, hydrogels that use natural crosslinking agent have better biocompatibility and less latent toxic effect.

Development of Saturated Fat Replacers: Conventional and Nano-Emulsions Stabilised by Lecithin and Hydroxylpropyl Methylcellulose

The combination of two emulsifiers, lecithin and hydroxypropyl methylcellulose (HPMC), into emulsions is an interesting strategy to design fat replacers in food matrices. The objective of this study was to investigate the effect of HPMC type and concentration on the formation, stability, and microstructure of conventional emulsions and nanoemulsions. Two different types of HPMC with low and high content of methyl and hydroxypropyl groups (HPMC-L and HPMC-H) were evaluated. The results showed that the molecular structure and concentration of HPMC play a major role in the viscoelastic behaviour, the gelation temperature, and the strength of gel formed. The firmness and work of shear of HPMC solutions increased significantly (p < 0.05) with increasing concentration. HPMC-L illustrated a more stable gel structure than the HPMC-H solution. Nanoemulsions showed lower moduli values, firmness, and work of shear than conventional emulsions due to the influence of high-pressure homogenization. A combination of lecithin and HPMC improved the physical and lipid oxidative stability of the emulsions, presenting a lower creaming index and thiobarbituric acid reactive substances (TBARS). In conclusion, HPMC-L at 2% w/w could be a suitable type and concentration combined with lecithin to formulate a saturated fat replacer that could mimic butter technological performance during food manufacturing operations.

Charge-assisted bond and molecular self-assembly drive the gelation of lenvatinib mesylate

Lenvatinib mesylate (LM) is a first-line anticancer agent for the treatment of unresectable hepatocellular carcinoma, while it formed viscoelastic hydrogel when contacting with aqueous medium, which would significantly hinder its in vitro dissolution. The aim of this study was to systematicly explore the gelation mechanism and gel properties via thermal analysis, rheology, morphology and spectroscopy studies. The formed hydrogel was found to be composed of a new polymorph of crystalline LM, and its mechanical strength depended on the cross-linking degree of the fibrillar network structure. Spectroscopy analyses revealed that the intermolecular hydrogen bonds (the bifurcated hydrogen bond between the adjacent urea groups and the NH⋯OC hydrogen bond between the primary amide groups) as well as π-π stacking interactions (between the benzene ring and the quinoline ring) were suggested to be the driving forces for the self-assembly of LM during gelation process. Additionally, no gelation phenomenon was observed when suspending the base form lenvatinib in water, while it could form gel in various acidic solutions (e.g. hydrochloric acid, phosphoric acid and methanesulfonic acid) because the regenerated N⁺-H group increased the solubility of lenvatinib and promoted the balance between the dissolution or aggregation of LX (X: acid radical ion) molecules in solutions. In conclusion, the charge-assisted bond N⁺-H in LM molecule and intermolecular non-covalent interactions drived the hydrogel formation of LM in aqueous media. This study elucidates the gelation mechanism and gel properties of LM hydrogel, which would be helpful to figure out strategy to eliminate its gelation fundamentally and pave the way for its further formulation development in future.

Nanosuspensions of a poorly soluble investigational molecule ODM-106: Impact of milling bead diameter and stabilizer concentration

Aqueous solubility of a drug substance is an important attribute affecting oral bioavailability. Nanonization, particle size reduction to submicron level, is an elegant approach to improve drug solubility and dissolution by increasing the surface energy, which in turn necessitates the use of stabilizers. The purpose of this study was to develop a nanosuspension of a practically water-insoluble investigational molecule by nanomilling approach using wet media milling. A variety of polymeric and surface active excipients were tested for their wettability. A combination of hydroxypropyl methylcellulose and sodium lauryl sulfate (SLS) were selected as stabilizers on the bases of compatibility studies and efficient wettability behaviour in contact angle measurements (≈80˚). A factorial design set-up was used to study the effect of milling bead diameter and stabilizer concentration on the efficiency of particle size reduction. Nanonization outcome was different when milling beads of 0.5 mm and 1 mm diameter were used at different concentrations of the stabilizers, which demonstrated the complex nature of the whole system. Storage of the nanosuspensions under different temperature conditions resulted only in minor changes of the particle size fractions.

Synthesis of plate-like β-tricalcium phosphate nanoparticles and their efficiency in remineralization of incipient enamel caries

The purpose of this study was to synthesize nano-sized β-tricalcium phosphate (nano-TCP) particles and determine its concentration-dependent properties on incipient enamel caries lesions. Nano-TCP was synthesized as a wet chemical through a method using low concentration of precursors and low addition rate of calcium nitrate tetrahydrate as a second phase. Morphology and phase composition of the particles were analyzed by SEM, XRD, and EDXA techniques. Incipient enamel lesions were created in human premolars with an acidic buffer. The teeth were then incubated in aqueous dispersions of nano-TCP as remineralization solutions. Sodium fluoride solution and deionized water were used as positive and negative control groups, respectively. The quality and thickness of the remineralized layer on enamel were investigated using SEM. The data were statistically analyzed by analysis of variance (ANOVA) and post hoc Tukey’s test. The synthesized nano-TCP mostly consisted of porous platelet-like crystals of 50–100 nm thickness and pore diameters of 100–300 nm. SEM observation showed that a homogenous layer was formed on the surface of the enamels remineralized in nano-TCP solutions. The thickness of the mineralized layer was dependent on the incubation time and nano-TCP concentration.

Rheological and Mechanical Properties of Thermoresponsive Methylcellulose/Calcium Phosphate-Based Injectable Bone Substitutes

In this study, a novel injectable bone substitute (IBS) was prepared by incorporating a bioceramic powder in a polymeric solution comprising of methylcellulose (MC), gelatin and citric acid. Methylcellulose was utilized as the polymeric matrix due to its thermoresponsive properties and biocompatibility. 2.5 wt % gelatin and 3 wt % citric acid were added to the MC to adjust the rheological properties of the prepared IBS. Then, 0, 20, 30 and 50 wt % of the bioceramic component comprising tetracalcium phosphate/hydroxyapatite (TTCP/HA), dicalcium phosphate dehydrate (DCPD) and calcium sulfate dehydrate (CSD) were added into the prepared polymeric component. The prepared IBS samples had a chewing gum-like consistency. IBS samples were investigated in terms of their chemical structure, rheological characteristics, and mechanical properties. After that, in vitro degradation studies were carried out by measurement of pH and % remaining weight. Viscoelastic characteristics of the samples indicated that all of the prepared IBS were injectable and they hardened at approximately 37 °C. Moreover, with increasing wt % of the bioceramic component, the degradation rate of the samples significantly reduced and the mechanical properties were improved. Therefore, the experimental results indicated that the P50 mix may be a promising candidates to fill bone defects and assist bone recovery for non-load bearing applications.

The innovative applications of therapeutic nanostructures in dentistry

Nanotechnology has paved multiple ways in preventing, reversing or restoring dental caries which is one of the major health care problems. Nanotechnology aided in processing variety of nanomaterials with innovative dental applications. Some showed antimicrobial effect helping in the preventive stage. Others have remineralizing potential intercepting early lesion progression as nanosized calcium phosphate, carbonate hydroxyapatite nanocrystals, nanoamorphous calcium phosphate and nanoparticulate bioactive glass particularly with provision of self-assembles protein that furnish essential role in biomimetic repair. The unique size of nanomaterials makes them fascinating carriers for dental products. Thus, it is recentlyclaimedthat fortifying the adhesives with nanomaterials that possess biological meritsdoes not only enhance the mechanical and physical properties of the adhesives, but also help to attain and maintain a durable adhesive joint and enhanced longevity. Accordingly, this review will focus on the current status and the future implications of nanotechnology in preventive and adhesive dentistry.

Designing Solvent Exchange-Induced In Situ Forming Gel from Aqueous Insoluble Polymers as Matrix Base for Periodontitis Treatment

An in situ forming gel is a dosage form which is promised for site-specific therapy such as periodontal pocket of periodontitis treatment. Ethylcellulose, bleached shellac, and Eudragit RS were applied in this study as a polymeric matrix for in situ forming gel employing N-methyl pyrrolidone (NMP) as solvent. Solutions comprising ethylcellulose, bleached shellac, and Eudragit RS in NMP were evaluated for viscosity, rheology, and rate of water penetration. Ease of administration by injection was determined as the force required to expel polymeric solutions through a needle using texture analyzer. In vitro gel formation and in vitro gel degradation were conducted after injection into phosphate buffer solution pH 6.8. Ethylcellulose, bleached shellac, and Eudragit RS could form the in situ gel, in vitro. Gel viscosity and pH value depended on percentage amount of the polymer, whereas the water diffusion at early period likely relied on types of polymer. Furthermore, the solutions containing higher polymer concentration exhibited the lower degree of degradation. All the preparations were acceptable as injectable dosage forms because the applied force was lower than 50 N. All of them inhibited Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyrommonas gingivalis growth owing to antimicrobial activity of NMP which exhibited a potential use for periodontitis treatment. Moreover, the developed systems presented as the solvent exchange induced in situ forming gel and showed capability to be incorporated with the suitable antimicrobial active compounds for periodontitis treatment which should be further studied.

One-pot synthesis of injectable methylcellulose hydrogel containing calcium phosphate nanoparticles

A thermo-sensitive hydrogel based on calcium phosphate nanoparticles was prepared using a novel one-pot method in which added precursor salts induced a salt-out effect in the methylcellulose (MC) solution. The calcium phosphate nanoparticles were synthesized in situ from precursor ions (Ca²⁺ and HPO₄^2-) in the hydrogel, and residual ions (HPO₄^2- and Cl^-) in the formation of the nanoparticles decreased the gelation temperature of the MC solution. This one-pot synthesis was an effective way to streamline the previous multi-step process and to easily prepare a thermo-sensitive hydrogel containing bioactive nanoparticles. The thermo-sensitive properties of different concentrations of MC hydrogels were characterized by a rheometer and infrared (IR) spectroscopy. The gelation behavior of MC according to the addition of various salts was monitored by rheometer. With respect to a selected concentration and precursor, the structure of the MC hydrogel containing calcium phosphate nanoparticles was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and IR.

Self-Assembled Thermoresponsive Nanogels Prepared by Reverse Micelle → Positive Micelle Method for Ophthalmic Delivery of Muscone, a Poorly Water-Soluble Drug

This study aimed to design a nanocarrier ophthalmic delivery system of muscone, a poorly water-soluble drug. The muscone thermoresponsive nanogels were self-assembled by reverse micelle → positive micelle method. Muscone was demonstrated to have uniform narrow particle size distribution in nanogel by the dynamic light scattering test. The developed nanocomposite hydrogel had a high muscone loading, and the rheology results showed that the phase transition temperature was 34.05°C. Thixotropy test indicated that the nanogel was able to resist the blinking of eyes because of the thixotropy recovery time, which is <5 s. Compared with muscone eye drops, muscone nanogels showed longer retention time on the corneal surface using fluorescent labeling technology and produced a 3.4-fold increase in apparent permeability coefficients (Papp). Draize testing showed that the developed nanogel caused no eye irritation. In vivo pharmacokinetic study indicated that the nanogel could significantly increase the bioavailability of muscone after administration compared with eye drops. These results indicate that self-assembled thermoresponsive nanogel prepared by reverse micelle → positive micelle method has potential for the ophthalmic delivery of poorly water-soluble drugs.

Solvent exchange-induced in situ forming gel comprising ethyl cellulose-antimicrobial drugs

Solvent-exchanged in situ forming gel is a drug delivery system which is in sol form before administration. When it contacts with the body fluid, then the water miscible organic solvent dissipates and water penetrates into the system, leading the polymer precipitation as in situ gel at the site of injection. The aim of this research was to study the parameters affecting the gel properties, drug release and antimicrobial activities of the in situ forming gels prepared from ethyl cellulose (EC) dissolved in N-methyl pyrrolidone (NMP) to deliver the antimicrobial agents (doxycycline hyclate, metronidazole and benzyl peroxide) for periodontitis treatment. The gel appearance, pH, viscosity, rheology, syringeability, gel formation, rate of water diffusion into the gels, in vitro degradation, drug release behavior and antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans and Porphyrommonas gingivalis were determined. Increasing the amount of EC increased the viscosity of system while still exhibiting Newtonian flow and increased the work of syringeability whereas decreased the releasing of drug. The system transformed into the rigid gel formation after being injected into the simulated gingival crevicular fluid. The developed systems containing 5% w/w antimicrobial agent showed the antimicrobial activities against all test bacteria. Thus the developed solvent exchange-induced in situ forming gels comprising EC-antimicrobial drugs exhibited potential use for periodontitis treatment.

The Role of Hydroxyl Channel in Defining Selected Physicochemical Peculiarities Exhibited by Hydroxyapatite

Mysteries surrounding the most important mineral for the vertebrate biology, hydroxyapatite, are many. Perhaps the Greek root of its name, απαταo, meaning 'to deceive' and given to its mineral form by the early gem collectors who confused it with more precious stones, is still applicable today, though in a different connotation, descriptive of a number of physicochemical peculiarities exhibited by it. Comparable to water as the epitome of peculiarities in the realm of liquids, hydroxyapatite can serve as a paradigm for peculiarities in the world of solids. Ten of the peculiar properties of hydroxyapatite are sketched in this review piece, ranging from (i) the crystal lattice flexibility to (ii) notorious surface layer instability to (iii) finite piezoelectricity, pyroelectricity and conductivity to protons to (iv) accelerated growth and improved osteoconductivity in the electromagnetic fields to (v) high nucleation rate at low supersaturations and low crystal growth rate at high supersaturations to (vi) higher bioactivity and resorbability of biological apatite compared to the synthetic ones, and beyond. An attempt has been made to explain this array of curious characteristics by referring to a particular element of the crystal structure of hydroxyapatite: the hydroxyl ion channel extending in the direction of the c-axis, through a crystallographic column created by the overlapping calcium ion triangles.

Effect of Nano-Tricalcium Phosphate and Nanohydroxyapatite on the Staining Susceptibility of Bleached Enamel

Objective. This study was designed to evaluate the effect of nano-tricalcium phosphate (n-TCP) and nanohydroxyapatite (n-HAP) on prevention of restaining of enamel after dental bleaching. Methods. Forty bovine incisors were bleached with 20% carbamide peroxide for two weeks. Afterward, they were divided into five groups based on remineralization solution: no treatment (control), 10% n-TCP, 5% n-TCP, 10% n-HAP, and 5% n-HAP. Each group was daily immersed for 10 minutes in the restaining solution (tea) and for 3 minutes in the remineralization agent, respectively. This protocol was repeated for five days. Subsequently, three digital photographs (baseline, after bleaching, and after restaining) were analyzed by Adobe Photoshop software. The obtained L^∗, a^∗, b^∗, and ΔE parameters were compared using ANOVA and Wilcoxon and Bonferroni tests. Results. After bleaching, there were significant changes in tooth colors (P < 0.001) while, after restaining and immersion in remineralization solutions, there were no significant differences in L^∗, a^∗, and b^∗ values of different groups (P > 0.05). However, ΔE of 10% TCP was significantly lower than the control (P = 0.02) while there were no significant differences between the other groups (P > 0.05). Conclusion. 10% n-TCP could significantly maintain the resultant color and reconstruct the enamel structure after bleaching.