Hydroxyethyl Cellulose Solutions Research Articles

Identification of lubricant viscosity to minimize the frictional impact of colonoscopy on colonic mucosa

Applying a lubricant to the colonic mucosa and reducing the dynamic friction coefficient (DFC) between the endoscopic shaft and colonic mucosa may reduce colonoscopy invasiveness. However, the ideal lubricant viscosity remains unknown. Here, we developed a DFC measurement model integrating samples of colonic mucosa from forensic autopsy specimens into a simulated bowel bend and determined the low-friction lubricant viscosity that minimizes the DFC. Carboxymethyl cellulose, xanthan gum, hydroxyethyl cellulose, sodium alginate, and sodium polyacrylate aqueous solutions of various concentrations were used as lubricants. Low-friction lubricants minimized the load on the colonic mucosa during colonoscope insertion and reduced the total endoscopy insertion time. The highest correlation was between the DFC and the lubricant viscosity at a shear rate of 100 1/s. The lowest DFC was almost constant at approximately 0.09, irrespective of the chemical composition of the lubricant, and the low-friction lubricant viscosity (100 1/s) was 0.031–0.086 (median: 0.059). The viscosities of conventional colonoscopic lubricants were suitable for lubricating the anorectal skin owing to their low DFC, but too high for lubricating the colonic mucosa because of their high DFC. The utilization of the low-friction lubricants with the optimal viscosity can reduce the stress on colonic mucosa during colonoscopy.

Evaluating bubble chain phenomena as a mechanism for open system degassing in basaltic systems

Passive degassing – i.e., the open-system degassing of a magmatic gas phase that is decoupled from the melt phase – is common at many basaltic volcanic systems and consistently makes a greater contribution to total volcanic gas emissions than eruptive degassing. However, the mechanism for passive degassing is not fully understood. We investigate the feasibility of permeable gas flow through connected bubbles or pathways using experiments with aqueous solutions of hydroxyethyl cellulose (HEC), a non-Newtonian analogue material for magma. Stable chains of connected bubbles have previously been reported in similar non-Newtonian polymer solutions. We observe a range of bubble chain phenomena and identified five regimes, numbering in order of increasing gas flow rate: 1) small individual bubbles; 2) chains of rounded bubbles; 3) chains of elongate bubbles; 4) pipe-like ‘winding flue’; 5) large individual bubbles. The bubble chain phenomena (regimes 2–4) are observed over a restricted interval of gas flow rates. We determine the rheology of the solutions and conclude that the HEC solutions that produced bubble chain phenomena in our experiments are well scaled to shear-thinning and viscoelastic magmas, hence bubble chain phenomena could form in magmas. Our analysis also suggests that the viscoelastic rheology of HEC plays a fundamental role in the observed bubble chain phenomena.

Hydroxyethyl cellulose functionalised with maleimide groups as a new excipient with enhanced mucoadhesive properties

Hydroxyethylcellulose (HEC) is a non-ionic water-soluble polymer with poor mucoadhesive properties. The mucoadhesive properties of hydroxyethylcellulose can be improved by modifying it through conjugation with molecules containing maleimide groups. Maleimide groups interact with the thiol groups present in cysteine domains in the mucin via Michael addition reaction under physiological conditions to form a strong mucoadhesive bond. This will prolong the residence time of a dosage form containing this modified polymer and drug on mucosal surfaces. In this study HEC was modified by reaction with 4-bromophenyl maleimide in varying molar ratios and the successful synthesis was confirmed using 1H NMR and FTIR spectroscopies. The safety of the newly synthesised polymer derivatives was assessed with in vivo planaria assays and in vitro MTT assay utilising Caco-2 cell line. The synthesized maleimide-functionalised HEC solutions were sprayed onto blank tablets to develop a model dosage form. The physical properties and mucoadhesive behavior of these tablets were evaluated using a tensile test with sheep buccal mucosa. The maleimide-functionalised HEC exhibited superior mucoadhesive properties compared to unmodified HEC.

Enhancement of Macromixing Performance of a Stirred Tank with a Novel V-Shaped Punched Baffle

A V-shaped punched baffle (VSPB) is developed to enhance fluid mixing in a stirred tank by producing impinging jet streams from face-to-face holes. Macromixing experiments and computational fluid dynamics (CFD) simulations are conducted with water and 0.5 wt % hydroxyethyl cellulose (HEC) solution as fluid to compare the performance of a standard baffle (SB), standard punched baffle (SPB) and VSPB. The experimental results show that the mixing time of VSPB is reduced by a maximum of 23 and 14.7% compared with those of SB and SPB at low speeds, respectively. With increasing stirring speed, the mixing time of all three baffles tends to be the same, but the power consumption of VSPB is less than that of SB and SPB with a Rushton turbine (RT). The simulation results show that the punched baffle can significantly increase the tangential velocity and turbulent kinetic energy of the fluid in the baffle region. Moreover, tiny vortices are at the back side of the punched baffles when the fluid is water. However, for a HEC solution, the flow field near the tank wall becomes disordered due to shear action caused by baffles and forms irregular vortices.

3D active mixing of confined power law aqueous polymer solutions: a comparative numerical study

PurposeThis paper aims to study the influence that the second invariant of the rate-of-strain tensor of a power law polymeric fluid (aqueous solution of hydroxyethyl cellulose [HEC]) has on convective mixing performance downstream of a 3D confined oscillating prism. Newtonian and non-Newtonian Reynolds numbers, the mass concentration of HEC and prism oscillation frequency were varied.Design/methodology/approachA conceptual problem was designed. Its objective was to analyze the convective mixing of two adjacent flow streams when they pass around a moving confined prism. The rectangular prism had a square section, and its sinusoidal motion was prescribed inside a channel with a square section too. OpenFOAM libraries were used to simulate the flow field. Regarding prism motion, the icoDyMFoam solver was used. The problem was analyzed both at the global level (mixing parameter) and local level (detailed flow topology).FindingsFor constant Reynolds number, increasing mass concentrations of HEC (in the range from 0.2% to 0.5%) led to better mixing parameters. The improvement was linked to the effect that the second invariant of the rate-of-strain tensor had on flow topology. It was found that mixing is maximum when the prism motion and its wake (the frequency of the first instability) are synchronized. In practical terms, this means that the optimum stirring frequency does not need to be very high; it suffices that it ensures that synchronization occurs. The dominant vorticity shedding pattern found was the so-called 2P mode. However, a significant difference was found when compared to the free-stream situation. While in the former, the two vorticity regions that make up the 2P pair come from the prism, in the present confined case, one came from the prism, and the other came from the wall. Another difference was that in the present case, the 2P pairs were much more elongated than in the free stream case, and this had a significant influence on the stretching and bending of streak lines and, therefore, on mixing.Practical implicationsThe study that has been presented has a practical industrial implication for the processes industry because it provides guidelines to design active mixers that deal with aqueous power law polymeric solutions. In parallel, it opens up some new research lines in the direction of studying whether the mixing concept might be modified so as to develop a fully passive system that could be far simpler and, possibly, more attractive to industry.Originality/valueThe originality and value of the study are associated to the systematic approach that has been followed. It has allowed to establish a clear pattern regarding the active mixing behavior of HEC solutions in confined flows. To the best of authors’ knowledge, this could be the first study of this type in the literature. Also, the study has contributed to understand the vorticity shedding patterns that appear in these types of problems and how they shape wake topology and, consequently, mixing performance. The finding that optimum mixing requires synchronization of stirring motion frequency and wake first natural frequency of instability may help to improve the design and operation of industrial mixers dealing with polymeric aqueous solutions.

The Effect of Molecular Mass of Hydroxyethyl Cellulose on the Performance of Capillary Electrophoretic Separation of Proteins

Capillary electrophoresis (CE) is a versatile analytical separation method in the field of biochemistry. Although it has been proved that the relative molecular mass (Mr) of the polymers determines the threshold concentration of the entangled polymer solution, which will affect the separation performance of DNA molecules, there is still no report on the effect of Mr on the separation performance of proteins. Herein, we have thoroughly performed the CE of proteins ranged from 14.3 kDa to 116 kDa in a mixed hydroxyethyl cellulose (HEC) solution. The mixed solution was obtained with various Mr including 90,000, 250,000, 720,000, and 1,300,000. Then, we found that the mixed polymer provided a high resolution for small protein molecules while increasing the efficiency of large ones. Results demonstrated that the migration time decreased if HEC (1,300,000) was mixed with the lower Mr one, and the mixed solution (1,300,000/250,000) offered the highest resolution. The resolution was negatively correlated with the electric field strength. Finally, we have employed the optimal electrophoretic conditions to separate proteins in human tears, and it showed that lysozyme, lipocalin, and lactoferrin from human tears were successfully resolved in the mixed HEC. Such work indicates that CE has the potential to be developed as a tool for the diagnosis of xerophthalmia, meibomian gland dysfunction, or other eye diseases.

Evaluation of the effect of maltodextrin and hydroxyethyl cellulose solution containing ZnO and Fe2O3 nanoparticles on the CO2 release in sodium bicarbonate coating process

Coating is a rapidly extending technology; especially in food and pharmaceutical industries. The coating process of sodium bicarbonate using ZnO and Fe2O3 nanoparticles (NPs) in aqueous solutions of maltodextrin (MD) and hydroxyethylcellulose (HEC) as wall materials has been studied in this work. The best operating conditions obtained by factorial design were the fluidization air flow rate of 100 m3/h, spraying pressure of 4 bars, drying air temperature of 60 °C, MD concentration of 30 % and HEC concentration of 0.1 %. The introduction of the NPs into the coating solution provides a heterogeneous surface, which enforces the wall material to a more uniform and faster crystallization. The applied conditions have been shown to be efficient for the coating process investigated in this study since they improve the coating characteristics such as CO2 release reduction, which is the most important one. CO2 release was reduced from 4 % for coated powders with no NPs in the coating solution to 2.4 % and 3.5 % for coated powders with Fe2O3 and ZnO NPs in the coating solution, repectively. The adsorption–desorption of N2 gas implies that the pore sizes of the coating layer surface have been significantly decreased by adding NPs to the coating solution.

Ethyl Hydroxyethyl Cellulose-A Biocompatible Polymer Carrier in Blood.

The biocompatibility of carrier nanomaterials in blood is largely hampered by their activating or inhibiting role on the clotting system, which in many cases prevents safe intravascular application. Here, we characterized an aqueous colloidal ethyl hydroxyethyl cellulose (EHEC) solution and tested its effect on ex vivo clot formation, platelet aggregation, and activation by thromboelastometry, aggregometry, and flow cytometry. We compared the impact of EHEC solution on platelet aggregation with biocompatible materials used in transfusion medicine (the plasma expanders gelatin polysuccinate and hydroxyethyl starch). We demonstrate that the EHEC solution, in contrast to commercial products exhibiting Newtonian flow behavior, resembles the shear-thinning behavior of human blood. Similar to established nanomaterials that are considered biocompatible when added to blood, the EHEC exposure of resting platelets in platelet-rich plasma does not enhance tissue thromboplastin- or ellagic acid-induced blood clotting, or platelet aggregation or activation, as measured by integrin αIIbβ3 activation and P-selectin exposure. Furthermore, the addition of EHEC solution to adenosine diphosphate (ADP)-stimulated platelet-rich plasma does not affect the platelet aggregation induced by this agonist. Overall, our results suggest that EHEC may be suitable as a biocompatible carrier material in blood circulation and for applications in flow-dependent diagnostics.

Comparison of the rate of release of active substances from solutions of hydroxymethylpropyl cellulose and hydroxyethyl cellulose for selecting the optimal polymer for the development of ear drops

Comparison of the rate of release of active substances from solutions of hydroxymethylpropyl cellulose and hydroxyethyl cellulose for selecting the optimal polymer for the development of ear drops

Friction Reduction Mechanism of Aqueous Hydroxyethyl Cellulose Solution Enhanced by Synergistic Effect of APTES

Friction Reduction Mechanism of Aqueous Hydroxyethyl Cellulose Solution Enhanced by Synergistic Effect of APTES

Wound closure, angiogenesis and antibacterial behaviors of tetracalcium phosphate/hydroxyethyl cellulose/hyaluronic acid/gelatin composite dermal scaffolds

Polymeric and tetracalcium phosphate (TTCP)-containing polymeric scaffolds were fabricated using a freeze-drying technique, with a homogenous solution of hydroxyethyl cellulose (HEC)/hyaluronic acid (HA)/gelatin (G) or suspension of 15 or 20% TTCP) particles in HEC/HA/G solution. The morphology, phase composition, chemical bands, and swelling behavior of the scaffold were determined. In vitro fibroblast cell viability and migration potential of the scaffolds were determined by MTT, live/dead staining, and scratch assay for wound healing. The in vivo chick embryo angiogenesis test was also carried out. Finally, the initial antibacterial activity of the scaffolds was determined using Staphylococcus aureus. The scaffolds exhibited an enormous porous structure in which the size of pores increased by the presence of TTCP particles. While the polymeric scaffold was amorphous, the formation of low crystalline hydroxyapatite phase and the initial TTCP particles was determined in the composition of TTCP-added scaffolds. TTCP increased swelling behavior of the polymeric scaffold in PBS. The results demonstrated that the amount of TTCP was a crucial factor in cell life. A high concentration of TTCP could restrict cell viability, although all the scaffolds were nontoxic. The scratch assessments determined better cell migration and wound closure in treating with TTCP-containing scaffolds so that after 24 h, a wound closure of 100% was observed. Furthermore, TTCP-incorporated scaffolds significantly improved the angiogenesis, in the chick embryo test. The presence of TTCP had a significant effect on reducing the bacterial activity and 20% TTCP-containing scaffold exhibited better antibacterial activity than the others.

Exploring the gelation of aqueous cellulose nanocrystals (CNCs)-hydroxyethyl cellulose (HEC) mixtures

We investigated the gelation and microstructure of cellulose nanocrystals (CNCs) in nonionic hydroxyethyl cellulose (HEC) solutions. Cellulose nanocrystals (CNCs) with a particle length of 90 nm and width of 8 nm currently produced by acid hydrolysis of wood pulp were used in this study. The microstructures of CNCs/polymer suspensions were investigated by performing linear small amplitude oscillatory shear (SAOS) and nonlinear large amplitude oscillatory shear (LAOS), in addition to constructing CNCs phase diagrams and measuring steady-state shear viscosities. Significant viscosity increases at low shear rates coupled with high shear thinning behaviors were observed in CNCs in HEC solutions above the overlapping concentration of HEC. The physical strength of CNCs/HEC solution gels increased with the increase in CNCs concentration and resembled the weakly crosslinked gels according to the scaling of linear dynamic mechanical experiments. According to LAOS analysis, CNCs/HEC mixtures showed type III behavior with intercycle stress softening, while the samples showed stress stiffening in single cycles.Graphical abstract

Nanocellulose-containing cellulose ether composite films prepared from aqueous mixtures by casting and drying method

A TEMPO-oxidized cellulose nanofibril (TEMPO-CNF)/water dispersion was mixed with an aqueous solution of hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), methyl cellulose (MC), or carboxymethyl cellulose sodium salt (CMC). The mixtures were converted into TEMPO-CNF/cellulose ether composite films containing 0–5% TEMPO-CNFs by casting and drying of the aqueous mixtures. All the composite films had high light transparency. However, the tensile properties of the composite films of a given TEMPO-CNF content differed for the HPC and HEC, MC, and CMC matrices. The nano-reinforcing effect owing to TEMPO-CNFs was evident in the TEMPO-CNF/HPC composite films, which became strong but brittle. In contrast, the TEMPO-CNF/HEC composite films did not exhibit this nano-reinforcing effect. Transmission electron microscopy observation of the film cross-sections revealed that the TEMPO-CNF elements were homogeneously distributed in the 5% TEMPO-CNF/HPC composite film. In contrast, the TEMPO-CNF elements were densely present on the top and bottom surfaces of the 5% TEMPO-CNF/HEC composite film; the TEMPO-CNFs were heterogeneously distributed in the HEC matrix. The low gelation or aggregation concentrations of TEMPO-CNFs in water may have resulted in the different distribution states of TEMPO-CNFs, depending on the cellulose ether matrix used, and hence the different tensile behaviors.

Path-dependent rheology of carbon particle-hydroxyethylcellulose fluids

Polymeric fluids with tunable viscosity find application in different sectors, ranging from enhanced oil recovery to environmental remediation. This study investigates polymeric fluids obtained with hydroxyethylcellulose (HEC) and biocarbon particles prepared at low (650⁰C, LM) and high (900⁰C, HM) temperature of pyrolization. High pyrolization temperatures increased the hydrophobicity of biocarbon particles. In the absence of HEC, HM particles partitioned preferentially in non-polar solvents (e.g. toluene, rather than in water). Without particles, the shear loss (G”) and storage (G’) moduli of aqueous hydroxyethylcellulose solutions slowly increased over time, due to HEC hydration. The progressive increase in molecular crowding and microviscosity due to the hydration of HEC was demonstrated using steady-state fluorescence spectroscopy with the molecular rotor 9-(dicyanovinyl)julolidine (DCVJ) as a probe. Particles added to HEC increased the viscoelastic moduli of HEC solutions only slightly (i.e. less than doubled them) when HEC was pre-hydrated, and significantly when HEC was not pre-hydrated. Specifically, addition of LM and HM particles (1−30 g/L) to non-hydrated HEC (16 g/L) increased the viscoelastic moduli of HEC solutions in water from below detection to G”>9 Pa and G’>6 Pa (in the whole range of biocarbon particle concentrations analyzed). Our study investigates for the first time the effect of path-dependence of the preparation method on the rheology of HEC-carbon particle fluids. The viscoelastic moduli increase of HEC is ascribed to hydrophobic interactions between biocarbon particles and non-hydrated HEC. The preferential particle partitioning in aqueous HEC solutions (rather than in toluene) is also attributed to these interactions. Such interactions were attributed to the partially hydrophobic nature of HEC, which partitioned at the air-water interface (rather than exclusively in bulk water), lowering the interfacial tension and producing interfacial films with compressional rigidity. HEC interfacial film rigidity changed upon particle addition, supporting the hypothesis of HEC-particle interactions. Compression isotherms modelled using the theory by Marczak et al. were used here for the first time as an indirect tool to gain insights regarding HEC-carbon particle interactions. Partial HEC hydrophobicity was also indicated by the higher viscosity measured in ethanol-water solutions than in water, which showed that ethanol-water was a better solvent than pure water. Steady state fluorescence measurements confirmed that the amount of HEC-bound solvent was greater in ethanol-water mixtures than in pure water. Biocarbon particles mixed with non-hydrated HEC were well-dispersed. Instead, biocarbon particles aggregated when they were mixed with hydrated HEC, indicating that the magnitude of attractive forces between particles and HEC decreased when HEC was hydrated. Compression isotherms measured at the air-water interface with non-hydrated HEC alone and with non-hydrated HEC-biocarbon particle mixtures differed, indicating HEC-particle co-adsorption at the air-water interface and the formation of HEC-particle aggregates.

Polymeric Inserts Containing Eudragit® L100 Nanoparticle for Improved Ocular Delivery of Azithromycin.

Polymeric inserts containing azithromycin-loaded Eudragit® L100 nanoparticles were developed to sustain the drug release and enhance its ocular performance. The solvent diffusion technique was employed to prepare nanoparticles. The developed nanoparticles (NPs) were fully characterized and investigated. The solvent casting method was used to prepare azithromycin ocular inserts (azithromycin, AZM film) by adding hydroxypropyl methylcellulose (HPMC) or hydroxyethyl cellulose (HEC) solutions after the incorporation of AZM-loaded Eudragit® L100 nanoparticles into plasticized PVA (polyvinyl alcohol) solutions. The optimized nanoparticles had a particle size of 78.06 ± 2.3 nm, zeta potential around −2.45 ± 0.69 mV, polydispersity index around 0.179 ± 0.007, and entrapment efficiency 62.167 ± 0.07%. The prepared inserts exhibited an antibacterial effect on Staphylococcus aureus and Escherichia coli cultures. The inserts containing AZM-loaded nanoparticles showed a burst release during the initial hours, followed by a sustained drug release pattern. Higher cumulative corneal permeations from AZM films were observed for the optimized formulation compared to the drug solution in the ex-vivo trans-corneal study. In comparison to the AZM solution, the inserts significantly prolonged the release of AZM in rabbit eyes (121 h). The mucoadhesive inserts containing azithromycin-loaded Eudragit® L100 nanoparticles offer a promising approach for the ocular delivery of azithromycin (antibacterial and anti-inflammatory) to treat ocular infections that require a prolonged drug delivery.

Hydroxyethyl cellulose/bacterial cellulose cryogel dopped silver@titanium oxide nanoparticles: Antimicrobial activity and controlled release of Tebuconazole fungicide

Cryogel materials are composed of porous and lightweight structures that can be used for many industrial applications, particularly, in agriculture for the controlled release of Tebuconazole fungicide. Accordingly, we prepared environmentally friendly cryogel using natural polymers such hydroxyethyl cellulose (HEC) and bacterial cellulose (BC). The cryogel was formed by blending aqueous solutions of both HEC and BC, which was then crosslinked with glyoxal and the mixture was underwent to drying using freeze drying technique. Different concentrations of the as prepared silver@titanium oxide nanoparticles (Ag@TiO2NPs) were incorporated within the cryogel formation in order to increase its antimicrobial efficiency. A mode pesticide Tebuconazole was encapsulated in the cryogel platform in order to control the release of Tebuconazole. Thus, the developed cryogel which was porous, cheap and had an antimicrobial effect, controlled pesticide release suggesting that it is a potential candidate for agricultural applications.

Power Laws Dominate Shear and Extensional Rheology Response and Capillarity-Driven Pinching Dynamics of Entangled Hydroxyethyl Cellulose (HEC) Solutions

Quantitative studies of capillarity-driven pinching and extensional rheology of aqueous solutions of polysaccharides like hydroxyethyl cellulose (HEC) are beyond the measurable range of most extens...

Size effect of curcumin nanocrystals on dissolution, airway mucosa penetration, lung tissue distribution and absorption by pulmonary delivery

Nanocrystals (NCs) have been introduced for use in pulmonary delivery in recent decades. Although the deposition and bioavailability have been extensively studied, little is known about the biofate, which influences the drug release and absorption process of NCs. In this study, we fabricated three different sized curcumin NCs by adjusting the parameters of mill machine using a wet milling method and studied the size effect on pulmonary absorption. The small nanocrystals (NC-S, 246.16 ± 21.98 nm) exhibited a faster dissolution rate and higher diffusion percentage in vitro compared with middle (NC-M, 535.26 ± 50.33 nm) and large nanocrystals (NC-L, 1089.53 ± 194.34 nm). Multiple particle tracking experiments revealed that NC-S had larger mean squared displacement during diffusion in simulated mucus of 0.5% hydroxyethyl cellulose solution. Moreover, enhanced cellular uptake and transport efficiency were achieved by NC-S in Calu-3 cells and an air-liquid interface culturing model. NCs were mainly absorbed in the dissolved drug form, as assessed by using the Förster resonance energy transfer (FRET) technique. In vivo lung retention and distribution revealed that few smaller sized nanocrystals were retained in the lung after intratracheal administration. The pharmacokinetic study showed that the AUC(0-t) values of small sized nanocrystals were 1.75- and 3.32-fold greater than NC-M and NC-L, respectively. In conclusion, this study demonstrated that smaller sized nanocrystals were more easily absorbed into the blood system by increasing the dissolution rate.

The Effect of Titanium Tetrafluoride Treatment and the CO2 Laser on Acid Resistance of Human Enamel.

Introduction: Titanium tetrafluoride (TiF4 ) is deemed more effective than the previous fluoride compounds. To enhance the effect of the fluoride compounds, researchers have suggested their association with lasers, although there are conflicting results in this area. We evaluated the acid resistance of enamel after treatment with the CO2 laser and TiF4 . Methods: Thirteen human premolar teeth were sectioned into 5 parts and each segment was assigned to a study group: co (control): without treatment, AF: enamel treatment with APF 1.23% for 4 minutes, TF: enamel treatment with TiF4 4% for 1 minute, TF-L: enamel treatment with TiF4 4% and then the CO2 laser (Peak power: 1 W, pulse duration: 10 ms, interval time: 500 ms, Beam spot size: 0.2 mm, distance: 2 cm), L-TF: enamel treatment with the CO2 laser and then TiF4 4%. Each sample was kept for 7 days in acidic solution of hydroxyethyl cellulose at pH=4.5, and the amount of the calcium ion released in the solution was measured by atomic absorption spectrometry. Data were analyzed by ANOVA and Bonferroni tests. The significance level was set at 0.05. Results: The average concentration of the calcium ion released in acidic solution was 197.46, 153.30, 99.23, 61.23, 55.46 ppm in the groups respectively. There was a significant difference between the study groups (P<0.0001). Only the difference between TF-L and L-TF was not significant (P>0.05). Conclusion: The loss of calcium from the enamel samples in the groups treated with a combination of the laser and TiF4 was significantly lower than the groups treated with fluoride alone, or the control group. It did not make a significant difference whether the CO2 laser was applied before or after TiF4 .

Gelation of hydroxyethyl cellulose aqueous solution induced by addition of colloidal silica nanoparticles

In this study, a series of hydrogels based on the physical adsorption between hydroxyethyl cellulose (HEC) and colloidal silica nanoparticles (SNPs) were developed, and the effects of SNPs addition on the prepared gels were also investigated. The addition of SNPs into the HEC solution (1.0 wt%) induced gelation, and the gel strength was enhanced by increasing the SNPs concentration from 5 to 20 wt%, which was due to the formation of a denser gel network, as evidenced by SEM observations. Rheological tests suggested that the gelation temperature (Tg) was decreased with the increasing SNPs addition, and the gels exhibited slightly thermal hysteresis, with a temperature lag of 6–7 °C. However, when the SNPs concentration was above 21 wt%, a phase separation was observed. Furthermore, it was found that the addition of SNPs led to the intensified hydrogen bonds between the HEC molecules and the added SNPs, which may be the predominant factor governing the adsorption process. Overall, a facile method for hydrogel preparation was proposed in this study, and the gel properties were also systematically investigated. These results may provide useful information to the field of material science.