Preparation and Application of a Novel Slow-Releasing with Core-Shell Deicer in Asphalt Mixtures.

The massive application of chloride salts has a direct effect on the corrosion of structures and vehicles and decreases durability as well as road pavement damage. A novel slow-release deicer with a core-shell structure was prepared to reduce the salts' impacts, subsequently characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). The conductivity evaluation, moisture absorption, and the snow or ice melting performance of the deicer were also tested. The core-shell deicer with different replacement rates was used to prepare the deicing asphalt mixture based on the equivalent volume replacement method. In this study, the high- and low-temperature performance, moisture damage resistance, and snow or ice melting capacity of mixtures were evaluated in the laboratory. The results show that the low-temperature and moisture stability performances decreased, and high-temperature performance improved, as the content of the core-shell deicer was increased. It is confirmed that the replacement rate of the deicer filler should be lower than 75% to meet the specification requirements. The prepared deicing asphalt mixture has good snow and ice melting performance and can reduce the bonding strength between ice and pavement surface. Durability and cost-benefit analysis are expected in further investigations.

Evaluating the efficacy of slow-releasing carbon source tablets for in situ biological heterotrophic denitrification of groundwater.

Slow-releasing precipitating tablets (SRPTs) and slow-releasing floating tablets (SRFTs) were formulated to release fumarate as a carbon source (CS) and/or electron donor (ED) in an in situ biological heterotrophic denitrification system. These tablets were prepared using pharmaceutical manufacturing. Soil column tests were conducted to evaluate nitrate denitrification efficacy, microbial population changes, and mass balance of fumarate and potential electron acceptors. Significant and simultaneous consumption of both fumarate and nitrate, and the production and consumption of nitrite were observed in both SRPT-treated and SRFT-treated soil columns. These results suggest that SRPT and SRFT releasing fumarate, induce heterotrophic biological denitrification. In the SRPT- and SRFT-treated columns, 65% and 73% of fumarate were associated with heterotrophic denitrification, respectively. Particularly, surplus citric acid, originally designed to serve as a floating agent, was utilized for 36% and 28% for SRFT flotation and denitrification, respectively. The results of 16s RNA analyses revealed that a bacterium that shared 99% 16s rRNA sequence similarity with those of Azoarcus sp. AN9, and Pseudogulbenkiania sp. NH8B, a facultative heterotrophic denitrifier, was detected in the column effluent. This study confirms that SRPT and SRFT can effectively operate long-term in situ biological denitrification processes, because it is possible to supply detailed CS and/or ED uniformly by applying both SRPT and SRFT in the well.

Fabrication of H2O2 slow-releasing composites for simultaneous Microcystis mitigation and phosphate immobilization.

Hydrogen peroxide (H2O2) is a widely accepted algicide in controlling cyanobacterial blooms. However, this method includes two disadvantages: 1) a low H2O2 concentration (<5 mg L-1) is required; 2) H2O2-induced cell lysis causes phosphorus (P) contamination. To overcome the drawbacks, a H2O2 slow-releasing composite (HSRC) based on calcium peroxide (CaO2) was fabricated to substitute liquid H2O2. According to the results, a higher CaO2 dose increased H2O2 yield and releasing rate. H2O2 yield of 160 mg L-1 CaO2 in HSRC reached 32.9 mg L-1 and its releasing rate was 0.407 h-1. In addition, a higher temperature decreased H2O2 yield and increased H2O2-releasing rate. Besides, HSRC endowed with a remarkable ability to immobilize P. Higher CaO2 dose, pH value, and temperature increased the rate of P immobilization. The highest rate was 0.185 h-1, which occurred with 160 mg L-1 CaO2 in HSRC at 25 °C and pH 8.0. Toxicity assays showed that HSRC exerted sustaining oxidative stress on Microcystis aeruginosa. Accumulation of intracellular reactive oxygen species resulted in the disruption of enzymatic systems and inactivation of photosystem. Tracking the variations of cell growth and H2O2 concentration during HSRC treatments, it suggested that the lethal effect on Microcystis aeruginosa was achieved with a super-low H2O2 concentration (<0.3 mg L-1). In addition, cell lysis did not cause a sudden rise in P concentration due to the P immobilization by HSRC. Therefore, HSRC successfully offsets the drawbacks of liquid H2O2 in mitigating cyanobacterial blooms. It may be a novel and promising algicide that not only kills cyanobacteria but also reduces eutrophication momentarily.

Diazotrophs for Lowering Nitrogen Pollution Crises: Looking Deep Into the Roots.

During and after the green revolution in the last century, agrochemicals especially nitrogen (N) were extensively used. However, it resulted in a remarkable increase in crop yield but drastically reduced soil fertility; increased the production cost, food prices, and carbon footprints; and depleted the fossil reserves with huge penalties to the environment and ecological sustainability. The groundwater, rivers, and oceans are loaded with N excess which is an environmental catastrophe. Nitrogen emissions (e.g., ammonia, nitrogen oxide, nitrous oxide) play an important role in global climate change and contribute to particulate matter and acid rain causing respiratory problems, cancers, and damage to forests and buildings. Therefore, the nitrogen-polluted planet Earth needs concerted global efforts to avoid the disaster. Improved agricultural N management focuses on the synchronization of crop N demand and N supply along with improving the N-use efficiency of the crops. However, there is very little focus on the natural sources of N available for plants in the form of diazotrophic bacteria present inside or on the root surface and the rhizosphere. These diazotrophs are the mini-nitrogen factories that convert available (78%) atmospheric N2 to ammonia through a process known as "biological nitrogen fixation" which is then taken up by the plants for its metabolic functioning. Diazotrophs also stimulate root architecture by producing plant hormones and hence improve the plant's overall ability to uptake nutrients and water. In recent years, nanotechnology has revolutionized the whole agri-industry by introducing nano-fertilizers and coated/slow-releasing fertilizers. With this in mind, we tried to explore the following questions: To what extent can the crop N requirements be met by diazotroph inoculation? Can N input to agriculture be managed in a way leading to environmental benefits and farmers saving money? Can nanotechnology help in technological advancement of diazotroph application? The review suggests that an integrated technology based on slow-releasing nano-fertilizer combined with diazotrophs should be adopted to decrease nitrogen inputs to the agricultural system. This integrated technology would minimize N pollution and N losses to much extent.

Effects of Rice Husk Biochar Coated Urea and Anaerobically Digested Rice Straw Compost on the Soil Fertility, and Cyclic Effect of Phosphorus.

Fertilizer application in rice farming is an essential requirement. Most of the high-yielding varieties which are extensively grown throughout the country require recommended levels of fertilizers to obtain their potential yields. However, effective, and efficient ways of fertilizer application are of utmost importance. Coated fertilizers are used to reduce leaching nutrients and improve the efficiency of fertilizer. However, conventional coated fertilizers such as Sulphur coated urea and urea super granules are not popular among rice farmers in Sri Lanka owing to the high cost. Mixing urea-coated rice husk biochar causes a slow release of nitrogen fertilizer. This coated fertilizer and rice straw compost reduction the cost of importations of nitrogen-based fertilizers per unit area of cultivation. The study aimed to evaluate the effects of rice husk biochar coated urea and anaerobically digested rice straw compost on the soil fertility, and the cyclic effect of phosphorus. Concerning the pot experiment, rice grain yield was significantly higher in Rice husk biochar coated urea, triple super phosphate (TSP), and muriate of potash (MOP) with anaerobically digested rice straw compost. The lowest yield was observed in the control. The release of phosphate shows a cycle effect which is an important finding. Rice husk biochar coated urea can potentially be used as a slow-releasing nitrogen fertilizer. In addition, the urea coated with biochar is less costly and contributes to mitigating pollution of water bodies by inorganic fertilizers (NPK).

Production, characterization, and evaluation of two types of slow-releasing carbon source tablets for in-situ heterotrophic nitrate denitrification in aquifers.

Slow-releasing carbon source tablets were manufactured for an in-situ biological denitrification system. The average zero-order nitrate degradation rates seen, from highest to lowest, were in microcosms to which lactate, fumarate, propionate, and formate had been added. Fumarate was approximately 80% cheaper than lactate, and consequently was determined to be the most optimal slow-releasing carbon source in tablet form. The slow-releasing precipitating tablet (SRPT) and slow-releasing floating tablet (SRFT) were manufactured with hydroxypropyl methylcellulose (HPMC) as the agent of release control, microcrystalline cellulose pH 101 (MCC 101) as the binder, #8 sand as the precipitation agent, and calcium carbonate and citric acid as floating agents. Fourier transform infrared spectroscopy and powder X-ray diffraction indicated that the crystal arrangement in the SRPTs and SRFTs was maintained and ordered in a manner similar to raw excipients. SRFTs floated in water within 30 min and remained so for 5 d due to the buoyancy of carbon dioxide. The carbon source release rate was proportional to the quantity of HPMC added. The longevities of SRPT with 300 mg of HPMC and SRFT with 400 mg of HPMC were 25.4 d and 37.3 d, respectively. This study observed that SRPT and SRFT were manufactured effectively and are suitable for in-situ slow-releasing biological systems.

Biochar phosphorus fertilizer effects on soil phosphorus availability.

Biochar is a potential material for making slow-releasing phosphorus (P) fertilizers for the sake of increasing soil P use efficiency and mitigating P losses. However, the long-term effects of P-laden biochars on soil P availability remains unconcerned. In this study, a laboratory-scale 70-days soil incubation experiment was conducted to study the effects of original and P-laden biochars on soil P availability and fractions. Two original biochars were derived from maize stalks by pyrolyzing at 350 °C and 600 °C. P was laden on those biochars by immersing biochars in saturated KH2PO4 solution for 24 h. Eight treatments were set for the incubation experiment, which were soil, soil + triple-superphosphate (TSP), soil + 350 °C biochar, soil + 600 °C biochar, soil + TSP + 350 °C biochar, soil + TSP + 600 °C biochar, soil + 350 °C P-laden biochar, and soil + 600 °C P-laden biochar. Results showed that original biochars could decrease soil available P through P adsorption. And there were no significant differences of soil P fractions under the treatments of mineral P fertilizer and P-laden biochars. Whereas, compared to mineral P fertilizer, P-laden biochars, especially 600 °C P-laden biochar, could maintain soil available P in a significantly higher level across the incubation. It was mainly because of the slow-releasing pattern of P laden on biochar and a more homogeneous soil P source distribution under P-laden biochar treatments. These results indicated that P-laden biochar could work as P fertilizer to improve soil P use efficiency.

Biological Effects of Morpholin-4-Ium 4 Methoxyphenyl (Morpholino) Phosphinodithioate and Other Phosphorothioate-Based Hydrogen Sulfide Donors.

Significance: Hydrogen sulfide (H2S) is regarded as the third gasotransmitter along with nitric oxide and carbon monoxide. Extensive studies have demonstrated a variety of biological roles for H2S in neurophysiology, cardiovascular disease, endocrine regulation, and other physiological and pathological processes. Recent Advances: Novel H2S donors have proved useful in understanding the biological functions of H2S, with morpholin-4-ium 4 methoxyphenyl (morpholino) phosphinodithioate (GYY4137) being one of the most common pharmacological tools used. One advantage of GYY4137 over sulfide salts is its ability to release H2S in a slow and sustained manner akin to endogenous H2S production, rather than the delivery of H2S as a single concentrated burst. Critical Issues: Here, we summarize recent progress made in the characterization of the biological activities and pharmacological effects of GYY4137 in a range of in vitro and in vivo systems. Recent developments in the structural modification of GYY4137 to generate new compounds and their biological effects are also discussed. Future Directions: Slow-releasing H2S donor, GYY4137, and other phosphorothioate-based H2S donors are potent tools to study the biological functions of H2S. Despite recent progress, more work needs to be performed on these new compounds to unravel the mechanisms behind H2S release and pace of its discharge, as well as to define the effects of by-products of donors after H2S liberation. This will not only lead to better in-depth understanding of the biological effects of H2S but will also shed light on the future development of a new class of therapeutic agents with potential to treat a wide range of human diseases.

Effects of Paclitaxel-conjugated N-Succinyl-Hydroxyethyl Chitosan Film for Proliferative Cholangitis in Rabbit Biliary Stricture Model.

BACKGROUND: Paclitaxel (PTX) could inhibit the growth of fibroblasts, which occurs in proliferative cholangitis and leads to biliary stricture. However, its use has been limited due to poor bioavailability and local administration for short time. This study designed and synthesized a new PTX-conjugated chitosan film (N-succinyl-hydroxyethyl chitosan containing PTX [PTX-SHEC]) and evaluated its safety and efficiency using in vivo and in vitro experiments. METHODS:: The SHEC conjugated with PTX was confirmed by nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FT-IR) measurements. Drug releases in vitro and in vivo were determined using high-performance liquid chromatography. Cell viability in vitro was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Rabbit biliary stricture model was constructed. All rabbits randomly divided into five groups (n = 8 in each group): the sham-operated rabbits were used as control (Group A), Groups B received laparotomies and suture, Group C received laparotomies and covered SHEC suture without the PTX coating, Group D received laparotomies and covered PTX-SHEC suture, and Group E received laparotomies and 1000 µmol/L PTX administration. Liver function tests and residual dosage of PTX from each group were measured by enzyme-linked immunosorbent assay. Histological data and α-smooth muscle actin (SMA) immunohistochemical staining of common bile duct were examined. RESULTS:: NMR and FT-IR indicated that PTX was successfully introduced, based on the appearance of signals at 7.41-7.99 ppm, 1.50 ppm, and 1.03 ppm, due to the presence of aromatic protons, methylene protons, and methyl protons of PTX, respectively. No bile leak was observed. The PTX-conjugated film could slowly release PTX for 4 weeks (8.89 ± 0.03 µg at day 30). The in vitro cell viability test revealed significantly different levels of toxicity between films with and without PTX (111.7 ± 4.0% vs. 68.1 ± 6.0%, P < 0.001), whereas no statistically significant difference was observed among the three sets of PTX-contained films (67.7 ± 5.4%, 67.2 ± 3.4%, and 59.1 ± 6.0%, P > 0.05). Histological examinations revealed that after 28 days of implantment, Groups D and E (but not Group C) had less granulation tissue and glandular hyperplasia in the site of biliary duct injury than Group B. The pattern was more obvious in Group D than Group E. Less α-SMA-positive cells were found in tissue from Groups D and E. Comparing with Group E, the liver function was improved significantly in Group D, including total bilirubin (2.69 ± 1.03 µmol/L vs. 0.81 ± 0.54 µmol/L, P = 0.014), alanine aminotransferase (87.13 ± 17.51 U/L vs. 42.12 ± 15.76 U/L, P = 0.012), and alkaline phosphatase (60.61 ± 12.31 U/L vs. 40.59 ± 8.78 U/L, P < 0.001). CONCLUSIONS: PTX-SHEC film effectively inhibites the myofibroblast proliferation and extracellular matrix over-deposition during the healing process of biliary reconstruction. This original film might offer a new way for reducing the occurrence of the benign biliary stricture.

Effects of Paclitaxel-conjugated N-Succinyl-Hydroxyethyl Chitosan Film for Proliferative Cholangitis in Rabbit Biliary Stricture Model / 中华医学杂志(英文版)

<p><b>Background</b>Paclitaxel (PTX) could inhibit the growth of fibroblasts, which occurs in proliferative cholangitis and leads to biliary stricture. However, its use has been limited due to poor bioavailability and local administration for short time. This study designed and synthesized a new PTX-conjugated chitosan film (N-succinyl-hydroxyethyl chitosan containing PTX [PTX-SHEC]) and evaluated its safety and efficiency using in vivo and in vitro experiments.</p><p><b>Methods:</b>The SHEC conjugated with PTX was confirmed by nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FT-IR) measurements. Drug releases in vitro and in vivo were determined using high-performance liquid chromatography. Cell viability in vitro was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Rabbit biliary stricture model was constructed. All rabbits randomly divided into five groups (n = 8 in each group): the sham-operated rabbits were used as control (Group A), Groups B received laparotomies and suture, Group C received laparotomies and covered SHEC suture without the PTX coating, Group D received laparotomies and covered PTX-SHEC suture, and Group E received laparotomies and 1000 μmol/L PTX administration. Liver function tests and residual dosage of PTX from each group were measured by enzyme-linked immunosorbent assay. Histological data and α-smooth muscle actin (SMA) immunohistochemical staining of common bile duct were examined.</p><p><b>Results:</b>NMR and FT-IR indicated that PTX was successfully introduced, based on the appearance of signals at 7.41-7.99 ppm, 1.50 ppm, and 1.03 ppm, due to the presence of aromatic protons, methylene protons, and methyl protons of PTX, respectively. No bile leak was observed. The PTX-conjugated film could slowly release PTX for 4 weeks (8.89 ± 0.03 μg at day 30). The in vitro cell viability test revealed significantly different levels of toxicity between films with and without PTX (111.7 ± 4.0% vs. 68.1 ± 6.0%, P < 0.001), whereas no statistically significant difference was observed among the three sets of PTX-contained films (67.7 ± 5.4%, 67.2 ± 3.4%, and 59.1 ± 6.0%, P > 0.05). Histological examinations revealed that after 28 days of implantment, Groups D and E (but not Group C) had less granulation tissue and glandular hyperplasia in the site of biliary duct injury than Group B. The pattern was more obvious in Group D than Group E. Less α-SMA-positive cells were found in tissue from Groups D and E. Comparing with Group E, the liver function was improved significantly in Group D, including total bilirubin (2.69 ± 1.03 μmol/L vs. 0.81 ± 0.54 μmol/L, P = 0.014), alanine aminotransferase (87.13 ± 17.51 U/L vs. 42.12 ± 15.76 U/L, P = 0.012), and alkaline phosphatase (60.61 ± 12.31 U/L vs. 40.59 ± 8.78 U/L, P < 0.001).</p><p><b>Conclusions</b>PTX-SHEC film effectively inhibites the myofibroblast proliferation and extracellular matrix over-deposition during the healing process of biliary reconstruction. This original film might offer a new way for reducing the occurrence of the benign biliary stricture.</p>

A novel slow-releasing hydrogen sulfide donor, FW1256, exerts anti-inflammatory effects in mouse macrophages and in vivo.

Exogenous hydrogen sulfide (H2S) is known to exert anti-inflammatory effects both in macrophages and in animal models. In this study, we first showed that NaHS caused a concentration dependent reduction in TNFα and IL-6 secretion in LPS-stimulated RAW264.7 macrophages in the absence of cell death. Thereafter, we screened a series of novel slow H2S donors for similar activity. One such compound, FW1256, concentration dependently decreased TNFα, IL-6, PGE2 and NO generation in LPS-stimulated RAW264.7 macrophages and BMDMs. FW1256 also significantly reduced IL-1ß, COX-2 and iNOS mRNA and protein in LPS-stimulated RAW264.7 macrophages. Mechanistically, FW1256 decreased NFκB activation as evidenced by reduced cytosolic phospho-IκBα levels and reduced nuclear p65 levels in LPS-stimulated RAW264.7 macrophages treated with FW1256. Using a H2S fluorescent probe in FW1256-treated RAW264.7 macrophages, H2S release from FW1256 was apparent over a period of 24h in these cells. Moreover, the effect of FW1256 on TNFα and IL-6 by FW1256 in LPS-stimulated RAW264.7 macrophages was reversed by treatment with the H2S scavenger, vitamin B12a. FW1256 had no cytotoxic effect on LPS-stimulated RAW264.7 macrophages or BMDMs. In vivo, FW1256 administration also reduced IL-1ß, TNFα, nitrate/nitrite and PGE2 levels in LPS-treated mice. We show here a novel slow H2S-releasing compound that exerts anti-inflammatory effects in macrophages and in vivo. FW1256 may be a useful tool to study the biological effects of exogenous H2S and could also have future therapeutic value in inflammatory conditions.

Slow-releasing rapamycin-coated bionic peripheral nerve scaffold promotes the regeneration of rat sciatic nerve after injury.

AIMS: To investigate the effect of locally slow-released rapamycin (RAPA) from the bionic peripheral nerve scaffold on rat sciatic nerve regeneration in the early phase of nerve injury. MAIN METHODS: Slow-releasing RAPA-polyhydroxy alcohol (PLGA) microspheres were prepared and tested for microsphere diameter and slow-release effect in vitro after loading onto nerve scaffold. A total of 48 male SD rats were randomly divided into control group and 3 experimental groups as follows: group 1: RAPA-PLGA scaffold; group 2: RAPA scaffold; and group 3: scaffold alone. In the control group, a 15mm sciatic nerve was excised and religated reversely. In the experimental groups, the scaffolds were used to bridge a defect of 15mm sciatic nerve. The outcome of nerve regeneration was evaluated using neurophysiological and neuromuscular morphological techniques. KEY FINDINGS: The RAPA-PLGA microspheres displayed a smooth exterior. The slow-release of RAPA in group 1 lasted for 14days. The sciatic nerve function index (SFI) and electrophysiological and morphological features were examined 12weeks after the surgery in all groups to reveal various degrees of ipsilateral sciatic nerve regeneration. The SFI values at 12weeks showed no significant difference between the RAPA-PLGA scaffold and control groups; morphological observations revealed that the outcomes of nerve regeneration in the above 2 groups were similar and significantly better than those in the RAPA scaffold and scaffold alone groups. SIGNIFICANCE: RAPA-PLGA microsphere-loaded bionic peripheral nerve scaffold gradually released RAPA locally in the early phase of sciatic nerve regeneration, reduced the secondary nerve injury, and evidently promoted the regeneration of peripheral nerve.

A slow-releasing form of prostacyclin agonist (ONO1301SR) enhances endogenous secretion of multiple cardiotherapeutic cytokines and improves cardiac function in a rapid-pacing-induced model of canine heart failure.

OBJECTIVES: Cardiac functional deterioration in dilated cardiomyopathy (DCM) is known to be reversed by intramyocardial up-regulation of multiple cardioprotective factors, whereas a prostacyclin analog, ONO1301, has been shown to paracrinally activate interstitial cells to release a variety of protective factors. We here hypothesized that intramyocardial delivery of a slow-releasing form of ONO1301 (ONO1301SR) might activate regional myocardium to up-regulate cardiotherapeutic factors, leading to regional and global functional recovery in DCM. METHODS AND RESULTS: ONO1301 elevated messenger RNA and protein level of hepatocyte growth factor, vascular endothelial growth factor, and stromal-derived factor-1 of normal human dermal fibroblasts in a dose-dependent manner in vitro. Intramyocardial delivery of ONO1301SR, which is ONO1301 mixed with polylactic and glycolic acid polymer (PLGA), but not that of PLGA only, yielded significant global functional recovery in a canine rapid pacing-induced DCM model, assessed by echocardiography and cardiac catheterization (n = 5 each). Importantly, speckle-tracking echocardiography unveiled significant regional functional recovery in the ONO1301-delivered territory, consistent to significantly increased vascular density, reduced interstitial collagen accumulation, attenuated myocyte hypertrophy, and reversed mitochondrial structure in the corresponding area. CONCLUSIONS: Intramyocardial delivery of ONO1301SR, which is a PLGA-coated slow-releasing form of ONO1301, up-regulated multiple cardiotherapeutic factors in the injected territory, leading to region-specific reverse left ventricular remodeling and consequently a global functional recovery in a rapid-pacing-induced canine DCM model, warranting a further preclinical study to optimize this novel drug-delivery system to treat DCM.

The effects of 5-fluorouracil on flexor tendon healing by using a biodegradable gelatin, slow releasing system: experimental study in a hen model.

This study investigated the effects of 5-fluorouracil in a slow-release biodegradable gelatin system on tendon healing. Gelatin blocks prepared in a size of 10 × 20 × 1 mm were loaded with 10, 20, and 30 mg of 5-fluorouracil, and 30 adult white Leghorn chickens were used. The tendons to the third and fourth toes were severed and repaired. The extremities were casted for three weeks. After sacrifice, the tendons were examined histologically and biomechanically for adhesion formation. The 10 mg-loaded gelatin group showed a decrease in adhesion formation when compared with the operative control group; the 20 and 30 mg groups showed signs of severe inflammation. Low doses of 5-fluorouracil applied via a slow-release gelatin system reduced adhesion formation in flexor tendon healing.

An in vitro study of fluoride release rate of F-containing thermoplastic resina / 实用口腔医学杂志

Objective:To observe the fluoride release rate of F-containing thermoplastic resina,trying to find a suitable concentration of fluoride in thermoplastic resina to prevent caries in base teeth of partial denture restorations.Methods:Na2(PO3)F-containing thermoplastic resina,respectively 0,10%,15%,20% and 25%(w/w)in concentration were cut into three 1 g blocks and immersed in 100,200 and 500 ml deionized water.These composite resins in 100 ml and 200 ml solutions were replaced every 1,2,3,6,9,16 days(every 7 days after that)until two months later,500 ml solution was reserved after 3,6,9 days every 7 days later until two months,2 ml of which were reserved every time.The fluoride release rates of these thermoplastic resina were tested by potentiometry.Results:All thermoplastic resina containing different concentrations of fluoride could release F-during the period of 65 days.Conclusion:When Na2(PO3)F is mixed in thermoplastic resina,it releases fluoride slowly.Thermoplastic resina containing 15% F-has higher release rates of fluoride.