Thermo-sensitive polymer nanospheres as a smart plugging agent for shale gas drilling operations

Emulsifier-free poly（methyl methacrylate-styrene） [P（MMA-St）] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcoholwater medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive mono- mer N-isopropylacrylamide （NIPAm） and hydrophilic monomer acrylic acid （AA） onto the surface of P（MMA- St） nanospheres at 80 ℃, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures （LCST）, were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD- SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability

Characterizations and identification of the candidate gene of rice thermo-sensitive genic male sterile gene tms5 by mapping

Previous study indicated that the thermo-sensitive genic malesterile(TGMS) gene in rice was regulated by temperature.TGMS rice plays an important role in hybrid rice production,because the application of the TGMS system in two-line breeding is laborsaving,timesaving,simple,inexpensive,efficient,and eliminating the limitations of the cytoplasmic male sterility(CMS) system.'AnnongS' is the first discovered and deeply studied TGMS rice lines in China.'AnnongS-1' and 'Y58S',two derivatives of TGMS line AnnongS,were both controlled by a single recessive gene named tms5,which was genetically mapped on chromosome 2.In this study,three populations('AnnongS-1' × 'Nanjing11','Y58S' × 'Q611',and 'Y58S' × 'Guanghui122') were developed and used for the molecular fine mapping of the tms5 gene.By analyzing recombination events in the sterile individuals using a total of 125 probes covering the tms5 region,the tms5 gene was physically mapped to a 19-kb DNA fragment between two markers 4039-1 and 4039-2,which were located on the BAC clone AP004039.After the construction of the physical map between two markers 4039-1 and 4039-2,a member(ONAC023) of the NAC(NAM-ATAF-CUC-related) gene family was identified as the candidate gene of the tms5 gene.

Molecular Markers and Candidate Genes for Thermo-Sensitive Genic Male Sterile in Rice

The discovery of thermo-sensitive genic male sterility(TGMS) has led to development of a simple and highly efficient two-line breeding system. In this study, genetic analysis was conducted using three F_2 populations derived from crosses between IR68301 S, an indica TGMS rice line, and IR14632(tropical japonica), Supanburi 91062(indica) and IR67966-188-2-2-1(tropical japonica), respectively.Approximately 1:3 ratio between sterile and normal pollen of F_2 plants from the three populations revealed that TGMS is controlled by a single recessive gene. Bulked segregant analysis using simple sequence repeat(SSR) and insertion-deletion(InDel) markers were used to identify markers linked to the tms gene. The linkage analysis based on the three populations indicated that the tms locus was located on chromosome 2 covering the same area. Using IR68301S × IR14632 F_2 population, the results showed that the tms locus was located between SSR marker RM12676 and InDel marker 2gAP0050058. The genetic distance from the tms gene to these two flanking markers were 1.10 and 0.82 cM, respectively.InDel marker 2gAP004045 located between these two markers showed complete co-segregation with the TGMS phenotype. In addition, InDel marker vf0206114052 showed 2.94 cM linked to the tms gene using F_2 populations of IR68301S × Supanburi 91062. These markers are useful tool for developing new TGMS lines by marker-assisted selection. There were ten genes located between the two flanking markers RM12676 and 2gAP0050058. Using quantitative real-time PCR for expression analysis, 7 of the 10 genes showed expression in panicles, and response to temperatures. These genes could be the candidate gene controlling TGMS in IR68301S.

Plant Temperature and Its Simulation Model of Thermo-Sensitive Genic Male Sterile Rice

Plant temperature （Tp） and its relations to the microclimate of rice colony and irrigation water were studied using a thermo-sensitive genic male sterile （TGMS） rice line, Pei＇ai 64S. Significant differences in the daily change of temperature were detected between Tp and air temperature at the height of 150 cm （TA）. From 8：00 to 20：00, Tp was lower than TA, but they were similar during 21：00 to next 7：00. The maximum Tp occurred one hour earlier than the maximum TA, though they both reached the minimum at 6：00. Tp fluctuated less than TA. At the same height, during 6：00-13：00, Tp was higher than air temperature （Ta）, and Tp reached the maximum one hour earlier than Ta. During the rest time on sunny day, Tp was close to or even a little lower than Ta. On overcast day, Tp was higher than Ta in the whole day, and both maximized at the same time. In addition, Tp was regulated by solar radiation, cloudage and wind speed in daytime, and by irrigation water at night. The present study indicated that a TA of 29.6℃ was the critical point, at which Tp was increased or decreased by irrigation water. Tp and the difference between water and air temperatures showed a conic relation. Tp fluctuation was also regulated by the absorption or reflection of solar radiation by leaves during daytime and release of heat energy during nighttime. By analysis on correlation and regression simulation, two models of Tp were established.

Mechanism of Sterility and Breeding Strategies for Photoperiod/Thermo-Sensitive Genic Male Sterile Rice

To understand the male sterility mechanism of photoperiod/thermo-sensitive genic male sterile [P（T）GMS] lines in rice, the research progress on genetics of photoperiod and/or temperature sensitive genic male sterility in rice was reviewed. A new idea was proposed to explain the sterility mechanism of P（T）GMS rice. The fertility transition from sterile to fertile is the result of cooperative regulation of major-effect sterile genes with photoperiod and/or temperature sensitive genes, but not the so-called pgms gene in P（T）GMS rice. The minor-effect genes, which exhibit accumulative effect on sterility, are the important factors for the critical temperature of sterility transition. The more minor-effect genes the sterile line holds, the lower the critical temperature of sterility transition is. The critical temperature of sterility transition will be invariable if all the minor-effect genes are homozygous. The strategies for breeding P（T）GMS rice were also proposed. The selective indices of critical photoperiod and temperature for sterility transition should be set according to varietal type and ecological region. Imposing selection pressure is a key technology for breeding P（T）GMS rice with lower critical temperature for sterility, and improving the comprehensive performance of the whole traits and combining ability is vital for breeding P（T）GMS rice lines.

Characterization and fine mapping of RTMS10, a semi-dominant reverse thermo-sensitive genic male sterile locus in rice

The discovery and application of environment-sensitive genic male sterile(EGMS) rice germplasm provide an easy method for hybrid rice breeding and have made great contributions to hybrid rice production. Typically, the photoperiod-and thermosensitive GMS(P/TGMS) lines utilized in two-line hybrid systems are male sterile under long day or/and high temperature but fertile under short day or/and low temperature conditions. However, Yannong S(Yn S), a reverse TGMS(rTGMS) line, is sterile under low temperature(<29℃) and fertile under high temperature(>29.5℃). Here, we report a genetic study on the rTGMS trait in Yn S. Interestingly, the F1 plants of the cross between Yn S and a cultivar, L422, were male sterile at 22℃ and completely fertile at 27℃. Moreover, the segregation ratio of fertile and sterile individuals in Yn S/L422 F2 populations changed from 1:3.05 to 2.95:1 when the ambient temperature increased, showing that the rTGMS trait exhibits semidominance in Yn S. We further found a locus on chromosome 10, termed RTMS10, which controls the rTGMS trait in Yn S. We then finely mapped RTMS10 to a ~68 kb interval between markers ID13116 and ID1318 by Yn S/L422 BC6 F2 populations. A near iso-genic line(NIL) NL1 from the BC6 F3 generation was developed and the pollen of NL1 became abnormal from the meiosis stage under low temperature. In summary, we identified an rTGMS locus, RTMS10, and provided co-segregated markers, which could help to accelerate molecular breeding of rTGMS lines and better understand the rTGMS trait in rice.

Marker-Assisted Breeding of Thermo-Sensitive Genic Male Sterile Line 1892S for Disease Resistance and Submergence Tolerance

Rice line 1892S is an elite thermo-sensitive genic male sterile(TGMS)line for two-line hybrid rice production.However,1892S is susceptible to rice blast,bacterial blight and submergence.Here we reported the introduction of blast resistance(R)gene Pi9,bacterial blight R gene Xa21 and submergence tolerance gene Sub1A into 1892S genetic background through backcrossing and marker-assisted selection.The improved TGMS line 31892S and its hybrids conferred disease resistance to rice blast and bacterial blight,and showed submergence tolerance for over 14 d without significant loss of viability.The sterility-fertility conversion of 31892S was similar to that of 1892S.31892S and its derived hybrid rice had similar agronomic traits and grain quality with 1892S and the control hybrid rice,respectively.The newly developed 31892S provided an improved TGMS line for two-line hybrid rice production with disease resistance to rice blast and bacterial blight,and submergence tolerance with no yield penalty or change in grain quality.

Improving Blast Resistance of a Thermo-Sensitive Genic Male Sterile Rice Line GD-8S by Molecular Marker-Assisted Selection

The broad-spectrum blast resistance gene Pi-1, from donor line BL122, was introduced into a thermo-sensitive genic male sterile rice line GD-8S, which possessed good grain quality but high susceptibility to rice blast, by using backcross breeding and molecular marker-assisted selection. Five elite improved male sterile lines, RGD8S-1, RGD8S-2, RGD8S-3, RGD8S-4 and RGD8S-5, were selected based on the results of molecular marker analysis, spikelet sterility, recovery rate of genetic background and agronomic traits. Thirty-three representative blast isolates collected from Guangdong Province, China were used to inoculate the improved lines and the original line GD-8S artificially. The resistance frequencies of the improved lines ranged from 76.47% to 100%, much higher than that of the original line GD-8S （9.09%）. On the agronomic characters, there were no significant differences between the improved lines and GD-8S except for flag leaf length and panicle number per plant. The improved lines could be used for breeding hybrid rice with high blast resistance.

A bull-heading water control technique of thermo-sensitive temporary plugging agent

Aimed at the disadvantages of secondary damage to oil layers caused by the conventional bull-heading water control technique, a thermo-sensitive temporary plugging agent for water control was synthesized by water solution polymerization and applied in the field with a new secondary temporary plugging technique. The optimization and performance evaluation of thermo-sensitive temporary plugging agent were carried out through laboratory experiments. The optimized formula is as follows:(6%-8%) acrylamide +(0.08%-0.12%) ammonium persulfate +(1.5%-2.0%) sepiolite +(0.5%-0.8%) polyethylene glycol diacrylate. The thermo-sensitive temporary plugging agent is suitable for formation temperatures of 70-90 ?C, it has high temporary plugging strength(5-40 k Pa), controllable degradation time(1-15 d), the apparent viscosity after degradation of less than 100 m Pa?S and the permeability recovery value of simulated cores of more than 95%. Based on the research results, secondary temporary plugging technique was used in a horizontal well in the Jidong Oilfield. After treatment, the well saw a drop of water cut to 27%, and now it has a water cut of 67%, its daily increased oil production was 4.8 t, and the cumulative oil increment was 750 t, demonstrating that the technique worked well in controlling water production and increasing oil production.

Introgression of Gene for Non-Pollen Type Thermo-Sensitive Genic Male Sterility to Thai Rice Cultivars

For the two-line hybrid rice system, pol en sterility is regulated by recessive gene that responds to temperature. The recessive gene controlling thermo-sensitive genetic male sterility （TGMS） is expressed when the plants are grown in conditions with higher or lower critical temperatures. To transfer tgms gene（s） control ing TGMS to Thai rice cultivars by backcross breeding method, a male sterile line was used as a donor parent while Thai rice cultivars ChaiNat 1, PathumThani 1, and SuphanBuri 1 were used as recurrent parents. The BC2F2 lines were developed from backcrossing and selfing. Moreover, the simple sequence repeat （SSR） markers were developed for identifying tgms gene and the linked marker was used for assisting selection in backcrossing. The identification lines were confirmed by pol en observation. The results showed the success of introgression of the tgms gene into Thai rice cultivars. These lines will be tested for combining ability and used as female parent in hybrid rice production in Thailand.

Inheritance of the Male Sterility in a New Photo/Thermo-Sensitive Genie Male Sterile Line B06S of Rice

The major male sterile genes in a new photo/thermo-sensitive genie male sterile (PTGMS) line B06S of rice were analyzed by the manipulation of mixture distribution theory. The results indicated that a pair of major male sterile nuclear genes with large effects were responsible for controlling the male sterility of B06S.

Elongation of the Uppermost Internode for Changxuan 3S,a Thermo-Sensitive Genic Male Sterile Rice Line

Changxuan 3S, a thermo-sensitive genic male sterile （TGMS） rice line with eui gene, is derived from the TGMS rice line Pei＇ai 64S by irradiation with 350 Gy of ^60Co γ-ray. To elucidate the uppermost internode elongation of the TGMS line with eui gene, Changxuan 3S and its parent Pei＇ai 64S were used to study the effects of temperature on panicle exsertion. At 24℃, the uppermost internode of Changxuan 3S elongated the fastest from the 4^th day before flowering to 0 day （flowering）, being 2.1-fold as that of Pei＇ai 64S, whereas it elongated slowly during the 12^th day to the 4^th day before flowering and the 1^st to the 3^rd day after flowering. The uppermost internode of Changxuan 3S exserted from the flag leaf sheath at 22℃, 24℃ and 26℃, and the length of elongated uppermost internode increased with the decreasing temperatures. At 28℃, though the panicles of Changxuan 3S were still enclosed in the leaf sheath, the degree of panicle enclosure was significantly lower compared with Pei＇ai 64S. Cytological studies on Changxuan 3S showed that the uppermost internode elongation was attributed to the increase of cell number and cell elongation, and the latter was more significant. Moreover, the numbers of outermost and innermost parenchyma cells and the cell length of the uppermost internode reduced with the increasing temperatures.

Genetic Analysis and Mapping of a Thermo-sensitive White Stripe-Leaf Mutant at Seedling Stage in Rice(Oryza sativa)

A thermo-sensitive white stripe-leaf mutant （tws） was selected from the M2 progeny of a japonica variety, Jiahua 1, treated by ^60 Co γ-radiation. In comparison with the wild type parent, the mutant displayed a phenotype of white stripe on the 3rd and 4th leaves, but began to turn normal green on the 5th leaf when grown at low temperatures （20℃ and 24℃）. Furthermore, the content of total chlorophyll showed an obvious decrease in the leaves with white stripe. These results suggest that the expression of the mutant trait was thermo-sensitive and correlated with the leaf age of seedlings. The genetic analysis indicated that the mutant trait was controlled by a single recessive nuclear gene, designated as tws. In addition, by using SSR markers and an F2 segregating population derived from the cross between the tws mutant and 9311, tws was mapped between the markers MM3907 and MM3928 with a physical distance of 86 kb on dce chromosome 4.

Simple and versatile in situ thermo-sensitive hydrogel for rectal administration of SZ-A to alleviate inflammation and repair mucosal barrier in ulcerative colitis

Ulcerative colitis(UC)is a chronic inflammatory bowel disease characterized by persistent inflammation of the colon and disrupted intestinal function.Ramulus mori(Sangzhi)alkaloids(SZ-A),derived from twigs of mulberry,were approved by the National Medical Products Administration in 2020 for treating type 2 diabetes mellitus.Accumulated evidence has confirmed that SZ-A also alleviates non-alcoholic fatty liver disease and ameliorates inflammation,indicating its potential to address inflammation in UC.However,the treatment of UC faces challenges due to low drug delivery efficiency and short retention time.To overcome these challenges,an injectable and adherent in-situ thermo-sensitive hydrogel containing SZ-A was developed for rectal drug delivery,utilizing the thermo-sensitive polymers Poloxamer 407and 188.The thermo-sensitive hydrogel system was designed with a moderate gelation temperature of 32±0.5℃,a short gelation time of 64 s,a p H range of 7-10,high moisturizing capability exceeding 90%,and moderate mechanical strength of 4-5 s.In a rat model with UC,the in situ thermo-sensitive hydrogel significantly extended the retention time at the colonic site and enabled sustained release after rectal administration.Symptoms of UC were markedly reduced following rectal administration of SZ-A thermosensitive hydrogel.Furthermore,the release of inflammatory factors,such as interleukin-1β(IL-1β),IL-6,IL-18,tumor necrosis factor-α(TNF-α),and transforming growth factor-β1(TGF-β1),significantly decreased in the SZ-A thermo-sensitive hydrogel group.The integrity of the colonic mucosal barrier was significantly enhanced following the application of SZ-A thermo-sensitive hydrogel.In conclusion,rectal administration of SZ-A in situ thermo-sensitive hydrogel effectively alleviated UC symptoms,inhibited the secretion of inflammatory factors,and promoted the repair of the colonic mucosal barrier.This approach holds promise as a potential treatment for UC.

Thermo-sensitive Porous Polymer Membrane-immobilized Cellulose as a Switchable Enzyme Reactor for Tuning Its Enzymolysis via Variation Temperature

Immobilization of enzymes onto porous membranes has attracted considerable attention in recent years.However,enhancing the enzymolysis efficiency of the resulting enzyme reactors by varying the environmental conditions poses a great challenge.In this work,poly(styrene-maleic anhydride-N,N-dimethylacrylamide)was prepared and utilized to construct a thermo-sensitive porous polymer membrane-based enzyme reactor(TS-PPMER)after cellulase was immobilized onto the support by covalent bonding.The catalytic activity of the nano-reactor was evaluated by measuring the yield of the product,glucose,at different temperatures with carboxymethylcellulose as the substrate.Interestingly,the polymer chains coiled and formed numerous nano-pores at a high temperature,which induced the confine effect and greatly boosted the enzymolysis efficiency of TS-PPMER.Furthermore,the proposed TS-PPMER was applied in the hydrolysis of green plant leaves in Epipremnum aureum.This work shows great potential in obtaining biological resources by an environmentally friendly approach using smart polymer-based nano-reactors.

Sustained co-delivery of 5-fluorouracil and cis-platinum via biodegradable thermo-sensitive hydrogel for intraoperative synergistic combination chemotherapy of gastric cancer

Gastric cancer is the fifth most common cancer and the third leading cause of cancer death worldwide,posing a severe threat to human health.Surgical resection remains the most preferred option for gastric cancer treatment.However,for advanced gastric cancer,the curative effect of surgical resection is usually limited by the local recurrence,peritoneal carcinomatosis,or distal metastasis.Intraoperative chemotherapy is an attractive in situ adjuvant treatment strategy to reduce the recurrence and metastasis after surgical resection.Here,we designed a 5-fluorouracil(5-FU)and cis-platinum(DDP)co-delivery system based on a biodegradable temperature-sensitive hydrogel(PDLLA-PEG-PDLLA,PLEL)for intraoperative adjuvant combination chemotherapy of gastric cancer.This 5-FU+DDP/PLEL hydrogel system characterized by a special sol-gel phase transition in response to physiological temperature and presented sustained drug release in vitro and in vivo.A strong synergistic cell proliferation inhibition and apoptosis promotion of 5-FU+DDP/PLEL were observed against gastric cancer MKN45-luc cells.After intraperitoneal injection,the dual-drug loaded hydrogel formulation showed superior anti-tumor effects than the single-drug carrying hydrogels and combination of free 5-FU and DDP on the gastric cancer peritoneal carcinomatosis model.The use of hydrogel for dual-drug delivery had benefited to fewer side effects as well.What’s more,we established a mouse model for postsurgical residual tumors and peritoneal carcinomatosis of gastric cancer,in which the intraoperative administration of 5-FU+DDP/PLEL also remarkably inhibited the local recurrence of the orthotopic tumors and the growth of the abdominal metastatic tumors,resulting in an extended lifetime.Hence,this developed dual-drug loaded hydrogel system has great potential in the intraoperative chemotherapy of gastric cancer,that suggests a clinically-relevant and valuable option for postsurgical management of gastric cancer.

Sustained co-delivery of gemcitabine and cis-platinum via biodegradable thermo-sensitive hydrogel for synergistic combination therapy of pancreatic cancer

Pancreatic cancer is one of the most devastating cancers with poor prognosis and no significant change in the survival rate over the past decades.Localized targeted drug delivery through interventional endoscopic ultrasonography-guided fine-needle injection (EUS-FNI) is an attractive and minimally invasive strategy for inoperable pancreatic cancer.An injectable in-situ formed long-lasting drug delivery system is a promising alternative for the localized treatment of pancreatic cancer via EUS-FNI.Here,a biodegradable thermo-sensitive copolymer hydrogel for the co-delivery of anticancer agents gemcitabine (GEM) and cis-platinum (DDP) was developed.This hydrogel is a free flowable liquid at room temperature that changes into a semi-solid hydrogel following injection in response to the physiological temperature.Both in vitro and in vivo drug release behaviors indicate sustained drug release of this delivery system.Synergistic cellular proliferation inhibition and desirable apoptosis promotion have been found when pancreatic cancer Bxpc-3 cells were co-cultured with this GEM-DDP/hydrogel system.After a single intratumoral injection,the dual-drug loaded hydrogel formulation exhibited superior anti-tumor efficacy and minimized systemic side effect on pancreatic cancer xenograft mouse model in comparison to the intravenously injected free GEM and DDP combination.In addition,a strong synergistic therapeutic effect of the GEM-DDP/hydrogel system against pancreatic cancer has been found in vitro and in vivo compared to the single-drug loaded hydrogel composites.The obtained findings suggest this developed thermo-sensitive copolymer hydrogel system as a potential universal carrier for the localized targeted delivery of multi-drugs,for use in a variety of inoperable solid tumors.

Construction and characterization of a bacterial artificial chromosome library of thermo-sensitive genic male-sterile rice 5460S

In order to develop a detailed physical map of the thermo-sensitive genie male-sterile (TGMS) gene-encompassing region and finally clone the TGMS gene, a high-quality rice bacterial artificial chromosome (BAC) library from TGMS rice 5460S was constructed. The method of constructing BAC library was examined and optimized. The 5460S library consists of 19 584 BAC clones with an average insert size of 110 kb, which represents about 5 times rice haploid genome equivalents. Rice inserts of up to 140 kb and 250 kb were isolated and appeared stable after 100 generations of serial growth. Hybridization of BAC clones with mitochondrial and chloroplastic genes as probes demonstrated that this library has no organellar contamination. The 5460S library was screened with 3 molecular markers linked to tmsl gene as probes and at least 1 BAC clone was identified with each probe. The insert ends of positive clones were successfully isolated using thermal asymmetric interlaced PCR (TAIL-PCR) technique.

Thermo-sensitive Microgels Supported Gold Nanoparticles as Temperature-mediated Catalyst

Microgels with a thermo-sensitive poly(N-isopropylacrylamide)(polyNIPAm) backbone and bis-imidazolium(VIM) ionic cross-links, denoted as poly(NIPAm-co-VIM), were successfully prepared. The as-synthesized ionic microgels were converted to nanoreactors, denoted as Au@PNI MGs, upon generation and immobilization of gold nanoparticles(Au NPs) of 5–8 nm in size into poly(NIPAm-co-VIM). The content of Au NPs in microgels could be regulated by controlling the 1,6-dibromohexane/vinylimidazole molar ratio in the quaternization reaction. The microgel-based nanoreactors were morphologically spherical and uniform in size, and presented reversible thermo-sensitive behavior with volume phase transition temperatures(VPTTs) at 39–40 °C. The Au@PNI MGs were used for the reduction of 4-nitrophenol, of which the catalytic activity could be modulated by temperature.

Controlled release behaviors of chitosan/α,β- glycerophosphate thermo-sensitive hydrogels

Chitosan/α,β-glycerophosphate （CS/α,β-GP） thermo-sensitive hydrogels presented flowable solution state at low temperature and semisolid hydrogel when the ambient temperature increased. In this research, different concentrations of metronida- zole encapsulated, CS and α,β-GP, as well as different acid solvents, were chosen to evaluate their influences on the drug release behaviors from CS/α,β-GP hydrogels. It was found that there was a sustaining release during the first 3 h followed by a plateau. SEM images showed that drugs were located both on the surface and in the interior of hydrogels. The optimal preparation conditions of this hydrogel for drug release were as follows： 1.8% （w/v） CS in HAc solvent, 5.6% （w/v） a, 13-GP and 5g/L metronidazole encapsulation. Cytotoxicity evaluation found no toxic effect. In order to control the release rate, 2.5 g/L chitosan microspheres with spherical shape and smooth surface were incorporated, and it was found that the initial release process was alleviated, while drug concentration had no obvious effect on the release rate. It could be concluded that the metronidzole release behaviors could be optimized according to practical applica- tions.