An accelerated method to evaluate thymopentin release from microspheres in vitro

To design an accelerated method to evaluate thymopentin release from PLGA microspheres in vitro. Microspheres were prepared by double emulsion technique, using poly（lactide-co-glycolide） （PLGA） as carrier. At higher medium temperature （45℃, 50℃ and 55℃）, an accelerated release testing in short time was studied and correlated with the conventional release （37℃） in vitro. The release in vitro of thymopentin from PLGA microspheres at 45 ℃, 50℃ and 55℃ was significantly accelerated （P 〈 0.05）. In particular, at 50℃, an accelerated release （30 h） of the hydrophilic peptide from the PLGA matrix was achieved and correlated well with the conventional release （30 d）. An accelerated release testing in vitro at higher temperature could be used to monitor thymopentin release from PLGA microspheres.

Effects of polyamines on the early development of cystocarps,spore release,survival,and germination rate of Gracilariopsis lemaneiformis

Three polyamines(PAs)(spermidine(Spd),spermine(Spm),and putrescine(Put))were used as growth regulators to the marine macroalgae Gracilariopsis lemaneiformis and to female gametophyte and reproductive tissues(cystocarps were constructed),which led to early maturation of cystocarps and spore release.Laboratory cultivation revealed that exogenous PA application accelerated the development of cystocarps,and the mean sporeling growth rate was 20%–50%/d during the initial week of cultivation.The spore count(SC),survival rate(SR),and germination rate(GR)of G.lemaneiformis showed different responses to PA(10-6 mol/L and 10-3 mol/L)treatments under different temperatures(18,26,and 34℃),light intensities(30,60,and 90μmol photons/(m^(2)·s)),salinities(25,30,and 35),and nutrient levels(25꞉2.5,50꞉5.0,and 75꞉7.5μmol/L NH4Cl꞉K2HPO4),and the optimal conditions were 26℃,light intensity of 60μmol/(m^(2)·s),salinity of 35,and nutrient level of 50꞉5.0μmol/L NH4Cl꞉K2HPO4.Under the optimum conditions,the SC per cystocarp increased by 82.38%,and the spore SR and GR increased by 33.07%and 46.44%,respectively.Each experiment lasted for 7 days,with the highest SC on Day 4 and plateauing on Day 7.The results indicate that PAs could promote the early maturation,spore release,survival,and germination of G.lemaneiformis under laboratory conditions.

Effect of nonionic surfactants in release media on accelerated in-vitro release profile of sirolimus eluting stents with biodegradable polymeric coating

It is a well-known fact that sirolimus(SRL) undergoes degradation process via hydrolysis in aqueous media, leading to incorrect assessment of drug amount and thus release characteristics of formulations.The main objective of the present study was to evaluate the effect of nonionic surfactants in media on invitro release profiles for sirolimus eluting stents(SES) coated with biodegradable polymeric matrix.Phosphate buffer and acetate buffer incorporating nonionic surfactants with varying concentrations were examined for adequate solubility and stability(by RP-HPLC). Good sink condition was achieved in phosphate buffer(at pH 4.0) with 1.0% Tween 20, 1.0% Brij 35% and 0.5% Brij 58. Hydrodynamic size(by DLS) and the micelle-water partition coefficient(P) with standard free energy of solubilization(ΔGs°) of drug were evaluated to get some understanding about the solubilization phenomena. About 80% of drug release during the period of 48 h was achieved in optimized drug release media which was 1.0% Tween20 in phosphate buffer pH 4.0. The obtained accelerated SRL release profile in optimized medium correlated well with the real time in-vitro release in phosphate buffer(pH 7.4). Surface morphology changes(by SEM), changes in gravimetric weights and molecular weight change(by GPC) were examined before and after drug release to understand the drug release mechanism which explains that the polymer did not undergo degradation during the drug release.

Preparation, Characterization and in Vitro Release of Ciprofloxacin Polylactic Acid Microspheres

Aim Ciprofloxacin polylactic acid microspheres (CFX-PLA-MS) were preparedusing solvent evaporation method from a solid-in-oil-in-water emulsion system. Methods Orthogonalexperiment was used to optimize the method of CFX-PLA-MS preparation. Microspheres werecharacterized in terms of morphology, size, encapsulation efficiency, drug loading and in vitro drugrelease. Results The physical state of CFX-PLA-MS was determined by scanning electron microscopy(SEM) and differential scanning calorimetry (DSC) . Microspheres formed were spherical with smoothsurfaces. Drug was enveloped in microspheres without mixing physically with PLA. The averageparticle size was 280.80 ± 0.15 μm, with over 90% of microspheres falling in the range of 250 -390 μm. The encapsulation efficiency was 65.8% ± 0.58% and the drug loading was 34.1% ± 0.51% .In vitro release study revealed a profile of sustained release of Ciprofloxacin from CFX-PLA-MS. Theaccumulated release percentage and half-life (T_(1/2) of Ciprofloxacin microspheres were 84.0% in53.2 h, and 31.9 h, respectively. Higuchi equation was Q= -0.0043 + 0.003 9 t^(1/2), r = 0.9941.Conclusion Ciprofloxacin microspheres have been successfully prepared and sustained release of CFXfrom microspheres is achieved.

Preparation and in vitro release studies of thymosin-loaded PLA microspheres

To obtain a kind of convenient oral dosage form of protein, which can be fully absorbed and is efficient and safe, the thymosin-loaded PLA（polylactic acid） microspheres are prepared by the emulsification- solvent evaporation method and the orthogonal design is used to optimize the technology of preparation. The form of the medicament microspheres of thymosin are proved by differential thermal analysis （DTA）. The drug content is determined by the Lowry method, and the package ratio of medicament microspheres of thymosin and drug release in vitro are calculated. The results show that the average diameter and encapsulation efficiency of the product prepared according to the optimized formulation are 13. 8 μm and 80. 7%, respectively. The in vitro release behavior within 12 h can be described by the Higuchi equation with T1/2 = 295 rain. There are no significant changes in size distribution and residual drug contents after being stored at 25℃ and 40 ℃ for 90 d, respectively. Due to the fact that its thymosin content and package ratio meet the requirement, and its releasing half life is long, the thymosin-loaded PLA microsohere has a favorable application future.

Studies on the Isolation, Identification and In Vitro Growth Rates of the Three Pathogenic Fungi from Panax notoginseng Cultivated in Wenshan Eparchy

Objective] The aim of this study was to simultaneously isolate and identify the main pathogenic fungi of the root rot, black spot and round spot from the Panax notoginseng plants cultivated in Wenshan Eparchy of Yunnan Province of China. [Method] The pathogenic fungi were isolated and purified by using potato dextrose agar （PDA） medium. The morphological identification was accomplished first according to the colony forms of the fungi when cultivated in vitro, then accord-ing to the symptom characteristics and colony forms of the re-isolated fungi in the reverse inoculation experiments. The molecular identification was performed accord-ing to the amplification and alignment of the internal transcribed space （ITS） se-quences of the fungi. The increases of the diameters and thickness of the colonies of the fungi cultivated in vitro were employed to indicate the growth rates of the fungi. [Results] The consistency of the colony forms and symptom characteristics and the 96%-99% similarities revealed in the ITS sequence alignments al proved that the main pathogenic fungi of the root rot, black spot and round spot of the P. notoginseng plants raised in Wenshan were Cylindrocarpon didymium, Alternaria panax and Mycocentrospora acerina, respectively. When cultivated in vitro in the same temperature, humidity and il umination, the increases of the colony diameters and thickness of C. didymium were the highest, fol owed by those of A. panax, then those of M. acerina. During different cultivation periods, the differences of the colony diameters and thickness of the three fungi al reached extremely significant level. However, at the same cultivation time, the differences of the diameters and thickness among the three fungi only reached significant level. [Conclusion] The main pathogenic fungi which result in the root rot, black spot and round spot of the P. notoginseng in Wenshan are C. didymium, A. panax and M. acerina, respec-tively. When these three diseases break out at the same time, the root rot wil spread fastest, fol owed orderly by the black spot and the round spot.

Studies on in vitro release of cyclosporine A-loaded microspheres

Aim This study was to prepare cyclosporine A （CyA） microspheres （Ms） using 75：25 poly （D, L-lactide-co-glycolide） polymer （PLGA）, and to evaluate the in vitro release of the CyA microspheres. Methods CyA-Ms were prepared by an oil-inwater （o/w） emulsion solvent extraction/evaporation process and characterized for drug content, particle size, surface morphology, and differential scanning calorimeter （DSC）. Accelerated in vitro release of cyclosporine A from the mieropsheres was studied at various conditions, such as temperatures, surfactants, pH values and organic solvents for a short period. Results CyA-Ms were in spherical shape with average particle size of 50 μm and loading efficiency of 13.0%. The results of DSC measurements suggested that at the dry state, CyA did interact very strongly with the hydrophilic PLGA polymer. In vitro release test in various release medium showed slight increase of CyA-Ms release profiles under various conditions of temperatures, surfactants and pH values. However, dramatical increase of CyA-Ms release was seen in the medium containing 30% isopropanol. Conclusion It was demonstrated that CyA could be incorporated into polymeric Ms prepared from PLGA using a solvent evaporation technique. The release medium containing 30% isopropanol might be the ideal condition for CyA-PLGA microspheres in vitro quality control test.

Microstructure, Content and in vitro Release of Brucine and Strychnine in Strychnos Nux-Vomica Powder with Different Particle Sizes

To explore the effect of particle size on the quality uniformity and in vitro release performance of Strychnos nux-vomica powder, seven samples of Strychnos nux-vomica powder with different particle sizes were prepared.Microstructures and particle sizes were analyzed, and high performance liquid chromatography(HPLC) was used to test the contents and in vitro release performances of brucine and strychnine in the samples. Results showed that the contents and the in vitro release rates of brucine(or strychnine) in different samples were different since there are different proportions of endosperms to epidermal cells in Strychnos nux-vomica powder with different particle sizes. Brucine and strychnine in each sample were promptly released in the first ten minutes and their cumulative release rates were higher than 70% after ten minutes. Eighty minutes later, the cumulative release rate tended to be a constant. Considering the quality uniformity and safety of Strychnos nux-vomica powder used as traditional Chinese medicine, it would be better to control the particle size of Strychnos nux-vomica powder between 100 and 140 mesh in which the maximum cumulative release rate in vitro of brucine and strychnine can be relatively low within this range.

The effect of enzymes on release of trace elements in feedstuffs based on in vitro digestion model for monogastric livestock

Background: This experiment was conducted to study the effect of different feed enzymes(phytase,xylanase,β-glucanase) on release rate of trace elements(Fe,Cu,Mn and Zn) in 6 commonly used feedstuffs(corn,wheat,barley,soybean meal,wheat bran,wheat middlings) by using an in vitro model,simulating the digestive processes in stomach for 2 h and then in small intestine for 6 h at 39 °C.Results: Phytase raised(P < 0.05) the release rate of Cu and Zn in corn,Cu,Zn and Mn in wheat,Cu in barley,Cu,Zn and Mn in soybean meal,Zn,Fe in wheat bran and Zn,Fe,Mn in wheat middlings.The release rate of various trace elements in feedstuffs was increased after xylanase addition.Compared with the control group,the release rate of soluble Cu in corn,wheat,barley and soybean meal,soluble Zn in corn,wheat and wheat middlings and soluble of Mn in corn,wheat,barley and wheat bran increased(P < 0.05) after xylanase treatment.After the treatment of β-glucanase,the release rate of soluble Cu in corn,wheat and wheat bran,soluble Fe in barley,soybean meal and wheat bran and soluble Mn in corn and wheat bran all increased(P < 0.05) compared with the control group.In each feedstuff,after corresponding enzyme treatment,the contents of phytic acid,xylan and β-glucan were significantly lower than those of the control group(P < 0.05).Conclusions: Results showed that bound trace elements in feedstuffs can be released by feed enzymes.It may be necessary to take the trace elements in feedstuffs into account in the actual feed preparation including feed enzymes.

Criterion of local energy release rate of gob instability in deep mines considering unloading stress path

The stress path characteristics of surrounding rock in the formation of gob were analyzed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analyzing the instability of deep gob was established based on the mechanism of stress relief in deep mining.The energy evolution law was analyzed by introducing the local energy release rate index(LERR), and the energy criterion of the instability of surrounding rock was established based on the cusp catastrophe theory. The results show that the evolution equation of the local energy release of the surrounding rock is a quartic function with one unknown and the release rate increases gradually during the mining process.The calculation results show that the gob is stable. The LERR per unit volume of the bottom structure is relatively smaller which means that the stability is better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meets the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release,transfer and dissipation and that provided an important reference for the study of the stability of deep mined out area.

负载藜麦皂苷Pickering乳液的制备、性质表征和体外消化特性

由于藜麦皂苷具有苦味,对人体黏膜有刺激性作用,研究用新型Pickering乳液递送系统包埋藜麦皂苷。制备了不同藜麦皂苷添加量、大豆油含量的多组乳液。通过表征乳液的包埋率、粒径、流变、微观结构、色度和苦味值对乳液性质进行研究,通过模拟体外消化实验测定负载藜麦皂苷Pickering乳液中藜麦皂苷在消化过程中的释放情况和生物利用率。结果表明,藜麦皂苷含量为1%(w/v)、大豆油含量为80%(v/v)的Pickering乳液(1%-80%)具有最高的包埋率、最小的粒径、最致密的微观结构和最稳定的乳液状态,并且可以有效遮盖藜麦皂苷的苦味。1%-80%组负载藜麦皂苷Pickering乳液在消化过程中藜麦皂苷释放较为缓慢,藜麦皂苷释放百分比较高且其生物利用率较高。因此,1%-80%组负载藜麦皂苷Pickering乳液具有良好的性质,可以作为递送系统包埋藜麦皂苷,在食品工业、医药领域上具有广阔的应用前景。

Sustained release donepezil loaded PLGA microspheres for injection:Preparation,in vitro and in vivo study

The purpose of this study was to develop a PLGA microspheres-based donepezil(DP)formulation which was expected to sustain release of DP for one week with high encapsulation efficiency(EE).DP derived from donepezil hydrochloride was encapsulated in PLGA microspheres by the O/W emulsion-solvent evaporation method.The optimized formulation which avoided the crushing of microspheres during the preparation process was characterized in terms of particle size,morphology,drug loading and EE,physical state of DP in the matrix and in vitro and in vivo release behavior.DP microspheres were prepared successfully with average diameter of 30m,drug loading of 15.92±0.31%and EE up to 78.79±2.56%.Scanning electron microscope image showed it has integrated spherical shape with no drug crystal and porous on its surface.Differential scanning calorimetry and X-ray diffraction results suggested DP was in amorphous state or molecularly dispersed in microspheres.The Tg of PLGA was increased with the addition of DP.The release profile in vitro was characterized with slow but continuous release that lasted for about one week and fitted well with first-order model,which suggested the diffusion governing release mechanism.After single-dose administration of DP microspheres via subcutaneous injection in rats,the plasma concentration of DP reached peak concentration at 0.50 d,and then declined gradually,but was still detectable at 15 d.A good correlation between in vitro and in vivo data was obtained.The results suggest the potential use of DP microspheres for treatment of Alzheimer’s disease over long periods.

Fabrication, characterization, in vitro drug release and glucose uptake activity of 14-deoxy,11, 12-didehydroandrographolide loaded polycaprolactone nanoparticles

Biodegradable polymer based novel drug delivery systems brought a considerable attention in enhancing the therapeutic efficacy and bioavailability of various drugs. 14-deoxy 11, 12-didehydro andrographolide(poorly water soluble compound) loaded polycaprolactone(nanoDDA) was synthesized using the solvent evaporation technique. Nano-DDA was characterized by scanning electron microscopy(SEM) and dynamic light scattering(DLS) studies. Fourier Transform InfraRed Spectroscopy(FTIR) was used to investigate the structural interaction between the drug and the polymer. Functional characterization of the formulation was determined using drug content, cellular uptake and in vitro drug release. 2-deoxy-D-[1-~3H] glucose uptake assay was carried out to assess the antidiabetic potential of nano-DDA in L6 myotubes.The nano-DDA displayed spherical shape with a smooth surface(252.898 nm diameter), zeta potential, encapsulation and loading efficiencies of -38.9 mV, 91.98 ± 0.13% and 15.09 ± 0.18% respectively. No structural alteration between the drug and the polymer was evidenced(FTIR analysis). Confocal microscopy studies with rhodamine 123 loaded polycaprolactone nanoparticles(Rh123-PCL NPs) revealed the internalization of Rh123-PCL NPs in a time dependent manner in L6 myoblasts. A dose dependent increase in glucose uptake was observed for nano-DDA with a maximal uptake of 108.54 ± 1.42% at 100 nM on L6 myotubes, thereby proving its anti-diabetic efficacy. A biphasic pattern of in vitro drug release demonstrated an initial burst release at 24 h followed by a sustained release for up to 11 days. To conclude,our results revealed that nano-DDA formulation can be a potent candidate for antidiabetic drug delivery.

Release rate kinetics of corrosion inhibitor loaded halloysite nanotube-based anticorrosion coatings on magnesium alloy AZ91D

Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce^(3+)-Zr^(4+),2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen.An acid assisted etching of the nanotubes was carried out with a view to increase the lumen diameter and thereby,increase the amount of loading of the corrosion inhibitor.The morphology of as-received and etched halloysite nanotubes was ob-served using TEM analysis.The loading of corrosion inhibitors was confirmed using SEM-EDS and BET analysis.Polymeric microcapsules were used as capping agents for the ends of the loaded HNTs following which,they were dispersed into a hybrid sol-gel silica matrix.Dip coating method was used to generate coatings on AZ91D substrates followed by heat treatment at 130℃ for 1 h.The release rate kinetics of corrosion inhibitors from as-received and etched nanotubes was investigated in buffer solutions of 3.5 wt%NaCl at different pH.The release mechanism of corrosion inhibitors from the HNT lumen was validated using various semi-empirical models.Coatings were also evaluated for their corrosion protection ability using electrochemical techniques after exposure to 3.5 wt%NaCl solution for 120 h.Coatings generated using Ce^(3+)-Zr^(4+)loaded into as-received halloysite nanotubes have shown more effective corrosion protection when compared to other corrosion inhibitors after 120 h exposure to the corrosive medium.

Preparation and <i>in Vitro</i>Drug Release Evaluation of Once-Daily Metformin Hydrochloride Sustained-Release Tablets

The objective of this study was to develop once-daily metformin hydrochloride sustained-release tablets (MHSRT) and evaluate their in vitro release behavior. MHSRT were prepared by the film coating method. The in vitro drug release rate of MHSRT and the commercial tablets Fortamet? made in the United States of America in water was fitted with zero order kinetic equation, and Ritger-Peppas kinetic equation in 0.1 M HCl and pH 6.8-phosphate buffer, respectively. The similarity factor f2 values of MHSRT in three different dissolution medium were 82, 80 and 74, respectively in comparison with imported Fortamet?, which were all greater than 50. The results of storage-stability showed that MHSRT were stable for at least 6 months under stress condition (40℃ ± 2℃, RH 75% ± 5%). Therefore, in this study, MHSRT were successfully prepared using optimized formulation technologies that meet mass produce. The in vitro release behavior of MHSRT was almost similar to that of imported Fortamet?.

Kidding after Transfer of in Vitro Produced Saanen Goat Embryos into Local Ukrainian Breed Recipients in Different Seasons

In recent years, the demand for goat products has been growing due to the fact that goat milk has a number of advantages over cow milk, for example, it is low in lactose, and is considered less allergenic and easier to digest. To increase production during both breeding and non-breeding seasons and reduce the price of dairy products, it is necessary to effectively use reproductive management and assisted reproductive technologies. In vitro embryo production makes it possible to obtain a large number of eggs from goats, which for some reason are unable to conceive, but have genetic value. Afterward in vitro produced embryos can be transferred into recipient goats of other less genetically valuable breeds, such as the Ukrainian local breed. Therefore, the aim of the present study was to investigate the effectiveness of transfers of in vitro produced embryos of Saanen goats into surrogate sires of the Ukrainian local breed in different seasons. All manipulations with animals were carried out following ethical standards (Strasbourg, 1986). Six Saanen goats were selected as the oocyte donors. After the hormonal stimulation oocytes were retrieved by laparoscopic ovum pick-up. In vitro produced embryos were transferred laparotomically into 24 recipients of Ukrainian local breed. Fifty days after embryo transfers, pregnancies were determined by ultrasound diagnostics. Although the embryo development rate in the breeding season was 20% higher than in the non-breeding season, there was no difference in pregnancy and kidding rates between seasons. In conclusion, the transfer of in vitro produced Saanen goat embryos to recipients of the Ukrainian local breed gives the opportunity to achieve pregnancy and kidding regardless of the breeding season, which will enable a faster and more efficient increase in the livestock of highly productive goats in Ukraine in the post-war period.

Acoustic emission characteristics and stress release rate of coal samples in different dynamic destruction time

Considering the importance of the prediction of rock burst disasters, and in order to grasp the law of acoustic emission(AE) of coal samples in different dynamic destruction time, the SH-II AE monitoring system was adopted to monitor the failure process of coal samples. The study of the change rule of the AE numbers, energy, ‘b' value and spectrum in the micro crack propagation process of the coal samples shows that as dynamic damage time went by, AE presented high-energy counts and the accumulated counts increased during the compression phase. The AE energy and cumulative counts increased during the elastic stage. The AE blank area increased gradually and the blank lines were more and more obvious in the molding stage. The AE counts and energy showed a trend of decrease in the residual damage phase.AE ‘b' values gradually became sparse, and the large scale cracks percentage compared with micro cracks decreased and the degree of damage decreased. The AE frequency spectrum peak went from the residual damage phase to the molding phase, and finally it was nearly stable, besides the bandwidth of the main frequency is gradually narrowed. Also, the frequency peak changed from single peak frequency to bi-peak frequency and to the single peak frequency. Uniaxial compressive strength is more sensitive than the elastic modulus to dynamic damage time.

The energy release rate for hygrothermal coupling elastic materials

In the fracture problems of hydrophilic elastic materials under coupling effects of heat conduction, moisture diffusion and mechanical deformation, the conventional J-integral is no longer path independent. The value of J is unequal to the energy release rate in hygrothermal coupling cases. In the present paper, we derived a general form of the energy release rate for hygrothermal fracture problems of the hydrophilic elastic materials on the basis of energy balance equation in cracked areas. By introducing the constitutive relations and the essential equations of irreversible thermodynamics, a specific expression of the energy release rate was obtained, and the expression can be reformmulated as path independent integrals, which is equivalent to the energy release rate of the fracture body. The path independence of the integrals is then verified numerically.

Does Lower Dose of Long-acting Triptorelin Maintain Pituitary Suppression and Produce Good Live Birth Rate in Long Down-regulation Protocol for In-vitro Fertilization?

The effects of pituitary suppression with one-third depot of long-acting gonadotropin-releasing hormone（Gn RH） agonist in Gn RH agonist long protocol for in vitro fertilization（IVF）/intracytoplasmic sperm injection（ICSI） were investigated. A retrospective cohort study was performed on 3186 cycles undergoing IVF/ICSI with Gn RH agonist long protocol in a university-affiliated infertility center. The pituitary was suppressed with depot triptorelin of 1.25 mg or 1.875 mg. There was no significant difference in live birth rate between 1.25 mg triptorelin group and 1.875 mg triptorelin group（41.2% vs. 43.7%）. The mean luteinizing hormone（LH） level on follicle-stimulating hormone（FSH） starting day was significantly higher in 1.25 mg triptorelin group. The mean LH level on the day of human chorionic gonadotrophin（h CG） administration was slightly but statistically higher in 1.25 mg triptorelin group. There was no significant difference in the total FSH dose between the two groups. The number of retrieved oocytes was slightly but statistically less in 1.25 mg triptorelin group than in 1.875 mg triptorelin group（12.90±5.82 vs. 13.52±6.97）. There was no significant difference in clinical pregnancy rate between the two groups（50.5% vs. 54.5%）. It was suggested that one-third depot triptorelin can achieve satisfactory pituitary suppression and produce good live birth rates in a long protocol for IVF/ICSI.

Fatigue Crack Propagation Law of Corroded Steel Box Girders in Long Span Bridges

In order to investigate the fatigue performance of orthotropic anisotropic steel bridge decks,this study realizes the simulation of the welding process through elastic-plastic finite element theory,thermal-structural sequential coupling,and the birth-death element method.The simulated welding residual stresses are introduced into the multiscale finite element model of the bridge as the initial stress.Furthermore,the study explores the impact of residual stress on crack propagation in the fatigue-vulnerable components of the corroded steel box girder.The results indicate that fatigue cracks at the weld toe of the top deck,the weld root of the top deck,and the opening of the transverse diaphragm will not propagate under the action of a standard vehicle load.However,the inclusion of residual stress leads to the propagation of these cracks.When considering residual stress,the fatigue crack propagation paths at the weld toe of the transverse diaphragm and the U-rib weld toe align with those observed in actual bridges.In the absence of residual stress,the cracks at the toe of the transverse diaphragm with a 15%mass loss rate are categorized as type I cracks.Conversely,when residual stress is considered,these cracks become I-II composite cracks.Residual stress significantly alters the cumulative energy release rate of the three fracturemodes.Therefore,incorporating the influence of residual stress is essential when assessing the fatigue performance of corroded steel box girders in long-span bridges.