Metal-Graphene Hybrid Terahertz Metasurfaces for Circulating Tumor DNA Detection Based on Dual Signal Amplification.

Terahertz (THz) spectroscopy has impressive capability for label-free biosensing, but its utility in clinical laboratories is rarely reported due to often unsatisfactory detection performances. Here, we fabricated metal-graphene hybrid THz metasurfaces (MSs) for the sensitive and enzyme-free detection of circulating tumor DNA (ctDNA) in pancreatic cancer plasma samples. The feasibility and mechanism of the enhanced effects of a graphene bridge across the MS and amplified by gold nanoparticles (AuNPs) were investigated experimentally and theoretically. The AuNPs serve to boost charge injection in the graphene film and result in producing a remarkable change in the graded transmissivity index to THz radiation of the MS resonators. Assay design utilizes this feature and a cascade hybridization chain reaction initiated on magnetic beads in the presence of target ctDNA to achieve dual signal amplification (chemical and optical). In addition to demonstrating subfemtomolar detection sensitivity and single-nucleotide mismatch selectivity, the proposed method showed remarkable capability to discriminate between pancreatic cancer patients and healthy individuals by recognizing and quantifying targeted ctDNAs. The introduction of graphene to the metasurface produces an improved sensitivity of 2 orders of magnitude for ctDNA detection. This is the first study to report the combined application of graphene and AuNPs in biosensing by THz spectroscopic resonators and provides a combined identification scheme to detect and discriminate different biological analytes, including nucleic acids, proteins, and various biomarkers.

Rapid and sensitive detection of Staphylococcus aureus using a THz metamaterial biosensor based on aptamer-functionalized Fe3O4@Au nanocomposites.

Staphylococcus aureus (S. aureus) poses a serious threat to global public health, necessitating the establishment of rapid and simple tools for its accurate identification. Herein, we developed a terahertz (THz) metamaterial biosensor based on aptamer-functionalized Fe3O4@Au nanocomposites for quantitative S. aureus assays in different clinical samples. Fe3O4@Au@Cys@Apt has the dual advantages of magnetism and a high refractive index in the THz range and was used to rapidly separate and enrich target bacteria in a complex environmental solution. Furthermore, conjugation to the nanocomposites significantly increased the resonance frequency shift of the THz metamaterial after target loading. Our results showed that the shifts in the metamaterial resonance frequency were linearly related to S. aureus concentrations ranging from 1.0 × 103 to 1.0 × 107 CFU/mL, with a detection limit of 4.78 × 102 CFU/mL. The biosensor was further applied to S. aureus detection in spiked human urine and blood with satisfactory recoveries (82.4-109.6%). Our approach also demonstrated strong concordance with traditional plate counting (R2 = 0.99306) while significantly lowering the analysis time from 24 h to <1 h. In conclusion, the proposed biosensor can not only perform culture-free and extraction-free detection of target bacteria but can also be easily extended to the determination of other pathogenic bacteria, rendering it suitable for various bacteria-related disease diagnoses.

A Novel Optical Fiber Terahertz Biosensor Based on Anti-Resonance for The Rapid and Nondestructive Detection of Tumor Cells.

The sensitive and accurate detection of tumor cells is essential for successful cancer therapy and improving cancer survival rates. However, current tumor cell detection technologies have some limitations for clinical applications due to their complexity, low specificity, and high cost. Herein, we describe the design of a terahertz anti-resonance hollow core fiber (THz AR-HCF) biosensor that can be used for tumor cell detection. Through simulation and experimental comparisons, the low-loss property of the THz AR-HCF was verified, and the most suitable fiber out of multiple THz AR-HCFs was selected for biosensing applications. By measuring different cell numbers and different types of tumor cells, a good linear relationship between THz transmittance and the numbers of cells between 10 and 106 was found. Meanwhile, different types of tumor cells can be distinguished by comparing THz transmission spectra, indicating that the biosensor has high sensitivity and specificity for tumor cell detection. The biosensor only required a small amount of sample (as low as 100 µL), and it enables label-free and nondestructive quantitative detection. Our flow cytometry results showed that the cell viability was as high as 98.5 ± 0.26% after the whole assay process, and there was no statistically significant difference compared with the negative control. This study demonstrates that the proposed THz AR-HCF biosensor has great potential for the highly sensitive, label-free, and nondestructive detection of circulating tumor cells in clinical samples.

Flexible Terahertz Metamaterial Biosensor for Ultra-Sensitive Detection of Hepatitis B Viral DNA Based on the Metal-Enhanced Sandwich Assay.

The high sensitivity and specificity of terahertz (THz) biosensing are both promising and challenging in DNA sample detection. This study produced and refined a flexible THz MM biosensor for ultrasensitive detection of HBV in clinical serum samples based on a gold magnetic nanoparticle-mediated rolling circle amplification (GMNPs@RCA) sandwich assay under isothermal conditions. Typically, solid-phase RCA reactions mediated by circular padlock probes (PLPs) are triggered under isothermal conditions in the presence of HBV DNA, resulting in long single-stranded DNA (ssDNA) with high fidelity and specificity. Then, the resultant ssDNA was conjugated with detection probes (DPs) immobilized on gold nanoparticles (DP@AuNPs) to form GMNPs-RCA-AuNPs sandwich complexes. The HBV DNA concentrations were quantified by introducing GMNPs-RCA-AuNPs complexes into the metasurface of a flexible THz metamaterial-based biosensor chip and resulting in a red shift of the resonance peak of the THz metamaterials. This biosensor can lead to highly specific and sensitive detection with one-base mismatch discrimination and a limit of detection (LOD) down to 1.27E + 02 IU/ml of HBV DNA from clinical serum samples. The HBV DNA concentration was linearly correlated with the frequency shift of the THz metamaterials within the range of 1.27E + 02∼1.27E + 07 IU/ml, illustrating the applicability and accuracy of our assay in real clinical samples. This strategy constitutes a promising THz sensing method to identify virus DNA. In the future, it is hoped it can assist with pathogen identification and clinical diagnosis.

Evaluation of classification ability of logistic regression model on SERS data of miRNAs.

Logistic regression (LR) is a supervised multiple linear regression model, which uses linear weighted calculation for input to obtain weight coefficients of model. The surface enhanced Raman spectroscopy (SERS) technology greatly enhances the Raman signal of analyte. LR model was used to analyze the data of seven types of pancreatic cancer-related miRNAs obtained from commercial SERS substrate. The classification ability of the model on such data was observed under the configurations of different key parameters (classification mode, regularization method and loss function optimization way), and the effect of the two types of data formats were also evaluated. The results showed that though LR model used to classify this data did not perform well as expected, miRNA-191 and miRNA-4306 still had high recalls (sensitivity), which laid a theoretical foundation for the purpose of using LR model to identify these two miRNAs to jointly diagnose of pancreatic cancer at miRNA level.

THz-ATR Spectroscopy Integrated with Species Recognition Based on Multi-Classifier Voting for Automated Clinical Microbial Identification.

The demand for rapid and accurate identification of microorganisms is growing due to considerable importance in all areas related to public health and safety. Here, we demonstrate a rapid and label-free strategy for the identification of microorganisms by integrating terahertz-attenuated total reflection (THz-ATR) spectroscopy with an automated recognition method based on multi-classifier voting. Our results show that 13 standard microbial strains can be classified into three different groups of microorganisms (Gram-positive bacteria, Gram-negative bacteria, and fungi) by THz-ATR spectroscopy. To detect clinical microbial strains with better differentiation that accounts for their greater sample heterogeneity, an automated recognition algorithm is proposed based on multi-classifier voting. It uses three types of machine learning classifiers to identify five different groups of clinical microbial strains. The results demonstrate that common microorganisms, once time-consuming to distinguish by traditional microbial identification methods, can be rapidly and accurately recognized using THz-ATR spectra in minutes. The proposed automatic recognition method is optimized by a spectroscopic feature selection algorithm designed to identify the optimal diagnostic indicator, and the combination of different machine learning classifiers with a voting scheme. The total diagnostic accuracy reaches 80.77% (as high as 99.6% for Enterococcus faecalis) for 1123 isolates from clinical samples of sputum, blood, urine, and feces. This strategy demonstrates that THz spectroscopy integrated with an automatic recognition method based on multi-classifier voting significantly improves the accuracy of spectral analysis, thereby presenting a new method for true label-free identification of clinical microorganisms with high efficiency.

A Novel and Rapid Serum Detection Technology for Non-Invasive Screening of Gastric Cancer Based on Raman Spectroscopy Combined With Different Machine Learning Methods.

Gastric cancer (GC) is the fifth most common cancer in the world and a serious threat to human health. Due to its high morbidity and mortality, a simple, rapid and accurate early screening method for GC is urgently needed. In this study, the potential of Raman spectroscopy combined with different machine learning methods was explored to distinguish serum samples from GC patients and healthy controls. Serum Raman spectra were collected from 109 patients with GC (including 35 in stage I, 14 in stage II, 35 in stage III, and 25 in stage IV) and 104 healthy volunteers matched for age, presenting for a routine physical examination. We analyzed the difference in serum metabolism between GC patients and healthy people through a comparative study of the average Raman spectra of the two groups. Four machine learning methods, one-dimensional convolutional neural network, random forest, support vector machine, and K-nearest neighbor were used to explore identifying two sets of Raman spectral data. The classification model was established by using 70% of the data as a training set and 30% as a test set. Using unseen data to test the model, the RF model yielded an accuracy of 92.8%, and the sensitivity and specificity were 94.7% and 90.8%. The performance of the RF model was further confirmed by the receiver operating characteristic (ROC) curve, with an area under the curve (AUC) of 0.9199. This exploratory work shows that serum Raman spectroscopy combined with RF has great potential in the machine-assisted classification of GC, and is expected to provide a non-destructive and convenient technology for the screening of GC patients.

Molecule-Specific Terahertz Biosensors Based on an Aptamer Hydrogel-Functionalized Metamaterial for Sensitive Assays in Aqueous Environments.

Metamaterial-inspired terahertz (THz) biosensors are devoted to developing high-sensitivity and label-free biosensing strategies. However, most meaningful molecular signals are obscured by the strong THz absorption of solvent water. Most reported THz biosensors require the tested samples to be tediously dried or replaced with a low-absorption medium, which impairs the original bioactivity and the distribution homogeneity of targets. As described in this proposed strategy, a molecule-specific THz biosensor was fabricated from an aptamer hydrogel-functionalized THz metamaterial. Benefitting from the strong interaction with the localized electric field of the metamaterial, trace thrombin-induced variations in the hydration state of the hydrogel can be sensitively probed, which was investigated experimentally and theoretically. The optimized THz biosensor exhibited remarkable specificity for actual serum sample assays and excellent sensitivity, with a relatively low detection limit of 0.40 pM in the human serum matrix. The proposed strategy could serve as a model system to develop various molecule-specific THz biosensors for aqueous molecule sensing.

Streptavidin-functionalized terahertz metamaterials for attomolar exosomal microRNA assay in pancreatic cancer based on duplex-specific nuclease-triggered rolling circle amplification.

Exosomal microRNA (miRNA) is a promising non-invasive biomarker for liquid biopsies. Herein, we fabricated a terahertz (THz) metamaterial biosensor that comprises an array of gold (Au) discs surrounded by annular grooves for exosomal miRNA assays based on duplex-specific nuclease (DSN)-triggered rolling circle amplification (RCA). In this strategy, the target miRNA is captured by a probe P0 immobilized on magnetic beads (MBs); it then repeatedly releases a primer P1 under the action of DSN, which acts as a highly specific initiator of the subsequent RCA step utilizing biotin-dUTP. After target recycling and nucleic acid amplification, the biotinylated amplification products were captured by the streptavidin (SA)-functionalized THz metamaterials, and further conjugated to SA-modified AuNPs that permit formation of a trimeric complex of SA-biotinylated RCA products-AuNP. The complex population scales with the starting concentration of the target miR-21, resulting in a red shift of the resonance peak of the THz metamaterials. This biosensor can lead to highly specific and sensitive detection with one-base mismatch discrimination and a limit of detection (LOD) down to 84 aM. Significant distinctions are seen in the frequency shifts for exosomal miR-21 quantitation in clinical plasma samples between pancreatic cancer patients and healthy controls. The frequency shifts of the THz metamaterials are consistent versus the reverse transcription-polymerase chain reaction (RT-PCR) results, illustrating the applicability and accuracy of our assay in real clinical samples.

A novel quantification platform for point-of-care testing of circulating MicroRNAs based on allosteric spherical nanoprobe.

MiRNA-150, a gene regulator that has been revealed to be abnormal expression in non-small cell lung cancer (NSCLC), can be regarded as a serum indicator for diagnosis and monitoring of NSCLC. Herein, a new sort of nanoprobe, termed allosteric spherical nanoprobe, was first developed to sense miRNA-150. Compared with conventional hairpin, this new nanoprobe possesses more enrichment capacity and reaction cross section. Structurally, it consists of magnetic nanoparticles and dual-hairpin. In the absence of miRNA-150, the spherical nanoprobes form hairpin structure through DNA self-assembly, which could promote the Förster resonance energy transfer (FRET) of fluorophore (FAM) and quencher (BHQ1) nearby. However, in the presence of target, the target-probe hybridization can open the hairpin and form the active "Y" structure which separated fluorophore and quencher to yield "signal on" fluorescence. In the manner of multipoint fluorescence detection, the target-bound allosteric spherical nanoprobe could provide high detection sensitivity with a linear range of 100 fM to 10 nM and a detection limit of 38 fM. More importantly, the proposed method can distinguish the expression of serum miRNA-150 among NSCLC patients and healthy people. Finally, we hoped that the potential bioanalytical application of this nanoprobe strategy will pave the way for point-of-care testing (POCT).

Indirect surface-enhanced Raman scattering assay of insulin-like growth factor 2 receptor protein by combining the aptamer modified gold substrate and silver nanoprobes.

An indirect aptamer-based SERS assay for insulin-like growth factor 2 receptor (IGF-IIR) protein was developed. The gold substrate and silver nanoparticles (AgNPs) were employed simultaneously to achieve double enhancement for SERS signals. Firstly, the five commercial SERS substrates including Enspectr, Ocean-Au, Ocean-AG, Ocean-SP and Q-SERS substrates were evaluated using 4-mercaptobenzoic acid (4-MBA). The Q-SERS substrate was selected based on low relative standard deviation (RSD, 8.6%) and high enhancement factor (EF, 8.7*105), using a 785 nm laser. The aptamer for IGF-IIR protein was designed to include two sequences: one grafted on gold substrate to specifically capture the IGF-IIR protein and a second one forming a 3' sticky bridge to capture SERS nanotags. The SERS nanotag was composed by AgNPs (20 nm), 4-MBA and DNA probes that can hybridize with the aptamer. Due to the steric-hindrance effect, when the aptamer doesn't combine with IGF-IIR protein, it only can capture the SERS nanotags. Therefore, there was a negative correlation between the concentration of IGF-IIR protein and the intensity of 4-MBA at 1076 cm-1. The detection limit reached to 141.2 fM and linear range was from 10 pM to 1 µM. The SERS aptasensor also exhibits a high reproducibility with an average RSD of 4.5%. The interference test was conducted with other four proteins to verify the accuracy of measuring. The study provides an approach to quantitative determination of proteins based on specific recognition and nucleic acid hybridization of aptamers, to establish sandwich structure for SERS enhancement. Graphical abstractSchematic representation of surface-enhanced Raman scattering (SERS) assay on insulin-like growth factor 2 receptor (IGF-IIR) protein by combining the aptamer modified gold substrate and 4-mercaptobenzoic acid (4-MBA) and DNA probe modified silver nanoparticles.

Surface-enhanced Raman scattering method for the identification of methicillin-resistant Staphylococcus aureus using positively charged silver nanoparticles.

The article describes a SERS-based method for diagnosis of bacterial infections. Positively charged silver nanoparticles (AgNPs+) were employed for identification of methicillin-resistant Staphylococcus aureus (MRSA). It is found that AgNPs+ undergo self-assembly on the surface of bacteria via electrostatic aggregation. The assembled AgNPs+ are excellent SERS substrates. To prove the capability of SERS to differentiate between S. aureus and other microorganisms, six standard strains including S. aureus 29213, S. aureus 25923, C. albicans, B. cereus, E. coli, and P. aeruginosa were tested. To further demonstrate its applicability for the identification of MRSA in clinical samples, 52 methicillin-sensitive S. aureus (MSSA) isolates and 215 MRSA isolates were detected by SERS. The total measurement time (include incubation) is 45 min when using a 3 µL sample. The method gives a strongly enhanced Raman signal (at 730 cm-1 and 1325 cm-1) with good reproducibility and repeatability. It was successfully applied to the discrimination of the six strain microorganisms. The typical Raman peaks of S. aureus at 730, 1154, 1325, and 1457 cm-1 were observed, which were assigned to the bacterial cell wall components (730 cm-1- adenine, glycosidic ring mode, 1154 cm-1- unsaturated fatty acid, 1325 cm-1- adenine, polyadenine, and 1457 cm-1 for -COO- stretching). S. aureus was completely separated from other species by partial least squares discriminant analysis (PLS-DA). Moreover, 52 MSSA isolates and 215 MRSA isolates from clinical samples were identified by PLS-DA. The accuracy was almost 100% when compared to the standard broth microdilution method. A classification based on latent structure discriminant analysis provided spectral variability directly. Conceivably, the method offers a potent tool for the identification of bacteria and antibiotics resistance, and for studies on antibiotic-resistance in general. Graphical abstract Schematic of the surface-enhanced Raman scattering (SERS) measurements on Staphylococcus aureus (S. aureus) using positively charged silver nanoparticles (AgNPs+). AgNPs+ are adsorbed on the bacterial cell wall by electrostatic attraction. SERS spectra were analyzed by PLS-DA for the identification of Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus aureus (MSSA). MRSA isolates were divided into four groups, including R1, R2, R3, and R4. MSSA just includes group S.

Clinical analysis of transvaginal hydrolaparoscopy in infertile patients.

OBJECTIVE: To evaluate the application of transvaginal hydrolaparoscopy for exploration of the pelvic cavity exploration in infertile women. STUDY DESIGN: A total of 510 infertile women were included in this study from May 1st, 2009 to April 30, 2012 in the clinic of the Hebei Research Institute for Family Planning. RESULTS: In 495 of 510 of the patients (97.06%), a successful operation was achieved at the first puncture. Of these 495 patients, 286 (57.78%) showed bilateral patency. Completely normal tubo-ovarian and pelvic structures were observed only in 79 patients (15.96%): 16 patients (3.23%) had bilateral tube obstruction, 18 (3.64%) had hydrosalpinx, and 8 (1.62%) had fimbrial stenosis. Pelvic abnormalities occurred in 240 patients (44.04%), including bilateral and/or unilateral tubo-ovarian adhesions in 80 patients (16.16%) and 160 (32.32%) found with adhesions in other parts of the pelvic cavity. Pelvic endometriosis was found in 82 patients (16.57%) and 19 (3.84%) had two or more lesions in the pelvic cavity. In addition, 9 cases (1.82%) of ovarian cysts, 7 (1.41%) of bilateral vesicular appendices and 43 cases (6.69%) of a unilateral vesicular appendix were observed. In addition, convoluted tubes such as bent or twisted tubes were found in 4 cases of bilateral fallopian tube occlusion patients (0.81%) and 17 cases of unilateral tubal occlusion patients (3.43%). CONCLUSIONS: Transvaginal hydrolaparoscopy is a feasible, safe, and cost-effective microinvasive technique. This technique can be considered as an alternative procedure for evaluating female infertility.

[Comparison of the effect of fluid resuscitation as guided either by lactate clearance rate or by central venous oxygen saturation in patients with sepsis].

OBJECTIVE: To compare the efficacy of fluid resuscitation as guided by lactate clearance rate (LCR) and central venous oxygen saturation (ScvO2) in patients with sepsis. METHODS: A prospective randomized control study was conducted. Fifty patients diagnosed with severe sepsis or septic shock from January 2011 to February 2012 in department of critical care medicine of Fourth Hospital of Hebei Medical University were enrolled in the study. The patients were randomly divided into two groups according to the sequence (each n=25): ScvO2 group and LCR group. After ICU admission, the patients were treated symptomatically timely, and fluid resuscitation was started as early as possible according to Surviving Sepsis Campaign guidance for management of severe sepsis and septic shock 2008. Central venous pressure (CVP)≥8 mm Hg (1 mm Hg=0.133 kPa), mean arterial pressure (MAP)≥65 mm Hg and ScvO2≥0.70 served as goal values to accomplish the fluid resuscitation therapy in ScvO2 group, while CVP≥8 mm Hg, MAP≥65 mm Hg, LCR≥10% served as goal value to accomplish the fluid resuscitation therapy in LCR group. The general condition and clinical characteristics on arrival in ICU, changes in CVP, MAP, ScvO2, lactate level and/or LCR before (0 hour) and 3, 6, 72 hours after the start of fluid resuscitation and the other related conditions during the therapy were recorded. RESULTS: There was no significant difference in general data or clinical characteristics before the start of therapy, occurrence of organ dysfunction, or treatment measures during different time periods after start of fluid resuscitation. Compared with the condition immediately before fluid resuscitation, at 3 hours after start of fluid resuscitation, CVP were improved in LCR and ScvO2 groups (8.58±1.17 mm Hg vs. 6.33±1.21 mm Hg, 9.08±2.43 mm Hg vs. 5.33±0.98 mm Hg, both P<0.05); at 6 hours after start of fluid resuscitation, heart rate (HR) and respiratory rate (RR) were lowered in LCR and ScvO2 groups (HR: 96±18 bpm vs. 127±13 bpm, 98±13 bpm vs. 116±19 bpm, RR: 23±3 times/min vs. 33±9 times/min, 24±5 times/min vs. 35±6 times/min, all P<0.05), oxygenation index (PaO2/FiO2) was increased in LCR and ScvO2 groups (179±41 mm Hg vs. 86±21 mm Hg, 202±33 mm Hg vs. 95±17 mm Hg, both P<0.05), and there was no significant difference in MAP in both groups. There was no significant difference in all indexes between two groups. In LCR group, 3 hours after start of fluid resuscitation, lactate level was significantly decreased (2.81±0.18 mmol/L vs. 3.43±1.31 mmol/L, P<0.05). Compared with the value 3 hours after start of fluid resuscitation, LCR was significantly improved at 6 hours and 72 hours after start of fluid resuscitation in LCR group [(42.69±8.75)%, (48.87±9.69)% vs. (20.32±4.58)%, both P<0.05]. Compared with that immediately before fluid resuscitation, ScvO2 was significant improved in ScvO2 group at 3 hours after start of fluid resuscitation (0.65±0.04 vs. 0.53±0.06, P<0.05). There was no significant difference in success rate of fluid resuscitation comparing that of 6 hours and that of 72 hours [6 hours: 72% (18/25) vs. 64% (16/25), χ(2)=0.368, P=0.762; 72 hours: 88% (22/25) vs. 88% (22/25) ,χ(2)=0.000, P=1.000], length of ICU stay (8±3 days vs. 10±4 days, t=0.533, P=0.874), length of hospital stay (29±11 days vs. 35±16 days, t=0.692, P=0.531), improvement rate [84% (21/25) vs. 76%(19/25), χ(2)=0.500, P=0.480] or 28-day mortality [20% (5/25) vs. 28% (7/25), χ(2)=0.439, P=0.742] between LCR and ScvO2 groups. CONCLUSIONS: Both LCR and ScvO2 can be taken as the index in confirming the endpoint of fluid resuscitation for patients with severe sepsis and septic shock. Fluid resuscitation therapy under the guidance of LCR is accurate and reliable in patients with severe sepsis and septic shock.

[Changes in adrenal cortex function and protective effect of dexamethasone in septic rats during early phases].

OBJECTIVE: To affirm the presence of relative adrenal insufficiency (RAI) in the early phases of sepsis and its probable mechanisms, and to study the optimal time for glucocorticoid replacement therapy. METHODS: A total of 260 healthy male Wistar rats were randomized into five groups (each group n=52), including normal control group, sham operation group, cecal ligation and puncture (CLP) group, dexamethasone prevention group (with 10 mg/kg dexamethasone injection into the abdominal cavity before CLP) and dexamethasone treatment group (with 10 mg/kg dexamethasone injection into the abdominal cavity 7 hours after CLP). Each group was subdivided into five subgroups according to five time points: 2, 4, 6, 8 and 12 hours. Adrenocorticotrophic hormone (ACTH) test was conducted at 8 hours and 12 hours, and before and after 30 minutes of ACTH administration, the cortisol content in serum was determined with radioimmunoassay (RIA) and the expressions of Toll-like receptor 4 (TLR4), tumor necrosis factor-alpha (TNF-alpha) mRNA in adrenal glands were detected with semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Ultrastructure of adrenal cortex was observed with transmission electron microscope. The survival rats was recorded in all groups. RESULTS: (1) The levels of cortisol in CLP group, dexamethasone prevention group and dexamethasone treatment group were respectively higher than those of normal control and sham operation groups (all P<0.05). But there was no marked change in the levels of cortisol between pre-and post-ACTH in rats with sepsis in the early phases. (2)The expressions of TLR4, TNF-alpha mRNA in adrenal both were significantly increased in CLP group, and they were higher than those in sham operation group (P<0.05 or P<0.01). The expressions of TLR4, TNF-alpha mRNA in dexamethasone prevention group and treatment group were significantly lower than those in CLP group, and those in the dexamethasone prevention group were lower than those in sham operation group. (3)In the groups of CLP, dexamethasone prevention and treatment, ultrastructure changes were observed in the adrenal, especially in CLP group. (4)The survival rate of the dexamethasone prevention and treatment groups at 12 hours were higher than that of CLP group (76.92%, 40.00% vs. 33.33%, P<0.01 and P<0.05). The survival rate of dexamethasone prevention group was higher than that of dexamethasone treatment group (P<0.05). CONCLUSION: (1)RAI occurs during the early stage of sepsis. (2)The expressions of TLR4, TNF-alpha mRNA in adrenal and changes in corticoadrenal ultrastructure participates in the pathogenesis of RAI in the early stage of sepsis in rat. (3) Dexamethasone therapy could effectively increase the survival rate and improve outcome through down-regulating the expression changes in TLR4, TNF-alpha mRNA and alleviating changes in ultrastructure of adrenal glands. Early administration of dexamethasone may give good result in the treatment of sepsis.