Directional screening and identification of potential cytotoxic components from Achnatherum inebrians by a combination of surface palsmon resonance and chromatography / 中草药·英文版

OBJECTIVE@#To establish a method for directional screening of the cytotoxic components from the medicinal herb of Achnatherum inebrians by a combination of surface plasmon resonance (SPR) biosensor and chromatographic isolation technology.@*METHODS@#Under the guidance of bioactive assessment based on binding abilities between objects and the α-Mannosidase (α-Man) target, the active components from different solvents extracts, different polar extraction parts and fractions were screened orderly and directionally using SPR. Components with a high binding ability to α-Man can be precisely oriented in a narrower fractions range and are easy to isolate. Three human cancer cells were used to evaluate the cytotoxic activity of component with the highest affinity to α-Man.@*RESULTS@#Eight compounds were isolated and identificated from A. inebrians for the first time. Deoxyvasicinone possessed the highest affinity to α-Man among them. Moreover, deoxyvasicinone showed good effects on inhibited proliferation of human hepatoma cells HepG2 (IC50 = 5.7 μmol/L), human breast cancer cells MCF7 (IC50 = 7.21 μmol/L) and human lung cancer cells HCC827 (IC50 = 0.75 μmol/L), respectively. In particular, its inhibitory effect on HCC827 was stronger than the positive drug gefitinib (IC50 = 1.65 μmol/L).@*CONCLUSION@#A comprehensive strategy of directional screening potential cytotoxic components from herb based on biomolecular interaction and chromatography was established. Deoxyvasicinone as an effective anti-cancer component was initially isolated from A. inebrians. It is expected that this screening strategy could provide new perspectives for rapid screening and identification of active components from natural plants with the complex matrix.

Screening of anti-SARS-CoV-2 ligands from Chinese herbs based on a dual-target surface plasmon resonance biosensor / 药学学报

The epidemic of COVID-19 has brought great challenges to the global public health prevention and control system combined with clinical diagnosis and treatment system, and it makes the development of effective antiviral drugs an important task in current pharmaceutical research. Traditional Chinese medicine (TCM) has played an important role in the prevention and control of COVID-19. Due to its numerous chemical components and various structural types, TCM becomes a natural library for searching for lead compounds against SARS-CoV-2. In this study, a novel dual-target surface plasmon resonance (SPR) biosensor was developed for S protein receptor binding domain (SRBD) and angiotensin converting enzyme 2 (ACE2) which are two key proteins in the process of SARS-CoV-2 invading cells according to characteristics of synergistic effects of multiple components and comprehensive regulation of multiple targets of TCM. The SPR biosensor was applied to screen and identify active components from six TCMs, and daidzin from Puerariae Lobatae Radix was identified to bind with SRBD and ACE2. The affinity constant (KD) of daidzin and ACE2 was 5.18 μmol·L-1 through the SPR affinity assay. Competitive ELISA assay showed that daidzin could inhibit the binding of SRBD and ACE2, and the inhibition rate of daidzin (20 μmol·L-1) was 38.6%. Molecular docking experiments further confirmed that daidzin had the best binding near the binding region of SRBD-ACE2 complex. This study shows that the dual-target SPR screening system is accurate and efficient, and is particularly suitable for screening of complex drug systems and effective substances study of TCM. It provides a material basis for exploring the mechanism of TCM active constituents against SARS-CoV-2, and provides a source of lead compounds for the development of anti-SARS-CoV-2 drugs.

Nano-therapeutic efficacy of green synthesized gold nanoparticles (gAuNPs) and its antibacterial efficacy

We report the efficacy of the gold nanoparticles (AuNPs) synthesized using the leaf extracts of Syzygium cumini (common name Jamun) with auric chloride (AuCl4) which was used as both reducing and capping agent at room temperatures- 25°C. Synthesized AuNPs were characterized using UV-Vis spectroscopy indicating a peak in the range of 520-540 nM. The hydrodynamic radii measured by DLS clearly indicated the size of AuNPs in the range of 14-64 nM. The biological efficacy in terms of antimicrobial activity was assessed by the Kirby Bauer method, applied for both Gram-positive and Gram-negative bacteria such as Staphylococcus aureus and Escherichia coli, respectively. The Zone of inhibition (ZOI) diameter was found to be 4 mM and 3 mM in S. aureus and E. coli, as indicated by the bactericidal activity. Hence, AuNPs synthesized by green synthesis are proposed as economical, environment friendly with immense potential as an antibacterial agent and for drug delivery.

Exploring the Serum Level of RE1 Silencing Transcription Factor in Alzheimer's Disease

Objectives:The aim of this study was to evaluate the serum RE1 silencing transcription factor (REST) level in Alzheimer's disease (AD), mild cognitive impairment (MCI), and elderly controls by using surface plasmon resonance (SPR) technology. Materials and Methods?In this case–control study of 133 subjects, 49 patients with AD, 49 patients with MCI, and 35 elderly controls were recruited. The REST protein concentrations were evaluated by SPR. The resonance unit for each sample was recorded and the concentration of serum REST of study group was derived from the standard curve. All the experiments were done in triplicates. Statistical analysis was done and p-value of < 0.05 was considered as statistically significant. Results?A significant difference was observed in the Montreal Cognitive Assessment score, Hindi Mental State Examination scale (HMSE) score education, disease duration, and gender among the groups. A significant (p>0.0001) difference in the duration of disease between AD and MCI was observed. It was observed that the mean concentration of serum REST was not significantly (p?=?0.266) different among the groups. Conclusion?This study first time evaluated the serum levels of REST in AD, MCI and age-matched elderly controls. The rest levels were similar in all groups; however, it can provide a new direction to future blood-based biomarker studies of REST.

A strategy of screening and binding analysis of bioactive components from traditional Chinese medicine based on surface plasmon resonance biosensor / 药物分析学报

Elucidating the active components of traditional Chinese medicine(TCM)is essential for understanding the mechanisms of TCM and promote its rational use as well as TCM-derived drug development.Recent studies have shown that surface plasmon resonance(SPR)technology is promising in this field.In the present study,we propose an SPR-based integrated strategy to screen and analyze the major active components of TCM.We used Radix Paeoniae Alba(RPA)as an example to identify the compounds that can account for its anti-inflammatory mechanism via tumor necrosis factor receptor type 1(TNF-R1).First,RPA extraction was analyzed using an SPR-based screening system,and the potential active in-gredients were collected,enriched,and identified as paeoniflorin and paeonol.Next,the affinity con-stants of paeoniflorin and paeonol were determined as 4.9 and 11.8 μM,respectively.Then,SPR-based competition assays and molecular docking were performed to show that the two compounds could compete with tumor necrosis factor-α(TNF-α)while binding to the subdomain 1 site of TNF-R1.Finally,in biological assays,the two compounds suppressed cytotoxicity and apoptosis induced by TNF-α in the L929 cell line.These findings prove that SPR technology is a useful tool for determining the active in-gredients of TCM at the molecular level and can be used in various aspects of drug development.The SPR-based integrated strategy is reliable and feasible in TCM studies and will shed light on the eluci-dation of the pharmacological mechanism of TCM and facilitate its modernization.

Functional and binding studies of gallic acid showing platelet aggregation inhibitory effect as a thrombin inhibitor / 中草药·英文版

Objective: This study was devoted to identifying natural thrombin inhibitors from traditional Chinese medicine (TCM) and evaluating its biological activity in vitro and binding characteristics. Methods: A combination strategy containing molecular docking, thrombin inhibition assay, surface plasmon resonance (SPR) and molecular dynamics simulation were applied to verify the study result. Results: Gallic acid was confirmed as a direct thrombin inhibitor with IC

Development of a surface plasmon resonance biosensor for accurate and sensitive quantitation of small molecules in blood samples / 药物分析学报

Therapeutic drug monitoring(TDM)has played an important role in clinical medicine for precise dosing.Currently,chromatographic technology and immunoassay detection are widely used in TDM and have met most of the needs of clinical drug therapy.However,some problems still exist in practical appli-cations,such as complicated operation and the influence of endogenous substances.Surface plasmon resonance(SPR)has been applied to detect the concentrations of small molecules,including pesticide residues in crops and antibiotics in milk,which indicates its potential for in vivo drug detection.In this study,a new SPR-based biosensor for detecting chloramphenicol(CAP)in blood samples was developed and validated using methodological verification,including precision,accuracy,matrix effect,and extraction recovery rate,and compared with the classic ultra-performance liquid chromatography-ultraviolet(UPLC-UV)method.The detection range of SPR was 0.1-50 ng/mL and the limit of detec-tion was 0.099±0.023 ng/mL,which was lower than that of UPLC-UV.The intra-day and inter-day ac-curacies of SPR were 98％-114％and 110％-122％,which met the analysis requirement.The results show that the SPR biosensor is identical to UPLC-UV in the detection of CAP in rat blood samples;moreover,the SPR biosensor has better sensitivity.Therefore,the present study shows that SPR technology can be used for the detection of small molecules in the blood samples and has the potential to become a method for therapeutic drug monitoring.

Calendula officinalis L. flower extract-mediated green synthesis of silver nanoparticles under LED light

Abstract Silver nanoparticles (AgNPs) are among the most known nanomaterials being used for several purposes, including medical applications. In this study, Calendula officinalis L. flower extract and silver nitrate were used for green synthesis of silver nanoparticles under red, green and blue light-emitting diodes. AgNPs were characterized by Ultraviolet-Visible Spectrophotometry, Field Emission Scanning Electron Microscopy, Dynamic Light Scattering, Electrophoretic Mobility, Fourier Transform Infrared Spectroscopy and X-ray Diffraction. Isotropic and anisotropic silver nanoparticles were obtained, presenting hydrodinamic diameters ranging 90 - 180 nm, polydispersity (PdI > 0.2) and moderate stability (zeta potential values around - 20 mV)

Assessment of the binding interactions of SARS-CoV-2 spike glycoprotein variants / 药物分析学报

Severe acute respiratory syndrome-associated coronavirus 2 is a major global health issue and is driving the need for new therapeutics.The surface spike protein,which plays a central role in virus infection,is currently the target for vaccines and neutralizing treatments.The emergence of novel variants with multiple mutations in the spike protein may reduce the effectiveness of neutralizing antibodies by altering the binding activity of the protein with angiotensin-converting enzyme 2(ACE2).To understand the impact of spike protein mutations on the binding interactions required for virus infection and the effectiveness of neutralizing monoclonal antibody(mAb)therapies,the binding activities of the original spike protein receptor binding domain(RBD)sequence and the reported spike protein variants were investigated using surface plasmon resonance.In addition,the interactions of the ACE2 receptor,an anti-spike mAb(mAb1),a neutralizing mAb(mAb2),the original spike RBD sequence,and mutants D614G,N501Y,N439K,Y453F,and E484K were assessed.Compared to the original RBD,the Y453F and N501Y mutants displayed a significant increase in ACE2 binding affinity,whereas D614G had a substantial reduction in binding affinity.All mAb-RBD mutant proteins displayed a reduction in binding affinities relative to the original RBD,except for the E484K-mAb1 interaction.The potential neutralizing capability of mAb1 and mAb2 was investigated.Accordingly,mAb1 failed to inhibit the ACE2-RBD interaction while mAb2 inhibited the ACE2-RBD interactions for all RBD mutants,except mutant E484K,which only dis-played partial blocking.

Screening potential P-glycoprotein inhibitors by combination of a detergent-free membrane protein extraction with surface plasmon resonance biosensor

P-glycoprotein (P-gp) highly expressed in cancer cells can lead to multidrug resistance (MDR) and the combination of anti-cancer drugs with P-gp inhibitor has been a promising strategy to reverse MDR in cancer treatment. In this study, we established a label-free and detergent-free system combining surface plasmon resonance (SPR) biosensor with styrene maleic acid (SMA) polymer membrane proteins (MPs) stabilization technology to screen potential P-gp inhibitors. First, P-gp was extracted from MCF-7/ADR cells using SMA polymer to form SMA liposomes (SMALPs). Following that, SMALPs were immobilized on an SPR biosensor chip to establish a P-gp inhibitor screening system, and the affinity between P-gp and small molecule ligand was determined. The methodological investigation proved that the screening system had good specificity and stability. Nine P-gp ligands were screened out from 50 natural products, and their affinity constants with P-gp were also determined. The in vitro cell verification experiments demonstrated that tetrandrine, fangchinoline, praeruptorin B, neobaicalein, and icariin could significantly increase the sensitivity of MCF-7/ADR cells to Adriamycin (Adr). Moreover, tetrandrine, praeruptorin B, and neobaicalein could reverse MDR in MCF-7/ADR cells by inhibiting the function of P-gp. This is the first time that SMALPs-based stabilization strategy was applied to SPR analysis system. SMA polymer can retain P-gp in the environment of natural lipid bilayer and thus maintain the correct conformation and physiological functions of P-gp. The developed system can quickly and accurately screen small molecule ligands of complex MPs and obtain affinity between complex MPs and small molecule ligands without protein purification.

Method for the detection of human immunoglobulin Fc function based on surface plasmon resonance: preliminary establishment and validation / 中国输血杂志

【Objective】 To establish a method for detecting human immunoglobulin Fc function based on surface plasmon resonance technology. 【Methods】 Based on the characteristic that FcγRI can be binded to the Fc segment of IgG, the affinity constant of the sample was detected by surface plasmon resonance, and its Fc function was the KD ratio of the sample to the standard. The method was validated for specificity/specificity, precision and robustness. The method and the pharmacopoeia method were used to detect the Fc function of 30 human immunoglobulins, and the correlation and consistency of the detection results were analyzed. 【Results】 The method validation results showed that this method has strong specificity/specificity (t values were 0.15, 0.22, both P>0.05), good precision (CV value 5.37%~10.69%) and good robustness (CV value 10.06%). The detection results of this method and the pharmacopoeia method have high correlation (r=0.96, P<0.05) and high consistency (Bias-2.060, 95% Limits of Agreement-5.628~1.508). 【Conclusion】 A method for detecting human immunoglobulin Fc function based on surface plasmon resonance has been successfully established.

A novel PGAM5 inhibitor LFHP-1c protects blood-brain barrier integrity in ischemic stroke

Blood-brain barrier (BBB) damage after ischemia significantly influences stroke outcome. Compound LFHP-1c was previously discovered with neuroprotective role in stroke model, but its mechanism of action on protection of BBB disruption after stroke remains unknown. Here, we show that LFHP-1c, as a direct PGAM5 inhibitor, prevented BBB disruption after transient middle cerebral artery occlusion (tMCAO) in rats. Mechanistically, LFHP-1c binding with endothelial PGAM5 not only inhibited the PGAM5 phosphatase activity, but also reduced the interaction of PGAM5 with NRF2, which facilitated nuclear translocation of NRF2 to prevent BBB disruption from ischemia. Furthermore, LFHP-1c administration by targeting PGAM5 shows a trend toward reduced infarct volume, brain edema and neurological deficits in nonhuman primate

Study on drug-target binding kinetics profiles of flavonoids in Chrysanthemum morifolium and xanthine oxidase / 中国中药杂志

Based on the target occupancy mathematical model, the binding kinetic process of potential active ingredients of lowering uric acid in Chrysanthemum morifolium with xanthine oxidase(XOD) was evaluated. The potential active ingredients of lowering uric acid in Ch. morifolium were screened by UPLC-Q-Exactivems MS technology, reference substance identification and in vitro enzymatic kinetics experiments. The binding kinetic parameters of xanthine oxidase and potential inhibitor in Ch. morifolium were determined by surface plasma resonance(SPR). The verified mathematical model of the XOD target occupancy evaluated the kinetic binding process of inhibitors and xanthine oxidase in vivo. According to UPLC-Q-Exactive MS and reference substance identification, 39 potential uric acid-lowering active ingredients in Ch. morifolium extracts were identified and the inhibitory activities of 23 compounds were determined. Three potential xanthine oxidase inhibitors were screened, namely genistein, luteolin, and apigenin. whose IC_(50 )were 1.23, 1.47 and 1.59 μmol·L~(-1), respectively. And the binding rate constants(K_(on)) were 1.26×10~6, 5.23×10~5 and 6.36×10~5 mol·L~(-1)·s~(-1), respectively. The dissociation rate constants(K_(off)) were 10.93×10~(-2), 1.59×10~(-2), and 5.3×10~(-2 )s~(-1), respectively. After evaluation by different administration methods, the three selected compounds can perform rapid and sustained inhibition of xanthine oxidase in vivo under combined administration. This study comprehensively evaluated the target occupancy process of three effective components in different ways of administration in vivo by UPLC-MS, concentration-response method, SPR technology and xanthine oxidase target occupancy model, which would provide a new research idea and method for screening active ingredients in traditional Chinese medicine.

Simulation Analysis of Occupancy Rates of Baicalein， Quercetin and Galangin on Target Sites of Xanthine Oxidase / 中国实验方剂学杂志

Objective:To simulate the occupancy rates of baicalein， quercetin and galangin on the target sites of xanthine oxidase <italic>in vivo</italic>. Method:In this experiment， the half inhibitory concentration （IC₅₀） of febuxostat， baicalein， quercetin and galangin against xanthine oxidase were determined by <italic>in vitro</italic> enzymatic reaction. Binding free energy was predicted by molecular docking technology and their association rate constant （k_on） and dissociation rate constant （k_off） were determined by surface plasmon resonance technology. Based on measured binding kinetic parameters （k_on and k_off） and extracted pharmacokinetic data， the target occupancy model <italic>in vivo</italic> was established. Result:The IC₅₀values of febuxostat， baicalein， quercetin and galangin were 0.002 7， 1.63， 0.38， 1.59 µmol·L^-1， respectively. The IC₅₀ of febuxostat was very close to that reported in the literature. The predicted curve of target occupancy rate <italic>in vivo</italic> of febuxostat was consistent with its duration of clinical efficacy. When single intragastric administration of long-circulating liposomes of quercetin with dose of 100 mg·kg^-1 in rats， the time of target occupancy rate >70% <italic>in vivo</italic> lasted for about 3.9 h. When rats were orally administered baicalein and galangin with dose of 200 mg·kg^-1， the time of target occupancy rate >50% <italic>in vivo </italic>lasted for about 10 h and 1.7 h， respectively. Conclusion:The prediction model of xanthine oxidase target occupancy constructed by drug target binding kinetics and <italic>in vivo</italic> pharmacokinetic curves can effectively evaluate the <italic>in vivo</italic> inhibitory activity of compounds against the target.

Screening small molecular inhibitors of STAT3 based on surface plasmon resonance technology / 药学实践杂志

Objective To find small molecules binding specifically to signal transducer and activator of transcription3 (STAT3) based on surface plasmon resonance (SPR) technology and confirm their inhibitory activities to STAT3. Methods The biomolecular interaction analysis T200 system based on SPR technology was used to couple the purified protein STAT3 to CM5 chip under the optimal pH conditions. The compounds with high binding response value were screened out from 50 candidate compounds derived from traditional Chinese medicines and the binding specificity was then confirmed. Biological experiments were performed to confirm the inhibitory effects of the screened compounds on STAT3. The binding pattern of STAT3 and the compound was fitted by molecular docking technique. Results More than 10 candidate molecules exhibited binding activities to STAT3 and kinetics assays revealed that only one candidate molecule, apigenin, showed specific binding. Western-blot analysis exhibited that apigenin inhibited the phosphorylation of STAT3 dose-dependently. Luciferase reporter gene assays demonstrated that apigenin also inhibited IL-6-induced STAT3 transcriptional activity in a dose-dependent manner. Molecular docking results showed that apigenin binds to the SH2 domain of STAT3, and interacts with key residues Glu638, Gln644, Gly656 and Lys658 by hydrogen bonds and with Tyr657 through π-π interactions. Conclusion Apigenin was a direct inhibitor of STAT3.

Application of SPR protein chip in screening for imported malaria / 生物工程学报

Imported malaria has become a major risk factor for malaria prevention and control in China. How to screen malaria quickly for people entering China is an urgent problem to be solved. Protein microarrays are widely used in high-throughput screening and diagnosis. In this study, surface plasmon resonance (SPR) technique for malaria detection was established by using the specific adsorption surface treated by polyethylene glycol polymer, and the malaria specific antigen HRP2 was used as capture probe. The optimal concentration of antigen, sensitivity and specificity of detection, as well as anti-interference ability of the chip were analyzed. The SPR protein chip was applied to detect specific antibodies of malignant malaria in serum with the advantage of label-free, instant and fast. Compared with fluorescence quantitative PCR, there were no significant difference in sensitivity and specificity between the two methods. This study lays a foundation for further development of protein microarray for malaria typing identification, and it is conducive to the rapid screening of malaria for people entering.

Clinical and biomedical applications of surface plasmon resonance systems

Abstract Surface plasmon resonance (SPR)-based biosensors offer superior analytical features such as simplicity, sensitivity, and specificity when compared to conventional methods in clinical analyses. In addition, they deliver real-time monitoring of label-free analytes with high-throughput approaches requiring little sample pretreatment that allows the analysis of virtually every clinical sample type to determine the amount and/or activity of any molecule of interest. Accordingly, SPR emerges as a novel, efficient, powerful, and relatively low-cost alternative tool for routine clinical analysis, opening also new horizons for developments in personalized medicine applied to diagnostics or therapeutics’ monitoring.

Diagnostic Significance of p38 Isoforms (p38α, p38β, p38γ, p38δ) in Head and Neck Squamous Cell Carcinoma: Comparative Serum Level Evaluation and Design of Novel Peptide Inhibitor Targeting the Same / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The p38 mitogen-activated protein kinase (MAPKs) play a crucial role in the production of pro-inflammatory cytokines and over-expression of it increase cytokines which promote cancer. Among four isoforms, p38α has been well studied in head and neck squamous cell carcinoma (HNSCC) and other cancers as a therapeutic target. p38δ has recently emerged as a potential disease-specific drug target. Elevated serum p38α level in HNSCC was reported earlier from our lab. This study aims to estimate the levels of p38 MAPK-isoforms in the serum of HNSCC and design peptide inhibitor targeting the same. MATERIALS AND METHODS: Levels of p38 MAPK isoforms in the serum of HNSCC and healthy controls were quantified by surface plasmon resonance technology. The peptide inhibitor for p38 MAPK was designed by molecular modeling using Grid-based Ligand Docking with Energetics tools and compared with known specific inhibitors. RESULTS: We have observed highly elevated levels of all four isoforms of p38 MAPK in serum of HNSCC patients compared to the control group. Further, serum p38α, p38β, and p38δ levels were down regulated after therapy in follow-up patients, while p38γ showed no response to the therapy. Present study screened designed peptide WFYH as a specific inhibitor against p38δ. The specific inhibitor of p38δ was found to have no effect on p38α due to great structural difference at ATP binding pocket. CONCLUSION: In this study, first time estimated the levels of p38 MAPK isoforms in the serum of HNSCC. It can be concluded that p38 MAPK isoforms can be a diagnostic and prognostic marker for HNSCC and p38δ as a therapeutic target.

Screening of 14-3-3τ protein inhibitors from natural products based on fluorescence spectroscopy, surface plasmon resonance and molecular docking technique / 国际药学研究杂志

Objective:To study and establish a method for the efficient screening of 14-3-3τ protein inhibitors from natural products, and analyze the sites of their interactions with the 14-3-3τ protein. Methods: The binding activity of natural compounds with the 14-3-3τ protein was tested by the liquid chromatography-fluorescence spectroscopy, and the binding activity of the potential compounds was further verified by the surface plasmon resonance(SPR)technique. The binding sites of the active compounds were predicted by the molecular docking technique. Furthermore, the key binding sites were selected and then validated using amino acid site-directed mutants. Results: A total of 17 different type compounds with potential 14-3-3τ binding activity were screened out from 82 natural products. The binding activi- ties of 10 compounds were verified by the SPR experiments. Then the binding sites of interactions between the 14-3-3τ protein and the 10 compounds were predicted by the molecular docking technology to be mainly at the Arg56, Arg127 and Y128A, dem- onstrate that the binding of five of the 10 compounds with the target protein was associated with the three sites Arg56, Arg127 and Tyr128. Conclusion: The established method is accurate and efficient, which could be used for rapid screening of small molecule 14-3-3τ inhibitors from natural products. The present study provides a reference and a new approach for the rapid screening of 14-3-3τ inhibitors for the new breast cancer therapeutic drugs.

Utility of cystatin C as a potential bladder tumour biomarker confirmed by surface plasmon resonance technique

Background & objectives: The determination of cystatin C (cysC) may be helpful in diagnosis and monitoring of cancer because the pathogenesis of cancer is linked with an increased activity of cysteine peptidases (cathepsins) and a decrease of cysC concentration. This study was aimed to examine the utility of cysC as a marker of bladder cancer (BCa) to be used in the diagnosis. Methods: This study was conducted with 90 patients with BCa and 27 healthy people. Patients with other cancers, inflammation process and impaired renal function were excluded from the study. The concentrations of cysC in the plasma and urine were measured by surface plasmon resonance imaging technique. Results: The concentration of cysC in the serum taken from the patients with BCa [0.35�02 ?g/ml (range: 0.20-0.78 ?g/ml)] was significantly (P<0.001) lower than the serum cysC concentration of the healthy people [0.68�05 ?g/ml (range: 0.52-0.89 ?g/ml)]. The urinary cysC concentration of the BCa patients [0.19�01 ?g/ml (range: 0.09-0.34 ?g/ml)] was not significantly different from the urinary cysC concentration of the healthy people [0.24�02 ?g/ml (range: 0.16-0.33 ?g/ml)]. Receiver operating characteristic (ROC) curve showed that BCa patients with cysC concentration <0.54 ?g/ml [sensitivity: 87%; specificity: 92%; area under the curve (AUC) of ROC: 0.927; P=0.02] could be optimally separated from healthy people. The ROC curve further showed that superficial low-grade patients with cysC concentration lower than 0.36 ?g/ml (sensitivity: 0.63%; specificity: 0.58%; AUC of ROC: 0.635; P=0.08) could not be optimally separated from high-risk tumour patients. Interpretation & conclusions: BCa patients have lower serum cysC concentration than the control group. Serum cysC may be considered as a potential marker of BCa but not its aggressiveness.