Surface plasmon resonance imaging biosensors for aromatase based on a potent inhibitor and a specific antibody: Sensor development and application for biological material

Is the leptin/BMI ratio a reliable biomarker for endometriosis?

Background

The aim of this study was to analyze the concentration of leptin in peritoneal fluid and plasma and to assess their role as potential biomarkers in the diagnosis of endometriosis.

Materials & methods

Leptin adjusted for BMI (leptin/BMI ratio) was measured using surface plasmon resonance imaging (SPRI) biosensors. Patients with suspected endometriosis were included in the study. Plasma was collected from 70 cases, and peritoneal fluid from 67 cases. Based on the presence of endometriosis lesions detected during laparoscopy, patients were divided into a study group and a control group (patients without endometriosis).

Results

Leptin/BMI ratio in plasma did not differ between women with endometriosis and the control group (0.7159 ± 0.259 vs 0.6992 ± 0.273, p= 0,7988). No significant differences were observed in peritoneal leptin/BMI ratio levels in patients with and without endometriosis (0.6206 ± 0.258 vs 0.6215 ± 0.264, p= 0,9896). Plasma and peritoneal leptin/BMI ratios were significantly lower in women with endometriosis - related primary infertility compared to women with endometriosis without primary infertility (0.640 ± 0.502 vs 0.878 ± 0.623, p < 0.05). The difference was observed in case of primary infertility, but not in terms of the secondary one. No significant differences were noted between leptin/BMI ratio in the proliferative phase and the secretory phase (0.716 ± 0.252 vs 0.697 ± 0.288, p= 0,7785).

Conclusion

The results of present study do not support the relevance of leptin concentration determination as a biomarker of the endometriosis. Due to the limited number of samples in the tested group, further studies are needed to confirm its role.

Development of an SPRi Test for the Quantitative Detection of Cadherin 12 in Human Plasma and Peritoneal Fluid

A new method for the determination of cadherin 12 (CDH12)-an adhesive protein that has a significant impact on the development, growth, and movement of cancer cells-was developed and validated. The method is based on a biosensor using surface plasmon resonance imaging (SPRi) detection. A quartz crystal microbalance was used to analyze the characteristics of the formation of successive layers of the biosensor, from the linker monolayer to the final capture of CDH12 from solution. The association equilibrium constant (KA = 1.66 × 1011 dm3 mol-1) and the dissociation equilibrium constant (KD = 7.52 × 10-12 mol dm-3) of the anti-CDH12 antibody-CDH12 protein complex were determined. The determined analytical parameters, namely the values determining the accuracy, precision, and repeatability of the method, do not exceed the permissible 20% deviations specified by the aforementioned institutions. The proposed method is also selective with respect to possible potential interferents, occurring in up to 100-fold excess concentration relative to the CDH12 concentration. The determined Limit of Quantification (LOQ = 4.92 pg mL-1) indicates the possibility of performing quantitative analysis in human plasma or peritoneal fluid without the need to concentrate the samples; however, particular attention should be paid to their storage conditions, as the analyte does not exhibit high stability. The Passing-Bablok regression model revealed good agreement between the reference method and the SPRi biosensor, with ρSpearman values of 0.961 and 0.925.

New Biosensor for Determination of Neuropilin-1 with Detection by Surface Plasmon Resonance Imaging

Neuropilin-1 is transmembrane protein with soluble isoforms. It plays a pivotal role in both physiological and pathological processes. NRP-1 is involved in the immune response, formation of neuronal circuits, angiogenesis, survival and migration of cells. The specific SPRI biosensor for the determination of neuropilin-1 was constructed using mouse monoclonal antibody that captures unbound NRP-1 form body fluids. The biosensor exhibits linearity of the analytical signal between 0.01 and 2.5 ng/mL, average precision value 4.7% and recovery between 97% and 104%. The detection limit is 0.011 ng/mL, and the limit of quantification is 0.038 ng/mL. The biosensor was validated by parallel determination of NRP-1 in serum and saliva samples using the ELISA test, with good agreement of the results.

A Multiple-Array SPRi Biosensor as a Tool for Detection of Gynecological-Oncological Diseases

Diagnostics based on the determination of biomarkers in body fluids will be more successful when several biomarkers are determined. A multiple-array SPRi biosensor for the simultaneous determination of CA125, HE4, CEA, IL-6 and aromatase has been developed. Five individual biosensors were placed on the same chip. Each of them consisted of a suitable antibody covalently immobilized onto a gold chip surface via a cysteamine linker by means of the NHS/EDC protocol. The biosensor for IL-6 works in the pg mL^-1 range, that for CA125 in the µg mL^-1 range, and the other three within the ng mL^-1 range; these are ranges suitable for the determination of biomarkers in real samples. The results obtained with the multiple-array biosensor are very similar to those obtained with a single biosensor. The applicability of the multiple biosensor was demonstrated using several examples of plasma from patients suffering from ovarian cancer and endometrial cyst. The average precision was 3.4% for the determination of CA125, 3.5% for HE4, 5.0% for CEA and IL-6, and 7.6% for aromatase. The simultaneous determination of several biomarkers may be an excellent tool for the screening of the population for earlier detection of diseases.

An Immunosensor for the Determination of Cortisol in Serum and Saliva by Array SPRi

Cortisol is a hormone which plays an essential role in the immune, endocrine, cardiovascular, renal and skeletal systems. Its level increases in response to stress, illness, injury or exhaustion, and it is therefore a significant diagnostic biomarker of stress. An immunosensor for the determination of cortisol by SPRi array was developed. The receptive part of the immunosensor is mouse monoclonal antibody against cortisol, immobilized via cysteamine linker. The optimum pH of the immunosensor is 7.4, and the optimum concentration of the antibody is 50 ng mL^-1. The immunosensor is specific for cortisol, and its linear response ranges from 0.20 ng mL^-1 (LOQ) to 8 ng mL^-1. The precision of the determination was between 3.1% and 3.3%, and the recovery between 99% and 102%. The immunosensor was validated by simultaneous determination of cortisol in serum and saliva samples by a standard method, with good agreement between the results.

Two Biosensors for the Determination of Interleukin-6 in Blood Plasma by Array SPRi

Interleukin-6 (IL-6) is a biomarker of inflammation, the advanced stage of COVID-19, and several cancers, including ovarian cancer. Two biosensors for the determination of IL-6 in blood plasma by array SPRi have been developed. One of these biosensors consists of the mouse monoclonal anti-IL-6 antibody as the receptor immobilized via the cysteamine linker. The second contains galiellalactone as the receptor, being an inhibitor specific for IL-6, immobilized via octadecanethiol (ODM) as the linker. Both biosensors are specific for IL-6. The biosensor with the antibody as the receptor gives a linear analytical response between 3 (LOQ) and 20 pg mL⁻¹ and has a precision between 8% and 9.8% and recovery between 97% and 107%, depending on the IL-6 concentration. The biosensor with galiellalactone as the receptor gives a linear analytical response between 1.1 (LOQ) and 20 pg mL⁻¹, and has a precision between 3.5% and 9.3% and recovery between 101% and 105%, depending on IL-6 concentration. Both biosensors were validated. Changes in IL-6 concentration in blood plasma before and after resection of ovarian tumor and endometrial cyst, as determined by the two developed biosensors, are given as an example of a real clinical application.

Plasma aromatase as a sensitive and selective potential biomarker of bladder cancer and its role in tumorigenesis

Bladder cancer (BCa) is the ninth most common cancer in the world and its early detection is crucial for successful therapy. Unfortunately, there are no satisfactory tools to detect BCa at early stages and BCa's confirmation muscle-invasive. The search for a suitable biomarker is therefore necessary and aromatase is a potential candidate. The purpose of the current study was to determine if aromatase serves as a biomarker of BCa. A Surface Plasmon Resonance Imaging biosensor was applied for the quantification and determination of aromatase. A total of 3 µl blood plasma was used for a single measurement. The results revealed that the aromatase concentration in the plasma of patients with BCa (n=78) ranged from 17.41-57.44 ng/ml. The range determined in healthy donors (n=18) was 2.59-7.74 ng/ml. Additionally, it was revealed that muscle invasive BCa samples exhibited elevated, statistically significant (P=0.01) average aromatase concentrations in blood plasma (38.64 ng/ml) when compared with non-muscle invasive samples (29.83 ng/ml). The results demonstrated that plasma aromatase may serve as an excellent bimarker of BCa with 100% sensitivity, 100% selectivity and an area under the curve value of the reciever operating characteristic curve equal to 1.0. Furthermore, the marker differenciated between muscle-invasive and non muscle-invasive BCa with a sensitivity of 60% and a specificity of 81%. In conclusion, aromatase may serve a role in bladder tumorigenesis.

A New Analytical Method for Determination of Cathepsin L Based on the Surface Plasmon Resonance Imaging Biosensor

The purpose of this study was to develop a new method for a determination of the cathepsin L—biosensor based on the Surface Plasmon Resonance Imaging technique. The cathepsin L is an endopeptidase, which degrades proteins and plays an important role in various processes occurring in the human body. The detection technique, Surface Plasmon Resonance Imaging, is an optical, label-free technique, which can be used for quantitative determination of the different proteins. In order to bind the enzyme, the cathepsin L inhibitor—RKLLW-NH₂ was used. The validation process showed that parameters: precision, accuracy, and selectivity of the method were acceptable. The analytically useful range of the standard curve was 0.50 ng/mL—15.00 ng/mL. The detection and quantification limit of method was 1.67 pg/mL and 5.07 pg/mL, respectively. The usefulness of the developed method was confirmed by the determination of the cathepsin L concentration in the blood plasma of some healthy persons and in the blood plasma of patients. The obtained results were compared with the results obtained by the ELISA. It was found that the correlation between these two methods was very strong, what suggest that the developed method can be used as the competitive method to the ELISA.

Concentration of Proteasome in the Blood Plasma of Children with Acute Appendicitis, Before and After Surgery, and Its Correlation with CRP

OBJECTIVE

The determination of 20S proteasome concentration in the blood plasma of children with appendicitis and its correlation with CRP.

DESIGN AND SETTING

Thirty-one children with acute appendicitis, were randomly included into the study (age 5 years up to 17 years, mean age 11.5 + 1 years).

PARTICIPANTS

There were 17 girls and 14 boys. Eighteen healthy, age-matched subjects, admitted for planned surgeries served as controls. Exclusion criteria were: severe preexisting infections, immunological or cardiovascular diseases that required long-term medication, and complicated cases of appendicitis with perforation of appendix and/or peritonitis.

MAIN OUTCOME MEASURES

The 20S proteasome concentrations in the blood plasma of patients with acute appendicitis were highest before the surgery and were above the range of concentrations measured in controls, and the difference was statistically significant.

RESULTS

The 20S proteasome concentration measured 24 and 72 h after the operation, slowly decreased over time, and still did not reach the normal range, when compared with the concentration measured in controls (p < 0.05).

CONCLUSIONS

20S proteasome concentration may reflect the metabolic response to acute state inflammation, and the process of gradual ebbing of the inflammation. The method of operation-classic open appendectomy, or laparoscopic appendectomy, does not influence the general trend in 20S proteasome concentration.

Environmental Stability of Plasmonic Biosensors Based on Natural versus Artificial Antibody

Plasmonic biosensors based on the refractive index sensitivity of localized surface plasmon resonance (LSPR) are considered to be highly promising for on-chip and point-of-care biodiagnostics. However, most of the current plasmonic biosensors employ natural antibodies as biorecognition elements, which can easily lose their biorecognition ability upon exposure to environmental stressors (e.g., temperature and humidity). Plasmonic biosensors relying on molecular imprints as recognition elements (artificial antibodies) are hypothesized to be an attractive alternative for applications in resource-limited settings due to their excellent thermal, chemical, and environmental stability. In this work, we provide a comprehensive comparison of the stability of plasmonic biosensors based on natural and artificial antibodies. Although the natural antibody-based plasmonic biosensors exhibit superior sensitivity, their stability (temporal, thermal, and chemical) was found to be vastly inferior to those based on artificial antibodies. Our results convincingly demonstrate that these novel classes of artificial antibody-based plasmonic biosensors are highly attractive for point-of-care and resource-limited conditions where tight control over transport, storage, and handling conditions is not possible.

Matrix metalloproteinase-2 and its correlation with basal membrane components laminin-5 and collagen type IV in paediatric burn patients measured with Surface Plasmon Resonance Imaging (SPRI) biosensors

The purpose of this study was the determination of matrix metalloproteinase-2 and its correlation with basal membrane components laminin-5 and collagen type IV in the blood plasma of burn patients measured with Surface Plasmon Resonance Imaging (SPRI) biosensors.

MATERIAL AND METHODS

31 children scalded by hot water who were managed at the Department of Paediatric Surgery between 2014-2015, after primarily presenting with burns in 4-20% TBSA were included into the study (age 9 months up to 14 years, mean age 2,5+1 years). There were 10 girls and 21 boys. Venous blood samples were drawn 2-6h, and 12-16h after the thermal injury, and on the subsequent days 3, 5 and 7. The matrix metalloproteinase-2, collagen type IV and laminin-5 concentrations were assessed using Surface Plasmon Resonance Imaging by the investigators blinded to the other data.

RESULTS

The MMP-2, laminin-5 and collagen type IV concentrations in the blood plasma of patients with burns, were highest 12-16h after thermal injury, the difference was statistically significant. The MMP-2, laminin-5 and collagen type IV concentrations measured 3 days, 5 days and 7 days after the thermal injury, slowly decreased over time, and on the 7th day reached the normal range, when compared with the concentration measured in controls.

CONCLUSION

Current work is the first follow-up study regarding MMP-2 in burns. MMP-2, laminin-5 and collagen type IV levels were elevated early after burn injury in the plasma of studied patients, and were highest 12-16h after the injury. MMP-2, laminin-5 and collagen type IV levels were not proportional to the severity of the burn. We believe in the possibility that the gradual decrease of MMP-2, collagen type IV and laminin-5 concentrations could be connected with the process of healing, but to prove it, more investigation is needed in this area. The SPR imaging biosensor is a good diagnostic tool for determination of MMP-2, laminin-5 and collagen type IV in blood plasma of patients with burns.

Overexpression of ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) in serum of children after thermal injury

PURPOSE

The study aims to determinate concentrations of ubiquitin C-terminal hydrolase 1 (UCHL1), which hydrolyzes amino acids from ubiquitin and cleave di-ubiquitins, in serum of children after thermal injury.

PATIENTS/METHODS

42 children scalded by hot water, managed at the Department of Pediatric Surgery, with burns in 4-20% TBSA were included into the study (age 9 months up to 14 years, mean age 2.5±1 years). Blood plasma UCHL1 concentration was assessed in 2-6h, 12-16h, 3d, 5d, and 7d after injury using surface plasmon resonance imaging biosensor. 18 healthy subjects admitted for planned surgeries served as controls.

RESULTS

The UCHL1 concentration in the blood plasma of patients with thermal injuries reached its peak 12-16h after thermal injury and slowly decreased over time, and still did not reach the normal range on the 7th day after thermal injury. Mean concentrations of UCHL1 after thermal injury were above the range measured in controls (0.12ng/ml): 2-6h after injury - 5.59ng/dl, 12-16h after injury - 9.16ng/dl, 3 days after injury - 6.94ng/dl, 5 days after 5.41ng/dl, 7 days after injury - 4.09ng/dl.

CONCLUSIONS

We observed sudden increase in the concentration of UCHL1 2-16h after thermal injury with the slow decrease in the UCHL1 concentration over the time. UCHL1 concentration was proportional to the severity of the burn. Further studies are needed to determine the mechanisms by which UCHL1 contributes to metabolic response following thermal injury.

SPR imaging biosensor for determination of laminin-5 as a potential cancer marker in biological material

A new method for the selective determination of laminin-5 concentration using a biosensor and surface plasmon resonance imaging (SPRI) technique is presented. A biosensor based on the specific interaction of laminin-5 with rabbit polyclonal antibody was constructed. The analytically useful dynamic response range of the biosensor is between 0.014 and 0.1 ng mL(-1). The detection limit is 4 pg mL(-1). The potential influence of interferences on the SPRI signal was investigated, and the high selectivity of the biosensor was confirmed. In order to demonstrate the potential application of the biosensor, laminin-5 concentration in blood plasma was determined. The results were compared with the laminin-5 concentration obtained by the commercial enzyme-linked immunosorbent assay (ELISA) kit. A comparison of results from healthy donors obtained by SPRI measurement and ELISA indicates that they are close and shows good agreement with the data reported in the literature. The plasma samples of bladder cancer patients gave higher concentration measured with specific biosensor than by ELISA assay. The study shows the clear difference in concentration of laminin-5 in healthy humans and patients with bladder cancer. Extensive clinical studies using the newly developed method can result in an increase in the use of laminin-5 as a potential cancer marker.

Surface plasmon resonance: advances of label-free approaches in the analysis of biological samples

Surface plasmon resonance sensors have made vast advancements in the sensing technology and the number of applications achievable. New developments in surface plasmon resonance sensors have gained considerable momentum promoted by the urgent needs of fast, reliable and label-free methods for detection and quantification of analytes in molecular biology, medicine and other life sciences. However, even if enormous improvements in the limits of detections have been achieved, this technology still faces important challenges to be translated to clinical practice or in-field measurements. This paper reviews the important recent advances of this technology for the label-free detection in real biological samples and we discussed the key challenges to be overcome to transit from prototypes to commercial biosensors.