Non-protein coding RNA sequences mediate specific colorimetric detection of Staphylococcus aureus on unmodified gold nanoparticles

Nonprotein coding RNA (npcRNA) is a transcribed gene sequence that is not able to translate into protein, yet it executes a specific function in modulation and regulation mechanisms. As npcRNA is highly resistant to the mutation, the Sau-02 npcRNA gene and its probe oligonucleotide, which are specifically present in Staphylococcus aureus and in methicillin-resistant S. aureus only, used to develop a highly specific and sensitive colorimetric assay on unmodified gold nanoparticles (AuNPs). Hybridization between the npcRNA Sau-02 gene sequences was detected through noncrosslinking AuNP aggregation in salt solution in the presence of probe-target gene sequences. AuNPs of 10 and 15 nm in sizes with monovalent ion salt (NaCl) solution were optimized as the ideal tool for investigating the stability of AuNPs upon the addition of gene sequences. The state dispersed and aggregated forms of 10 nm AuNPs with the presented colorimetric assay were justified through field emission scanning electron microscopy and atomic force microscopy. The particle distribution of two different AuNP states was evaluated through particle distribution analysis. The lowest detection amount of S. aureus npcRNA from the colorimetric assay performed was 6 pg/µL, as the color of AuNPs turned blue with the presence of probe oligonucleotides and target gene sequences.

Carbon Material Hybrid Construction on an Aptasensor for Monitoring Surgical Tumors

Carcinoembryonic antigen (CEA) is a glycoprotein, one of the common tumor biomarkers, found at low levels in body fluids. Generally, overexpression of CEA is found in various cancers, including ovarian, breast, lung, colorectal, gastric, and pancreatic cancers. Since CEA is an important tumor biomarker, the quantification of CEA is helpful for diagnosing cancer, monitoring tumor progression, and the follow-up treatment. This research develops a highly sensitive sandwich aptasensor for CEA identification on an interdigitated electrode sensor. Carbon-based material was used to attach a higher anti-CEA capture aptamer onto the sensor surface through a chemical linker, and then, CEA was quantified by the aptamer. Furthermore, CEA-spiked serum was tested by using the immobilized aptamer, which was found to not affect the target validation. The limit of detection for CEA in PBS and serum is calculated from a linear regression graph to be 0.5 ng/mL with R ² values of 0.9593 and 0.9657, respectively, over a linear range from 0.5 to 500 ng/mL. This CEA quantification by the aptasensor can help diagnose various surgical tumors and monitor their progression.

Aluminum Microcomb Electrodes on Silicon Wafer for Detecting Val66Met Polymorphism in Brain-Derived Neurotrophic Factor

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) dysregulation is widely related with various psychiatric and neurological disorders, including schizophrenia, depression, Rett syndrome, and addiction, and the available evidence suggests that BDNF is also highly correlated with Parkinson's and Alzheimer's diseases.

METHODS

The BDNF target sequence was detected on a capture probe attached on aluminum microcomb electrodes on the silicon wafer surface. A capture-target-reporter sandwich-type assay was performed to enhance the detection of the BDNF target.

RESULTS

The limit of detection was noticed to be 100 aM. Input of a reporter sequence at concentrations >10 aM improved the detection of the target sequence by enhancing changes in the generated currents. Control experiments with noncomplementary and single- and triple-mismatches of target and reporter sequences did not elicit changes in current levels, indicating the selective detection of the BDNF gene sequence.

CONCLUSION

The above detection strategy will be useful for the detection and quantification of BDNF, thereby aiding in the provision of suitable treatments for BDNF-related disorders.

Alzheimer's Disease Determination by a Dual Probe on Gold Nanourchins and Nanohorn Hybrids

Background

Alzheimer’s disease (AD) is a neurodegenerative chronic disorder that causes dementia and problems in thinking, cognitive impairment and behavioral changes. Amyloid-beta (Aβ) is a peptide involved in AD progression, and a high level of Aβ is highly correlated with severe AD. Identifying and quantifying Aβ levels helps in the early treatment of AD and reduces the factors associated with AD.

Materials and Methods

This research introduced a dual probe detection system involving aptamers and antibodies to identify Aβ. Aptamers and antibodies were attached to the gold (Au) urchin and hybrid on the carbon nanohorn-modified surface. The nanohorn was immobilized on the sensor surface by using an amine linker, and then a Au urchin dual probe was immobilized.

Results

This dual probe-modified surface enhanced the current flow during Aβ detection compared with the surface with antibody as the probe. This dual probe interacted with higher numbers of Aβ peptides and reached the detection limit at 10 fM with R²=0.992. Furthermore, control experiments with nonimmune antibodies, complementary aptamer sequences and control proteins did not display the current responses, indicating the specific detection of Aβ.

Conclusion

Aβ-spiked artificial cerebrospinal fluid showed a similar response to current changes, confirming the selective identification of Aβ.

Anticancer potential of rhizome extract and a labdane diterpenoid from Curcuma mutabilis plant endemic to Western Ghats of India

Zingiberaceae plants are well known for their use in ethnomedicine. Curcuma mutabilis Škorničk., M. Sabu & Prasanthk., is an endemic Zingiberaceae species from Western Ghats of Kerala, India. Here, we report for the first time, the anticancer potential of petroleum ether extract from C. mutabilis rhizome (CMRP) and a novel labdane diterpenoid, (E)-14, 15-epoxylabda-8(17), 12-dien-16-al (Cm epoxide) isolated from it. CMRP was found to be a mixture of potent bioactive compounds including Cm epoxide. Both the extract and the compound displayed superior antiproliferative activity against several human cancer cell lines, without any display of cytotoxicity towards normal human cells such as peripheral blood derived lymphocytes and erythrocytes. CMRP treatment resulted in phosphatidylserine externalization, increase in the levels of intracellular ROS, Ca²⁺, loss of mitochondrial membrane potential as well as fragmentation of genomic DNA. Analyses of transcript profiling and immunostained western blots of extract-treated cancer cells confirmed induction of apoptosis by both intrinsic and extrinsic pathways. The purified compound, Cm epoxide, was also found to induce apoptosis in many human cancer cell types tested. Both CMRP and the Cm epoxide were found to be pharmacologically safe in terms of acute toxicity assessment using Swiss albino mice model. Further, molecular docking interactions of Cm epoxide with selected proteins involved in cell survival and death were also indicative of its druggability. Overall, our findings reveal that the endemic C. mutabilis rhizome extract and the compound Cm epoxide isolated from it are potential candidates for development of future cancer chemotherapeutics.

MXene Surface on Multiple Junction Triangles for Determining Osteosarcoma Cancer Biomarker by Dielectrode Microgap Sensor

Background

In recent years, nanomaterials have justified their dissemination for biosensor application towards the sensitive and selective detections of clinical biomarkers at the lower levels. MXene is a two-dimensional layered transition metal, attractive for biosensing due to its chemical, physical and electrical properties along with the biocompatibility.

Materials and Methods

This work was focused on diagnosing osteosarcoma (OS), a common bone cancer, on MXene-modified multiple junction triangles by dielectrode sensing. Survivin protein gene is highly correlated with OS, identified on this sensing surface. Capture DNA was immobilized on MXene by using 3-glycidoxypropyltrimethoxysilane as an amine linker and duplexed by the target DNA sequence.

Results

The limitation and sensitivity of detection were found as 1 fM with the acceptable regression co-efficient value (y=1.0037⨰ + 0.525; R²=0.978) and the current enhancement was noted when increasing the target DNA concentrations. Moreover, the control sequences of single- and triple-mismatched and noncomplementary to the target DNA sequences failed to hybridize on the capture DNA, confirming the specificity. In addition, different batches were prepared with capture probe immobilized sensing surfaces and proved the efficient reproducibility.

Conclusion

This microgap device with Mxene-modified multiple junction triangles dielectrode surface is beneficial to quantify the survivin gene at its lower level and diagnosing OS complication levels.

Graphene oxide-gold nanoparticle-aptamer complexed probe for detecting amyloid beta oligomer by ELISA-based immunoassay

Highly sensitive and easy detection method for Alzheimer's disease (AD) with a suitable biomarker is mandatory for preventing the factors resulting from AD. This research reports a modified ELISA with graphene for the detection of AD biomarker amyloid beta (Aβ) oligomer. Gold nanoparticle (AuNP) conjugated aptamer was used as the capture probe and attached on ELISA-graphene oxide surface through the amine linker. Antibody was used as the detection molecule to reach the maximum detection of Aβ oligomer. Suitable level of APTMS (2%), size of AuNP (30 nm) and aptamer concentration (2 μM) were optimized. This sandwich pattern of aptamer-Aβ oligomer-antibody helps to reach the detection at 50 pM on the optimized ELISA surface and the control experiments in the absence of Aβ oligomer or anti-Aβ oligomer antibody did not show the significant optical detection at 492 nm, indicting the specific detection. Further, Aβ oligomer spiked artificial cerebrospinal fluid did not interfere the detection of Aβ oligomer, confirming the selective detection. This new and modified ELISA surface helps to reach the lower detection of Aβ oligomer and diagnose AD.

Electroanalysis on an Interdigitated Electrode for High-Affinity Cardiac Troponin I Biomarker Detection by Aptamer-Gold Conjugates

The primary reasons for myocardial infarction (MI) are pericarditis, arrhythmia, and heart failure, causing predominant deaths worldwide. Patients need a potential diagnostic system and treatment before cardiomyocyte damage. Cardiac biomarkers are released from myocytes immediately after a heart attack. Troponin is an efficient biomarker released from dead cells within a few hours. Aptamers are artificial antibodies used effectively in the biosensor field for biomarker detection. Along with aptamers, the application of nanomaterials is also expected to enhance the detection limits of biosensors. In this investigation, selected aptamers against cardiac troponin I (cTnI) were conjugated with gold nanoparticles (GNPs) to diagnose MI and compared with an aptamer-only control group on an interdigitated electrode surface. Based on electroanalysis, cTnI was detected at concentrations as low as 1 fM, and the detection limit improved to 100 aM when the aptamer was conjugated with GNP. In addition, aptamer-GNP conjugates increased the current level at the tested concentrations of cTnI. Control experiments with noncomplementary aptamers and relevant proteins did not result in notable changes in the current, demonstrating the selective detection of cTnI.

Synthesis and characterization of reduced graphene oxide using the aqueous extract of Eclipta prostrata

In this study, biological deoxygenation of graphene oxide (GO) using an Eclipta prostrata phytoextract was performed via the infusion method. The presence of oxide groups on the surface of graphene and removal of oxides groups by reduction were characterized through morphological and structural analyses. Field emission scanning electron microscopy images revealed that the synthesized GO and rGO were smooth and morphologically sound. Transmission electron microscopy images showed rGO developing lattice fringes with smooth edges and transparent sheets. Atomic force microscopy images showed an increase in the surface roughness of graphite oxide (14.29 nm) compared with that of graphite (1.784 nm) due to the presence of oxide groups after oxidation, and the restoration of surface roughness to 2.051 nm upon reduction. Energy dispersive X-ray analysis indicated a difference in the carbon/oxygen ratio between GO (1.90) and rGO (2.70). Fourier-transform infrared spectroscopy spectrum revealed peak stretches at 1029, 1388, 1578, and 1630 cm^-1 for GO, and a decrease in the peak intensity after reduction that confirmed the removal of oxide groups. X-ray photoelectron microscopy also showed a decrease in the intensity of oxygen peak after reduction. In addition, thermogravimetric analysis suggested that rGO was less thermally stable than graphite, graphite oxide, and GO, with rGO decomposing after heating at temperatures ranging from room temperature to 600 °C.

Heart Infection Prognosis Analysis by Two-dimensional Spot Tracking Imaging

Cardiovascular death is one of the leading causes worldwide; an accurate identification followed by diagnosing the cardiovascular disease increases the chance of a better recovery. Among different demonstrated strategies, imaging on cardiac infections yields a visible result and highly reliable compared to other analytical methods. Two-dimensional spot tracking imaging is the emerging new technology that has been used to study the function and structure of the heart and test the deformation and movement of the myocardium. Particularly, it helps to capture the images of each segment in different directions of myocardial strain values, such as valves of radial strain, longitudinal strain, and circumferential strain. In this overview, we discussed the imaging of infections in the heart by using the two-dimensional spot tracking.

Detection of microRNA-335-5p on an Interdigitated Electrode Surface for Determination of the Severity of Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) refers to the enlargement of the lower artery of the abdominal aorta, and identification of an early detection tool is urgently needed for diagnosis. In the current study, an interdigitated electrode (IDE) sensing surface was used to identify miRNA-335-5p, which reflects the formation of AAAs. The uniformity of the silica material was observed by 3D profilometry, and the chemically modified highly conductive surface improved the detection via the I-V mode. The targeted miRNA-335-5p was detected in a dose-dependent manner and based on linear regression and 3σ analyses, the sensitivity was determined to be 1 fM with a biotinylated probe. The high specificity was shown by discriminating the target sequence from noncomplementary and single- and triple-mismatched sequences. These outputs demonstrated the high-performance detection of miRNA-335-5p with good reproducibility for determination of the severity of AAA.

Aluminosilicate Nanocomposites from Incinerated Chinese Holy Joss Fly Ash: A Potential Nanocarrier for Drug Cargos

An incredible amount of joss fly ash is produced from the burning of Chinese holy joss paper; thus, an excellent method of recycling joss fly ash waste to extract aluminosilicate nanocomposites is explored. The present research aims to introduce a novel method to recycle joss fly ash through a simple and straightforward experimental procedure involving acidic and alkaline treatments. The synthesized aluminosilicate nanocomposite was characterized to justify its structural and physiochemical characteristics. A morphological analysis was performed with field-emission transmission electron microscopy, and scanning electron microscopy revealed the size of the aluminosilicate nanocomposite to be ~25 nm, while also confirming a uniformly spherical-shaped nanostructure. The elemental composition was measured by energy dispersive spectroscopy and revealed the Si to Al ratio to be 13.24 to 7.96, showing the high purity of the extracted nanocomposite. The roughness and particle distribution were analyzed using atomic force microscopy and a zeta analysis. X-ray diffraction patterns showed a synthesis of faceted and cubic aluminosilicate crystals in the nanocomposites. The presence of silica and aluminum was further proven by X-ray photoelectron spectroscopy, and the functional groups were recognized through Fourier transform infrared spectroscopy. The thermal capacity of the nanocomposite was examined by a thermogravimetric analysis. In addition, the research suggested the promising application of aluminosilicate nanocomposites as drug carriers. The above was justified by an enzyme-linked apta-sorbent assay, which claimed that the limit of the aptasensing aluminosilicate-conjugated ampicillin was two-fold higher than that in the absence of the nanocomposite. The drug delivery property was further justified through an antibacterial analysis against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive).

Nanodetection of Head and Neck Cancer on Titanium Oxide Sensing Surface

Head and neck cancer is a heterogeneous disease, originating in the squamous cells lining the larynx (voice box), mouth, pharynx (throat), nasal cavity and salivary glands. Head and neck cancer diagnosis at the later stage is greatly influencing the survival rate of the patient. It makes a mandatory situation to identify this cancer at the earlier stages of development with a suitable biomarker. Squamous cell carcinoma antigen (SCC-Ag) is a circulating serum tumour biomarker, and the elevated level has been found in the head and neck cancer patients and highly correlated with the tumour volume. The present research was carried out to detect and quantify the level of SCC-Ag on titanium oxide (TiO₂)-modified interdigitated electrode sensor (IDE) by SCC-Ag antibody. The detection of SCC-Ag was found at the level of 100 fM, while it was improved to 10 fM when the antibody was conjugated with gold nanostar, representing a 10-fold improvement. Interestingly, this enhancement in sensitivity is 1000-folds higher than other substrates. Moreover, the specificity analysis was carried out using two different control proteins and noticed that the antibody only recognised SCC-Ag, indicating the specific detection on IDE-TiO₂ sensing surface.

High-Affinity Detection of Alpha-Synuclein by Aptamer-Gold Conjugates on an Amine-Modified Dielectric Surface

Parkinson's disease (PD) is a progressive health issue and influences an increasingly larger number of people, especially at older ages, affecting the central nervous system (CNS). Alpha-synuclein is a biomarker closely correlated with the CNS and PD. The loss of neuronal cells in the substantia nigra leads to the aggregation of alpha-synuclein in the form of Lewy bodies, and Lewy neuritis is a neuropathological hallmark. The therapeutic approach of PD focuses on alpha-synuclein as an important substrate of PD pathology. So far, research has focused on antialpha-synuclein to minimize the burden of extracellular alpha-synuclein in the brain, and as a consequence, it ameliorates inflammation. Interdigitated electrode (IDE) biosensors are efficient tools for detecting various analytes and were chosen in this study to detect alpha-synuclein on amine-modified surfaces by using antiaptamer-alpha-synuclein as the probe. In addition, a gold nanoparticle-conjugated aptamer was used to enhance the detection limit. The limit of detection for the binding between alpha-synuclein and aptamer was found to be 10 pM. Control experiments were performed with two closely related proteins, amyloid-beta and tau, to reveal the specificity; the results show that the aptamer only recognized alpha-synuclein. The proposed strategy helps to identify the binding of aptamer and alpha-synuclein and provides a possible method to lower alpha-synuclein levels and inflammation in PD patients.

Coordinated Dispersion and Aggregation of Gold Nanorod in Aptamer-Mediated Gestational Hypertension Analysis

Gestational hypertension is one of the complicated disorders during pregnancy; it causes the significant risks, such as placental abruption, neonatal deaths, and maternal deaths. Hypertension is also responsible for the metabolic and cardiovascular issues to the mother after the years of pregnancy. Identifying and treating gestational hypertension during pregnancy by a suitable biomarker is mandatory for the healthy mother and foetus development. Cortisol has been found as a steroid hormone that is secreted by the adrenal gland and plays a pivotal role in gestational hypertension. A normal circulating level of cortisol is involved in the regulation of blood pressure, and it is necessary to monitor the changes in the level of cortisol during pregnancy. In this work, aptamer-based colorimetric assay is demonstrated as a model with gold nanorod to quantify the level of cortisol using the coordinated aggregation (at 500 mM of NaCl) and dispersion (with 10 μM of aptamer), evidenced by the scanning electron microscopy observation and UV-visible spectroscopy analysis. This colorimetric assay is an easier visual detection and reached the limit of detection of cortisol at 0.25 mg/mL. This method is reliable to identify the condition of gestational hypertension during the pregnancy period.

Aptamer-Antibody Complementation On Multiwalled Carbon Nanotube-Gold Transduced Dielectrode Surfaces To Detect Pandemic Swine Influenza Virus

BACKGROUND

A pandemic influenza viral strain, influenza A/California/07/2009 (pdmH1N1), has been considered to be a potential issue that needs to be controlled to avoid the seasonal emergence of mutated strains.

MATERIALS AND METHODS

In this study, aptamer-antibody complementation was implemented on a multiwalled carbon nanotube-gold conjugated sensing surface with a dielectrode to detect pandemic pdmH1N1. Preliminary biomolecular and dielectrode surface analyses were performed by molecular and microscopic methods. A stable anti-pdmH1N1 aptamer sequence interacted with hemagglutinin (HA) and was compared with the antibody interaction. Both aptamer and antibody attachments on the surface as the basic molecule attained the saturation at nanomolar levels.

RESULTS

Aptamers were found to have higher affinity and electric response than antibodies against HA of pdmH1N1. Linear regression with aptamer-HA interaction displays sensitivity in the range of 10 fM, whereas antibody-HA interaction shows a 100-fold lower level (1 pM). When sandwich-based detection of aptamer-HA-antibody and antibody-HA-aptamer was performed, a higher response of current was observed in both cases. Moreover, the detection strategy with aptamer clearly discriminated the closely related HA of influenza B/Tokyo/53/99 and influenza A/Panama/2007/1999 (H3N2).

CONCLUSION

The high performance of the abovementioned detection methods was supported by the apparent specificity and reproducibility by the demonstrated sensing system.

Glucose oxidase complexed gold-graphene nanocomposite on a dielectric surface for glucose detection: a strategy for gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus is a commonly occurring metabolic disorder during pregnancy, affecting >4% of pregnant women. It is generally defined as the intolerance of glucose with the onset or initial diagnosis during pregnancy. This illness affects the placenta and poses a threat to the baby as it affects the supply of proper oxygen and nutrients.

PURPOSE

Due to the high percentage of affected pregnant women, it should be mandatory to evaluate glucose levels during pregnancy and there is a need for a continuous monitoring system.

METHODS

Herein, the investigators modified the interdigitated (di)electrodes (IDE) sensing surface to detect the glucose on covalently immobilized glucose oxidase (GOx) with the graphene. The characterization of graphene and gold nanoparticle (GNP) was performed by high-resolution microscopy.

RESULTS

Sensitivity was found to be 0.06 mg/mL and to enhance the detection, GOx was complexed with GNP. GNP-GOx was improved the sensitive detection twofold from 0.06 to 0.03 mg/mL, and it also displayed higher levels of current changes at all the concentrations of glucose that were tested. High-performance of the above IDE sensing system was attested by the specificity, reproducibility and higher sensitivity detections. Further, the linear regression analysis indicated the limit of detection to be between 0.02 and 0.03 mg/mL.

CONCLUSION

This study demonstrated the potential strategy with nanocomposite for diagnosing gestational diabetes mellitus.

Hydrocephaly Analysis Supported by Computerized Tomography and Nuclear Magnetic Resonance

Hydrocephalus is widely known as "hydrocephaly" or "water in the brain," a building up of abnormal cerebrospinal fluid in the brain ventricles. Due to this abnormality, the size of the head becomes larger and increases the pressure in the skull. This pressure compresses the brain and causes damage to the brain. Identification by imaging techniques on the hydrocephalus is mandatory to treat the disease. Various methods and equipment have been used to image the hydrocephalus. Among them, computerized tomography (CT) scan and nuclear magnetic resonance (NMR) are the most considered methods and gives accurate result of imaging. Apart from imaging, cerebrospinal fluid-based biomarkers are also used to identify the condition of hydrocephalus. This review is discussed on "hydrocephalus" and its imaging captured by CT scan and NMR to support the biomarker analysis.

Recent Advances in Identifying Biomarkers and High-Affinity Aptamers for Gynecologic Cancers Diagnosis and Therapy

Cancer is the uncontrollable abnormal division of cell growth, caused due to the varied reasons. Cancer can be expressed in any part of the body, and it is one of the death-causing diseases. Human reproductive organs are commonly damaged by cancer. In particular, the women reproductive system is affected by various cancers including ovarian, cervical, endometrial, vaginal, fallopian tube, and vulvar cancers. Identifying these cancers at earlier stages prevents the damage to the organs. Aptamer is the potential probe that can identify these cancers. Aptamer is an artificial antibody selected from the randomized library of molecules and has a high binding affinity to the target biomarker. Targeting cancers in the reproductive organs using aptamers showed an excellent efficiency of detection compared to other probes. Different aptamers have been generated against the gynaecological cancer biomarkers, which include HE4, CA125, VEGF, OCCA (for ovarian cancer), EGFR, FGFR1, K-ras (for endometrial cancer), HPV E-16, HPV E-7, HPV E-6, tyrosine, and kinase (for cervical cancer), which help to identify the cancers in woman reproductive organs. In this overview, the biomarkers for gynecologic cancers and the relevant diagnosing systems generated using the specific aptamers are discussed. Furthermore, the therapeutic applications of aptamer with gynaecological cancers are narrated.

Gold Nanorod Integrated Electrochemical Sensing for Hyperglycaemia on Interdigitated Electrode

Gestational diabetes (hyperglycaemia) is an elevated blood sugar level diagnosed during the period of pregnancy and affects the baby's health. Hyperglycaemia has been found within the gestational weeks between 24 and 28, and the foetus has also the possibility of getting out prior to this test frame; it causes excessive birth weight, early birth, low-blood sugar level, respiratory distress syndrome, and type-2 diabetes to the mother. It creates a mandatory situation to identify the hyperglycaemia at least during the pregnancy weeks from 18 to 20. Further, a continuous monitoring of the level of glucose is necessary for the proper delivery. In this work, a method is introduced for glucose detection at 0.06 mg/mL, assisted by gold nanorod (GNR)-conjugated glucose oxidase (GOx) on interdigitated electrode sensor. In the absence of GNR, GOx shows the limit of glucose detection to be 0.25 mg/mL. Moreover, with GOx-GNR the reactions of all the glucose concentrations have recorded higher levels of the current from the baseline. With the specificity analysis, it was found that the glucose only reacts with GOx-GNR and discriminates other sugars efficiently. This method of detection is useful to diagnose and continuously monitor the glucose level during the pregnancy period.

Complementation of ELISA and an Interdigitated Electrode Surface in Gold Nanoparticle Functionalization for Effective Detection of Human Blood Clotting Defects

Developing an enhanced diagnosis using biosensors is important for the treatment of patients before disease complications arise. Improving biosensors would enable the detection of various low-abundance disease biomarkers. Efficient immobilization of probes/receptors on the sensing surface is one of the efficient ways to enhance detection. Herein, we introduced the pre-alkaline sensing surface with amine functionalization for capturing gold nanoparticle (GNP) conjugated to human blood clotting factor IX (FIX), and we demonstrated the excellent performance of the strategy. We have chosen the enzyme-linked immunosorbent assay (ELISA) and the interdigitated electrode (IDE), which are widely used, to demonstrate our method. The optimal amount for silanization has been found to be 2.5%, and 15-nm-sized GNPs are ideal and characterized. The limit of FIX detection was attained with ELISA at 100 pM with the premixed GNPs and FIX, which shows 60-fold improvement in sensitivity without biofouling, as compared to the conventional ELISA. Further, FIX was detected with higher specificity in human serum at a 1:1280 dilution, which is equivalent to 120 pM FIX. These results were complemented by the analysis on IDE, where improved detection at 25 pM was achieved, and FIX was detected in human serum at the dilution of 1:640. These optimized surfaces are useful for improving the detection of different diseases on varied sensing surfaces.

Gold nano-urchin integrated label-free amperometric aptasensing human blood clotting factor IX: A prognosticative approach for "Royal disease"

This article is clearly presenting the development of a biosensor for human factor IX (FIX) to diagnose the blood clotting deficiency, a so-called 'Royal disease' using an interdigitated electrode (IDE) with the zinc oxide surface modification. Gold nano-urchins (GNUs) with 60 nm in diameter was integrated into a streptavidin-biotinylated aptamer strategy to enhance the active surface area. Two different comparative studies have been done to validate the system to be practiced in the current work holds with a higher capability for the high-performance sense. Whereby, the presence and absence of GNUs in the aptasensing system for FIX interaction were investigated using the amperometric measurement, using a linear sweep voltage of 0-2 V at 0.01 V step voltage. The detection limit was 6 pM based on 3σ calculation when GNUs integrated aptamer assay was utilized for FIX detection, which shows 8 folds sensitivity enhancement comparing the condition in the absence of GNU and 50 folds higher than sensitive radio-isotope and surface plasmon resonance assays. Albeit, the surface and molecular characterizations were well demonstrated by scanning electron microscopy, atomic force microscopy, 3D nano-profilometry and further supports were rendered by UV-Vis spectroscopy and Enzyme-linked apta-sorbent assay (ELASA). Furthermore, the spiking experiment was done by FIX-spikes in human blood serum in order to demonstrate the stability with a higher non-fouling.

Amine-Aldehyde Chemical Conjugation on a Potassium Hydroxide-Treated Polystyrene ELISA Surface for Nanosensing an HIV-p24 Antigen

The enzyme-linked immunosorbent assay (ELISA) has been widely used for disease surveillance and drug screening due to its relatively higher accuracy and sensitivity. Fine-tuning the ELISA is mandatory to elevate the specific detection of biomolecules at a lower abundance. Towards this end, higher molecular capture on the polystyrene (PS) ELISA surface is crucial for efficient detection, and it could be attained by immobilizing the molecules in the correct orientation. It is highly challenging to immobilize protein molecules in a well-aligned manner on an ELISA surface due to charge variations. We employed a 3-(aminopropyl) triethoxysilane (APTES)- and glutaraldehyde (GLU)-coupled PS surface chemical strategy to demonstrate the high performance with ELISA. A potassium hydroxide treatment followed by an equal ratio of 1% APTES and GLU attachment was found to be optimal, and a longer incubation with GLU favored maximum sensitivity. p24 is a vital early secreting antigen for diagnosing human immunodeficiency virus (HIV), and it has been used for efficient detection with the above chemistry. Three different procedures were followed, and they led to the improved detection of the HIV-p24 antigen at 1 nM, which is a 30-fold higher level compared to a conventional ELISA surface. The surface chemical functionalization shown here also displays a higher specificity with human serum and HIV-TAT. The above approach with the designed surface chemistry could also be recommended for disease diagnosis on other sensing surfaces involving the interaction of the probe and the analyte in heterogeneous test samples.

Diagnosing Perioperative Cardiovascular Risks in Noncardiac Surgery Patients

Every year, over 200 million adults are undergoing noncardiac surgery. These noncardiac surgery patients may face the risk of cardiac mortality and morbidity during the perioperative and recovery periods. Around ten million patients who underwent noncardiac surgery experience cardiac complications within the first 30 days of the postoperative period; the complications are myocardial infarction, cardiac death, and cardiac arrest. This cardiovascular risk is mostly faced by the patients having cerebrovascular or cardiac disease and the patients with the age greater than 50 years. Monitoring and treating cardiac diseases with a suitable biomarker during the perioperative period is necessary for the early recovery of noncardiac surgery patients. This review discussed the risk factors and the key guidelines to avoid the cardiovascular risks during the perioperative period of noncardiac surgery patients. In addition, the biomarkers and identification strategies for cardiac diseases are discussed.

Aptamer: A Versatile Probe in Medical Diagnosis

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Red Spectral Shift in Sensitive Colorimetric Detection of Tuberculosis by ESAT-6 Antigen-Antibody Complex: a New Strategy with Gold Nanoparticle

Tuberculosis (TB) is a highly contagious life-threatening disease caused by the bacterial pathogen Mycobacterium tuberculosis. ESAT-6, an abundant early secretory antigenic target protein by M. tuberculosis, found to play a vital role in virulence. Developing a friendly method for the detection of ESAT-6 at the lower concentration facilitates to treat TB at an earlier stage and helps to control the spreading of disease. Herein, a new single-step approach was designed and was done by pre-mixing ESAT-6 and antibody before being added to the gold nanoparticle (GNP) followed by the salt-induced aggregation. We could attain the detection limit of 1.25 pM, showing the aggregation of GNP and the red spectral shift. Further, a higher specificity was demonstrated with the lack of electrostatic biofouling by ESAT-6 on GNP and retained the dispersed GNP in the presence of 10-kDa culture filtrate protein from M. tuberculosis. The required precise antibody concentration for this assay was found to be 60 nM. The increment in the antibody concentration from 75 nM drastically diminishes the sensitivity to ~ 680-fold, due to the crowding effect. With this assay, we attested the suitability of colorimetric assay for efficiently detecting the smaller-sized protein.

Diagnosing human blood clotting deficiency

There are different clotting factors present in blood, carries the clotting cascade and excessive bleeding may cause a deficiency in the clotting Diagnosis of this deficiency in clotting drastically reduces the potential fatality. For enabling a sensor to detect the clotting factors, suitable probes such as antibody and aptamer have been used to capture these targets on the sensing surface. Two major clotting factors were widely studied for the diagnosis of clotting deficiency, which includes factor IX and thrombin. In addition, factor IX is considered as the substitute for heparin and the prothrombotic associated with the increased thrombin generation are taking into account their prevalence. The biosensors, surface plasmon resonance, evanescent-field-coupled waveguide-mode sensor, metal-enhanced PicoGreen fluorescence and electrochemical aptasensor were well-documented and improvements have been made for high-performance sensing. We overviewed detecting factor IX and thrombin using these biosensors, for the potential application in medical diagnosis.

Selective induction of DNA damage, G2 abrogation, and mitochondrial apoptosis by leaf extract of traditional medicinal plant Wrightia arborea in K562 cells

Plants have proved to be an important source of anti-cancer drugs. Wrightia arborea, an Indian Ayurvedic medicinal plant, is used traditionally to treat a variety of ailments. This study evaluates the antiproliferative/apoptotic potential of Wrightia arborea leaf extracts, prepared in different organic solvents, on cancer cell lines. MTT assay, light and fluorescence microscopy, flow cytometry, DNA laddering, alkaline comet assay, and western blotting were some of the techniques used for evaluation. Combinations of camptothecin, either with CHK1 inhibitor-PD407824 or with W. arborea leaf extract, were deployed to determine the G2 abrogating potential of the extract. The chloroform extract (WAC) selectively killed K562 cells, without affecting cancerous MCF-7, Hep G2 cells, and normal human peripheral blood lymphocytes. Cell death was characterized by observation of apoptotic bodies, increased Ca2+ and ROS, phosphatidyl serine externalization, mitochondrial membrane depolarization, DNA laddering, increased sub-G1 population, and altered expression of caspase 3, -9, and PARP. WAC also induced DNA damage, alterations in key G2/M phase protein expression, cell cycle perturbation, and potent G2 abrogation. The present study showed that W. arborea leaf extract, WAC, is capable of selectively killing leukemic cancer cells leaving normal lymphocytes unaffected. Our results indicate that this is effectuated through DNA damage and G2 abrogation leading to mitochondrial apoptosis. Taken together, this report contributes toward a better understanding of the anticancer properties of this traditional medicinal plant extract possessing valuable bioactive constituents which can serve as a bioresource for promising complimentary/alternative/chemopreventive therapeutics.

Biotin-Streptavidin Competition Mediates Sensitive Detection of Biomolecules in Enzyme Linked Immunosorbent Assay

Enzyme Linked Immunosorbent Assay (ELISA) is the gold standard assay for detecting and identifying biomolecules using antibodies as the probe. Improving ELISA is crucial for detecting disease-causing agents and facilitating diagnosis at the early stages of disease. Biotinylated antibody and streptavidin-conjugated horse radish peroxide (streptavidin-HRP) often are used with ELISA to enhance the detection of various kinds of targets. In the present study, we used a competition-based strategy in which we pre-mixed free biotin with streptavidin-HRP to generate high-performance system, as free biotin occupies some of the biotin binding sites on streptavidin, thereby providing more chances for streptavidin-HRP to bind with biotinylated antibody. ESAT-6, which is a protein secreted early during tuberculosis infection, was used as the model target. We found that 8 fM of free biotin mixed with streptavidin-HRP anchored the higher detection level of ESAT-6 by four-fold compared with detection without free biotin (only streptavidin-HRP), and the limit of detection of the new method was 250 pM. These results suggest that biotin-streptavidin competition can be used to improve the diagnosis of analytes in other types of sensors.

Co-immobilized poly(ethylene glycol)-block-polyamines promote sensitivity and restrict biofouling on gold sensor surface for detecting factor IX in human plasma

In order to detect an extremely low amount of human coagulation factor IX (FIX), poly(ethylene glycol) (PEG)/aptamer co-immobilized surface was constructed using original PEG-polyamine surface modification agents on surface plasmon resonance (SPR) sensor chip. Initially, a gold (Au) sensor chip of SPR was modified using poly(ethylene glycol)-b-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PEG-b-PAMA) followed by treatment with SH-dT20 and was duplexed with anti-FIX aptamer extended using A24. Furthermore, the co-immobilization of pentaethylenehexamine-terminated poly(ethylene glycol) (N6-PEG) on the sensing surface completely quenched bio-fouling. On this dual tethered PEG-surface, we determined that the dissociation constant for FIX-aptamer interaction was 37 ± 10 pM, and the sensitivity of detection could reach up to 800 fM on using aptamer-FIX-antibody sandwich pattern detected by gold nanoparticle-conjugated anti-mouse antibody. We could detect FIX in the presence of abundant albumin. Furthermore, to mimic the actual detection of FIX in clinical samples, we demonstrated our experimental results with human blood plasma instead of FIX. Higher-sensitivity was attained because of dual polymers immobilized on Au surface, and this can emerge as a common strategy for any aptamer-protein interactions. The selective binding of aptamer in human blood plasma described here indicates the suitability of the present strategy for detection in clinically relevant samples.

The influence of the earthworm Lampito mauritii (Kinberg) on the activity of selected soil enzymes in cadmium-amended soil

The effects of cadmium (CdCl2·7H2O) on cellulase, urease, amylase, invertase and phosphatase were assessed for a period of 45 days in the presence and absence of earthworms [Lampito mauritii (Kinberg)] in alfisol soil. The activities of all enzymes significantly increased with longer incubation times (45 days) under laboratory conditions in both control and Cd-amended soils (both with and without earthworm incubation). However, the activities of all enzymes decreased with increasing Cd concentrations under laboratory conditions, both in the presence and absence of earthworms. In the presence of earthworms, cellulase, urease, invertase and amylase activities increased. However, phosphatase activity was lower in most of the Cd-amended soils in the presence of earthworms compared to its activity levels in soils lacking earthworms. These results show that earthworms modulated the stress imposed by Cd by providing suitable substrates, which in turn acted as stimulants for extracellular enzyme secretion by microbes, and by removing Cd through its accumulation in the tissues of the earthworms.

Assessment of cell cycle phase-specific effects of zerumbone on mitotically synchronous surface cultures of Physarum polycephalum

Zerumbone, a natural cyclic sesquiterpene, has been the focus of recent research as it has been found to exhibit selective toxicity towards cancer cells compared to normal cells. Studies on the cell cycle phase-specific effects of this interesting compound, however, remain sparse. Hence, concentration and time-dependent effects of zerumbone were evaluated employing a suitable model system, the naturally synchronous surface cultures of Physarum polycephalum. Zerumbone treatment in S, early, and late G2 phases resulted in G2 arrest. Early G2 phase exhibited the highest sensitivity (P < 0.001) to the compound. Protein profiles showed a complete inhibition of cyclin B1 expression following zerumbone treatment. Furthermore, FACS and comet analysis revealed that zerumbone inhibited DNA synthesis (P < 0.001) without being genotoxic at the concentrations tested. Differential display of mRNA showed distinct zerumbone-induced variations in transcript profiles, an analysis of which suggested a likely link between cellular networks involving stress-related gene expression and G2 arrest in P. polycephalum.

Colorimetric detection of controlled assembly and disassembly of aptamers on unmodified gold nanoparticles

Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes. As these kinds of assay systems are rapid and can be visualized unaided by instruments, they have recently become an attractive method of choice. The formation of purple-colored aggregates (attraction) from the red dispersed (repulsion) state of GNPs in the presence of mono- or divalent ions is the key principle behind this assay. Due to its simplicity and versatility, this assay can be an alternative to existing diagnostic assays. Here, we have investigated the critical elements involved in colorimetric assays, and have screened different proteins and small ligands to evaluate biofouling on GNPs.

Generation of anti-influenza aptamers using the systematic evolution of ligands by exponential enrichment for sensing applications

The systematic evolution of ligands by exponential enrichment (SELEX) is a selection process for identifying high-affinity selective molecules from a randomized combinatorial nucleic acid library against a wide range of target molecules. Using a pool of N25 RNA molecules, the SELEX process was performed against two targets from influenza viruses, namely, intact influenza B/Tokio/53/99 and hemagglutinin of infuluenza B Jilin/20/2003. The selection processes were evaluated by surface plasmon fluorescence spectroscopy (SPFS), and the result was compared to that obtained by a conventional radioisotope method. Clear discrimination among different selection cycles was displayed by SPFS, indicating that this method can be used as an alternative method of radioisotope labeling. The dissociation constant of the selected aptamers against the targets was in the low nanomolar range. The sensitivity of the selected aptamer against intact influenza B/Tokio/53/99 to detect the influenza virus was the low ng/mL level, an approximately 250-fold higher sensitivity than that of the commercially obtained antibody. The target binding sites on the aptamer were predicted by mapping analyses. The selected aptamer could discriminate other influenza strains, and the sensitivity of the selected aptamer was further confirmed by gold-nanoparticle-based sensing on a waveguide-mode sensor. This finding demonstrates that the selected aptamer would be useful for detecting influenza viruses at an early stage of infection and for the purpose of influenza surveillance.