Development of a gold nanoparticle-based lateral flow immunochromatographic assay for the rapid and quantitative detection of thymidine kinase 1 in human serum.

Thymidine kinase 1 (TK1) is a marker of cell proliferation that can be used for early screening, treatment monitoring, and evaluating the prognosis of patients with tumors. The main purpose of this study was to develop clinically applicable TK1 antibodies, establish an appropriate detection method, and provide material and technical support for the research and clinical application for different types of tumors. Experimental mice were immunized with the C-terminal 31 peptide of human TK1 to screen monoclonal cell lines capable of stably secreting specific antibodies. Monoclonal antibodies were then prepared, purified and screened for optimal pairing following the identification of purity and isotype. Finally, based on the principles adopted by the double-antibody sandwich detection method, we constructed a lateral flow immunochromatographic assay (LFIA) to quantify the concentration of TK1 in serum samples when using a gold nanoparticle-labeled anti-TK1 monoclonal antibody as a probe. The limit of detection for TK1 in serum was 0.31 pmol/L with a detection range of 0.31-50 pmol/L. The spiked recoveries ranged from 97.7% to 109.0% with an analytical precision of 5.7-8.2%; there was no cross-reactivity with common proteins in the serum. The established LFIA also exhibited good consistency with commercially available chemiluminescent immunoassay kits for the detection of clinical samples. The LFIA developed in this study has the advantages of high sensitivity, accuracy, reproducibility and strong specificity, and provides a new technical tool for the quantitative detection of TK1.

Establishment and application of a gold nanoparticle-based immunochromatographic test strip for the detection of avian leukosis virus P27 antigen in egg white samples.

Avian leukemia is an infectious tumorous disease of chickens caused by subgroup A of the avian leukemia virus (ALV-A), which mainly causes long-term viremia, slow growth, immune suppression, decreased production performance, multi-tissue tumors, and even death. The infection rate of this disease is very high in chicken herds in China, causing huge economic losses to the poultry industry every year. We successfully expressed the specific antigen protein of ALV (P27) through recombinant protein technology and screened a pair of highly sensitive monoclonal antibodies (mAbs) through mouse immunity, cell fusion, and antibody pairing. Based on this pair of antibodies, we established a dual antibody sandwich ELISA and gold nanoparticle immunochromatographic strip (AuNP-ICS) detection method. In addition, the parameters of the dual antibody sandwich ELISA and AuNP-ICS were optimized under different reaction conditions, which resulted in the minimum detection limits of 0.2 ng mL-1 and 1.53 ng ml-1, respectively. Commonly available ELISA and AuNP-ICS products on the market were compared, and we found that our established immune rapid chromatography had higher sensitivity. This established AuNP-ICS had no cross-reactivity with Influenza A (H1N1), Influenza A (H9N2), respiratory syncytial virus (RSV), varicella-zoster virus (VZV), Listeria monocytogenes listeriolysin (LLO), and Staphylococcal enterotoxin SED or SEC. Finally, the established AuNP-ICS was used to analyze 35 egg samples, and the results showed 5 positive samples and 30 negative samples. The AuNP-ICS rapid detection method established by our group had good specificity, high sensitivity, and convenience, and could be applied to the clinical sample detection of ALV-A.

On-site rapid detection of perfluorooctanoic acid by visual immunochromatographic strip biosensor in domestic water and real human samples.

The International Agency for Research on Cancer (IARC) classifies PFOA as a Class 1 carcinogen. Here, a new naked-eye PFOA immunochromographic strip was developed to recognize PFOA in domestic water and real human samples within 10 min based on a novel custom designed anti-PFOA monoclonal antibody (mAb) 2A3, which was firstly an immune rapid detection method for PFOA has been proposed. Using computer simulation techniques such as quantum computing to assist in designing the structural formula of PFOA semi antigen, which hapten was firstly proposed. The half maximal inhibitory concentration of PFOA monoclonal antibody (mAb) 2A3 was 2.4 µg/mL. Using mAb 2A3, we developed an immunochromatographic strip (ICS) for detecting PFOA in real samples. The developed method generated results in 10 min, with visual detection limits of 20, 20, and 200 µg/mL and limit of detection of 50, 200, and 500 µg/mL for water, blood and urine samples, respectively. The established ICS and indirect competitive enzyme-linked immunosorbent assay were used to analyze the actual samples, and the results were confirmed by LC-MS/MS. Our study findings showed that the ICS and ic-ELISA can quickly detect PFOA in actual samples.

Tri-mode Responses to Reactive Oxygen Species In Vivo by Chiral Vanadium-Based Nanoparticles.

Reactive oxygen species (ROS) are closely associated with the redox balance of the physiological environment, and monitoring ROS can aid in the early diagnosis of many diseases, including cancer. In this study, chiral vanadium trioxide/vanadium nitride (V2O3/VN) nanoparticles (NPs) modified with an organic dye (cyanine 3 [Cy3]) were prepared for ROS sensing. Chiral V2O3/VN NPs were prepared with the "ligand-induced chirality" strategy and showed a g-factor of up to 0.12 at a wavelength of 512 nm. To the best of our knowledge, this g-factor is the highest value of all chiral ceramic nanomaterials. The very high g-factor of the nanoprobe confers very high sensitivity, because the higher g-factor, the higher sensitivity. In the presence of ROS, V3+ in the chiral V2O3/VN nanoprobe undergoes a redox reaction to form V2O5, reducing the circular dichroism and absorbance signals, whereas the fluorescence signal of Cy3 is restored. With this nanoprobe, the limits of detection for the circular dichroic and fluorescence signals in living cells are 0.0045 nmol/106 and 0.018 nmol/106 cells, respectively. This chiral nanoprobe can also monitor ROS levels in vivo by fluorescence. This strategy provides an innovative approach to the detection of ROS and is expected to promote the wider application of chiral nanomaterials for biosensing.

Modulation by Co (II) Ion of Optical Activities of L/D-glutathione (GSH)-modified Chiral Copper Nanoclusters for Sensitive Adenosine Triphosphate Detection.

Chiral nanoscale enantiomers exhibit different biological effects in living systems. However, their chirality effect on the detection sensitivity for chiral biological targets still needs to be explored. Here, we discovered that Co2+ can modulate the luminescence performance of L/D-glutathione (GSH)-modified copper nanoclusters (L/D-Cu NCs) and induce strong chiroptical activities as the asymmetric factor was enhanced 223-fold with their distribution regulating from the ultraviolet to visible region. One Co2+ coordinated with two GSH molecules that modified on the surface of Cu NCs in the way of CoN2O2. On this basis, dual-modal chiral and luminescent signals of Co2+ coordinated L/D-Cu NCs (L/D-Co-Cu NCs) were used to detect the chiral adenosine triphosphate (ATP) based on the competitive interaction between surficial GSH and ATP molecules with Co2+. The limits of detection of ATP obtained with fluorescence and circular dichroism intensity were 9.15 µM and 15.75 nM for L-Co-Cu NCs, and 5.35 µM and 4.69 nM for D-Co-Cu NCs. This demonstrated that selecting suitable chiral configurations of nanoprobes effectively enhances detection sensitivity. This study presents not only a novel method to modulate and enhance the chiroptical activity of nanomaterials but also a unique perspective of chirality effects on the detection performances for bio-targets.

Ultrasensitive detection of imatinib in human serum using a gold-based paper sensor.

Imatinib is the tyrosine kinase inhibitor of choice for the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. However, imatinib has drawbacks such as drug resistance and significant differences in pharmacokinetics within patients. Therefore, a colloidal gold-based immunochromatographic assay (CG-IA) was developed for measuring and monitoring imatinib in human serum. An imatinib derivative containing carboxyl groups was used for the synthesis of the immunogen, and 4-(4-methyl-1-piperazinylmethyl) benzoic acid was selected as the hapten for the heterologous coating antigen. Next, a highly sensitive and specific monoclonal antibody (mAb), 2F7 was screened for the construction of a CG-IA, with an IC50 value of 0.091 ng/mL. For the qualification of imatinib in human serum, the visual limit of detection (vLOD) and cut-off values of the CG-IA were 2 and 20 ng/mL, respectively. For quantitative detection, the calculated LOD value of the CG-IA was 0.068 ng/mL, with a linearity range of 1.004 and 23.087 ng/mL. The recovery rate of spiked serum samples was between 88.24 % and 104.75 %. In addition, the concentration of imatinib in the serum samples from 10 patients was detected by CG-IA and revealed a good correlation with those from LC-MS/MS. These results indicated that the developed gold-based paper sensor could become an effective tool for the rapid monitoring of imatinib in human serum samples.

Chiral Nanomaterials for Cancer Vaccines.

Chirality is a fundamental characteristic of living organisms and is commonly observed at the biomolecule, cellular, and tissue levels. Chiral nanomaterials play an irreplaceable role in nanomedicine and nanobiology because of their unique enantioselectivity with biological components. Here, research progress relating to chiral nanomaterials in the field of vaccines is reviewed, including antigen presenting systems, immune adjuvants, and cancer vaccines. First, the common synthesis methods are outlined for different types of chiral nanomaterials, as well as their chiral sources, optical properties, and potential biological applications. Then, the application of chiral nanomaterials are discussed in the field of vaccines with reference to the promotion of antigen presentation and activation of the immune system for tumor immunotherapy. Finally, the current obstacles and future research directions of chiral nanomaterials are revealed with regard to regulating the immune system.

Interfacial Self-assembly of Chiral Selenide Nanomembrane for Enantiospecific Recognition.

Here, we report the synthesis of chiral selenium nanoparticles (NPs) using cysteine and the interfacial assembly strategy to generate a self-assembled nanomembrane on a large-scale with controllable morphology and handedness. The selenide (Se) NPs exhibited circular dichroism (CD) bands in the ultraviolet and visible region with a maximum intensity of 39.96 mdeg at 388 nm and optical anisotropy factors (g-factors) of up to 0.0013 while a self-assembled monolayer nanomembrane exhibited symmetrical CD approaching 72.8 mdeg at 391 nm and g-factors up to 0.0034. Analysis showed that a photocurrent of 20.97±1.55 nA was generated by the D-nanomembrane when irradiated under light while the L-nanomembrane generated a photocurrent of 20.58±1.36 nA. Owing to the asymmetric intensity of the photocurrent with respect to the handedness of the nanomembrane, an ultrasensitive recognition of enantioselective kynurenine (Kyn) was achieved by the ten-layer (10L) D-nanomembrane exhibiting a photocurrent for L-kynurenine (L-Kyn) that was 8.64-fold lower than that of D-Kyn, with a limit of detection (LOD) of 0.0074 nM for the L-Kyn, which was attributed to stronger affinity between L-Kyn and D-Se NPs. Noticeably, the chiral Se nanomembrane precisely distinguished L-Kyn in serum and cerebrospinal fluid samples from Alzheimer's disease patients and healthy subjects.

Chiral Iron Oxide Supraparticles Enable Enantiomer-Dependent Tumor-Targeted Magnetic Resonance Imaging.

The chemical, physical and biological effects of chiral nanomaterials have inspired general interest and demonstrated important advantages in fundamental science. Here, chiral iron oxide supraparticles (Fe3 O4 SPs) modified by chiral penicillamine (Pen) molecules with g-factor of ≈2 × 10-3 at 415 nm are fabricated, and these SPs act as high-quality magnetic resonance imaging (MRI) contrast agents. Therein, the transverse relaxation efficiency and T2 -MRI results demonstrated chiral Fe3 O4 SPs have a r2 relaxivity of 157.39 ± 2.34 mM-1 ·S-1 for D-Fe3 O4 SPs and 136.21 ± 1.26 mM-1 ·S-1 for L-Fe3 O4 SPs due to enhanced electronic transition dipole moment for D-Fe3 O4 SPs compared with L-Fe3 O4 SPs. The in vivo MRI results show that D-Fe3 O4 SPs exhibit two-fold lower contrast ratio than L-Fe3 O4 SPs, which enhances targeted enrichment in tumor tissue, such as prostate cancer, melanoma and brain glioma tumors. Notably, it is found that D-Fe3 O4 SPs have 7.7-fold higher affinity for the tumor cell surface receptor cluster-of-differentiation 47 (CD47) than L-Fe3 O4 SPs. These findings uncover that chiral Fe3 O4 SPs act as a highly effective MRI contrast agent for targeting and imaging broad tumors, thus accelerating the practical application of chiral nanomaterials and deepening the understanding of chirality in biological and non-biological environments.

A colloidal gold immunoassay strip assay for cadmium detection in oilfield chemicals.

Cadmium ions (Cd2+) are some of the major pollutants in oilfield chemicals. To reduce the pollution of oilfield chemicals, it is necessary to detect and control the content of Cd2+. In this study, we synthesized a highly sensitive and specific monoclonal antibody against Cd2+ with an IC50 of 1.97 ng mL-1 and no cross-reactivity. Based on this antibody, a colloidal gold immunoassay strip detection assay with an IC50 of 1 mg kg-1 and a detection range of 1.0-20 mg kg-1 in oilfield chemicals was developed. This assay could be completed in 20 min and can be used for Cd2+ on-site testing in oilfield chemicals and improve supervision efficiency in oil exploration and development.

A Rapid Immunochromatographic Method Based on Gold Nanoparticles for the Determination of Imidacloprid on Fruits and Vegetables.

Imidacloprid (IMP) is toxic and a potential carcinogen that is most widely used as an insecticide for pest control and seed treatment. It is important to produce a rapid and sensitive assay for on-site monitoring. We have developed a novel lateral flow assay (LFA) using a sensitive monoclonal antibody (mAb) for monitoring IMP residues on fruits and vegetables. The 50% inhibition concentration result that was found when using the ELISA method was 0.247 ng mL-1, with the cut-off limits using the LFA method the result was 10 ng mL-1 (0.01 M PBS), and in the samples it was 20 ng mL-1 (with a recovery rate of 96-104.7% for Chinese cabbage, cowpea, apple, and pear samples, respectively). All of the results can be determined within seven minutes. The proposed LFA method is a valid, quick, and stable assay for the on-site detection of IMP in large numbers of samples.

Chiral Se@CeO2 superparticles for ameliorating Parkinson's disease.

In this study, we prepare chiral D-/L-type Se@CeO2 superparticles (D-/L-SPs) with a g-factor of 0.018 using D-/L-cysteine as chiral ligands. The chiral SPs demonstrate ultra-high enzyme activity of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Due to the synergistic effect between Se and CeO2, the maximum initial velocity of GPx, CAT, and POD for L-SP is 10, 7, and 5.6 times higher than that of a mixture of Se nanoparticles (NPs) and CeO2 NPs. Significantly, the chiral L-SPs show much stronger ROS scavenging ability than D-SP in the PD-like cell model. Moreover, the amount of α-synuclein (α-syn) in the cerebrospinal fluid of PD mice is reduced by 70.7% within two weeks. The L-SPs effectively alleviate neurodegeneration in a mouse model of PD, showing potential applications in the clinical treatment of neurodegenerative diseases.

Development of a colloidal gold immunochromatographic strip for rapid and sensitive detection of nicotine.

Nicotine (NCT) is commonly contained in e-cigarette oils, and long-term nicotine intake can exacerbate cardiovascular disease, neurodegenerative disease, and lung cancer. Therefore, there is a need to develop a fast and sensitive method for detecting NCT in e-cigarette oils. We prepared anti-NCT monoclonal antibodies (mAbs), which belong to the IgG2 subclass. The optimum mAb had a half-maximal inhibitory concentration (IC50) of 6.81 ng/mL for NCT. We developed a colloidal gold immunochromatographic strip (CG-ICS) to detect NCT content with a visual cut-off and limit of detection of 20 ng/mL and 0.40 ng/mL, respectively. The recovery rates of NCT from spiked samples ranged between 100.36% and 109.96% based on CG-ICS. These results were consistent with those obtained from high performance liquid chromatography (HPLC). We confirmed the reliability of CG-ICS using NCT-positive samples. Therefore, CG-ICS represents an effective and rapid on-site screening tool for the detection of NCT in e-cigarette oils.

Chiral MoSe2 Nanoparticles for Ultrasensitive Monitoring of Reactive Oxygen Species In Vivo.

Reactive oxygen species (ROS) are involved in neurodegenerative diseases, cancer, and acute hepatitis, and quantification of ROS is critical for the early diagnosis of these diseases. In this work, a novel probe is developed, based on chiral molybdenum diselenide (MoSe2 ) nanoparticles (NPs) modified by the fluorescent molecule, cyanine 3 (Cy3). Chiral MoSe2 NPs show intensive circular dichroism (CD) signals at 390 and 550 nm, whereas the fluorescence of Cy3 at 560 nm is quenched by MoSe2 NPs. In the presence of ROS, the probe reacts with the ROS and then oxidates rapidly, resulting in decreased CD signals and the recovery of the fluorescence. Using this strategy, the limit of detection values of CD and fluorescent signals in living cells are 0.0093 nmol/106 cells and 0.024 nmol/106 cells, respectively. The high selectivity and sensitivity to ROS in complex biological environments is attributed to the Mo4+ and Se2- oxidation reactions on the surface of the NPs. Furthermore, chiral MoSe2 NPs are able to monitor the levels of ROS in vivo by the fluorescence. Collectively, this strategy offers a new approach for ROS detection and has the potential to inspire others to explore chiral nanomaterials as biosensors to investigate biological events.

Development of monoclonal antibodies for the detection of diuron in water and sugarcane and their application in immunochromatographic strips.

Diuron (DR) as a chemical herbicide persists in soil and water for a long time and causes extensive harm to humans. We have produced an excellent monoclonal antibody (mAb) with the ability to sensitively and specifically recognize DR in water and sugarcane samples. The semi-inhibitory concentration (IC50) of this mAb was 0.28 ng mL-1, and the limit of detection (LOD) was 0.07 ng mL-1. Based on the mAb, an immunochromatographic assay (ICA) strip was developed. The visual detection limits of the strip assay were estimated, and the critical values of DR in water and sugarcane samples were determined to be 5 and 10 ng mL-1, respectively, when assessed by the naked eye. The ICA strip was validated by HPLC-MS for water and sugarcane samples which had been spiked with DR. This ICA strip could be a useful tool for in-site and rapid detection of DR in water and sugarcane samples.

Enantiomeric NIR-II Emitting Rare-Earth-Doped Ag2 Se Nanoparticles with Differentiated In Vivo Imaging Efficiencies.

Here, chiral second near-infrared (NIR-II) emitting rare-earth doped silver selenide nanoparticles (R- or S-Ag2 Se:Nd/Yd/Er NPs) were fabricated, exhibiting circular dichroism peak at 850 nm and fluorescence peak at 1550 nm, with 145.7-fold enhanced intensity compared to the reported Ag2 Se NPs. Compared with S-Ag2 Se:Nd/Yd/Er NPs, imaging efficiency of R-Ag2 Se:Nd/Yd/Er NPs in living cells was significantly improved due to a higher cellular uptake rate and 927.7-fold higher affinity. Furthermore, R-Ag2 Se:Nd/Yd/Er NPs reached at the tumor 2-fold faster than S type of NPs in vivo. We discover that chirality leads to differences in the affinity between chiral Ag2 Se:Nd/Yd/Er NPs and cluster of differentiation 44 (CD44) onto the surface of murine mammary carcinoma cell to cause different in vivo imaging efficiency. These results reveal that chiral Ag2 Se:Nd/Yd/Er NPs have high photoluminescence intensity and high in vivo imaging efficiency reflecting wide applications in biomedical diagnosis.

Development of a colloidal gold strip assay for the detection of total homocysteine in serum samples.

Homocysteine (Hcy) is an amino acid found in the human body and has the potential to predict cardiovascular risk where timely detection and treatment are very important. In this study, we established a method to combine enzymatic hydrolysis with a colloidal gold lateral flow immunoassay (LFIA) for the detection of total Hcy (tHcy) based on the monoclonal antibody (mAb) 3B3 against S-adenosyl-L-homocysteine (SAH). The 50% inhibitory concentration (IC50) for this mAb against SAH was 2.94 nM with a linear range of 0.73-11.75 nM. The developed LFIA could detect SAH with a vLOD and cLOD of 10 nM and 2.07 nM, respectively. For tHcy detection in serum samples, the LFIA strip was able to detect tHcy after enzymatic hydrolysis, and the results correlated well with that of an enzymatic cycling test kit.

Rapid and sensitive detection of tert-butylhydroquinone in soybean oil using a gold-based paper sensor.

tert-Butylhydroquinone (TBHQ) residues in foods pose a threat to human health. Therefore, it is necessary to develop a rapid method for TBHQ detection. In this study, a sensitive monoclonal antibody 5C3 (IgG2a subclass) against TBHQ was produced. It possessed a half maximal inhibitory concentration of 7.43 ng mL-1. A gold nanoparticle-based immunochromatographic assay (ICA) was established for the rapid and sensitive screening of TBHQ in soybean oil. Qualitative analysis results were obtained within 10 min and observed with the naked eye. The visual limit of detection (LOD) was 50 ng g-1 and the cut-off value was 1000 ng g-1. A hand-held strip reader was used for quantitative analysis, in which the calculated LOD was defined as 18.68 ng g-1. The average recoveries of TBHQ ranged from 89.55% ± 2.70% to 100.66% ± 3.02% for soybean oil, with a coefficient of variation of 2.89%-7.05%. Therefore, our developed ICA is a useful tool for the rapid and on-site detection of TBHQ in real food samples.

The Development of Chiral Nanoparticles to Target NK Cells and CD8+ T Cells for Cancer Immunotherapy.

The chirality of nanomaterials (nanoparticles, NPs) can influence their interaction with cells and biological systems. However, how chirality can exert impact on the immune response has yet to be investigated. Here, the immunological effect of chiral nanomaterials is investigated as a therapeutic and preventive option against tumors. Compared with achiral nanoparticles, chiral NPs with a g-factor of 0.44 are shown to enhance both innate and acquired immunity against tumor growth. It is also found that chiral NPs enhance the activation of CD8+ T and natural killer cells (CD69+ NK cells) by stimulating dendritic cells (DCs). Importantly, L-type NPs induce a 1.65-fold higher proportion of CD8+ T and CD69+ NK cells than D-type NPs. Next, the therapeutic and preventative effects of chiral NPs against tumors in a EG7.OVA tumor model are investigated. It is found that L-type NPs have a significant greater ability to induce apoptosis in tumor cells and prolong the survival time of model mice than D-type NPs. Mice treated with L-type NPs induce the activation of 84.98 ± 6.63% CD8+ T cells and 33.62 ± 3.41% of NK cells in tumor tissues; these are 1.62-fold and 1.39-fold higher than that seen in the mice treated with D-type NPs. Mechanistic studies reveal that chiral NPs exert mechanical force on bone-marrow-derived dendritic cells (BMDCs) and stimulate the expression of cytokines to induce cytotoxic activity in NK cells. Synergistically, the CD8+ T cells are stimulated to eliminate tumor cells via antigen cross presentation. The force of interaction between L-type NPs and cells is higher than that for D-NPs, thus further promoting the activation of NK cells and CD8+ T cells and their infiltration into tumor tissue. These findings open up a new avenue for chiral nanomaterials to act as immunoadjuvants for the prevention and treatment of cancer.

Ultrasmall Magneto-chiral Cobalt Hydroxide Nanoparticles Enable Dynamic Detection of Reactive Oxygen Species in Vivo.

Biological application of chiral nanoparticles (NPs) has aroused enormous levels of attention over recent years. Here, we synthesized magneto-chiral cobalt hydroxide (Co(OH)2) NPs that exhibited strong chiroptical and unique magnetic properties and applied these NPs to detect and monitor reactive oxygen species (ROS) in living cells and in vivo. Circular dichroism (CD) and magnetic resonance imaging (MRI) signals of the magneto-chiral Co(OH)2 NPs exhibited a wide intracellular ROS detection range from 0.673 to 612.971 pmol/106 cells with corresponding limits of detection (LOD) at 0.087 and 0.179 pmol/106 cells, far below that of currently available probes; the LOD for d-aspartic acid coated Co(OH)2 NPs (d-Co(OH)2 NPs) was 5.7 times lower than that for l-aspartic acid coated Co(OH)2 NPs (l-Co(OH)2 NPs) based on the CD signals. In addition, d-Co(OH)2 NPs also exhibited dynamic ROS monitoring ability. The high levels of selectivity and sensitivity to ROS in complex biological environments can be attributed to the Co2+ oxidation reaction on the surface of the NPs. Furthermore, magneto-chiral Co(OH)2 NPs were able to quantify the levels of ROS in living mice by fluorescence and MRI signals. Collectively, these results reveal that magneto-chiral Co(OH)2 NPs exhibit a remarkable ability to quantify ROS levels in living organisms, and could therefore provide new tools for exploring chiral nanomaterials as a potential biosensor to investigate biological events.