Effect of DNA aptamer through blocking of negative regulation of Wnt/ß-catenin signaling in human hair follicle dermal papilla cells.

BACKGROUND: When Wnt binds to the N-terminal of Frizzled, a conformational change occurs in the C-terminal of Frizzled, which binds to Dishevelled1 (Dvl1), a Wnt signaling component protein. When Dvl1 binds to the C-terminal of Frizzled, the concentration of ß-catenin increases and it enters the nucleus to transmit cell proliferation signals. CXXC-type zinc finger protein 5 (CXXC5) binds to the Frizzled binding site of Dvl1 and interferes with Dvl1-Frizzled binding. Therefore, blocking CXXC5-Dvl1 binding may induce Wnt signal transduction. MATERIALS AND METHODS: We used WD-aptamer, a DNA aptamer that specifically binds to Dvl1 and interferes with CXXC5-Dvl1 interaction. We confirmed the penetration of WD-aptamer into human hair follicle dermal papilla cells (HFDPCs) and measured ß-catenin expression following treatment with WD-aptamer in HFDPCs, wherein Wnt signaling was activated by Wnt3a. In addition, MTT assay was performed to investigate the effect of WD-aptamer on cell proliferation. RESULTS: WD-aptamer penetrated the cell, affected Wnt signaling, and increased ß-catenin expression, which plays an important role in signaling. Additionally, WD-aptamer induced HFDPC proliferation. CONCLUSION: CXXC5-associated negative feedback of Wnt/ß-catenin signaling can be regulated by interfering with CXXC5-Dvl1 interaction.

Aptamer Nanoconstructs Crossing Human Blood-Brain Barrier Discovered via Microphysiological System-Based SELEX Technology.

Blood-brain barrier (BBB) remains one of the critical challenges in developing neurological therapeutics. Short single-stranded DNA/RNA nucleotides forming a three-dimensional structure, called aptamers, have received increasing attention as BBB shuttles for efficient brain drug delivery owing to their practical advantages over Trojan horse antibodies or peptides. Aptamers are typically obtained by combinatorial chemical technology, termed Systemic Evolution of Ligands by EXponential Enrichment (SELEX), against purified targets, living cells, or animal models. However, identifying reliable BBB-penetrating aptamers that perform efficiently under human physiological conditions has been challenging because of the poor physiological relevance in the conventional SELEX process. Here, we report a human BBB shuttle aptamer (hBS) identified using a human microphysiological system (MPS)-based SELEX (MPS-SELEX) method. A two-channel MPS lined with human brain microvascular endothelial cells (BMECs) interfaced with astrocytes and pericytes, recapitulating high-level barrier function of in vivo BBB, was exploited as a screening platform. The MPS-SELEX procedure enabled robust function-based screening of the hBS candidates, which was not achievable in traditional in vitro BBB models. The identified aptamer (hBS01) through five-round of MPS-SELEX exhibited high capability to transport protein cargoes across the human BBB via clathrin-mediated endocytosis and enhanced uptake efficiency in BMECs and brain cells. The enhanced targeting specificity of hBS01 was further validated both in vitro and in vivo, confirming its powerful brain accumulation efficiency. These findings demonstrate that MPS-SELEX has potential in the discovery of aptamers with high target specificity that can be widely utilized to boost the development of drug delivery strategies.

Development of a Low-Molecular-Weight Aß42 Detection System Using a Enzyme-Linked Peptide Assay.

Alzheimer's disease (AD) is a degenerative brain disease that is the most common cause of dementia. The incidence of AD is rapidly rising because of the aging of the world population. Because AD is presently incurable, early diagnosis is very important. The disease is characterized by pathological changes such as deposition of senile plaques and decreased concentration of the amyloid-beta 42 (Aß42) peptide in the cerebrospinal fluid (CSF). The concentration of Aß42 in the CSF is a well-studied AD biomarker. The specific peptide probe was screened through four rounds of biopanning, which included the phage display process. The screened peptide showed strong binding affinity in the micromolar range, and the enzyme-linked peptide assay was optimized using the peptide we developed. This diagnostic method showed specificity toward Aß42 in the presence of other proteins. The peptide-binding site was also estimated using molecular docking analysis. Finally, the diagnostic method we developed could significantly distinguish patients who were classified based on amyloid PET images.

Development of a Novel ssDNA Sequence for a Glycated Human Serum Albumin and Construction of a Simple Aptasensor System Based on Reduced Graphene Oxide (rGO).

Diabetes is one of the top 10 global causes of death. About one in 11 global adults have diabetes. As the disease progresses, the mortality rate increases, and complications can develop. Thus, early detection and effective management of diabetes are especially important. Herein, we present a novel glycated human serum albumin (GHSA) aptamer, i.e., GABAS-01, which has high affinity and specificity. The aptamer was selected by reduced graphene oxide-based systematic evolution of ligands by exponential enrichement (rGO-based SELEX) against GHSA. After five rounds of selection through gradually harsher conditions, GABAS-01 with high affinity and specificity for the target was obtained. GABAS-01 was labeled by FAM at the 5'-end and characterized by measuring the recovery of a fluorescence signal that is the result of fluorescence quenching effect of rGO. As a result, GABAS-01 had low-nanomolar Kd values of 1.748 ± 0.227 nM and showed a low limit of detection of 16.40 µg/mL against GHSA. This result shows the potential application of GABAS-01 as an effective on-site detection probe of GHSA. In addition, these properties of GABAS-01 are expected to contribute to detection of GHSA in diagnostic fields.

Development of peptide aptamers as alternatives for antibody in the detection of amyloid-beta 42 aggregates.

Alzheimer's disease (AD) causes cognitive impairment and serious social isolation. However, there are no effective treatments and even no established confirmatory diagnostic tools for the disease. Amyloid beta (Aß) aggregation in the brain is the best-known pathognomonic mechanism of AD, so various methods for Aß detection have been developed for the diagnosis of this disease. We synthesized two novel, ultra-sensitive peptide probes specialized in detecting Aß aggregates, and examined their potential for future diagnostic application. The peptides are produced through phage high-throughput screening (HTS) and amplified through a serial process called biopanning, which is a repeating method of elution and amplification of probes. We picked phages specific for amyloid from two kinds of phage display. The synthesized peptides were confirmed to have excellent binding affinity to Aß aggregates, by immunohistochemical staining and western blotting using the brains of 3X transgenic (Tg) AD mice at different stages (5-7, 12-17 months old) of AD severity. In the present study, it was confirmed that newly developed amyloid-binding peptides could be used as novel probes for the detection of Aß aggregates, which can be used for clinical diagnosis of AD in the future.

Development of ssDNA Aptamers for Diagnosis and Inhibition of the Highly Pathogenic Avian Influenza Virus Subtype H5N1.

Avian influenza (AI) has severely affected the poultry industry worldwide and has caused the deaths of millions of birds. Highly pathogenic avian influenza virus is characterized by high mortality and the ability to transmit from birds to humans. Early diagnosis is difficult because of the variation in pathogenicity and the genetic diversity between virus subtypes. Therefore, development of a sensitive and accurate diagnostic system is an urgent priority. We developed ssDNA aptamer probes to detect AI viruses. Through seven rounds of SELEX to search for a probe specific to the highly pathogenic AI virus subtype H5N1, we identified 16 binding aptamers and selected two with the highest binding frequency. These two aptamers had strong binding affinities and low detection limits. We found that they could bind more specifically to H5N1, as compared to other subtypes. Furthermore, these aptamers inhibited hemagglutination, which is caused by the virus surface protein hemagglutinin. Our results indicate that our screened aptamers are effective molecular probes for diagnosing H5N1 and can be used as therapeutic agents to inhibit viral surface proteins. Sensitive diagnosis and suppression of avian influenza will help maintain a stable and healthy livestock industry, as well as protect human health.

Advances in dermatology using DNA aptamer "Aptamin C" innovation: Oxidative stress prevention and effect maximization of vitamin C through antioxidation.

BACKGROUND: Vitamin C (also known as L-ascorbic acid) plays a critical role in reactive oxygen species (ROS) reduction and cell regeneration by protecting cell from oxidative stress. Although vitamin C is widely used in cosmetic and therapeutic markets, there is considerable evidence that vitamin C easily undergoes oxidation by air, pH, temperature, and UV light upon storage. This deficiency of vitamin C decreases its potency as an antioxidant and reduces the shelf-life of products containing vitamin C as its ingredient. To overcome the deficiency of vitamin C, we have developed Aptamin C, an innovative DNA aptamer maximizing the antioxidant efficacy of vitamin C by binding to the reduced form of vitamin C and delaying its oxidation. METHODS: Binding of Aptamin C with vitamin C was determined using ITC analysis. ITC experiment was performed 0.2 mmol/L vitamin C that was injected 25 times in 2 µL aliquots into the 1.8 mL sample cell containing the Aptamin C at a concentration of 0.02 mmol/L. The data were fitted to a one-site binding isotherm using with origin program for ITC v.5.0. RESULTS: To investigate the effect of Aptamin C and vitamin C complex in human skins, both in vitro and clinical tests were performed. We observed that the complex of Aptamin C and vitamin C was significantly effective in wrinkle improvement, whitening effect, and hydration increase. In the clinical test, subjects treated with the complex showed dramatic improvement in skin irritation and itching. No adverse reaction was presented by Aptamin C complex in the test. CONCLUSION: Taken together, these results showed that Aptamin C, an innovative novel compound, should potentially be served as a key cosmeceutical ingredient for a range of skin conditions.

Development of a ssDNA aptamer system with reduced graphene oxide (rGO) to detect nonylphenol ethoxylate in domestic detergent.

Endocrine-disrupting chemicals are a major public health problem throughout the world. In the human body, these compounds functionalize the same as sexual hormones, inducing precocious puberty, gynecomastia, etc. To help prevent this occurrence, a simple detection system is needed. In this study, a nonylphenol ethoxylate (NPE)-specific aptamer was selected by reduced graphene oxide-systematic evolution of ligands by exponential enrichment. A random ssDNA library was incubated with rGO for adsorption, followed by elution with the target molecule. As a result of screening, a DNA aptamer was found that specifically bounds to the target with high binding affinity (Kd  = 100.9 ± 13.2 nM) and had a low limit of detection (LOD = 696 pM). Furthermore, this NPE-binding aptamer bounds selectively to the target. Characterization of the aptamer was confirmed by measuring the fluorescence signal recovery from rGO. In addition, detection of NPE was performed with several water samples, and the detection accuracy was 100 ± 10%. From these results, we expect that this aptamer could be applied to an on-site detection system for NPE in industrial sites or domestic fields.

Detection of Nonylphenol with a Gold-Nanoparticle-Based Small-Molecule Sensing System Using an ssDNA Aptamer.

Endocrine-disrupting chemicals (EDCs) threaten many kinds of life throughout the world. These compounds function the same as sexual hormones, inducing precocious puberty, gynecomastia, etc., in the human body. To prevent excess exposure to nonylphenol (NP), a simple and rapid detection system is needed. In this study, we develop a nonylphenol-specific aptamer from a random single-stranded DNA library and test a rapid sensor system based on the aptamer and gold nanoparticles (AuNPs). The aptamer was screened by a methodology involving reduced graphene oxide (rGO). As a result of screening and sequencing, a DNA aptamer was developed that recognizes the target with high binding affinity (Kd = 194.2 ± 65.9 nM) and specificity. The sensor system developed using the aptamer and gold nanoparticles is sensitive (LOD = 2.239 nM). Circular dichroism (CD) spectrometry results show that the free aptamer binds to the target molecule. The aptamer was characterized using gold nanoparticles to measure UV absorbance. Our results suggest that the sensor system developed using this aptamer is useful for field diagnosis of small molecules.

Development of quantum dot aptasensor and its portable analyzer for the detection of di-2-ethylhexyl phthalate.

We have developed a quantum dot aptasensor (QD-aptasensor) and its accompanying portable analyzer for the detection of di-2-ethylhexyl phthalate (DEHP). This sensor is based on a newly screened aptamer (60-mer) via SELEX and shows a binding affinity of 213 nmol/L with DEHP. The 60-mer aptamer together with its three shorter truncated aptamers (45, 28, and 22-mer) as well as three different DNA probes (12, 9, and 13-mer) were further investigated to form the best combination for the QD-aptasensor. Using a 22-mer-truncated aptamer and a 12-mer DNA probe combination, the QD-aptasensor demonstrated excellent DEHP sensitivity with an LOQ = 0.5 pg/mL as well as good selectivity in the presence of other phthalate analogs. The binding between the truncated aptamers and DEHP was also characterized. Finally, a QD-aptasensor-based portable analyzer was also developed, and its equivalence to the laboratory protocol was established with a correlation coefficient r = 0.86 for DEHP concentrations ranging from 0.0005 to 100 ng/mL.

Development of a ssDNA aptamer for detection of residual benzylpenicillin.

Antibiotics are useful for improving the living conditions of livestock. However, residual antibiotics induce several human diseases such as food-borne illness and infection of carbapenem-resistant Enterobacteriaceae (CRE). In this study, the identification of a benzylpenicillin-specific aptamer was selected by rGO-SELEX (reduced Graphene Oxide-Systematic Evolution of Ligands by EXponential enrichment). A random ssDNA library was incubated with rGO for adsorption and eluted with benzylpenicillin. As a result of the selection process, a DNA aptamer was found that specifically bound to benzylpenicillin with high binding affinity, Kd = 383.4 nM, and had a low limit of detection (LOD) of 9.2 nM. The characterization of the aptamer was performed through the fluorescence recovery signal from rGO surface. In addition, detection of benzylpenicillin was performed in pretreated milk samples, and its detection accuracy was shown to be 100± 10%. This represented that BBA1 was used for fluorescence aptasensor system in real sample. Furthermore, this benzylpenicillin binding aptamer showed high specificity against other antibiotics except for ampicillin. With these advantageous characteristics, we expect that this aptamer could be applied to an on-site detection system for residual benzylpenicillin.

Mutation analysis of the interactions between Mycobacterium tuberculosis caseinolytic protease C1 (ClpC1) and ecumicin.

Ecumicin is a well-known and potent inhibitor of Mycobacterium tuberculosis. Although the target of ecumicin is caseinolytic protease C1 (ClpC1), the exact mechanism by which ecumicin inhibits ClpC1 has not been identified. To analyze ecumicin's action on ClpC1, site-directed mutagenesis was performed on its binding site. The estimated binding residues within ClpC1 to ecumicin were selected via in silico analysis using molecular docking. The selected residues were mutated by site-directed mutagenesis and the effects on ecumicin binding were analyzed. Mutation at the R83 residue, especially the R83A mutation, in ClpC1 resulted in strong resistance to ATPase activation and inhibition of proteolytic activity. In addition, binding of ecumicin to the R83A ClpC1 N-terminal domain (residues 1-145) was not observed in native gel analysis. These results reveal that the R83 residue plays an important role in the binding of ecumicin. This result provides a basis for the development of an anti-tuberculosis agent based on ecumicin derivatives.

Development of a novel imaging agent using peptide-coated gold nanoparticles toward brain glioma stem cell marker CD133.

CD133 is known as biomarker for glioblastoma (GBM) and also serves as a marker for cancer stem cells (CSCs), which carry out tumorigenesis and resist conventional therapeutics. The presence of CD133-presenting CSC is a one of the factors in maintenance of the tumorigenic potential of GBM. Thus, CD133 is a potential target for accurate diagnosis of GBM, which could improve its poor prognosis for patients when CSCs are present. Herein we designed a small peptide-based imaging agent with stimulus-responsive properties. A novel small peptide, CBP4, was screened by a phage display technique, and demonstrated binding to the target CD133 (ECD) comparable to that of an antibody. As a quencher, we used gold nanoparticles (GNPs); the targeting peptide was conjugated to GNPs with high efficiency. By means of a quenching effect, the peptide-coated GNP showed 'signal on-off' properties depending upon the presence of the target. In addition, the particles exhibited biocompatibility when localized in the cytosol. Thus, this study demonstrated that the peptide-coated GNPs can be utilized as an imaging agent for accurate diagnosis of GBM, and further as a drug carrier for therapeutic approaches. STATEMENT OF SIGNIFICANCE: The diagnosis and determination of prognosis made by cancer stem cell markers could be a key strategy to eradicate cancer stem cells and cure the cancer. The significance of this study is the characterization of quenching-based signal on-off mechanism and showed that the active targeting via peptide can contribute to the design of a stimulus-responsive cellular imaging agent. Moreover, small peptide based nano complexation showed specific recognition of the target stem cell and internalized on cellular cyotosol with stimulus responsive fluorescence. With its novel biocompatibility, the strategy might be a promising tool for drug carrier systems able to measure and visualize the delivered efficiency at intracellular sites.