Highly emissive blue graphene quantum dots with excitation-independent emission via ultrafast liquid-phase photoreduction.

Graphene oxide quantum dots (GOQDs) are promising candidates for biomedical applications since they have lower toxicity and higher biocompatibility than traditional semiconductor quantum dots. However, oxygen functional groups such as epoxy and hydroxyl groups usually induce nonradiative relaxation, which leads to GOQDs exhibiting nonemissive properties. For the enhancement of the emission efficiency of GOQDs, the number of nonradiative relaxation sites should be reduced. This paper reports the synthesis of highly luminescent reduced GOQDs prepared by liquid-phase photoreduction (LPP-rGOQDs). First, GOQDs was fabricated from single-walled carbon nanotubes through chlorate-based oxidation and separation after acoustic cavitation. Subsequently, LPP-rGOQDs were obtained by liquid-phase photoreduction of the GOQD suspension under intense pulsed light irradiation. Liquid-phase photoreduction selectively reduced epoxy groups present on the basal plane of GOQDs, and hydrogenated the basal plane without removal of carbonyl and carboxyl groups at the edges of the GOQDs. Such selective removal of oxidative functional groups was used to control the reduction degree of GOQDs, closely related to their optical properties. The optimized LPP-rGOQDs were bright blue in color and showed quantum yields up to about 19.7%, which was 10 times the quantum yield of GOQDs. Furthermore, the LPP-rGOQDs were utilized to image a human embryonic kidney (HEK293A), and a low cytotoxicity level and satisfactory cell imaging performance were observed.

Evaluation of PDL1 positive cancer cell-specific binding activity of recombinant anti-PDL1 scFv.

Programmed cell death-ligand 1 (PDL1) is a transmembrane protein that is characterized as an immune regulatory molecule. We recently developed a recombinant single-chain fragment of variable domain (scFv) against PDL1, which showed high binding efficiency to purified recombinant PDL1 protein. However, at that time, proof-of-concept data for the effect of scFv using PDL1-expressing cells was lacking. In this study, we conducted two kinds of cell-based immunoassays, western blotting and enzyme-linked immunosorbent assay, using anti-PDL1 scFv. The results indicate that scFv can selectively and sensitively detect PDL1 from PDL1 positive human cancer cell lines. Our findings suggest that scFv could be used as a potential PDL1 inhibitor agent and probe for cell-based immunoassays to detect PDL1.

Fluorogenic enzyme-linked immunosorbent assay with a dual color variation.

The development of accurate and high-throughput biomarker detection tools is crucial for the diagnosis, monitoring, and treatment of various diseases. In this study, a sensitive fluorogenic enzyme-linked immunosorbent assay (FELISA) using Amplex Red or QuantaBlu fluorescent substrate was developed for the detection of tumor necrosis factor alpha and programmed cell death-ligand 1. The limit of detection of FELISA was in the nanogram order and multiple samples were conveniently assayed within 20 h using FELISA, demonstrating its applicability as a powerful immunoassay tool. FELISA can be widely used for rapid and accurate TNFα and PDL1 detection and applied to various fluorogenic immunoassays against other antigens of interest.

Development of fluorescence-linked immunosorbent assay for rapid detection of Staphylococcus aureus.

Staphylococcus aureus is a major pathogen that causes infections and life-threatening diseases. Although antibiotics, such as methicillin, have been used, methicillin-resistant S. aureus (MRSA) causes high morbidity and mortality rates, and conventional detection methods are difficult to be used because of time-consuming process. To control the spread of S. aureus, a development of a rapid and simple detection method is required. In this study, we generated a fluorescent anti-S. aureus antibody, and established a novel fluorescence-linked immunosorbent assay (FLISA)-based S. aureus detection method. The method showed high sensitivity and low limit of detection toward MRSA detection. The assay time for FLISA was 5 h, which was faster than that of conventional enzyme-linked immunosorbent assay (ELISA) or rapid ELISA. Moreover, the FLISA-based detection method was applied to diagnose clinically isolated MRSA samples that required only 5.3 h of preincubation. The FLISA method developed in this study can be widely applied as a useful tool for convenient S. aureus detection. KEY POINTS: • A fluorescence-linked immunosorbent assay-based S. aureus detection method • Simultaneous quantification of a maximum of 96 samples within 5 h • Application of the novel system to diagnosis clinical isolates.

Discovery of Orally Bioavailable Phthalazinone Analogues as an ENPP1 Inhibitor for STING-Mediated Cancer Immunotherapy.

A lack of the T cell-inflamed tumor microenvironment limits the efficacy of immune checkpoint inhibitors (ICIs). Activation of stimulator of interferon genes (STING)-mediated innate immunity has emerged as a novel therapeutic approach in cancer therapy. 2',3'-Cyclic GMP-AMP (cGAMP) is a natural STING agonist; however, cGAMP is subjected to endogenous degradation by ecto-nucleotide pyrophosphatase phosphodiesterase 1 (ENPP1). To improve the ICI response rate, we developed 29f, a novel ENPP1 inhibitor with phthalazin-1(2H)-one as the core scaffold. 29f inhibited the cGAMP hydrolysis by ENPP1 in vitro (IC50 = 68 nM) and enhanced the STING-mediated type I interferon response in both immune and tumor cells. 29f demonstrated excellent metabolic stability and bioavailability (F = 65%). Orally administered 29f promoted tumor growth inhibition in a CT26 syngeneic model and increased the anti-PD-L1 response. Furthermore, 29f-induced immunological memory prevented the tumor relapse against tumor rechallenge, suggesting the promising therapeutic potential of 29f.

Quenchbodies That Enable One-Pot Detection of Antigens: A Structural Perspective.

Quenchbody (Q-body) is a unique, reagentless, fluorescent antibody whose fluorescent intensity increases in an antigen-concentration-dependent manner. Q-body-based homogeneous immunoassay is superior to conventional immunoassays as it does not require multiple immobilization, reaction, and washing steps. In fact, simply mixing the Q-body and the sample containing the antigen enables the detection of the target antigen. To date, various Q-bodies have been developed to detect biomarkers of interest, including haptens, peptides, proteins, and cells. This review sought to describe the principle of Q-body-based immunoassay and the use of Q-body for various immunoassays. In particular, the Q-bodies were classified from a structural perspective to provide useful information for designing Q-bodies with an appropriate objective.

Generation of a Recombinant scFv against Deoxycholic Acid and Its Conversion to a Quenchbody for One-Step Immunoassay.

Development of a rapid detection method for deoxycholic acid (DCA) is crucial for its diagnosis in the early stages of inflammation and cancer. In this study, we expressed a soluble recombinant anti-DCA single-chain variable fragment (scFv) in Escherichia coli. To convert scFv into a Quenchbody (Q-body), we labeled scFv using commercially available maleimide-linked fluorophores. The TAMRA-C5-maleimide-conjugated Q-body showed the highest response within a few minutes of DCA addition, indicating its applicability as a wash-free immunoassay probe for onsite DCA detection.

Production and engineering of nanobody-based quenchbody sensors for detecting recombinant human growth hormone and its isoforms.

Due to athletes' misuse of recombinant human growth hormone (rhGH) for performance improvement, the World Anti-Doping Agency has designated rhGH as a prohibited substance. This study focuses on the development and improvement of a simple and fast rhGH detection method using a fluorescence-incorporated antibody sensor "Quenchbody (Q-body)" that activates upon antigen binding. Camelid-derived nanobodies were used to produce stable Q-bodies that withstand high temperatures and pH levels. Notably, pituitary human growth hormone (phGH) comprises two major isoforms, namely 22 and 20 kDa GH, which exist in a specific ratio, and the rhGH variant shares the same sequence as the 22 kDa GH isoform. Therefore, we aimed to discriminate rhGH abuse by analyzing its specific isoform ratio. Two nanobodies, NbPit (recognizing phGH) and NbRec (preferentially recognizing 22 kDa rhGH), were used to develop the Q-bodies. Nanobody production in Escherichia coli involved the utilization of a vector containing 6xHis-tag, and Q-bodies were obtained using a maleimide-thiol reaction between the N-terminal of the cysteine tag and a fluorescent dye. The addition of tryptophan residue through antibody engineering resulted in increased fluorescence intensity (FI) (from 2.58-fold to 3.04-fold). The limit of detection (LOD) was determined using a fluorescence response, with TAMRA-labeled NbRec successfully detecting 6.38 ng/ml of 22 kDa rhGH while unable to detect 20 kDa GH. However, ATTO520-labeled NbPit detected 7.00 ng/ml of 20 kDa GH and 2.20 ng/ml 22 kDa rhGH. Q-bodies successfully detected changes in the GH concentration ratio from 10 to 40 ng/ml in human serum within 10 min without requiring specialized equipment and kits. Overall, these findings have potential applications in the field of anti-doping measures and can contribute to improved monitoring and enforcement of rhGH misuse, ultimately enhancing fairness and integrity in competitive sports.

Three-Component Coupling Reactions Involving Arynes, Phosphites, and Aldehydes toward 3-Mono-Substituted Benzoxaphosphole 1-Oxides.

A mild, efficient, and transition-metal-free three-component coupling reaction involving arynes, phosphites, and aldehydes was established to afford 3-mono-substituted benzoxaphosphole 1-oxides. A range of 3-mono-substituted benzoxaphosphole 1-oxides was obtained from both aryl- and aliphatic-substituted aldehydes in moderate to good yields. Moreover, the synthetic utility of the reaction was demonstrated by a Gram-scale reaction and the transformation of the products into various P-containing bicycles.

Generation of Q-bead against bone Gla protein with simplified preparation steps.

Quenchbody (Q-body)-based immunoassays enable the detection of antigen within a few minutes with high sensitivity and specificity, thereby revealing their applicability as biosensors for quantifying several biomolecules of interest; however, while producing a Q-body, it is necessary to eliminate the unconjugated dye after labeling to separate the Q-body from the capturing bead and to change the buffer using ultrafiltration, which is time-consuming and leads to yield reduction. In this study, we generated a recombinant single chain variable fragment against bone Gla protein as a model antibody. We labeled the antibody with a dye to generate a Q-body and subsequently added affinity beads to the Q-body mixture. After washing, we directly added antigen without extracting the Q-body from the bead and then measured the fluorescence intensity. As a result, the antigen-dependent fluorescence response was obtained from "Q-bead", which was almost the same as that of the Q-body generated according to the conventional method. The Q-bead was generated within only 2.5 h, thus requiring an hour and two steps less than those required for the generation of the traditional Q-body. No expensive Flag peptide was required to recover the total antibody from beads. Moreover, the ultra-filtration step was eliminated in this bead-based method, leading to improved convenience and cost- and time-saving attributes. The Q-bead-based assay can be used as a standard protocol for simple and rapid analysis of antibody-based molecular detection.

Bacterial Production of Recombinant Coagulation Factor VIII Domains.

Factor VIII (F8) is a blood coagulation protein prearranged in six domains, and its deficiency causes hemophilia A. To fashion functional F8 therapeutics, development of a recombinant F8 (rF8) domain is essential not only for F8 substitution, but also to decipher the F8-related mechanisms. In this study, we generated Glutathione S-transferase (GST)-conjugated recombinant A2 and A3 domains of F8 using Escherichia coli. The high growth rate and economically advantageous protein production system in terms of inexpensive reagents and materials in E. coli cells facilitated the completion of entire process from protein expression to purification in 3-4 days with low production cost. Subsequent assessment of these purified proteins using enzyme-linked immunosorbent assay (ELISA) and antibodies against F8 revealed enhanced detection of rF8-A2 or rF8-A3 in a concentration dependent manner, indicating the presence of the antibody-binding epitopes in these proteins. Furthermore, these proteins are suitable for generating novel antibodies against the F8 domain and F8 domain-capturing affinity columns by enabling their conjugation to GST-capturing beads. Additionally, the recombinant F8 domains produced herein can be used for various studies, which include investigating the explicit roles of the F8 domain in the coagulation process, with domain-specific binding partners, and antibodies.

Generation of a novel monoclonal antibody against inflammatory biomarker S100A8 using hybridoma technology.

OBJECTIVES: S100A8 is highly expressed in several inflammatory and oncological conditions. To address the current lack of a reliable and sensitive detection method for S100A8, we generated a monoclonal antibody with a high binding affinity to human S100A8 to enable early disease diagnosis. RESULTS: A soluble recombinant S100A8 protein with a high yield and purity was produced using Escherichia coli. Next, mice were immunized with recombinant S100A8 to obtain anti-human S100A8 monoclonal antibodies using hybridoma technology. Lastly, the high binding activity of the antibody was confirmed and its sequence was identified. CONCLUSIONS: This method, including the production of antigens and antibodies, will be useful for the generation of hybridoma cell lines that produce anti-S100A8 monoclonal antibodies. Moreover, the sequence information of the antibody can be used to develop a recombinant antibody for use in various research and clinical applications.

Synthesis and biological evaluation of N-(3-fluorobenzyl)-4-(1-(methyl-d3)-1H-indazol-5-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-amine as a novel, potent ALK5 receptor inhibitor.

Specific inhibition of ALK5 provides a novel method for controlling the development of cancers and fibrotic diseases. In this work, a novel series of N-(3-fluorobenzyl)-4-(1-(methyl-d3)-1H-indazol-5-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-amine (11), a potential clinical candidate, was synthesized by strategic incorporation of deuterium at potential metabolic soft spots and identified as ALK5 inhibitors. This compound has a low potential for CYP-mediated drug-drug interactions as a CYP450 inhibitor (IC50 = >10 µM) and showed potent inhibitory effects in cellular assay (IC50 = 3.5 ± 0.4 nM). The pharmacokinetic evaluation of 11 in mice demonstrated moderate clearance (29.0 mL/min/kg) and also revealed high oral bioavailability in mice (F = 67.6%).

Generation of a novel antibody against BxPrx, a diagnostic marker of pine wilt disease.

BACKGROUND: Bursaphelenchus xylophilus is a pathogenic nematode that causes pine wilt disease (PWD). To prevent the rapid spread of this pathogen, developing a method for rapid and accurate detection of B. xylophilus is required. METHODS AND RESULTS: In this study, we produced a B. xylophilus peroxiredoxin (BxPrx), which is a protein that is overexpressed in B. xylophilus. Using recombinant BxPrx as an antigen, we generated and selected a novel antibody that binds to BxPrx via phage display and biopanning. We subcloned the anti-BxPrx single-chain variable fragment-encoding phagemid DNA to mammalian expression vector. We transfected the plasmid into mammalian cells and produced a highly sensitive recombinant antibody that enabled nanogram order detection of BxPrx. CONCLUSION: The sequence of anti-BxPrx antibody as well as the rapid immunoassay system described here can be applied for rapid and accurate diagnosis of PWD.

Tiered human health risk assessment of antibacterial quaternary ammonium compounds (QACs) in dishwashing detergents.

Quaternary ammonium compounds (QACs) are widely used in consumer products because of their unique antibacterial properties, and dishwashing detergents are a major source of exposure through oral, inhalation, and dermal routes. The three classes of QACs, including benzalkonium chloride (BAC), n-alkyldimethylethylbenzylammonium chloride (ADEBAC), and di-n-alkyldimethylammonium chloride (DDAC), in spray and non-spray types of dishwashing detergents were quantified by high-performance liquid chromatography-mass spectrometry. A tiered risk assessment approach was also considered. In the Tier 1 assessment, the mean and worst-case exposure were estimated to screen for rough exposure and risk levels. In the Tier 2 assessment, mean and upper-tail exposure levels were calculated based on the exposure parameters of Korean consumers using Monte Carlo simulation. QACs had a low frequency of detection of up to 20% in dishwashing detergents, and the contents of detected QACs varied depending on the individual samples. Based on the results of the Tier 1 assessment, BACs and DDACs posed potential health risks via inhalation and dermal routes. Tier 2 assessment suggested that the current level of oral and dermal exposure of Korean consumers to QACs in dishwashing detergents is unlikely to pose a health risk, even for upper-tail exposure groups. However, the present results suggest that spray-type DDACs may pose a health risk in the upper-tail inhalation exposure group, and further investigation is required to clarify this risk.

Flow cytometry-based rapid detection of Staphylococcus aureus and Pseudomonas aeruginosa using fluorescent antibodies.

Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) are major pathogens frequently detected in food and beverage poisoning, and persistent infections. Therefore, the development of a rapid method that can detect these pathogens before serious multiplication is required. In this study, we established a flow cytometry (FCM)-based detection method that allows rapid acquisition of cell populations in fluid samples by using a fluorescent antibody against S. aureus or P. aeruginosa. Using this method, we detected these pathogens with a 103 to 105 CFU order of limit of detection value within 1 hour. The FCM-based method for the detection of S. aureus and P. aeruginosa offers the possibility of high-throughput analysis of pathogens in food, environmental, and clinical sources.

A rapid ELISA for the detection of matrix metallopeptidase 9 using a recombinant Fab-type antibody.

Matrix metalloproteinase 9 (MMP9) contributes to several aspects of inflammation and cancer pathology, including invasion, metastasis, and angiogenesis. In this study, we expressed a recombinant fragment antigen-binding (Fab)-type anti-MMP9 antibody in Escherichia coli with high purity within five days and confirmed the nanomolar order of antigen-binding efficiency of the recombinant Fab. Moreover, we optimized the experimental time for performing enzyme-linked immunosorbent assay (ELISA), and decreased the reaction time from the conventional 20.5 h to 3.5 h. The rapid and sensitive MMP9 detection system developed in this study can be applied to a range of applications, including the diagnosis of diseases with MMP9 overexpression including inflammatory and cancer-related diseases.

Identification of novel pyrrolopyrimidine and pyrrolopyridine derivatives as potent ENPP1 inhibitors.

In an effort to discover novel scaffolds of non-nucleotide-derived Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) inhibitors to stimulate the Stimulator of Interferon Genes (STING) pathway, we designed and synthesised pyrrolopyrimidine and pyrrolopyridine derivatives and performed structure-activity relationship (SAR) study. We found 18p possessed high potency (IC50 = 25.0 nM) against ENPP1, and activated STING pathway in a concentration dependent manner. Also, in response to STING pathway activation, cytokines such as IFN-ß and IP-10 were induced by 18p in a concentration dependent manner. Finally, we discovered that 18p causes inhibition of tumour growth in 4T1 syngeneic mouse model. This study provides new insight into the designing of novel ENPP1 inhibitors and warrants further development of small molecule immune modulators for cancer immunotherapy.

Generation of a recombinant antibody for sensitive detection of Pseudomonas aeruginosa.

Pseudomonas aeruginosa (P. aeruginosa) is a major pathogen that causes nosocomial infections and often exhibits antibiotic resistance. Therefore, the development of an accurate method for detecting P. aeruginosa is required to control P. aeruginosa-related outbreaks. In this study, we established an enzyme-linked immunosorbent assay method for the sensitive detection of three P. aeruginosa strains, UCBPP PA14, ATCC 27853, and multidrug-resistant ATCC BAA-2108. We produced a recombinant antibody (rAb) against P. aeruginosa V-antigen (PcrV), which is a needle tip protein of the type III secretion system of P. aeruginosa using mammalian cells with high yield and purity, and confirmed its P. aeruginosa binding efficiency. The rAb was paired with commercial anti-P. aeruginosa Ab for a sandwich ELISA, resulting in an antigen-concentration-dependent response with a limit of detection value of 230 CFU/mL. These results suggest that the rAb produced herein can be used for the sensitive detection of P. aeruginosa with a wide range of applications in clinical diagnosis and point-of-care testing.

Discovery of 3,4-dihydropyrimido[4,5-d]pyrimidin-2(1H)-one and 3,4-dihydropyrido[2,3-d]pyrimidin-2(1H)-one derivatives as novel ENPP1 inhibitors.

Ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1) negatively regulates the anti-cancer Stimulator of Interferon Genes (STING) pathway. We discovered that 3,4-dihydropyrimido[4,5-d]pyrimidin-2(1H)-one and 3,4-dihydropyrido[2,3-d]pyrimidin-2(1H)-one derivatives possessed inhibitory activities on ENPP1. A structure-activity relationship (SAR) study led to the identification of 46 and 23 as potent ENPP1 inhibitors. Also, compounds 46 and 23 possessed high microsomal stabilities in human, rat, and mouse liver microsome. Additionally, CYPs (1A2, 2C9, 2C19, 2D6, and 3A4) were not inhibited by 46 and 23. Molecular dynamics simulations provided an insight of binding modes between ENPP1 and compounds (46 and 23).