Mediated Reactions Research Articles

A Enamide‐Based Diastereoselective Synthesis of Isoindolo[2,1‐a]quinolin‐11(5H)‐ones with Three Contiguous Stereogenic Centers

AbstractA stereoselective synthesis of isoindolo[2,1‐a]quinolin‐11(5H)‐ones containing three contiguous stereogenic centers is described. This Lewis‐acid mediated reaction of enamides with N‐aryl‐acylimines affords the desired fused heterocyclic isoindolinones in high yields and diastereoselectivities. Scope and limitations of this method are discussed. The stereochemical outcome of this transformation indicates a stepwise reaction pathway.

Electrochemical Mediated Esterification Reaction of Carboxylic Acids and Alcohols

Electrochemical Mediated Esterification Reaction of Carboxylic Acids and Alcohols

Effects of Water Miscible Organic Co-solvents on Enzyme Kinetic Parameters of Drug Metabolizing Enzymes in Rat Liver Microsomes

We have investigated the effects of methanol, acetonitrile, dimethyl sulphoxide or dioxane on enzyme kinetic parameters (Km and Vmax) of p-nitrophenol hydroxylation, phenacetin deethylation and metoprolol metabolism in rat liver microsomes, at different solvent concentrations. In the case of p-nitrophenol hydroxylation, methanol (0.1 %-0.75 % v/v) and dimethyl sulphoxide (0.01 %-0.075 % v/v) showed 1.3 and 2.5-fold increase respectively, in the Km with a less marked effect on the Vmax. In contrast, dimethyl sulphoxide (0.1 %-0.75% v/v) showed a 1.96-fold decrease in the Vmax. Unlike, methanol and dimethyl sulphoxide, acetonitrile showed activation of the p-nitrophenol hydroxylation activity as indicated by a 0.7-fold decrease in the Km. In the case of metoprolol metabolism, dioxane resulted in a 1.5 to 3.1-fold increase in the Km of all the three metabolite formation pathways in concentration dependent manner, with less marked effect on Vmax of the reaction. Interestingly, while acetonitrile did not affect the Km for metabolite 1 and 2 formation, the Km of metabolite 3 formation was decreased in a concentration dependent manner again with little effect on all the three Vmax values. Further, methanol had little to no effect on the Vmax of metabolite 1 and 2 formation while metabolite 3 formation was increased by 2-fold. The Km of all three metabolite formations was found to be decreased in presence of methanol. The phenacetin deethylation activity in rat liver microsomes followed atypical kinetics. Methanol and dimethyl sulphoxide did not affect the auto activation kinetics at concentration range studied. Dimethyl sulphoxide and dioxane appeared to be unsuitable for characterizing the Cytochrome450 mediated reactions because they showed a very significant effect on the Vmax/Km ratio, starting at concentrations of 0.025 % v/v and 0.25 % v/v, respectively. Methanol and acetonitrile at concentration <0.5 % v/v appeared to be acceptable solvents for solubilization of substrates metabolized by Cytochrome450s.

Copper-catalysed dehydrogenative self-coupling/cyclization of 5-aminopyrazoles: synthesis and photophysical study of pyridazines.

An interesting self-coupling/cyclization of 5-aminopyrazoles is revealed, which provides a variety of pyridazine cores in reasonable yields. In this reaction, C(sp2)-C(sp2) and N-N bond formation occurs simultaneously in one reaction vessel. The photophysical properties of the synthesized compounds were also studied and some of them exhibited fluorescence properties with good quantum yields. A radical mediated reaction mechanism is proposed with the help of control experiments.

Visible-light-mediated radical reactions of indoles with para-quinone methides using eosin Y as an organophotoredox catalyst.

Herein, we demonstrate a redox-neutral, operationally simple, atom-economical, and additive-free approach for the synthesis of indolyl diarylmethanes via a radical reaction of indoles with para-quinone methides (p-QMs) under visible-light mediated reaction conditions using eosin Y as an organophotoredox catalyst. This protocol was found to be compatible with a wide range of differently substituted p-QMs and indoles in organic as well as in aqueous media under visible-light irradiation, furnishing the desired products in good to excellent yields.

Celebrating the 15th Anniversary ofImmunotherapy: A Reflection on 2022

Celebrating the 15th Anniversary of<i>Immunotherapy</i>: A Reflection on 2022

Evidence of Sulfur Non-Innocence in [CoII (dithiacyclam)]2+ -Mediated Catalytic Oxygen Reduction Reactions.

In many metalloenzymes, sulfur-containing ligands participate in catalytic processes, mainly via the involvement in electron transfer reactions. In a biomimetic approach, we now demonstrate the implication of S-ligation in cobalt mediated oxygen reduction reactions (ORR). A comparative study between the catalytic ORR capabilities of the four-nitrogen bound [Co(cyclam)]2+ (1; cyclam=1,5,8,11-tetraaza-cyclotetradecane) and the S-containing analog [Co(S2 N2 -cyclam)]2+ (2; S2 N2 -cyclam=1,8-dithia-5,11-diaza-cyclotetradecane) reveals improved catalytic performance once the chalcogen is introduced in the Co coordination sphere. Trapping and characterization of the intermediates formed upon dioxygen activation at the CoII centers in 1 and 2 point to the involvement of sulfur in the O2 reduction process as the key for the improved catalytic ORR capabilities of 2.

Beweis von Schwefel‐non‐Innocence in [CoII(Dithiacyclam)]2+‐vermittelten, katalytischen Sauerstoff‐Reduktions‐Reaktionen

AbstractIn vielen Metallenzymen sind Schwefel‐enthaltende Liganden an Elektronen‐Transfer‐Reaktionen beteiligt. In dem hier diskutierten biomimetischen Ansatz wird der Einfluss einer Schwefelkoordination auf eine Kobalt‐katalysierte Sauerstoff‐Reduktionsreaktion (ORR) demonstriert. Ein Vergleich des ORR‐Vermögens eines vierfach Stickstoff‐koordinierten [Co(Cyclam]2+‐Komplexes (1; Cyclam=1,5,8,11‐Tetraaza‐cyclotetradecan) und dessen Schwefel‐Analogons [Co(S2N2‐Cyclam)]2+(2; S2N2‐Cyclam=1,8‐Dithia‐5,11‐diazacyclotetradecan) zeigt verbesserte katalytische Eigenschaften mit dem in die Ligandensphäre am Kobalt eingeführten Chalkogen. Isolierung und Charakterisierung der Intermediate, die sich im Zuge der Sauerstoffaktivierung an den Kobalt(II)‐Zentren von1und2bilden, identifizieren eine Beteiligung des Schwefels am O2‐Reduktionsprozess als entscheidenden Faktor für die verbesserten Eigenschaften von2bei der katalytischen ORR.

Na2CO3 Mediated Silver Mirror Reaction of General Aldehyde at Room Temperature

The classic silver mirror reaction at room temperature in textbooks usually used glucose to react with silver nitrate and ammonium nitrate with the presence of caustic alkalis. But the aldehydes such as acetaldehyde and propionaldehyde were difficult to react under the same condition. In this paper, Na2CO3 was used to mediate the reaction instead of caustic alkalis. In a newly formed ammoniacal-silver solution, a certain dose of Na2CO3 solution and aldehydes (formaldehyde, propionaldehyde, n-butyraldehyde and glucose) were added in, and then a silver mirror formed within 2 min at room temperature without stirring or continuous shaking. This result broadened the knowledge of silver mirror reactions with aldehydes and made the scheme simple and easy, enabling the teaching to be more interesting. A survey result showed that 68.4% of preservice teachers at Anhui Normal University are willing to teach the experiment using this improved method.

1833. Evaluating the Impact of Reported Beta-Lactam Allergies on Clinical Outcomes in Gram-Negative Bloodstream Infections: A Retrospective Cohort Study

Abstract Background Approximately 15% of hospitalized patients are labeled as beta-lactam (BL) allergic. Despite this, it is estimated that &amp;gt; 90% of patients do not have clinically significant hypersensitivity reactions and are BL-tolerant. The BL allergy label is associated with a host of downstream consequences, including receipt of suboptimal antibiotic therapy, healthcare-associated infections, and bacterial resistance. There are limited data investigating the impact of this allergy label on clinical outcomes in bloodstream infections caused by Gram-negative pathogens (GN-BSI). Methods This was a retrospective, single center, cohort study evaluating the impact of BL allergies on clinical outcomes in patients with GN-BSI from January 2017 to August 2021. Adult inpatients with index blood cultures positive for Pseudomonas species or Enterobacterales who received intravenous antibiotics with Gram-negative activity were included. The primary endpoint was time to effective therapy (defined as treatment with in vitro activity against a causative pathogen, as determined by phenotypic susceptibilities) and the key secondary endpoint was 30-day all-cause mortality. Results Overall, 120 patients were included, representing 30 BL-allergic (BL-A) and 90 BL-non-allergic (BL-NA) patients. Blood cultures positive for Pseudomonas species or Enterobacterales were evenly distributed (Table 1). Among Enterobacterales, Escherichia coli was implicated in 25% of cases overall. The most common source of infection was intra-abdominal infection. Across groups, median quick Pitt Bacteremia Score was 1 (IQR 0-2). Infectious Diseases was consulted in 37% of BL-A patients vs. 29% of BL-NA patients. Of BL allergies reported, 86% were classified as likely immunoglobulin E (IgE) mediated reactions. Allergy was not consulted in any of these cases. Median time to effective therapy was 162 minutes (IQR 20-824 minutes) vs. 103 minutes (IQR 27-775 minutes) in the BL-A and BL-NA groups, respectively. Thirty-day mortality occurred in 31% of BL-A and 21% of BL-NA patients. Conclusion Increased time to effective therapy and mortality rates were observed among patients with reported BL allergies. These findings highlight the importance of allergy clarification in antibiotic stewardship. Disclosures Kathleen Degnan, MD, Gilead: Grant/Research Support.

1750. Evaluation of Antibiotic Allergy in the Ambulatory Setting

Abstract Background It is not uncommon for patients to have a labeled allergy to antibiotics without thorough investigation of their adverse reactions. The adverse reactions described by some patients are not immune-mediated and these patients are incorrectly labeled as having an antibiotic allergy. As clinical testing for antibiotic allergy is expensive and time intensive, recent initiatives have successfully used patient interviewing to differentiate non-immune mediated reactions from true antibiotic allergies. We investigated the prevalence of patients with non-immune mediated reactions to antibiotics among patients with documented antibiotic allergy by using a standardized questionnaire in the outpatient setting. Methods Patients with a documented antibiotic allergy were identified and recruited from 2 clinics located in the greater Chicagoland area. Subjects completed one standardized questionnaire regarding each of their previous adverse reaction to antibiotics. We then evaluated the questionnaire responses to extricate the non-immune-mediated adverse reactions. The full symptom classification can be found in Table 1 and Table 2. Results 98 patients were recruited with a total of 159 antibiotic questionnaires completed. At the patient level, 18 individuals had no immune-mediated reactions despite antibiotic allergy labels: 18.37% (95% CI: 10.7%, 26.3%). At the antibiotic level, 35 labels had corresponding clinical histories that were likely non-immune mediated: 22.0% (95% CI: 14.7%, 29.4%). Macrolides (8/11, 72.7%), nitrofurantoin (1/2, 50%), and amoxicillin/clavulanate (2/8, 25%) were the antibiotics with the highest percentage of corresponding clinical histories that were likely non-immune mediated (Figure 1). Penicillin was the most prevalently listed antibiotic allergy (43/159, 27.0%), followed by sulfonamides (25/159, 15.7%) and fluoroquinolones (21/159, 13.2%). Conclusion This study demonstrated the feasibility of using a standardized questionnaire to discern true antibiotic allergies from non-immune mediated adverse reactions. The improved accuracy of documented allergies allows for better optimization of antibiotic prescribing. Disclosures All Authors: No reported disclosures.

Synthesis of molnupiravir (MK-4482, EIDD-2801): a promising oral drug for the treatment of COVID-19 starting from cytidine

The present work describes the synthesis of molnupiravir by employing commercially available inexpensive materials in two steps with an overall yield of 85.7%. The synthetic methodology starts with an eco-friendly starting material, that is, cytidine and establishes an alternative way to avoid costly enzyme mediated reactions. This synthetic strategy involves a selective acylation of cytidine as the first key step followed by the second step, that is, hydroxamination reaction. The major advantage of this protocol is that it is completely free of protection and deprotection reactions. Chemoselective acylation of cytidine’s primary alcohol was achieved using isobutyryl chloride, Et3N, and DMF solvent (89.3% yield). The aqueous phase transformation was achieved for the hydroxamination reaction with a 96% yield.

Piezoelectrically Mediated Reactions: From Catalytic Reactions to Organic Transformations

Comprehensive SummaryRecently, piezocatalysis has attracted considerable attention as a new type of renewable mechanical energy conversion technology, which relies on the strain induced polarization of the piezoelectric material. This new technology has been extensively applied in the applications of water splitting, water remediation, gas purification and tumor therapy. Despite the rapid development in the piezocatalysis, the utilization of piezoelectric materials for synthetic purpose is still under exploration. Piezoelectric means to promote organic reactions expand the scope of piezoelectrically mediated reactions and show successes in both organic and polymer synthesis. Herein, we provide a comprehensive review on recent progress of piezoelectrically mediated reactions, catalytic mechanisms and applications in the last few years. The limitations and future directions of this area are also discussed. We believe this review will provide new insights into the underlying mechanism of piezoelectric mediated electron transfer process and guide the design of new chemistry.

Electrochemically CO2 conversion using homogeneous and nanostructured heterogeneous Ru (II) electrocatalysts

The reduction of carbon dioxide to desirable products is an urgent goal in favour of the environment, the energy-cycle and mankind. We report the electrochemical reduction of CO2 to carbon monoxide by means of the homogeneous electrocatalyst (1), [Ru(bpy)2(L1)](ClO4)2, and the heterogeneous one (2), [Ru(bpy)2L1](ClO4)2@SiO2-NH2@Fe3O4) (meaning 1 fixed onto functionalized nanoparticles). The catalysts have been synthesized and characterized using different spectroscopies (IR, UV–vis, EDAX, SEM and PXRD(. The crystal structure of 1, determined by X-ray diffraction, revealed a distorted octahedral coordination of the Ru (II) center. In 1 the electrocatalytic activity of the complex was investigated for the CO2 reduction under various reaction conditions; this complex is stable and active for the CO2 reduction to CO in 0.5 M of a TBHP acetonitrile electrolyte. Under heterogeneous condition, both 1 and 2 show small electrocatalytic activity for CO2 reduction and remarkable electrocatalytic activity for H2 evolution in 0.5 M KHCO3 aqueous electrolyte, which can be attributed to the HCO3¯ mediated hydrogen evolution reaction (HER) process. It is expected that this could introduce a new type of the electrocatalysts for syngas production from CO2 and H2O in both homogeneous and heterogeneous catalytic systems.

Toward green nano adsorbents and catalysts: Highly active Fe/Mn nanoparticles for enhanced oxidation of oxytetracycline and levofloxacin

The widespread use of antibiotics, such as oxytetracycline (OTC) and levofloxacin (LEV), has led to dangerous levels of environmental contamination. In this study, functionalized iron/manganese nanoparticles (Fe/Mn NPs), which act as both adsorbent and Fenton catalyst, were green-synthesized using a reducing agent derived from a tea extract. The resulting pre-sorption/Fenton-like oxidation system effectively removed both OTC and LEV from the aqueous solution with adsorption capacities of Fe/Mn NPs for OTC and LEV of 58.8 and 192.3 mg·g−1, respectively. In addition, Fe/Mn NPs also showed high catalytic activity, oxidizing more than 99.9 % of both OTC and LEV, while sodium persulfate (PDS) removed only 26.6 and 29.0 % of OTC and LEV, respectively. Mechanisms of PDS activation typically involve either catalyst-initiated or mediated electron transfer reactions. Fe/Mn NPs through heterogeneous catalytic and metal leaching-induced homogeneous Fenton reactions, which generated various reactive oxygen species (ROS) including 1O2, ·OH, SO4-· and ·O2–. Characterization of Fe/Mn NPs before and after reaction, and the identification of specific OTC and LEV degradation products by LC-MS, helped to elucidate a potential degradation pathway, as well as the removal mechanism. Finally, the practicality of using this system for wastewater treatment was demonstrated using real wastewater samples indicating that the system has great potential for simultaneously degrading both OTC and LEV in contaminated wastewater.

THE USE OF MULTI-OMICS TO IDENTIFY PREDICTIVE FACTORS FOR FOOD REACTIONS

<h3>Introduction</h3> The pathophysiology of IgE mediated food reactions (FR) is multifactorial. This multi-omic analyses utilized host and microbial factors to better understand the immunological origins of FR's. <h3>Methods</h3> This longitudinal cohort study included 129 term infants, identified as FR (n=27) or non-FR (n=92) using the Infant Feeding Practices-II survey (confirmed with medical records). Saliva was collected at 6 months for multi-omic analysis of cytokines, mRNA, microRNAs, and the microbiome. <h3>Results</h3> None of the salivary cytokines (CXCL10, IL-8, IL-6, IL-18) displayed differences between groups. However, the Th1/Th2 ratio (IL-8/IL-6) was nominally higher (d = 0.56, p = 0.043, FDR = 0.30) among infants with a food reaction. One mRNA (STAT6, p = 0.039, FDR = 0.17, d = 0.045), two miRNAs (let-7e-5p, p = 0.031, FDR = 0.12, d = 0.51; miR-151a-5p, p = 0.041, FDR = 0.13, d = 0.52), and one bacterial phylum (Cyanobacteria, p = 0.024, FDR = 0.19, d = 0.72) displayed nominal differences between 27 infants with food reactions (FR) and 92 peers with no food reactions (NFR). All four omics features were higher in infants with FR. A logistic regression model employing maternal/infant traits and environmental exposures and four multi-omic features (IL-8/IL-6, miR-151a-5p, STAT6, Cyanobacteria) accounted for an additional 31% of the variance between groups (p = 0.15, AUC = 0.83, sensitivity = 97%, specificity = 48%). <h3>Conclusion</h3> Multi-omic analysis of saliva may enhance understanding of key biological factors that contribute towards developing immune mediated food reactions.

NOT ALL RASHES ASSOCIATED WITH INFANT FEEDING ARE FROM COW MILK PROTEIN ALLERGY!

<h3>Introduction</h3> Cow's milk protein allergy (CMPA) is the most common food allergy in the infancy period. The prevalence of CMPA in the United States has been increasing rapidly over the last decade. CMPA can be IgE-mediated or non-IgE-mediated. Non-IgE mediated reactions are often difficult to diagnose as there is no substantiative test. Many diagnoses of non-IgE mediated reactions are thus unconfirmed and may be incorrect. Facial rashes could occur because of other disorders too. <h3>Case Description</h3> Our patient is a 4-month-old infant, who presented with a facial rash that sometimes spread to the torso after feeds. The patient was born at term via prolonged vaginal delivery due to facial presentation. He was breastfed until two months, then switched to formula due to colic. Subsequently, the mother noticed a facial rash with feeds that resolved quickly without intervention. He was tried on different formulae, but the symptoms persisted. Upon admission, he was noted to develop facial flushing on the cheeks and forehead even with Pedialyte administration, along the distribution of the auriculotemporal nerve. Laboratory investigations (CBC, IgE for milk and soy, tryptase) were within normal limits. <h3>Discussion</h3> The infant was suspected immediately of having CMPA, but the presentation was inconsistent with an allergic reaction (absence of hives, itching, discomfort, other system involvement, and quick resolution without intervention). On the contrary, he developed flushing even with Pedialyte, which was more suggestive of a nervous system-related phenomenon, such as Frey's syndrome. He was transitioned back to cow milk-based formula, and the facial flushing improved over time.

OUTCOMES OF SINGLE BAG PROTOCOLS FOR DESENSITIZATION TO ANTINEOPLASTIC AGENTS

<h3>Introduction</h3> The typical drug desensitization process includes three separate intravenous infusions with each bag containing an increasing concentration of the drug. Many biologics and chemotherapy agents may not be diluted past a specific concentration or diluted protocols are prohibitively long, making a single bag desensitization protocol useful. The aim of this case series is to describe the safety and efficacy of single bag desensitization protocols in two oncology patients. <h3>Case Description</h3> Patient A is a 55 year-old male with metastatic prostate cancer who required desensitization to Carbazitaxel following an IgE mediated reaction to another member of the taxane drug class. Patient B is a 89 year old female with metastatic squamous cell carcinoma of the tongue who required desensitization to Ceftuximab following grade 3 cyctokine release syndrome. Both patients tolerated single bag desenstization protocols in the MICU without adverse events. Both patients went on to tolerate readministration of their culprit agents in outpatient infusion centers. <h3>Discussion</h3> Developments in medical oncology are providing an increasing number of treatment modalities, making drug reactions to antineoplastic agents more common. Patients may have only one viable treatment option, necessitating desensitization following an adverse reaction. Single bag desensitization protocols may be undiluted or have a single dilution. This method should be considered as it can be well tolerated in both IgE mediated and cytokine mediated drug reactions. Single bag protocols can simplify the procedure and decrease the time required to reach the target dose, aiding transition to outpatient infusion centers thus reducing costs and increasing patient's quality of life.

Tools to improve the diagnosis and management of T-cell mediated adverse drug reactions.

Delayed drug T-cell immune-mediated hypersensitivity reactions have a large clinical heterogeneity varying from mild maculopapular exanthema (MPE) to severe cutaneous adverse reactions (SCARs) such as acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS) and severe skin necrosis and blistering as seen in Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Given the knowledge gaps related to the immunopathogenesis of these conditions, the absence of validated diagnostic tools and the significant associated morbidity and mortality, patients with SCARs often have limited drug choices. We performed a comprehensive review aiming to evaluate in vivo diagnostic tools such as delayed intradermal skin and patch testing and ex vivo/in vitro research assays such as the lymphocyte transformation test (LTT) and the enzyme-linked ImmunoSpot (ELISpot) assay. We searched through PubMed using the terms “drug allergy,” “in vivo” and “ex vivo” for original papers in the last 10 years. A detailed meticulous approach adapted to the various clinical phenotypes is recommended for the diagnostic and management of delayed drug hypersensitivity reactions. This review highlights the current diagnostic tools for the delayed drug hypersensitivity phenotypes.

(Digital Presentation) In-Situ Electro-Organic Synthesis and Functionalization of Catechol Derivative on Carbon Black and Its Interference-Free Voltammetric pH Sensing Application

Catechol, 1,2-dihydroxybenzene (1,2-DHB), is a well-known organic redox molecule and a potent biological electron-transfer mediator widely used in electrocatalysis, bio-electrocatalysis, energy-storage and pH sensing applications. Functionalization of catechol (CA) over the carbon-electrode is an essential step to achieving the desired application. There are several studies reported for the chemical synthesis of functionalized CA derivatives following surface immobilization procedure [1-3]. Indeed, preparation of a simple and stable catechol functionalized electrochemically modified electrode is a challenging task. For instance, 4-[2-(2-naphthyl)vinly]catechol and 4-[2-(9,10-ethanoanthracen-9-yl)vinlyl]catechol grafted graphite electrodes and a library of 26 different dihydroxy benzene derivatives covalently attached to glassy carbon via ethylenediamine and C6H4-CH2-NH linkers have showed serious surface fouling during their voltammetric experiments [1,4]. In this work, we report a simple in-situ electrochemical method for functionalizing catechol derivative (ferulic acid, FA) on a low-cost carbon black (CB) modified electrode surface suitable for voltammetric pH sensing. The precursor organic compound, FA has been electrochemically oxidized over the CB modified glassy carbon electrode, GCE/CB, by performing the electrochemical-potential treatment in pH 7 phosphate buffer solution that leads to a high redox-active surface-confined FA-catechol derivative (GCE/CB@FA-Redox). Cyclic voltammetric response of the GCE/CB@FA-Redox showed a well-defined and stable redox peak at a standard electrode potential, Eo’ = 0.160 V vs Ag/AgCl with a peak-to-peak potential difference, ∆E = 0.044 V vs Ag/AgCl and surface excess value, Γ = 1.88×10-7 mol cm-2. Unlike the previously reported CA-based chemically modified electrodes which showed a well-defined mediated oxidation reaction of cysteine (CySH), hydrazine and sulfide ion [5-7], the GCE/CB@FA-Redox modified electrode didn’t show any interference to common electroactive biochemicals and chemicals such as ascorbic acid, glucose, cysteine, caffeic acid, hydrazine, hydrogen peroxide, uric acid, dopamine, creatinine, urea, nitrite, sulfide and sulfate ions. There was no alteration in the peak potential and peak current responses in the presence of the chemicals mentioned above. It is a clear advantage of using this new redox electrode for the voltammetric pH sensing application. The surface orientation of the FA-Redox system on the CB surface is the likely reason for the non-selective voltammetry response.In further, scanning electrochemical microscopy (SECM) technique along with feedback current mode was adopted for the electrochemical mapping of the hot spot of the active site. In the typical experimental procedure, the CB@FA-Redox modified electrode was chosen as a substrate, and an ultramicro-platinum electrode (25µm) was used as a probe for the surface imaging using potassium hexacyanoferrate as the redox couple (in 0.1 M KCl) (Figure 1D). Figure 1E showed a typical SECM study of the present system showing a cloud-like surface morphology of the active site.The GCE/CB@FA-Redox modified electrode was subjected to various pH solutions by performing CV studies at a fixed scan rate, 50 mV s-1. (Figure 1B). The voltammetric peak potential, Epa and Epc values were found to shift systematically against an increase in pH from 3 to 11, with a slope value of (∂Ep/∂pH) -58 ± 3 mV pH-1 (Figure 1C), matching with the ideal Nernstian value obeying the Nernstian equation, (E = Eo - ((0.0591/n)ln(RT/F)).Selective and low volume pH sensing of specific clinical samples like saliva, urine and and tears will provide vital information about the health disorder [8-9]. For instance, alteration in urine and saliva samples' urinary pH values and its associated clinical diseases like kidney stones and oral health disruption. Similarly, variation in the pH value is observed during the E.coli growth, wherein, acidic by-products such as acetic acid is released into the medium, which can cause specific decrement in the solution pH. As an independent study, a three-in-one screen-printed electrode modified with CB@FA-Redox has been developed for the pH sensor applications. As a practical application, selective voltammetric pH monitoring of real biological samples like urine, saliva and E.coli culture grown has been demonstrated. References D.C.S. Tse and T. Kuwana, Anal. Chem., 50, 1315 (1978).E. Aydindogan, E.G. Celik, D.O. Demirkol, S. Yamada, T. Endo, S. Timur and Y. Yagci, Biomacromolecules, 19, 3067 (2018).B. Wang, J. Hua, R. You, K. Yan and L. Ma, Inter. J. Biol. Macromol., 181, 435 (2021).M.A. Ghanem, J.-M. Chretien, J.D. Kilburn and P.N. Barlett, Bioelectrochemistry, 76, 115 (2009).A. Salimi, L. Miranzadeh and R. Hallaj, Talanta, 75, 147 (2008).B. Jahanshahi, J.B. Raoof, M. Amiri-Aref and R. Ojani, J. Nanosci. Nanotechnol., 15, 3429 (2015).G. Emir, S. Karakaya and Y. Dilgin, J. Electrochem. Sci. Technol., 11, 248 (2020).S. Saikrithika and A.S. Kumar, J. Chem. Sci., 133, 46 (2021).M.B. Abelson, I.J. Udell and J.H. Weston, Arch. Opthalmol., 99, 301 (1981). Figure 1