Inhibition of staphylococcal nuclease by benzimidazole-based Ligand: Implications in DNA-Mediated entrapment and uptake of MRSA by Macrophage-like cells.

The staphylococcal nuclease also referred as micrococcal nuclease (MNase) is a key drug target as the enzyme degrades the neutrophil extracellular trap (NET) and empowers the pathogen to subvert the host innate immune system. To this end, the current study presents a critical evaluation of MNase inhibition rendered by benzimidazole-based ligands (C1 and C2) and probes its therapeutic implications. A nuclease assay indicated that MNase inhibition rendered by C1 and C2 was âˆ¼ 55 % and âˆ¼ 72 %, respectively, at the highest tested concentration of 10 µM. Studies on enzyme kinetics revealed that C2 rendered non-competitive inhibition and significantly reduced MNase turnover number (Kcat) and catalytic efficiency (Kcat/Km) with an IC50 value of âˆ¼ 1122 nM. In CD spectroscopy, a notable perturbation in the ß-sheet content of MNase was observed in presence of C2. Fluorescence-microscope analysis indicated that MNase inhibition by C2 could restore entrapment of methicillin-resistant Staphylococcus aureus (MRSA) in calf-thymus DNA (CT-DNA). Flow cytometry and confocal microscope analysis revealed that uptake of DNA-entrapped MRSA by activated THP-1 cells was reinstated by MNase inhibition rendered by C2. Inhibition of nuclease by the non-toxic ligand C2 holds therapeutic prospect as it has the potential to bolster the DNA-mediated entrapment machinery and mitigate MRSA infections.

Anthraquinone-Based Ligands as MNase Inhibitors: Insights from Inhibition Studies and Generation of a Payload Nanocarrier for Potential Anti-MRSA Therapy.

The present study highlights the prospect of an anthraquinone-based ligand (C1) as an inhibitor of micrococcal nuclease (MNase) enzyme secreted by Staphylococcus aureus. MNase inhibition rendered by 5.0 µM C1 was ∼96 % and the ligand could significantly distort the ß-sheet conformation present in MNase. Mechanistic studies revealed that C1 rendered non-competitive inhibition, reduced the turnover (Kcat ) and catalytic efficiency (Km /Kcat ) of MNase with an IC50 value of 323 nM. C1 could also inhibit nuclease present in the cell-free supernatant (CFS) of a methicillin-resistant Staphylococcus aureus (MRSA) strain. A C1-loaded human serum albumin (HSA)-based nanocarrier (C1-HNC) was developed, which was amicable to protease-triggered release of payload in presence of the CFS of an MRSA strain. Eluates from C1-HNC could effectively reduce the rate of MNase-catalyzed DNA cleavage. The non-toxic nature of C1-HNC in conjunction with the non-competitive mode of MNase inhibition rendered by C1 offers interesting therapeutic prospect in alleviation of MRSA infections.

Quinoxaline-based membrane-targeting therapeutic material: Implications in rejuvenating antibiotic and curb MRSA invasion in an in vitro bone cell infection model.

Manifestation of resistance in methicillin-resistant Staphylococcus aureus (MRSA) against multiple antibiotics demands an effective strategy to counter the menace of the pathogen. To address this challenge, the current study explores quinoxaline-based synthetic ligands as an adjuvant material to target MRSA in a combination therapy regimen. Amongst the tested ligands (C1-C4), only C2 was bactericidal against the MRSA strain S. aureus 4 s, with a minimum inhibitory concentration (MIC) of 32 µM. C2 displayed a membrane-directed activity and could effectively hinder MRSA biofilm formation. A quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that C2 downregulated expression of the regulator gene agrC and reduced the fold change in the expression of adhesin genes fnbA and cnbA in MRSA in a dose-dependent manner. C2 enabled a 4-fold reduction in the MIC of ciprofloxacin (CPX) and in presence of 10 µM C2 and 8.0 µM CPX, growth of MRSA was arrested. Furthermore, a combination of 10 µM C2 and 12 µM CPX could strongly inhibit MRSA biofilm formation and reduce biofilm metabolic activity. The minimum biofilm inhibitory concentration (MBIC) of CPX against S. aureus 4 s biofilm was reduced and a synergy resulted between C2 and CPX. In a combinatorial treatment regimen, C2 could prevent emergence of CPX resistance and arrest growth of MRSA till 360 generations. C2 could also be leveraged in combination treatment (12 µM CPX and 10 µM C2) to target MRSA in an in vitro bone cell infection model, wherein MRSA cell adhesion and invasion onto cultured MG-63 cells was only ~17 % and ~ 0.37 %, respectively. The combinatorial treatment regimen was also biocompatible as the viability of MG-63 cells was high (~ 91 %). Thus, C2 is a promising adjuvant material to counter antibiotic-refractory therapy and mitigate MRSA-mediated bone cell infection.

Urea-Based Ligand as an Efflux Pump Inhibitor: Warhead to Counter Ciprofloxacin Resistance and Inhibit Collagen Adhesion by MRSA.

Methicillin-resistant Staphylococcus aureus (MRSA) is a frontline human pathogen in which efflux pump activity confers high levels of antibiotic-resistance and poses a therapeutic challenge in the clinics. The present study illustrates the potential of urea-based ligand as an efflux pump inhibitor (EPI) in order to restore the efficacy of ciprofloxacin (CPX) against MRSA. Among eight structurally varying urea-based ligands, the ligand C8 could significantly inhibit efflux pump activity in the clinical MRSA strain S. aureus 4s and was superior to the known EPI reserpine. In combinatorial treatment, C8 enhanced cellular accumulation of CPX, rendered a 16× decrease in the MIC of CPX, and restored the susceptibility of S. aureus 4s to CPX. Notably, C8 downregulated the expression of norA gene coding for the efflux pump in MRSA and treatment with 10 µM C8 and 2.0 µM CPX prevented emergence of the CPX resistance trait and suppressed MRSA cell growth till 120 generations. For potential anti-MRSA therapy, C8-loaded poly(d,l-lactide-co-glycolide) nanocarrier (C8-PNC) was generated, which facilitated facile release of C8 in physiologically relevant fluid. C8-PNC (loaded with 50 µM C8) rendered efflux pump inhibition and eliminated MRSA in combination with only 2.0 µM CPX. Treatment with the non-toxic C8-PNC (loaded with 50 µM C8) and CPX (2.0 µM) also hindered MRSA adhesion on collagen manifold higher as compared to cells treated with 32 µM CPX and significantly downregulated norA gene expression in non-adhered MRSA cells. The urea-based ligand presented herein is a promising biocompatible therapeutic material for effective mitigation of MRSA infections.

Interplay between Supramolecular and Coordination Interactions in Synthetic Amphiphiles: Triggering Metal Starvation and Anchorage onto MRSA Cell Surface.

The present work highlights the implications of supramolecular interaction and metal coordination on the self-assembly behavior and bactericidal potential of salicaldehyde-(C1) and napthaldehyde-based (C2) amphiphiles against methicillin-resistant Staphylococcus aureus (MRSA). LB trough and atomic force microscope (AFM) analysis indicated the propensity of the amphiphiles to form a monolayer as well as spherical aggregates, with the critical micelle concentration (CMC) for C2 (7.0 µM) being lower than C1 (18.5 µM) in water. Formation of an amphiphile-metal complex was evidenced by ESI-MS, FTIR, FETEM-EDX, and ITC analysis. Growth of S. aureus MRSA 100 cells was remarkably impaired in the presence of 5.0 µM C1 or 20 µM C2 as compared to free cells or cells grown in the presence of equivalent levels of amphiphile-metal complexes, suggesting that the amphiphiles perhaps sequester metal and induce metal starvation in MRSA. C1 and C2 rendered superior membrane damage in MRSA and were less toxic to human embryonic kidney (HEK 293) cells as compared to their metal complexes. C1 and C2 rendered a dose-dependent inhibition of S. aureus biofilm formation, while revival of biofilm upon Zn(II) addition suggested that zinc starvation rendered by the amphiphiles may induce biofilm inhibition. C1 imposed a concentration-dependent metal starvation response in MRSA as there was an upregulation of the cntL gene and downregulation of cntA gene, which are involved in synthesis of the zincophore staphylopine (Stp) and transport of the Stp-Zn complex, respectively. ITC analysis revealed that binding of C1 and C2 to staphylococcal lipoteichoic acid (LTA) was stronger than the corresponding Zn(II) complexes, which perhaps accounted for the higher bactericidal potency of the amphiphiles. The study provides a fundamental understanding on how the chemistry-driven multimodal interaction of the amphiphile translates into growth inhibition and metal starvation in MRSA and advances the idea of combating drug resistance in pathogenic bacteria through amphiphiles, which are pluri-active.

Multifunctional Synthetic Amphiphile for Niche Therapeutic Applications: Mitigation of MRSA Biofilms and Potential in Wound Healing.

The relentless menace of implant- and skin wound-associated infections caused by methicillin-resistant Staphylococcus aureus (MRSA) biofilms demands the design of therapeutics that have an edge over conventional antibiotics. The present study reports the potential of pluri-active amphiphiles having a 12-carbon alkyl chain and a salicaldehyde head group (C1) or a napthaldehyde head group (C2) in mitigating wound site- and implant-associated MRSA biofilms and as a topical wound healing agent. The amphiphiles impeded S. aureus MRSA 100 biofilm formation on collagen both on extraneous addition and on impregnation into collagen and inflicted damage to MRSA cells embedded in collagen matrix infused with simulated wound fluid, with C1 being more potent than C2. Adhesion of the MRSA biofilm was hampered on C1-coated orthopedic stainless-steel wire, while eluates from C1-coated wires were non-toxic to HEK 293 cells, highlighting the prospect of C1 as an implant-associated antibacterial coating. Upon treatment with C1, expression of the adhesin fnbA gene was low in the MRSA biofilm and downregulated in non-adherent MRSA cells, while δ-toxin (hld) gene expression in the MRSA biofilm increased, implying that C1 hindered cell-cell adhesion and planktonic-biofilm transition and also reduced biofilm adhesion. Oral administration of C1 (300 and 1000 mg/kg) was non-toxic to BALB/c mice as evidenced in stable hematological parameters and normal histopathological features of vital organs. Topical application of C1 (50 and 100 mg/kg) on a skin excision wound in female BALB/c mice resulted in effective wound closure, fibrous tissue proliferation, and tissue reorganization. Confocal microscopy revealed that topical application of C1 in an ex vivo murine skin explant could alleviate invasion of skin by MRSA, while solution-based studies indicated subdued MRSA adhesion onto the skin explants. The pluri-active synthetic amphiphile C1 provides a framework for developing antibacterials that hold translational potential as a therapeutic for implant- and skin wound-associated MRSA infections.

Biocompatible Nanocomposite Tailored to Endure the Gastric Niche Renders Effective in Vitro Elimination of Intestinal Pathogenic Bacteria and Supports Adhesion by Beneficial Bacteria.

Bacteriocins produced by lactic acid bacteria (LAB) are potent therapeutic arsenals for targeting gastrointestinal pathogens and a promising alternative to antibiotics, because of their selective activity and reduced propensity to trigger collateral damage to the beneficial gut microbes. However, proteolytic inactivation in the gastric niche renders bacteriocins ineffective. The present study addresses this challenge and demonstrates that a biocompatible milk protein fraction can be leveraged to generate a robust nanocargo, which renders protection from proteolysis in the gastric milieu and facilitates delivery of the encapsulated bacteriocin pediocin. In a simulated gastric transit experiment, pediocin-loaded milk protein nanocomposite (Ped-MNC) could render a 3.0 log reduction in the viability of model gastrointestinal pathogens. Ped-MNC is nontoxic to cultured human intestinal cells (HT-29 cells) and effectively abrogates pathogenic bacteria adhering onto intestinal cells. In a combinatorial regimen, Ped-MNC and the beneficial LAB Lactobacillus plantarum DF9 could substantially reduce the levels of the pathogen Enterococcus faecalis MTCC 439 adhering onto HT-29 cells and interestingly the nanocomposite does not hinder adhesion of intestinal cells by the beneficial LAB. The developed nanocomposite holds promise as a niche specific therapeutic for selective mitigation of intestinal pathogens.

Generation of a Hydroxyapatite Nanocarrier through Biomineralization Using Cell-Free Extract of Lactic Acid Bacteria for Antibiofilm Application.

Nanoscale materials hold considerable promise in the mitigation of bacterial infections. In order to exploit nanomaterials as delivery systems in an antibacterial therapeutic paradigm, it is critical to ensure that the generated material is nontoxic. Based on the fundamental principle of biomineralization, we herein report the generation of biocompatible hydroxyapatite nanoparticles (HANPs) in the presence of proteins secreted by the lactic acid bacteria (LAB) Lactobacillus plantarum MTCC 1325, Lactobacillus plantarum CRA52, and Pediococcus pentosaceus CRA51. The biogenic HANPs were characterized by AFM, FETEM, powder XRD, DLS, and FTIR analysis. Interestingly, HANPs could also be synthesized using an ∼20 kDa protein purified from the secreted protein extract obtained from L. plantarum MTCC 1325, which suggested that this lower molecular weight protein fraction was perhaps significantly involved in biomineralization-based generation of HANPs. In order to develop a therapeutic bactericidal nanocomposite, HANPs were loaded with the antibiotic polymyxin B (PB). A Langmuir isotherm model was evident in the studies that measured adsorption of PB onto HANPs. A sustained release profile of PB from the nanocomposite was observed in buffers having varying pH and in simulated body fluid. The nanocomposite (PB-HNC) exhibited bactericidal as well as antibiofilm activity against Pseudomonas aeruginosa MTCC 2488 and was nontoxic to cultured human embryonic kidney cells.

Al3+ sensing through different turn-on emission signals vis-à-vis two different excitations: Applications in biological and environmental realms.

A rationally designed Schiff base chemosensor (L) could render specific detection of Al3+ ions with two distinct turn-on emission signals, separated by over 100 nm upon excitation at two different wavelengths. The utility of the probe lies in facilitating sensing in 80% aqueous medium with an emission close to 600 nm via an intramolecular charge transfer (ICT) mechanism. The biocompatible and cell permeable probe could readily sense Al3+ in live HeLa cells as well. The affinity of the probe for Al3+could be leveraged to specifically study DNA- Al3+ interaction in solution.

Potential of Pyridine Amphiphiles as Staphylococcal Nuclease Inhibitor.

The present study explores the potential of pyridine-based synthetic amphiphiles C1 and C2 having 4-carbon and 12-carbon hydrophobic tails, respectively, as staphylococcal nuclease inhibitors. UV-visible titration with calf-thymus DNA (CT-DNA) revealed a hypochromic shift in the absorbance bands of C1 and C2, whereas fluorescence titration indicated a reduction in the emission intensity of the monomer bands of the amphiphiles. Interaction of deoxyribonuclease I (DNase 1) and micrococcal nuclease (MNase) with C1 or C2 led to a decrease in the emission intensity of tryptophan at λ=345 nm along with an increase in the monomer emission intensity of C1 and C2 at λ=375 nm for DNase I and excimer emission intensity at λ=470 nm for both DNase I and MNase. Scatchard's analysis indicated superior interaction of C2 with DNase I. Circular dichroism spectroscopy revealed major changes in the secondary structures of both DNase I and MNase upon interaction with the amphiphiles. A solution-based nuclease assay in conjunction with gel electrophoresis indicated amphiphile-mediated protection against nuclease-directed DNA cleavage. Interestingly, C2 could render inhibition of nuclease present in the culture supernatant of Staphylococcus aureus MTCC 96, which highlights the therapeutic prospect of the amphiphile against S. aureus.

Micellar chemotherapeutic platform based on a bifunctional salicaldehyde amphiphile delivers a "combo-effect" for heightened killing of MRSA.

The devastating infections caused by methicillin-resistant Staphylococcus aureus (MRSA) coupled with its high resistance towards antibiotics underscores the need for an effective anti-MRSA therapeutic. The present study illustrates the use of a salicylaldehyde based bactericidal amphiphile (C1) in generating a micellar carrier that renders delivery of therapeutic antibiotics. The inherent membrane-targeting activity of C1 present in the micelle could be leveraged to counter the resistance of MRSA and enhance cellular uptake of the released antibiotics, resulting in effective elimination of the pathogen. The inherent bactericidal and antibiofilm activity of C1 was captured in FESEM analysis, solution-based assays and fluorescence microscopy. ANS-based fluorescence spectroscopy indicated that the critical micelle concentration (CMC) for C1 was 18.5 µM in water. DLS studies and FESEM analysis indicated that the average particle size for micelles based on C1 (C1M) and rifampicin-loaded C1M (C1M- R) was smaller than vancomycin-loaded C1M (C1M- V). C1M- R and C1M- V rendered sustained release of the antibiotics in physiologically relevant fluids. Notably, following interaction with MRSA for 3 h, the relative anti-MRSA activity of C1M- R and C1M- V was nearly 12-fold and 8-fold higher, respectively, as compared to the free antibiotics at equivalent concentration, highlighting the merit of leveraging the activity of C1 and the antibiotic concurrently in the micellar system. The relative cell-free antibiotic was also manifold lower in the case of C1M- R and C1M- V treated MRSA as against treatment with free antibiotics, suggesting that the amphiphilic warhead breached the membrane barrier and enhanced cellular uptake of the released antibiotics. Interestingly, C1M- R and C1M- V exhibited a high therapeutic index, being non-toxic to HEK 293 cells at concentrations higher than their minimum inhibitory concentration (MIC) against MRSA and they could be employed as an antibacterial coating to prevent MRSA biofilm formation on surgical silk sutures. The antibiotic-replete biocompatible micelles based on a self-assembling membrane-targeting amphiphile described herein represent a promising framework to integrate multiple warheads and generate a potent anti-MRSA therapeutic material.

Dual-label flow cytometry-based host cell adhesion assay to ascertain the prospect of probiotic Lactobacillus plantarum in niche-specific antibacterial therapy.

Host cell adhesion assays that provide quantitative insight on the potential of lactic acid bacteria (LAB) to inhibit adhesion of intestinal pathogens can be leveraged for the development of niche-specific anti-adhesion therapy. Herein, we report a dual-colour flow cytometry (FCM) analysis to assess the ability of probiotic Lactobacillus plantarum strains to impede adhesion of Enterococcus faecalis, Listeria monocytogenes and Staphylococcus aureus onto HT-29 cells. FCM in conjunction with a hierarchical cluster analysis could discern the anti-adhesion potential of L. plantarum strains, wherein the efficacy of L. plantarum DF9 was on a par with the probiotic L. rhamnosus GG. Combination of FCM with principal component analysis illustrated the relative influence of LAB strains on adhesion parameters kd and em of the pathogen and identified probiotic LAB suitable for anti-adhesion intervention. The analytical merit of the FCM analysis was captured in host cell adhesion assays that measured relative elimination of adhered LAB vis-à-vis pathogens, on exposure to either LAB bacteriocins or therapeutic antibiotics. It is envisaged that the dual-colour FCM-based adhesion assay described herein would enable a fundamental understanding of the host cell adhesion process and stimulate interest in probiotic LAB as safe anti-adhesion therapeutic agents against gastrointestinal pathogens.

A ratiometric fluorogenic probe for the real-time detection of SO32- in aqueous medium: application in a cellulose paper based device and potential to sense SO32- in mitochondria.

A new water soluble and fluorogenic probe (L) that can demonstrate a specific ratiometric detection of a SO2 derivative (SO32-) in 100% aqueous medium and live cells has been designed and synthesized. The detection process can be visualized by the naked eye, as the orange-red fluorescence of L turns into a strong blue fluorescence upon interaction with SO32-. L displayed several beneficial attributes such as detection in complete aqueous medium, extremely fast response time along with high selectivity and sensitivity. The ratiometric sensing was attributed to the selective nucleophilic addition reaction of SO32- with L. The probe was further used to develop a low cost microfluidic sensor device (µPAD). The probe was biocompatible and its potential to sense SO32- in mitochondria was captured in live HeLa cells.

Amphiphilic Cargo-Loaded Nanocarrier Enhances Antibiotic Uptake and Perturbs Efflux: Effective Synergy for Mitigation of Methicillin-Resistant Staphylococcus aureus.

A pyridinium-amphiphile-loaded poly(lactic-co-glycolic acid) (PLGA) nanocarrier (C1-PNC) was developed as an adjuvant in order to break the resistance and restore the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) cells to therapeutic antibiotics. Notably, against a clinical MRSA strain, C1-PNC was found to render 8- and 6-fold decreases in the minimum biofilm eradication concentration (MBEC90 ) of gentamicin and ciprofloxacin, respectively. Mechanistic studies on MRSA planktonic cells revealed that in the case of gentamicin, C1-PNC promotes enhanced cellular uptake of the antibiotic, whereas the propensity of C1-PNC to inhibit efflux pump activity could be leveraged to enhance cellular accumulation of ciprofloxacin, leading to effective killing of MRSA cells. Interestingly, the combinatorial dosing regimen of C1-PNC and the antibiotics was nontoxic to cultured HEK293 cells. This nontoxic amphiphile-loaded nanomaterial holds considerable promise as an adjuvant for antibiotic-mediated alleviation of MRSA biofilms.

A Nonbactericidal Zinc-Complexing Ligand as a Biofilm Inhibitor: Structure-Guided Contrasting Effects on Staphylococcus aureus Biofilm.

Zinc-complexing ligands are prospective anti-biofilm agents because of the pivotal role of zinc in the formation of Staphylococcus aureus biofilm. Accordingly, the potential of a thiosemicarbazone (compound C1) and a benzothiazole-based ligand (compound C4) in the prevention of S. aureus biofilm formation was assessed. Compound C1 displayed a bimodal activity, hindering biofilm formation only at low concentrations and promoting biofilm growth at higher concentrations. In the case of C4, a dose-dependent inhibition of S. aureus biofilm growth was observed. Atomic force microscopy analysis suggested that at higher concentrations C1 formed globular aggregates, which perhaps formed a substratum that favored adhesion of cells and biofilm formation. In the case of C4, zinc supplementation experiments validated zinc complexation as a plausible mechanism of inhibition of S. aureus biofilm. Interestingly, C4 was nontoxic to cultured HeLa cells and thus has promise as a therapeutic anti-biofilm agent. The essential understanding of the structure-driven implications of zinc-complexing ligands acquired in this study might assist future screening regimes for identification of potent anti-biofilm agents.

A solo fluorogenic probe for the real-time sensing of SO3(2-) and SO4(2-)/HSO4(-) in aqueous medium and live cells by distinct turn-on emission signals.

A judiciously designed fluorogenic probe (L) rendered rapid and differential turn-on responses by exhibiting strong blue fluorescence (λem = 442 nm) for SO3(2-) and greenish-yellow fluorescence (λem = 511 nm) for SO4(2-)/HSO4(-) in 100% aqueous medium and live cells.

Bacteriocin-producing strains of Lactobacillus plantarum inhibit adhesion of Staphylococcus aureus to extracellular matrix: quantitative insight and implications in antibacterial therapy.

In the present study, the adhesion of bacteriocin-producing probiotic strains of Lactobacillus plantarum onto extracellular matrix (ECM) proteins such as collagen and mucin and their potential to prevent pathogen invasion onto the ECM was ascertained. Fluorescence-based in vitro assays indicated that L. plantarum strains CRA21, CRA38 and CRA52 displayed considerable adhesion to ECM molecules, which was comparable to the probiotic Lactobacillus rhamnosus GG. Flow cytometry-based quantitative assessment of the adhesion potential suggested that L. plantarum CRA21 exhibited superior adhesion onto the ECM as compared with other lactic acid bacteria strains. Furthermore, fluorescence-based assays suggested that the highest inhibition of Staphylococcus aureus adhesion onto collagen and mucin by bacteriocin-producing L. plantarum strains was observed in the exclusion mode as compared with the competition and displacement modes. This observation was supported by the higher binding affinity (k(d)) for the ECM exhibited by the L. plantarum strains as compared with S. aureus. Interestingly, a crude plantaricin A extract from food isolates of L. plantarum displayed potent antibacterial activity on ECM-adhered S. aureus cells. It is envisaged that the L. plantarum isolates displaying bacteriocinogenic and ECM-adhering traits can perhaps be explored to develop safe antibacterial therapeutic agents.

A near-infrared emissive Al(3+) sensing platform for specific detection in solution, cells and probing DNase activity.

A new tricarbocyanine-based chemosensor exhibited a dramatic Al(3+)-specific fluorescence turn-on response in the near-infrared (NIR) region. The receptor was found to be highly selective towards Al(3+) over other metal ions in physiological condition. The sensor was non-toxic and could thus be employed as an imaging probe for detecting intracellular Al(3+) in live cells. Interestingly, upon interaction with DNA in solution, the L-Al(3+) ensemble rendered tracking of DNase activity in solution through a systematic reduction in the fluorescence emission intensity.

A sole multi-analyte receptor responds with three distinct fluorescence signals: traffic signal like sensing of Al(3+), Zn(2+) and F(-).

A dialdehyde-based multi-analyte sensor renders distinctive emission spectra for Al(3+), Zn(2+) and F(-) ions. The ligand exhibited different types of interactions with these three different ions resulting in the enhancement of fluorescence intensity at three different wavelengths. All the sensing processes were studied in detail by absorption spectroscopy, emission spectroscopy and (1)H-NMR titration experiment. The ligand has the working ability in a wide pH range including the physiological pH. The ligand is non-toxic and amicable for sensing intracellular Al(3+) and Zn(2+) in live HeLa cells.