Ultrasensitive NIR fluorometric assay for inorganic pyrophosphatase detection via Cu2+-PPi interaction using bimetallic Au-Ag nanoclusters.

BACKGROUND: Inorganic pyrophosphatase (PPase) is key enzyme playing a key role in biochemical transformations such as biosynthesis of DNA and RNA, bone formation, metabolic pathways associated with lipid, carbohydrate and phosphorous. It has been reported that lung adenocarcinomas, colorectal cancer, and hyperthyroidism disorders can result from abnormal level of PPase. Therefore, it is of notable significance to develop simple and effective real time assay for PPase enzyme activity monitoring for screening of many metabolic pathways as well as for early disease diagnosis. RESULT: The fluorometric detection of PPase enzyme in near infrared region-1 (NIR-1) has been carried out using bimetallic nanoclusters (LA@AuAg NCs). The developed sensing strategy was based on quenching of fluorescence intensity of LA@AuAg NCs upon interaction with copper (Cu2+) ions. The off state of LA@AuAg_Cu2+ ensemble was turned on upon addition of pyrophosphate anion (PPi) due to strong binding interaction between PPi and Cu2+. The catalytic conversion of PPi into phosphate anion (Pi) in the presence of PPase led to liberation of Cu2+ ions, and again quenched off state was retrieved due to interaction of free Cu2+ with LA@AuAg NCs. The ultrasensitive detection of PPase was observed in the linear range of 0.06-250 mU/mL with LOD as 0.0025 mU/mL. The designed scheme showed good selectivity towards PPase enzyme in comparison to other bio-substrates, along with good percentage recovery for PPase detection in real human serum samples. SIGNIFICANCE: The developed NIR based assay is ultrasensitive, highly selective and robust for PPase enzyme and can be safely employed for other enzymes detection. This highly sensitive nature of biosensor was result of involvement of fluorescence-based technique and synergistic effect of dual metal in NIR based bimetallic NCs. Moreover, owing to the emission in NIR domain, in future, these nanoclusters can be safely employed for many biomedical applications for In vivo studies.

Chitosan functionalized doxorubicin loaded poly(methacrylamide) based copolymeric nanoparticles for enhanced cellular internalization and in vitro anticancer evaluation.

Doxorubicin (Dox), a chemotherapeutic agent, encounters challenges such as a short half-life, dose-dependent toxicity, and low solubility. In this context, the present study involved the fabrication of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-(3-aminopropyl)methacrylamide (APMA) bearing P(HPMA-s-APMA) copolymeric nanoparticles (P(HPMA-s-APMA) NPs) and their investigation for efficient delivery of Dox. Furthermore, the synthesized nanoparticles (NPs) were coated with chitosan (Cht) to generate positively charged nanoformulations. The prepared formulations were evaluated for particle size, morphology, surface charge analysis, percentage encapsulation efficiency (EE%), and drug release studies. The anticancer activity of Cht-P(HPMA-s-APMA)-Dox NPs was assessed in the HeLa cancer cell line. The prepared P(HPMA-s-APMA)-Dox NPs exhibited an average particle size of 240-250 nm. Chitosan decorated P(HPMA-s-APMA)-Dox NPs displayed a significant increase in particle size, and the zeta potential shifted from negative to positive. The EE% for Cht-P(HPMA-s-APMA)-Dox NPs was calculated to be 68.06 %. The drug release studies revealed a rapid release of drug from Cht-P(HPMA-s-APMA)-Dox NPs at pH 4.8 than pH 7.4, demonstrating the pH-responsiveness of nanoformulation. Furthermore, the cell viability assay and internalization studies revealed that Cht-P(HPMA-s-APMA)-Dox NPs had a high cytotoxic response and significant cellular uptake. Hence, the Cht-P(HPMA-s-APMA)-Dox NPs appeared to be a suitable nanocarrier for effective, and safe chemotherapy.

Recent advancements in nanomaterial based optical detection of food additives: a review.

Food additives have become a critical component in the food industry. They are employed as preservatives to decelerate the negative effects of environmental and microbial factors on food quality. Currently, food additives are used for a variety of purposes, including colorants, flavor enhancers, nutritional supplements, etc., owing to improvements in the food industry. Since the usage of food additives has increased dramatically, the efficient monitoring of their acceptable levels in food products is quite necessary to mitigate the problems associated with their inappropriate use. The traditional methods used for detecting food additives are generally based on standard spectroscopic and chromatographic techniques. However, these analytical techniques are limited by their high instrumentation cost and time-consuming procedures. The emerging field of nanotechnology has enabled the development of highly sensitive and specific sensors to analyze food additives in a rapid manner. The current article emphasizes the need to detect various food additives owing to their potential negative effects on humans, animals, and the environment. In this article, the role of nanomaterials in the optical sensing of food additives has been discussed owing to their high accuracy, ease-of-use, and excellent sensitivity. The applications of nanosensors for the detection of various food additives have been elaborated with examples. The current article will assist policymakers in developing new rules and regulations to mitigate the adverse effects of toxic food additives on humans and the environment. In addition, the prospects of nanosensors for the optical detection of food additives at a commercial scale have been discussed to combat their irrational use in the food industry.

Tuning the Luminescence of Microwave-Assisted N-Doped Fluorescent Carbon Dots: Bioimaging Applications and Label-Free Anti-Cancer Drug Delivery.

Nanosized fluorescent carbon dots (Cdots) have gained a lot of attention in the recent years because of their superior properties, such as good biocompatibility, low toxicity, excellent chemical stability, resistance to photobleaching, and ease of chemical modification. Cdots are promising candidates for considerable applications in various fields: sensors, bioimaging, and drug delivery. Specifically, nitrogen-doped Cdots have attracted a huge interest because of their applicability in bioimaging and drug delivery. Conventional methods for the synthesis of Cdots have drawbacks, such as the use of organic solvents, the presence of side products, and the time required for synthesis. Keeping all these points in mind, herein, we report green methodology for the synthesis of water-soluble, blue-emitting, nitrogen-doped multifunctional Cdots under microwave irradiation within 3 min. The Cdots were prepared using citric acid and arginine as source materials and were characterized using various physicochemical techniques. A pH-responsive drug delivery system was then designed using anticancer drug doxorubicin and the synthesized Cdots. The biocompatibility of synthesized Cdots was analyzed against L929 normal cell line. The Cdots-DOX conjugates exhibited efficient anticancer activity against HeLa cells and also acted as excellent bioimaging agents.

Design of Fmoc-Phenylalanine Nanofibrillar Hydrogel and Mechanistic Studies of Its Antimicrobial Action against Both Gram-Positive and Gram-Negative Bacteria.

In pursuit of efficient antimicrobial agents, biomaterials such as hydrogels have drawn a considerable amount of attention due to their numerous advantages such as a high degree of hydration, biocompatibility, stability, and direct application at an infectious site. Particularly, biomaterials such as hydrogels based on Fmoc-protected peptides and amino acids have proven to be immensely advantageous. Such biomaterials can undergo gelation by simple pH modulation and can be used for various biological applications. Keeping this in mind, in this work, we reported the synthesis of Fmoc-phenylalanine (Fmoc-F)-based hydrogels using trisodium citrate as a pH modulator and compared them with the previously reported pH modulator glucono-δ-lactone. The gels were compared using various characterization techniques such as rheometry, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), small angle X-ray scattering (SAXS), FT-IR, thioflavin T (ThT) binding assay, and zeta potential studies. These studies highlighted the role of pH modulators in affecting various parameters such as the ability to alter the zeta potential of the nanofibrils, improve their bactericidal action, reduce the amyloidic characters, shift the lattice packing from amorphous to crystalline, and introduce fluorescence and thermoreversibility. Interestingly, this is the first report where the Fmoc-F-based hydrogel has been shown to be effective against Gram-negative bacteria along with Gram-positive bacteria as well. Additionally, the mechanism of antimicrobial action was investigated using docking and antioxidant studies.

Targeting bacterial biofilms using vancomycin and multivalent cell-penetrating peptide labeled quantum dots.

Bacterial biofilms are highly resilient microbial musters that are difficult to eradicate, driving the development of novel therapeutic strategies. The current study aims to investigate the therapeutic efficacy of cell-penetrating peptide-based targeted delivery of vancomycin functionalized quantum dots in eradicating biofilm formation in gram-positive and gram-negative bacterial strains. The conjugate was characterized using fluorimetry, UV-visible spectroscopy, gel electrophoresis, and zeta potential. The conjugate was then tested for antimicrobial and antibiofilm activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, and it demonstrated excellent antimicrobial as well as antibiofilm activity against all the tested strains. The findings indicated that the conjugate was capable of overcoming bacterial resistance of bacteria in addition to the eradication of biofilms at effective concentrations.

Femtomolar detection of staphylococcal enterotoxin 'B' using a fluorescent quantum dot based hybrid Apta-immunosensor.

Food poisoning is a gastrointestinal illness caused by food-borne enterotoxin produced by the bacterium Staphylococcus aureus. The effective dose of Staphylococcal enterotoxin 'B' (SEB) is estimated to be 0.4 ng/kg of body weight, whereas the 50 % lethal dose is found to be 20 ng/kg of body weight for humans exposed by the inhalation route. The present report highlights the development of a fluorescence resonance energy transfer (FRET) based assay for the detection of Staphylococcal enterotoxin. Highly fluorescent, aqueous quantum dots were synthesized and conjugated with Staphylococcal enterotoxin 'B' specific bioreceptors. SEB specific aptamer and SEB antibody were labeled with fluorescent quantum dots for recognizing and binding two separate epitopes in the SEB. A combination of two probes against different epitopic regions in a homogeneous sandwich assay format enhanced the sensitivity and specificity of SEB detection. In the presence of the enterotoxin, both the aptamer and antibody came in close proximity with each other and FRET was observed. A linear decrease in the fluorescence at 562 nm and a corresponding increase in the signal at 644 nm was observed with increasing concentrations of SEB, when excited at the absorption maximum of quantum dots. The limit of detection for the developed assay obtained was less than 1 ng/ml. The method was employed in apple juice and quantitated using Enzyme-linked Immunosorbent Assay (ELISA). The designed assay was rapid and robust and can be extrapolated as a platform for the detection of various disease-causing agents of biomedical significance.

Self-Assembled Peptide Hydrogel for Accelerated Wound Healing: Impact of N-Terminal and C-Terminal Modifications.

Wound dressings are required to provide a moist environment for wounds, protect against invading infections, expedite tissue regeneration, and improve wound healing efficiency. Developing biomaterials with all aforesaid properties is still a big challenge. However, peptide-based hydrogels have the potential to overcome these challenges as they are biocompatible, biodegradable as well as have the ability to mimic the extracellular matrix and provide an appropriate moist environment which is important for wound healing. With this in mind, we report the preparation and comparison of three hexapeptide-based hydrogels, LIVAGD, with the aim to understand the importance of the N-terminal protecting group as well as the C-terminal amino acid substitution on its various biological efficacies. Fmoc and acetyl groups were used for N-terminal peptide protection, while aspartic acid was substituted with lysine at the C-terminus. The resulting peptide-based hydrogels were compared. Fmoc peptide-based hydrogels exhibited efficient anti-inflammatory action along with improved biocompatibility while lysine provided enhanced antibacterial effect to the hydrogel. Additionally, in vivo efficacy was examined using a mouse model, and Fmoc hydrogels demonstrated an improved wound healing ability with ∼40 % faster healing rate in comparison to the reported acetylated peptide hydrogels.

Ultrasensitive aptasensor for arsenic detection using quantum dots and guanylated Poly(methacrylamide).

The present study demonstrate the first time usage of poly (HPMA-s-GPMA) copolymer for the fabrication of three-component based aptasensor for simple, selective, rapid and label free detection of arsenite (As3+). For this purpose, guanidinium bearing poly (HPMA-s-GPMA) copolymer and MPA-CdTe@CdS quantum dots (QDs) was employed in conjunction with As3+ specific aptamer. This protocol utilizes the quenching phenomena displayed by QDs due to the competitive binding of As3+ ions and cationic copolymer to the aptamer. In particular, the As3+ bind to the specific aptamer, leaving poly (HPMA-s-GPMA) freely available for its electrostatic intercations with QDs, which quenches the fluorescent signal. Contrarily, in the absence of As3+ ions, the aptamer can electrostatically bind to poly (HPMA-s-GPMA); making copolymer inactive to affect the fluorescence signal of the QDs. The efficiency of the proposed fluorescence nanoprobe was further tested using linear calibration curves. The obtained data in the range of 0.01-100 nM showed excellent specificity for As3+ ions with the limit of detection (LOD) of 246.77 pM. Moreover, the "on-off" fluorescent aptasensor is highly selective for As3+ ions in the presence of other interfering metal ions by utilizing As3+ specific aptamer. Furthermore, the reported study showed outstanding applicability in the real-world samples (water, food and soil) containing preservatives, metal ions, minerals, and other moieties. The proposed sensing platform not only exhibits the trace level detection of As3+ ions in cost-effective manner but also opens a pathway for the development of state-of-art device fabrication for on-site detection of arsenic.

Sensing platform for pico-molar level detection of ethyl parathion using Au-Ag nanoclusters based enzymatic strategy.

This work demonstrates a simple, cost effective and ultrasensitive detection of ethyl parathion, an organophosphorus (OPs) pesticide, using enzyme based fluorometric sensing strategy by employing bimetallic BSA@AuAg nanoclusters (NC). The sensing assay is based on the "quenched off" state of bimetallic NC with the addition of Cu2+ ions that can be "switched on" due to generation of thiocholine (TCh), a catalytic product of enzymatic reaction of acetylthiocholine (ATCh) using acetylcholinesterase (AChE) enzyme. The generated TCh preferably seize Cu2+ ions from BSA@AuAg NC-Cu2+ ensemble and recovered the fluorescence of BSA@AuAg NC. The presence of ethyl parathion can be monitored optically due to its inhibitory action towards AChE enzyme leading to suppression of thiocholine (TCh) formation and subsequently decreases TCh-Cu2+ interaction that ultimately retrieved quenched off state of bimetallic NC. The synthesized biosensor is appropriate for the ultrasensitive sensing of ethyl parathion in pM range, exhibiting 2.40 pM as lowest limit of detection (LOD) which is the least known so far. Further, the real sample analysis adds on for the appropriateness of the synthesized nanoprobe by depicting excellent reproducibility and robustness. The designed assay proved its specificity towards pesticides in general and ethyl parathion in particular when employed with other commonly used non-OPs pesticides.

Quantification of adsorbed and dangling citrate ions on gold nanoparticle surface using thermogravimetric analysis.

A novel approach involving thermo-gravimetricanalysis (TGA) for the quantification of citrate ions present on the surface of gold nanoparticles has been reported. TGA study was carried out on AuNPs in response to parameters such as concentration of tri-sodium citrate and pH of gold nanoparticles depicting that the number of citrate ion present on gold nanoparticles is highly pH dependent. In general, the citrate ions were observed to be higher in alkaline conditions contradicting earlier beliefs. These results also underline the significance of TGA as a novel tool for quantification of citrate molecules present on gold nanoparticle surface. Thus, the present approach not only provides with an insight into mechanistic details of gold nanoparticle synthesis but also opens the usage of TGA for understanding the nano range association of molecules.

Phenylalanine dimer assembly structure as the basic building block of an amyloid like photoluminescent nanofibril network.

A phenylalanine dimer assembly (Phe-DA) is reported as a basic constituent of a light emitting ß-amyloid type nanofibril network. The size and composition of the Phe-DA structure were characterized using various theoretical and experimental techniques. Further, the mechanism involved in the phenylalanine self-assembly process from Phe-DA to the nanofibril network was studied using optical spectroscopy and small angle X-ray scattering (SAXS). The discovery of Phe-DA and its unique optical properties may pave the way for design and development of novel theranostics against metabolite based pathalogical disorders. Further, the role of the Phe-DA structure as the elementary unit in the formation of a long range assembly structure may provide vital understanding for the development of functional materials using simple organic molecules.

Interplay of Self-Assembling Aromatic Amino Acids and Functionalized Gold Nanoparticles Generating Supramolecular Structures.

In the recent years, protein metabolite-based self-assembled supramolecular structures have been linked to various pathological disorders. The self-assembly of protein over nanoparticle surfaces can lead to the formation of corona aggregates that have gained much attention owing to biomedical healthcare relevance. However, limited studies are available at the interface of amyloid formation and nanoparticle surfaces. In this context, the present study demonstrated the effect of specifically functionalized gold nanoparticles on the potential amyloid formation by self-assembled aromatic amino acids. The coassembly of aromatic amino acids and gold nanoparticles was utilized to gain mechanistic insight into altered intermolecular interactions between amino acid monomers. The polymorphism, thermal stability, and morphological pattern of coassembled aromatic amino acids and gold nanoparticle (Co-AA:AuNP) structures were analyzed using X-ray diffraction, thermogravimetric analysis, and field emission scanning electron microscopy, respectively. Finally, amyloid like aggregation of Co-AA:AuNP structures were evaluated using thioflavin T fluorescence assay in solution as well as the deposited phase. The present work is crucial for the design and usage of nanoparticles in biomedical applications, which may trigger amyloid-like metabolite aggregation leading to pathological disorders.

Peptide- and Drug-Functionalized Fluorescent Quantum Dots for Enhanced Cell Internalization and Bacterial Debilitation.

This report illustrates a strategy for designing a nanoconjugate derived vector that efficiently delivers antimicrobial drug directly into bacterial cells. The nanoconjugate comprises of negatively charged CDTe@CdS quantum dots (QDs) with its surface functionalized using cationic BP-100 (KKLFKKILKYL-amide), a known cell-penetrating peptide (CPP), via electrostatic approach. The interactions between QD and CPP in QD-functionalized CPPs (QD-CPP) have been well analyzed using fluorescence spectroscopy, gel electrophoresis, and ζ-potential analysis. The QD-CPP conjugate was internalized into Gram negative (Escherichia coli) as well as Gram positive (Staphylococcus aureus) bacterial strains with confocal studies exhibiting a strong signal in tested microorganisms. Further, to check the applicability of QD-CPP conjugate as a delivery vector for generating an effective therapeutics, ampicillin molecules were conjugated on QD-CPP surface to generate QD-CPP-Amp conjugate. The CPP and drug molecules on the surface of QDs were well quantified using high-performance liquid chromatography (HPLC) data. It was observed that the internalization and bacterial debilitation of the QD-CPP-Amp conjugate is 2- to 4-fold effective as compared to that of bare ampicillin. The morphological changes to the bacterial cells upon the treatment with QD-CPP-Amp conjugates were noted with no cytotoxic effect on tested mammalian cell lines. The results inferred that the proposed QD-CPP vector provides a targeted and proficient approach for cellular internalization of cargo (drug) in bacterial cells with effective tracking through florescent QDs.

Enhanced and selective adsorption of cationic dyes using novel biocompatible self-assembled peptide fibrils.

Herein, bio-compatible self-assembled peptide fibrils have been developed for adsorption of organic pollutants for water remediation with high adsorption capacity. The different morphological motifs of self-assembled dipeptide Fmoc-FW-OMe was formulated using solvent modulation which was characterized by optical microscopy, SEM, XRD and FT-IR. Specifically, the fibril structures were used for selective adsorption of cationic dyes from aqueous solutions with exceptional adsorption capacity noted for crystal violet (625 mg/g). To understand the mechanism of dye adsorption, kinetics studies and adsorption isotherm studies were carried out which proved that the adsorption follows second order kinetics and Langmuir adsorption isotherm. The pH studies suggested that the adsorption of dye is much higher in alkaline conditions as compared to acidic conditions. The self-assembled peptide fibrils showed high reusability over five cycles with negligible effect on the dye adsorption capacity. Notably, this is the first report that discusses the application of self-assembled short peptide based fibrils for removal of dyes from waste water and in particular, it demonstrates the highest adsorption capacity reported for crystal violet dye so far. In general, this efficient capturing of dye pollutants with minimum usage of biocompatible adsorbents presents a simple and cost effective method for water remediation.

Optical pico-biosensing of lead using plasmonic gold nanoparticles and a cationic peptide-based aptasensor.

A novel biosensor for the rapid detection of lead ions employing the optical properties of AuNPs, a lead-specific aptamer and a cationic peptide has been demonstrated. The limit of detection of the biosensor was 98.7 pM, the lowest so far obtained using colorimetry.

Effective Topical Delivery of H-AgNPs for Eradication of Klebsiella pneumoniae-Induced Burn Wound Infection.

The aim of the present study was to explore the therapeutic efficacy of microemulsion-based delivery of histidine-capped silver nanoparticles in eradicating Klebsiella pneumoniae-induced burn wound infection. The developed microemulsion was characterized on the basis of differential light scattering, phase separation, refractive index, and specific conductance. Emulgel was prepared and characterized on the basis of thixotropy, texture, differential scanning calorimetry, and release kinetics. Emulgel was further evaluated in skin irritation and in vivo studies, namely full-thickness K. pneumoniae-induced burn wound infection treatment via topical route. Efficacy of treatment was evaluated in terms of bacterial load, histopathology, wound contraction, and other infection markers. The developed emulgel provided significant in vivo antibacterial activity of histidine-capped silver nanoparticle preparations via topical route and resulted in reduction in bacterial load, wound contraction, and enhanced skin healing as well as decrement of inflammatory markers such as malondialdehyde, myeloperoxidase, and reactive nitrogen intermediate compared to untreated animals. The present study encourages the further employment of histidine-capped silver nanoparticles along with microemulsion-based drug delivery system in combating antibiotic-resistant topical infections.

Insights into cell penetrating peptide conjugated gold nanoparticles for internalization into bacterial cells.

Gold nanoparticles (AuNPs) functionalized with different biomolecules find extensive application in therapy, clinical diagnosis and biomedical imaging. Herein, two derivatives of TAT peptide with sequences YGRKKRRQRRR and YGRKKRRQRRR-(ß-ala)3-Cys-amide were conjugated with tannic acid capped gold nanoparticles which acted as a carrier for cell penetrating peptides (CPPs) into the bacterial cells. The interaction of YGRKKRRQRRR peptide with AuNPs was non-covalent in nature whereas YGRKKRRQRRR-(ß-ala)3-Cys-amide interacted covalently with the AuNPs due to presence of thiol group in cysteine which bind strongly to gold nanoparticles surface. Further, tannic acid functionalised AuNPs conjugated CPPs constructs were duly characterized using critical flocculation essay test, UV-visible and TEM. FITC was tagged over AuNPs-CPPs in order to study the intracellular distribution using confocal microscopy. The confocal results revealed that nanoconjugates (AuNP-CPPs) of 5 nm diameter exhibited strong fluorescent signal in Gram positive and Gram negative bacterial strains. The present method can also be used for the killing of bacterial cells using photo-thermal therapy and therefore can be highly useful for targeting multi-drug resistant bacteria.

A Facile Approach for Synthesis and Intracellular Delivery of Size Tunable Cationic Peptide Functionalized Gold Nanohybrids in Cancer Cells.

Peptide-based drug delivery systems have become a mainstay in the contemporary medicinal field, resulting in the design and development of better pharmaceutical formulations. However, most of the available reports employ tedious multiple reaction steps for the conjugation of bioactive cationic peptides with drug delivery vehicles. To overcome these limitations, the present work describes a one-step approach for facile and time efficient synthesis of highly cationic cell penetrating peptide functionalized gold nanoparticles and their intracellular delivery. The nanoconstruct was synthesized by the reduction of gold metal ions utilizing cell penetrating peptide (CPP), which facilitated the simultaneous synthesis of metal nanoparticles and the capping of the peptide over the nanoparticle surface. The developed nanoconstruct was thoroughly characterized and tested for intracellular delivery into HeLa cells. Intriguingly, a high payload of cationic peptide over gold particles was achieved, in comparison to conventional conjugation methods. Moreover, this method also provides the ability to control the size and peptide payload of nanoparticles. The nanoconstructs produced showed enhanced cancer cell penetration (µM) and significant cytotoxic effect compared to unlabeled gold nanoparticles. Therefore, this novel approach may also have significant future potential to kill intracellular hidden dreaded pathogens like the human immunodeficiency virus, Mycobacterium tuberculosis, and so forth.

A supersensitive silver nanoprobe based aptasensor for low cost detection of malathion residues in water and food samples.

In the present study, we report a highly sensitive, rapid and low cost colorimetric monitoring of malathion (an organophosphate insecticide) employing a basic hexapeptide, malathion specific aptamer (oligonucleotide) and silver nanoparticles (AgNPs) as a nanoprobe. AgNPs are made to interact with the aptamer and peptide to give different optical responses depending upon the presence or absence of malathion. The nanoparticles remain yellow in color in the absence of malathion owing to the binding of aptamer with peptide which otherwise tends to aggregate the particles because of charge based interactions. In the presence of malathion, the agglomeration of the particles occurs which turns the solution orange. Furthermore, the developed aptasensor was successfully applied to detect malathion in various water samples and apple. The detection offered high recoveries in the range of 89-120% with the relative standard deviation within 2.98-4.78%. The proposed methodology exhibited excellent selectivity and a very low limit of detection i.e. 0.5pM was achieved. The developed facile, rapid and low cost silver nanoprobe based on aptamer and peptide proved to be potentially applicable for highly selective and sensitive colorimetric sensing of trace levels of malathion in complex environmental samples.