Gold-nanoparticles-modified cellulose membrane coupled with laser desorption/ionization mass spectrometry for detection of iodide in urine

Bacterial cellulose composite hydrogel for pre-concentration and mass spectrometric detection of thiol-containing biomarker

Simple soaking of bacterial cellulose (BC) membrane in carboxymethyl cellulose (CMC) solution yielded BC/CMC hydrogel having re-swellable property. Then, gold nanoparticles (AuNPs) were embedded in the BC/CMC hydrogel via in situ chemical reduction to form BC/CMC/AuNPs composite hydrogel. It was found that the composite hydrogel exhibited physical/chemical characteristics similar to those of BC. The AuNPs with an average diameter of 13 nm distributed uniformly within the BC/CMC matrix as verified by transmission electron microscopy. The novelty of this work is the application of the BC/CMC/AuNPs composite hydrogel for selective adsorption of an important thiol-containing biomarker of Alzheimer's disease, glutathione (GSH), prior to direct laser desorption/ionization mass spectrometric (LDI-MS) detection. GSH adsorbed in the BC/CMC/AuNPs composite hydrogel showed the high ionization signal in LDI-MS providing a linear range of 50-10,000 nM with a limit of detection as low as 54.1 nM, which is a cut-off level for distinguishing between normal individuals and Alzheimer's patients. It should be emphasized that an additional matrix was not necessary as AuNPs can act as self-matrix for LDI-MS analysis. Furthermore, the BC/CMC/AuNPs composite hydrogel can effectively preconcentrate GSH approximately 10 times upon adsorption allowing for ultrasensitive detection of GSH required for disease diagnosis.

Protocol for optical detection of iodide ions in aqueous environments using a zirconium(IV)-enhanced strategy

Detection of radioactive iodide ions (I^-) is important for protecting human beings from the hazards of radioactive pollution. Herein, we present a protocol for detecting I^- using a zirconium(IV)-enhanced strategy. We describe steps for optimizing the I^- detection approach, establishing standard curves, and finally applying the approach. The use of zirconium(IV) greatly improves the detection performance and endows this approach with an ultralow detection limit of 0.176 nM together with wide applicability in various aqueous environments. For complete details on the use and execution of this protocol, please refer to Feng et al. (2022).¹.

Covalent Bonding and Coulomb Repulsion-Guided AuNP Array: A Tunable and Reusable Substrate for Metabolomic Characterization of Lung Cancer Patient Sera

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has gained increased attention in the metabolic characterization of human biofluids. However, the stability and reproducibility of nanoparticle-based substrates remain two of the biggest challenges in high-salt environments. Here, by controlling the extent of Coulomb repulsion of 26 nm positively charged AuNPs, a homogeneous layer of covalently bonded AuNPs on a coverslip with tunable interparticle distances down to 16 nm has been successfully fabricated to analyze small biomolecules in human serum. Compared with the self-assembled AuNP array, the covalently bonded AuNP array showed superior performances on stability, reproducibility, and sensitivity in high-salt environments. The stable attachment of AuNPs maintained a detection reproducibility with a RSD less than 12% and enabled the reusability of the array for 10 experiments without significant signal deterioration (<15%) and carryover effects. Moreover, the closely positioned AuNPs allowed the coupling of photoinduced plasmons to generate an enhanced electric field, which promotes the generation of excited electrons to facilitate the desorption/ionization processes instead of the heat dissipation, thus enhancing the detection sensitivity with detection limits down to the femtomole level. Combined with machine learning methods, the AuNP array has been successfully applied to discover seven biomarkers for differentiating early-stage lung cancer patients from healthy controls. It is anticipated that this simple approach of developing robust AuNP arrays can also be extended to other types of NP arrays for wider applications of SALDI-MS technology.

Significance of an Electrochemical Sensor and Nanocomposites: Toward the Electrocatalytic Detection of Neurotransmitters and Their Importance within the Physiological System

A prominent neurotransmitter (NT), dopamine (DA), is a chemical messenger that transmits signals between one neuron to the next to pass on a signal to and from the central nervous system (CNS). The imbalanced concentration of DA may cause numerous neurological sicknesses and syndromes, for example, Parkinson's disease (PD) and schizophrenia. There are many types of NTs in the brain, including epinephrine, norepinephrine (NE), serotonin, and glutamate. Electrochemical sensors have offered a creative direction to biomedical analysis and testing. Researches are in progress to improve the performance of sensors and develop new protocols for sensor design. This review article focuses on the area of sensor growth to discover the applicability of polymers and metallic particles and composite materials as tools in electrochemical sensor surface incorporation. Electrochemical sensors have attracted the attention of researchers as they possess high sensitivity, quick reaction rate, good controllability, and instantaneous detection. Efficient complex materials provide considerable benefits for biological detection as they have exclusive chemical and physical properties. Due to distinctive electrocatalytic characteristics, metallic nanoparticles add fascinating traits to materials that depend on the material's morphology and size. Herein, we have collected much information on NTs and their importance within the physiological system. Furthermore, the electrochemical sensors and corresponding techniques (such as voltammetric, amperometry, impedance, and chronoamperometry) and the different types of electrodes' roles in the analysis of NTs are discussed. Furthermore, other methods for detecting NTs include optical and microdialysis methods. Finally, we show the advantages and disadvantages of different techniques and conclude remarks with future perspectives.

Pulsed laser irradiation induces the generation of alloy cluster ions for the screening of protease activity

Pulsed laser irradiation can cause the fragmentation of nanoparticles, which generates cluster ions. This allows nanoparticles to be adopted as mass tag/signal amplifiers in laser desorption/ionization mass spectrometry (LDI-MS) bioassays. Herein, we demonstrate the potential of using the signal from alloy cluster ions in bioassays through a fibrin clot model to determine the activity of thrombin. A mixed solution of silver and gold nanoparticles functionalized with fibrinogen (Fg‒Ag NPs/Fg‒Au NPs) treated with thrombin can form clots composed of aggregated fibrin-Au NPs/Ag NPs. These clots analyzed with LDI-MS are noted to form intense Ag-Au alloy cluster ions, especially [Ag₂Au]⁺, which were used to detect thrombin concentration with a dynamic range of 2.5-50 pM in human plasma. This sensing platform was further employed for the screening of direct thrombin inhibitors. This work developed a novel bioassay utilizing metallic gas-phase reactions generated from pulsed laser irradiation of aggregated nanoparticles to monitor enzymatic activity and to screen inhibitors. We believe that LDS-MS can serve as a new platform for gas-phase reaction-based bioassays.

Engineering of nanomaterials for mass spectrometry analysis of biomolecules

Mass spectrometry (MS) based analysis has received intense attention in diverse biological fields. However, direct MS interrogation of target biomolecules in complex biological samples is still challenging, due to the extremely low abundance and poor ionization potency of target biological species. Innovations in nanomaterials create new auxiliary tools for deep and comprehensive MS characterization of biomolecules. More recently, growing research interest has been directed to the compositional and structural engineering of nanomaterials for enriching target biomolecules prior to MS analysis, enhancing the ionization efficiency in MS detection and designing biosensing nanoprobes in sensitive MS readout. In this review, we mainly focus on the recent advances in the engineering of nanomaterials towards their applications in sample pre-treatment, desorption/ionization matrices and ion signal amplification for MS profiling of biomolecules. This review will provide a toolbox of nanomaterials for researchers devoted to developing analytical methods and practical applications in the biological MS field.

Polymeric membranes for biomedical applications

The rapid development of nanotechnology paved the way for further expansion of polymer chemistry and the fabrication of advanced polymeric membranes. Such modifications allowed enhancing or adding some unique properties, including mechanical strength, excellent biocompatibility, easily controlled degradability, and biological activity. This chapter discusses various applications of polymeric membranes in three significant areas of biomedicine, including tissue engineering, drug delivery systems, and diagnostics. It is intended to highlight here possible ways of improvement the properties of polymeric membranes, by modifying with other polymers, functional groups, compounds, drugs, bioactive components, and nanomaterials.

A general purpose MALDI matrix for the analyses of small organic, peptide and protein molecules

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) has been widely applied for the analysis of large biomolecules. The emergence of inorganic material substrates and new organic matrices extends the use of MALDI MS for small molecule analyses. However, there are usually preferred matrices for different types of analytes. Here, an organic compound, 4-hydroxy-3-nitrobenzonitrile, was found to be a general purpose matrix for the analyses of small organic, peptide and protein molecules. In particular, 4-hydroxy-3-nitrobenzonitrile has a strong UV absorption property, and it provides a clean background in the low mass range. Its analytical performances as a UV-laser matrix were demonstrated for different types of analytes, including organic drugs, peptides, proteins, mouse brain tissue and bacteria. Compared with commercial matrices, this new matrix has better performances when analyzing small molecules, such as drugs, peptides and lipids, while it has similar performances when analyzing proteins.

Porous TiO2 Film Immobilized with Gold Nanoparticles for Dual-Polarity SALDI MS Detection and Imaging

Surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) has become an attractive complementary approach to matrix-assisted laser desorption/ionization (MALDI) MS. SALDI MS has great potential for the detection of small molecules because of the absence of applied matrix. In this work, a functionalized porous TiO₂ film immobilized with gold nanoparticles (AuNPs-FPTDF) was prepared to enhance SALDI MS performance. The porous TiO₂ films were prepared by the facile sol-gel method and chemically functionalized for dense loading of AuNPs. The prepared AuNPs-FPTDF showed superior performance in the detection and imaging of small molecules in dual-polarity modes, with high detection sensitivity in the low pmol range, good repeatability, and low background noise compared to common organic MALDI matrixes. Its usage efficiently enhanced SALDI MS detection of various small molecules, such as amino acids and neurotransmitters, fatty acids, saccharides, alkaloids, and flavonoids, as compared with α-cyano-4-hydroxycinnamic acid, 9-aminoacridine, and the three precursor substrates of AuNPs-FPTDF. In addition, the blood glucose level in rats was successfully determined from a linearity concentration range of 0.5-9 mM, as well as other biomarkers in rat serum with SALDI MS. More importantly, the spatial distribution of metabolites from the intact flowers of the medicinal plant Catharanthus roseus was explored by using the AuNPs-FPTDF as an imprint SALDI MS substrate in dual-polarity modes. These results demonstrate wide applications and superior performances of the AuNPs-FPTDF as a multifunctional SALDI surface with enhanced detection sensitivity and imaging capabilities.

Recent Advances in Luminescent Recognition and Chemosensing of Iodide in Water

This Minireview covers the latest developments of chemosensors based on transition-metal receptors and organic fluorophores with specific binding sites for the luminescent detection and recognition of iodide in aqueous media and real samples. In all selected examples within the last decade (made-post 2010), the iodide sensing and recognition is probed by monitoring real-time changes of the fluorescence or phosphorescence properties of the chemosensors. This review highlights effective strategies to iodide sensing from a structural approach where the iodide recognition/sensing process, through supramolecular interactions as coordination bonds, hydrogen bonds, halogen bonds and electrostatic interactions, is transduced into an optical change easily measurable. The selective iodide sensing is an active field of research with global interest due to the importance of iodide in biological, medicinal, industrial, environmental and chemical processes.

Superior Resonant Nanocavities Engineering on the Photonic Crystal-Coupled Emission Platform for the Detection of Femtomolar Iodide and Zeptomolar Cortisol

Although luminescence spectroscopy has been a promising sensing technology with widespread applications in point-of-care diagnostics and chem-bio detection, it fundamentally suffers from low signal collection efficiency, considerable background noise, poor photostability, and intrinsic omnidirectional emission properties. In this regard, surface plasmon-coupled emission, a versatile plasmon-enhanced detection platform with >50% signal collection efficiency, high directionality, and polarization has previously been explored to amplify the limit of detection of desired analytes. However, high Ohmic loss in metal-dependent plasmonic platforms has remained an inevitable challenge. Here, we develop a hybrid nanocavity interface on a template-free and loss-less photonic crystal-coupled emission (PCCE) platform by the quintessential integration of high refractive index dielectric Nd₂O₃ "Huygens sources" and sharp-edged silver nanoprisms (NPrs). While efficient forward light scattering characteristics of Nd₂O₃ nanorods (NRs) present 460-fold emission enhancements in PCCE, the tunable localized plasmon resonances of NPrs display high electromagnetic field confinement at sharp nanotips and protrusions, boosting the enhancements 947-fold. The judicious use of silver NPr (AgNPr) metal-Nd₂O₃ dielectric hybrid resonances in conjugation with surface-trapped Bloch surface waves of the one-dimensional photonic crystal (1DPhC) displayed unprecedented >1300-fold enhancements. The experimental results are validated by excellent correlations with numerical calculations. The multifold hotspots generated by zero and nonzero nanogaps between the coassembly of NPrs, NRs, and 1DPhCs are used for (i) determination of hyper and hypothyroidism levels through monitoring the concentration of iodide (I^-) ions and (ii) single-molecule detection (zeptomolar) of the stress hormone, cortisol, through the synthesized cortisol-rhodamine B conjugate obtained using a simple esterification reaction.

Gold Nanoparticles (AuNPs) as Reactive Matrix for Detection of Trace Levels of HCN in Air by Laser Desorption/Ionization Mass Spectrometry (LDI-MS)

Under direct laser desorption/ionization mass spectrometric conditions, the irradiation of target spots made of gold nanoparticle residues generates a series of peaks at m/z 197, 394, 591… representing Au_n^- ions (n = 1-3). In contrast, spectra recorded from gold nanoparticles directly mixed with an alkali cyanide exhibited an additional peak at m/z 249, indicating an abundant generation of gaseous [Au(CN)₂]^- ions upon irradiation. The relative intensity of the m/z 249 peak surged when the amount of cyanide in the mixture was increased. Most remarkably, a peak at m/z 249 was observed even from neat AuNPs upon irradiation, if a nearby spot, which was not irradiated, happened to bear a cyanide sample. We postulated that traces of HCN emanating from the headspace of aqueous cyanide solution during the sample-plate preparation is sufficient to convert gold to AuCN, which is subsequently detected as [Au(CN)₂]^-. Further experiments demonstrated that the relative intensity of the m/z 249 peak diminishes exponentially as the AuNP spot becomes more distant from the putative HCN source. Eventually, the method was developed as an efficient procedure to detect HCN or alkali cyanides. Using KCN, the detection limits were determined to be below 10 pg of CN^- per spot. The method also demonstrated that, upon crushing, the seeds or roots of certain fruits and vegetables such as apple, peach, radish, and cassava, but not carrot, release HCN in amounts detectable by this method. Graphical Abstract.

A novel supramolecular organogel based on acylhydrazone functionalized pillar[5]arene acts as an I- responsive smart material

A novel organic gelator (PZ) has been synthesized by rationally connecting a pillar[5]arene moiety and a bis(hexadecyloxy)phenyl functionalized acylhydrazone moiety. PZ could self-assemble into a supramolecular polymer and form a stable organogel (OPZ) in cyclohexanol by multi-self-assembly driving forces such as C-Hπ, ππ, vdW and hydrogen bonding interactions. The organogel (OPZ) shows blue aggregation-induced emission (AIE). Interestingly, the organogel OPZ could sense iodide ions (I^-) in the gel-gel state with high selectivity and sensitivity. The detection limit of OPZ for I^- is 9.4 × 10^-8 M, indicating high sensitivity to I^-. Furthermore, a thin film based on OPZ was prepared, which could be used as a smart material for the detection of I^- as well as a fluorescent security display material.

Structural Characterization of Biofunctionalized Gold Nanoparticles by Ultrahigh-Resolution Mass Spectrometry

Biofunctionalized gold nanoparticles (AuNPs) enable innovative translational research and development in biomedicine. Biomolecules such as peptides, proteins, lipids, and carbohydrates can be assembled onto AuNPs to yield nanomaterials with unique properties for applications in imaging, photothermal therapy, vaccination strategies, and drug delivery. The characterization of functionalized AuNPs still remains an analytical challenge that normally requires the combination of multiple techniques. Laser desorption/ionization (LDI) and matrix-assisted LDI (MALDI) have been applied successfully in combination with time-of-flight (TOF) mass spectrometry (MS) for the analysis of the surface chemistry of AuNPs functionalized with synthetic ligands, however only for ligands with a molecular mass limited to 1000 Da. TOF-MS-based approaches in addition exhibit limited performance in terms of mass resolution and MS/MS possibilities. To overcome these limitations, we designed an approach for the analysis of AuNPs based on ultrahigh resolution Fourier transform ion cyclotron resonance (FTICR) MS and a combination of LDI and MALDI. To illustrate the performance of the method, we present a comprehensive characterization of the surface chemistry of AuNPs conjugated via a thiol-ending linker to either the ovalbumin peptide (OVA 323-339), the Lewis X antigen (Galβ1-4[Fucα1-3]GlcNAcβ1) trisaccharide, the tetramannoside Manα1-2Manα1-2Manα1-3Manα1, or a mixture of both carbohydrates. Collision-induced dissociation (CID) was used to characterize the structure of pseudomolecular ions generated by LDI/MALDI in-depth. These included [M + H]⁺ and [M + Na]⁺, and importantly also [M + Au]⁺ and [M + 2Au-H]⁺ ions. This first observation of gold-containing pseudomolecular ions provides direct evidence for the Au-conjugation of ligands. In addition, we show the applicability of the method to monitor proteolytic cleavage of peptides that are conjugated to the AuNP surface. The presented LDI/MALDI-FTICR-MS and MS/MS approach will be applicable to the characterization of a wide range of functionalized AuNPs.

Sunlight Induced Preparation of Functionalized Gold Nanoparticles as Recyclable Colorimetric Dual Sensor for Aluminum and Fluoride in Water

A sunlight induced simple green route has been developed for the synthesis of polyacrylate functionalized gold nanoparticles (PAA-AuNPs), in which poly(acrylic acid) functions as a reducing as well as stabilizing agent. This material has been characterized on the basis of spectroscopic and microscopic studies; it exhibited selective colorimetric detection of Al³⁺ in aqueous media, and the Al³⁺ induced aggregated PAA-AuNPs exhibited detection of F^- with sharp color change and high selectivity and sensitivity out of a large number of metal ions and anions tested. The mechanistic study revealed that, for Al³⁺, the color change is due to a shift of the SPR band because of the Al³⁺ induced aggregation of PAA-AuNPs, whereas for F^-, the reverse color change (blue to red) with return of the SPR band to its original position is due to dispersion of aggregated PAA-AuNPs, as F^- removes Al³⁺ from the aggregated species by complex formation. Only concentration-dependent fluoride ion can prevent Al³⁺ from aggregating PAA-AuNPs. The method is successfully used for the detection of F^- in water collected from various sources by the spiking method, in toothpastes of different brands by the direct method. The solid Al³⁺-PAA-AuNPs were isolated, adsorbed on ZIF@8 (zeolitic imidazolate framework) and on a cotton strip, and applied as solid sensing material for detection of F^- in aqueous media.

Simultaneous and direct analysis of multiple types of organic contaminants in water based on a MOF decorated with a suitable quantity of Au nanoparticles, using SALDI-TOF MS

Simultaneous, fast and sensitive analysis of multiple types of organic contaminants using SALDI-TOF MS was realized for the first time.

Thymine Functionalized Graphene Oxide for Fluorescence "Turn-off-on" Sensing of Hg2+ and I- in Aqueous Medium

Selective detection of either mercury (Hg2+) or iodide (I-) ion using fluorescence turn-on or turn-off processes is an important area of research. In spite of intensive research, simultaneous detection of both mercury and iodide using fluorescence turn-off-on processes, high sensitivity and theoretical support concerning the mechanisms are still lacking. In the present work, graphene oxide is functionalized by thymine to realize simultaneous detection of both Hg2+ and I- selectively using fluorescence turn-off-on mechanism. Ultra high sensitivity to the extent of ppb level exploiting large surface area of graphene is achieved. DFT calculations also assist to realize the detailed mechanisms involving this PL quenching and also its regain during sensing of these ions in aqueous solution.

A highly sensitive fluorescence turn-on platform with silver nanoparticles aptasening for human platelet-derived growth factor-BB

In this paper, we demonstrated a simple and highly sensitive fluorescence platform for protein detection. Silver nanoparticles (AgNPs) worked as carriers and quenchers for FAM labeled aptamers (FAM-apt). Biotin labeled aptamers (Bio-apt), FAM-apt functionalized AgNPs (Ag-FAM-apt), and a target protein, human platelet-derived growth factor-BB (PDGF-BB) could form a sandwich-type complex. Once the etching solvents were added, AgNPs were dissolved and the fluorescence resonance energy transfer (FRET) between AgNPs and FAM was broken. FAM-apt were no longer quenched and released into the solution in the 96-well microplates, so the fluorescence signal would turn from "off" state to "on" state. This method had possessed several advantages: Firstly, increased specificity which was contributed by the sandwich binding of aptamers; Secondly, quenching ability of AgNPs which was utilized to make signal turn-on; Thirdly, high throughout in which 96 samples could be detected simultaneously. The results showed a linear relationship between fluorescence intensity and PDGF-BB concentration (10 ng mL(-1)-100 ng mL(-1)), and the detection limit was 7 ng mL(-1). This simple and sensitive method would have a promising future for development and application.

Optically tunable chiral nematic mesoporous cellulose films

Demand for sustainable functional materials has never been larger. The introduction of functionality into pure cellulose might be one step forward in this field as it is one of the most abundant natural biopolymers. In this paper, we demonstrate a straightforward and scalable way to produce iridescent, mesoporous cellulose membranes with tunable colors and porosity. Concomitant assembly of cellulose nanocrystals (CNCs) and condensation of silica precursors results in CNC-silica composites with chiral nematic structures and tunable optical properties. Removal of the stabilizing silica matrix by alkaline or acid treatment gives access to novel chiral nematic mesoporous cellulose (CNMC) films. Importantly, the optical properties and the mesoporosity can be controlled by either varying the silica-to-CNC ratio, or by varying the substrate used during the evaporation-induced self-assembly process. In order to introduce additional functionality, CNMC has been used to stabilize gold nanoparticles with three different concentrations by wet impregnation. These materials are stable in water and can potentially function in sensors, tissue engineering or functional membranes.

Gold nanoparticle-enhanced target (AuNPET) as universal solution for laser desorption/ionization mass spectrometry analysis and imaging of low molecular weight compounds

Preparation is described of a durable surface of cationic gold nanoparticles (AuNPs), covering commercial and custom-made MALDI targets, along with characterization of the nanoparticle surface properties and examples of the use in MS analyses and MS imaging (IMS) of low molecular weight (LMW) organic compounds. Tested compounds include nucleosides, saccharides, amino acids, glycosides, and nucleic bases for MS measurements, as well as over one hundred endogenous compounds in imaging experiment. The nanoparticles covering target plate were enriched in sodium in order to promote sodium-adduct formation. The new surface allows fast analysis, high sensitivity of detection and high mass determination accuracy. Example of application of new Au nanoparticle-enhanced target for fast and simple MS imaging of a fingerprint is also presented.

PolyA-tailed and fluorophore-labeled aptamer-gold nanoparticle conjugate for fluorescence turn-on bioassay using iodide-induced ligand displacement

Depending on the strong affinity of polyA sequence to gold (or silver) surface, applicability of polyA-tailed DNA-gold (or silver) nanoparticle conjugates in homogeneous and heterogeneous protein assays was first demonstrated. Interestingly, when using polyA-tailed, fluophore-labeled DNA-AuNP conjugate, it was found that iodide and thiosulfate anions could act as the ligand displacing reagent to detach polyA-tailed DNA strands from AuNP surface and simultaneously activate the AuNP-quenched fluorophores by destroying the polyA-AuNP interaction via a divide-and-conquer strategy. Based on this new discovery, we have developed a novel, cost-effective and sandwich-type fluorescence turn-on aptasensor for highly sensitive and specific thrombin detection, what took advantage of aptamer-conjugated magnetic beads (apt-MBs) for protein capture and separation, and iodide-induced fluorescence recovery of activatable polyA-based AuNP probes through ligand displacement for fluorescence turn-on detection. This proposed aptasensor could detect thrombin specifically with a detection limit as low as 89pM, which was better than or comparable to many existing fluorescent thrombin assays. Importantly, employment of such polyA-based AuNP conjugate not only avoids the use of thiolated oligonucleotides and thiol-containing displacing reagents, but also offers new possibilities for fabricating convenient and cost-effective bioanalytical applications.

Membrane-based assay for iodide ions based on anti-leaching of gold nanoparticles

We report a label-free colorimetric strategy for the highly selective and sensitive detection of iodide (I(-)) ions in human urine sample, seawater and edible salt. A poly(N-vinyl-2-pyrrolidone)-stabilized Au nanoparticle (34.2-nm) was prepared to detect I(-) ions using silver (Ag(+)) and cyanide (CN(-)) ions as leaching agents in a glycine-NaOH (pH 9.0) solution. For the visual detection of the I(-) ions by naked eye, and for long time stability of the probe, Au nanoparticles (NPs) decorated mixed cellulose ester membrane (MCEM) was prepared (Au NPs/MCEM). The Au NPs-based probe (CN(-)/Ag(+)-Au NPs/MCEM) operates on the principle that Ag(+) ions form a monolyar silver atoms/ions by aurophilic/argentophilic interactions on the Au NPs and it accelerates the leaching rate of Au atoms in presence of CN(-) ions. However, when I(-) is introduced into this system, it inhibits the leaching of Au atoms because of the strong interactions between Ag/Au ions and I(-) ions. Inductively coupled plasma mass spectrometry, surface-assisted laser desorption/ionization time-of-flight mass spectrometry were used to characterize the surface properties of the Au NPs in the presence of Ag(+) and I(-). Under optimal solution conditions, the CN(-)/Ag(+)-Au NPs/MCEM probe enabled the detection of I(-) by the naked eye at nanomolar concentrations with high selectivity (at least 1000-fold over other anions). In addition, this cost-effective probe allowed the determination of I(-) ions in complex samples, such as urine, seawater, and edible salt samples.