Chemical binding of pyrrolidinyl peptide nucleic acid (acpcPNA-T9) probe with AuNPs toward label-free monitoring of miRNA-21: A novel biosensing platform for biomedical analysis and POC diagnostics.

miRNAs are attractive factors in cancer research studies due to their important roles for regulating of gene expression. Because of miRNA-21 expression surplus in many types of cancers, so accurate identification is important. Increasing efforts have caused different methods to improve the sensitivity and specificity of detection. Present study is an attempt to report a new electrochemical label-free PNA-based bioassay for detection of miRNA-21. In this study, gold electrode was modified by gold nanoparticles to improve a functional PNA-based biosensor. The EDS and field emission scanning electron microscope (FE-SEM) were used to detect fabrication of biosensor. The electrochemical behavior of sensor was evaluated after inserting of acpcPNA probes and miRNA-21 on the stucture of electrode and analyzed essential parameters such as various concentration of target miRNA, hybridization time, reproducibility, stability, and applicability. The results of study demonstrated that engineered biosensor was successfully fabricated. The findings showed the highest amount of current in 5 minutes hybridization time, with suitable reproducibility and stability. This innovative miRNA-based biosensor presents a sensitive and specific method in fast and may be lab-on chip assay in future.

Chemical binding of molecular-imprinted polymer to biotinilated antibody: Utilization of molecular imprinting polymer as intelligent synthetic biomaterials toward recognition of carcinoma embryonic antigen in human plasma sample.

In this study, a novel biosensor based on molecular imprinting polymer (MIP) methodology was fabricated toward recognition of carcinoembryonic antigen (CEA). For this purpose, poly (toluidine blue) (PTB) was electropolymerized on the surface of gold electrode in the absence and presence of CEA. So, the target molecules were entrapped into the imprinted specific cavities of MIP. Obtained results show that, the binding affinity of the MIP system was significantly higher than that of revealed for the nonimprinted polymer (NIP) system, MIP-based biosensor revealed linear response from (0.005 to 75 µg/L) and low limit of quantification of (0.005 µg/L) by using chronoamperometry technique, leading to CEA monitoring in real and clinical samples. Thus, a novel technique for rapid, simple, sensitive and affordable monitoring of CEA (LLOQ = 0.005 µg/L) has provided through developed biosensor. From a future perspective, moreover, this method can be considered as an applicable candidate in biomedical and clinical analysis for point-of-care usages.

Visual monitoring and optical recognition of digoxin by functionalized AuNPs and triangular AgNPs as efficient optical nano-probes.

In this study, we presented elective, sensitive, and rapid UV-Vis spectrophotometry and calorimetric assay for the recognition of digoxin. Therefore, cysteamine-gold nanoparticles (Cys A-AuNPs) in the presence of cysteine acid amine and Silver nanoparticles in the presence of tetramethyl benzidine and hydrogen peroxide (AgNPs-TMB [3,3',5,5'-tetramethylbenzidine]-H2 O2 ) were synthesized and utilized as the desired probe. Finally, color variation of probes was observed in the absence and presence of digoxin. Obtained results indicate that the color of Cys A-AuNPs changed from dark pink to light in the absence and the presence of digoxin, respectively. Also, the color of AgNPs-TMB-H2 O2 changed from dark blue to light blue, in the absence and the presence of digoxin, respectively. Moreover, UV-Vis spectroscopies results indicate digoxin with a low limit of quantification of 0.125 ppm in human plasma samples which linear range was 0.125 to 11 ppm.

Identification of Tyrosinase Inhibitors and Their Structure-Activity Relationships via Evolutionary Chemical Binding Similarity and Structure-Based Methods.

Tyrosinase is an enzyme that plays a crucial role in the melanogenesis of humans and the browning of food products. Thus, tyrosinase inhibitors that are useful to the cosmetic and food industries are required. In this study, we have used evolutionary chemical binding similarity (ECBS) to screen a virtual chemical database for human tyrosinase, which resulted in seven potential tyrosinase inhibitors confirmed through the tyrosinase inhibition assay. The tyrosinase inhibition percentage for three of the new actives was over 90% compared to 61.9% of kojic acid. From the structural analysis through pharmacophore modeling and molecular docking with the human tyrosinase model, the pi-pi interaction of tyrosinase inhibitors with conserved His367 and the polar interactions with Asn364, Glu345, and Glu203 were found to be essential for tyrosinase-ligand interactions. The pharmacophore features and the docking models showed high consistency, revealing the possible essential binding interactions of inhibitors to human tyrosinase. We have also presented the activity cliff analysis that successfully revealed the chemical features related to substantial activity changes found in the new tyrosinase inhibitors. The newly identified inhibitors and their structure-activity relationships presented here will help to identify or design new human tyrosinase inhibitors.

Evolutionary chemical binding similarity approach integrated with 3D-QSAR method for effective virtual screening.

BACKGROUND: Despite continued efforts using chemical similarity methods in virtual screening, currently developed approaches suffer from time-consuming multistep procedures and low success rates. We recently developed a machine learning-based chemical binding similarity model considering common structural features from molecules binding to the same, or evolutionarily related targets. The chemical binding similarity measures the resemblance of chemical compounds in terms of binding site similarity to better describe functional similarities that arise from target binding. In this study, we have shown how the chemical binding similarity could be used in virtual screening together with the conventional structure-based methods. RESULTS: The chemical binding similarity, receptor-based pharmacophore, chemical structure similarity, and molecular docking methods were evaluated to identify an effective virtual screening procedure for desired target proteins. When we tested the chemical binding similarity method with test sets of 51 kinases, it outperformed the traditional structural similarity-based methods as well as structure-based methods, such as molecular docking and receptor-based pharmacophore modeling, in terms of finding active compounds. We further validated the results by performing virtual screening (using the chemical binding similarity and receptor-based pharmacophore methods) against a completely blind dataset for mitogen-activated protein kinase kinase 1 (MEK1), ephrin type-B receptor 4 (EPHB4) and wee1-like protein kinase (WEE1). The in vitro kinase binding assay confirmed that 6 out of 13 (46.2%) for MEK1 and 2 out of 12 (16.7%) for EPHB4 were newly identified only by the chemical binding similarity model. CONCLUSIONS: We report that the virtual screening results could further be improved by combining the chemical binding similarity model with 3D-QSAR pharmacophore and molecular docking models. Not only the new inhibitors are identified in this study, but also many of the identified molecules have low structural similarity scores against already reported inhibitors and that show the revelation of novel scaffolds.

Binding of Leishmania spp with gold nanoparticles supported polyethylene glycol and its application for the sensitive detection of infectious photogenes in human plasma samples: A novel biosensor.

The management of pathogen detection using a rapid and cost-effective method presents a major challenge to the biological safety of the world. The field of pathogen detection is nascent and therefore, faces a dynamic set of challenges as the field evolves. Visceral leishmaniasis (VL), or kala-azar is the most severe form of leishmaniasis. Delay to the accurate diagnosis and treatment is likely to lead to fatality. The reliable, fast and sensitive detection is closely linked to safe and effective treatment of Leishmania spp. Despite several routine and old method for sensitive and specificity detection of Leishmania spp, there is highly demand for developing modern and powerfully system. In this study a novel ultra-sensitive DNA-based biosensor was prepared for detection of Leishmania spp. For the first time, the specific and thiolated sequences of the Leishmania spp genome (5'-SH-[CH2 ]6 ATCTCGTAAGCAGATCGCTGTGTCAC-3') were recognized by electrochemical methods. Also, selectivity of the proposed bioassay was examined by three sequences that were mismatched in 1, 2, and 3 nucleotides. The linear range (10-6 to 10-21 M) and limit of detection (LLOQ = 1 ZM) obtained are remarkable in this study. Also, simple and cost-effective construction of genosensors was another advantage of the proposal DNA-based assay. The experimental results promise a fast and simple method in detection of kala-azar patients with huge potential of the nanocomposite-based probe for development of ideal biosensors.

Spectrophotometric study of ketoconazole binding with citrate capped silver nanoparticles and its monitoring in human plasma samples.

Ketoconazole or Nizoral is an antifungal medication used to treat various type of fungal infections. It has been reported that this antifungal agent is able to induce a variety of heart function side effects, such as long-QT syndrome, and ventricular arrhythmias. Hence, prescribing, identifying and controlling the side effects of medications such as ketoconazole is essential for human safety. In this study, a distinct and fast colorimetric probe based on citrate capped silver nanoparticles (Cit-AgNPs) was introduced for determination of trace amounts of ketoconazole. Cit-AgNPs were synthesized trough a novel method and applied for the quantification of ketoconazole in human plasma samples. Ultraviolet-visible spectroscopy, transmission electron microcopy, dynamic light scattering, and energy dispersive X-ray spectroscopy analysis, have been utilized for characterization of Cit-AgNPs. It was revealed that in the presence of ketoconazole, the absorption intensity of Cit-AgNPs was decreased by increasing the ketoconazole concentration. Moreover, this reaction is accompanied by a color change from shiny yellow to brown/red in acidic pH. Under acidic pH and optimum condition, the calibration graph of the assay was linear in the range of 0.1 to 0.8 µM. According to the obtained results Cit-AgNPs can be used as a novel probe for the sensitive and specific detection and determination of similar drugs in clinical samples. Also, this method open a new way to biomedical analyses of pharmaceutical samples which is necessary in TDM.

A novel optical probe based on d-penicillamine-functionalized graphene quantum dots: Preparation and application as signal amplification element to minoring of ions in human biofluid.

In this study, d-penicillamine-functionalized graphene quantum dots (DPA-GQD) has been synthesized, which significantly increases the fluorescence intensity of GQD. We used this simple fluorescent probe for metal ions detection in human plasma samples. Designed DPA-GQD respond to Hg2+ , Cu2+ , Au2+ , Ag+ , Co2+ , Zn2+ , and Pb2+ with high sensitivity. The fluorescence intensity of this probe decreased significantly in the presence of metal ions such as, Hg2+ , Cu2+ , Au2+ , Ag+ , Co2+ , Zn2+ , and Pb2+ . In this work, a promising probe for ions monitoring was introduced. Moreover, DPA-GQD probe has been tested in plasma samples. The functionalized DPA-GQDs exhibits great promise as an alternative to previous fluorescent probes for bio-labeling, sensing, and other biomedical applications in aqueous solution.

Synthesis of folic acid functionalized terbium-doped dendritic fibrous nano-silica and Interaction with HEK 293 normal, MDA breast cancer and HT 29 colon cancer cells.

A novel folic acid functionalized terbium-doped dendritic fibrous nanoparticle (Tb@KCC-1-NH2 -FA) with high surface area was synthesized using a novel hydrothermal protocol. In the present work, we report the fluorescent Tb-doted nanomaterial with emission wavelength at 497 nm which confirms the formation of Tb@KCC-1-NH2 -FA. Synthesized nanoparticles were investigated through transmission electron microscope, field emission scanning electron Microscopy, Fourier transform infrared spectra, Brunauer-Emmett-Teller, energy dispersive X-ray, Zeta potential and particle size distribution values and AFM (Atomic force microscopy) techniques. Specially, our desired nanomaterial which has FA moieties on the surface of Tb@KCC-1-NH2-FA where interact with folate receptor (FR) which there is on the surface of the various cancer cells. For this purpose, fluorescence microscopy images were used to prove the uptake of FA based nanomaterial with FR-positive MDA breast cancer and HT 29 colon cancer cells. Also HEK 293 normal cells as FR-negative cells verified the specificity of our desired nanomaterial toward the FR-positive cells. The cytotoxicity survey of Tb@KCC-1-NH2 -FA was examined by MTT assays against MDA breast cancer, HT 29 colon cancer and HEK 293 Normal cell lines which confirmed their biocompatible nature with any significant cytotoxic effects even for concentration higher than 900 µg/mL which could be used as a non-toxic catalyst or carrier in biological ambient. Hence, Tb@KCC-1-NH2 -FA were synthesized using green and hydrothermal method; the process was simple with good productivity and desired nanocomposite was non-toxic.

Double Variational Binding--(SMILES) Conformational Analysis by Docking Mechanisms for Anti-HIV Pyrimidine Ligands.

Variational quantitative binding-conformational analysis for a series of anti-HIV pyrimidine-based ligands is advanced at the individual molecular level. This was achieved by employing ligand-receptor docking algorithms for each molecule in the 1,3-disubstituted uracil derivative series that was studied. Such computational algorithms were employed for analyzing both genuine molecular cases and their simplified molecular input line entry system (SMILES) transformations, which were created via the controlled breaking of chemical bonds, so as to generate the longest SMILES molecular chain (LoSMoC) and Branching SMILES (BraS) conformations. The study identified the most active anti-HIV molecules, and analyzed their special and relevant bonding fragments (chemical alerts), and the recorded energetic and geometric docking results (i.e., binding and affinity energies, and the surface area and volume of bonding, respectively). Clear computational evidence was also produced concerning the ligand-receptor pocket binding efficacies of the LoSMoc and BraS conformation types, thus confirming their earlier presence (as suggested by variational quantitative structure-activity relationship, variational-QSAR) as active intermediates for the molecule-to-cell transduction process.

Binding profiles of human and mouse complement component 8γ to trisubstituted organometallic compounds.

Complement component 8gamma (C8γ), a member of the lipocalin protein family, is suggested to act as a carrier protein for various chemicals. Although C8γ has been identified in both humans and rodents for some time, our understanding of the species differences in its chemical binding properties remains limited. In the present study, with the aim to elucidate the potential role of C8γ as a carrier protein in both humans and mice, we conducted a radioligand binding assay to examine the chemical binding properties of human C8γ (hC8γ) and mouse C8γ (mC8γ). Scatchard analysis revealed that [14C]TPT bound to hC8γ with an equilibrium dissociation constant (Kd) of 64.2 ± 32.4 nM, comparable to that of [14C]TPT to mC8γ. Competitive ligand-binding assays demonstrated binding of TPT and TBT to hC8γ, while diphenyltin, dibutyltin, monophenyltin, monobutyltin, and tetrabutyltin did not exhibit binding. These results suggest that for effective binding to C8γ, chemicals must possess substituents of appropriate bulkiness. Further analyses with other group 14 compounds with triphenyl substituents revealed that a central metal atom, rather than a central non-metal or semi-metal atom, is crucial for specific binding to both hC8γ and mC8γ. Overall our findings imply that C8γ may play a role in the physiological or toxicological actions of group 14 metal compounds with tributyl or triphenyl substituents by binding to these chemicals in both humans and mice.

Iterative machine learning-based chemical similarity search to identify novel chemical inhibitors.

Machine learning-based chemical screening has made substantial progress in recent years. However, these predictions often have low accuracy and high uncertainty when identifying new active chemical scaffolds. Hence, a high proportion of retrieved compounds are not structurally novel. In this study, we proposed a strategy to address this issue by iteratively optimizing an evolutionary chemical binding similarity (ECBS) model using experimental validation data. Various data update and model retraining schemes were tested to efficiently incorporate new experimental data into ECBS models, resulting in a fine-tuned ECBS model with improved accuracy and coverage. To demonstrate the effectiveness of our approach, we identified the novel hit molecules for the mitogen-activated protein kinase kinase 1 (MEK1). These molecules showed sub-micromolar affinity (Kd 0.1-5.3 µM) to MEKs and were distinct from previously-known MEK1 inhibitors. We also determined the binding specificity of different MEK isoforms and proposed potential docking models. Furthermore, using de novo drug design tools, we utilized one of the new MEK inhibitors to generate additional drug-like molecules with improved binding scores. This resulted in the identification of several potential MEK1 inhibitors with better binding affinity scores. Our results demonstrated the potential of this approach for identifying novel hit molecules and optimizing their binding affinities.

Overcoming Perovskite Corrosion and De-Doping Through Chemical Binding of Halogen Bonds Toward Efficient and Stable Perovskite Solar Cells.

4-tert-butylpyridine (TBP) is an indispensable additive for the hole transport layer in highly efficient perovskite solar cells (PSCs), while it can induce corrosion decomposition of perovskites and de-doping effect of spiro-OMeTAD, which present huge challenge for the stability of PSCs. Herein, halogen bonds provided by 1,4-diiodotetrafluorobenzene (1,4-DITFB) are employed to bond with TBP, simultaneously preventing perovskite decomposition and eliminating de-doping effect of oxidized spiro-OMeTAD. Various characterizations have proved strong chemical interaction forms between 1,4-DITFB and TBP. With the incorporation of halogen bonds, perovskite film can maintain initial morphology, crystal structure, and light absorbance; meanwhile, the spiro-OMeTAD film shows a relatively stable conductivity with good charge transport property. Accordingly, the device with TBP complex exhibits significantly enhanced stability in N2 atmosphere or humidity environment. Furthermore, a champion power conversion efficiency of 23.03% is obtained since perovskite is no longer damaged by TBP during device preparation. This strategy overcomes the shortcomings of TBP in n-i-p PSCs community and enhances the application potential of spiro-OMeTAD in fabricating efficient and stable PSCs.

Annotation and Analysis of 3902 Odorant Receptor Protein Sequences from 21 Insect Species Provide Insights into the Evolution of Odorant Receptor Gene Families in Solitary and Social Insects.

The gene family of insect olfactory receptors (ORs) has expanded greatly over the course of evolution. ORs enable insects to detect volatile chemicals and therefore play an important role in social interactions, enemy and prey recognition, and foraging. The sequences of several thousand ORs are known, but their specific function or their ligands have only been identified for very few of them. To advance the functional characterization of ORs, we have assembled, curated, and aligned the sequences of 3902 ORs from 21 insect species, which we provide as an annotated online resource. Using functionally characterized proteins from the fly Drosophila melanogaster, the mosquito Anopheles gambiae and the ant Harpegnathos saltator, we identified amino acid positions that best predict response to ligands. We examined the conservation of these predicted relevant residues in all OR subfamilies; the results showed that the subfamilies that expanded strongly in social insects had a high degree of conservation in their binding sites. This suggests that the ORs of social insect families are typically finely tuned and exhibit sensitivity to very similar odorants. Our novel approach provides a powerful tool to exploit functional information from a limited number of genes to study the functional evolution of large gene families.

Optimizing Surface Chemistry of PbS Colloidal Quantum Dot for Highly Efficient and Stable Solar Cells via Chemical Binding.

The surface chemistry of colloidal quantum dots (CQD) play a crucial role in fabricating highly efficient and stable solar cells. However, as-synthesized PbS CQDs are significantly off-stoichiometric and contain inhomogeneously distributed S and Pb atoms at the surface, which results in undercharged Pb atoms, dangling bonds of S atoms and uncapped sites, thus causing surface trap states. Moreover, conventional ligand exchange processes cannot efficiently eliminate these undesired atom configurations and defect sites. Here, potassium triiodide (KI3) additives are combined with conventional PbX2 matrix ligands to simultaneously eliminate the undercharged Pb species and dangling S sites via reacting with molecular I2 generated from the reversible reaction KI3 â‡Œ I2 + KI. Meanwhile, high surface coverage shells on PbS CQDs are built via PbX2 and KI ligands. The implementation of KI3 additives remarkably suppresses the surface trap states and enhances the device stability due to the surface chemistry optimization. The resultant solar cells achieve the best power convention efficiency of 12.1% and retain 94% of its initial efficiency under 20 h continuous operation in air, while the control devices with KI additive deliver an efficiency of 11.0% and retains 87% of their initial efficiency under the same conditions.

Suppressing Redox Shuttle with MXene-Modified Separators for Li-O2 Batteries.

Redox mediators (RMs) have been developed as efficient approaches to lower the charge polarization of Li-O2 batteries. However, the shuttle effect resulting from their soluble nature severely damages the battery performance, causing failure of the RM and anode corrosion. In this work, a chemical binding strategy based on a MXene-modified separator with a 3D porous hierarchical structure design was developed to suppress the I3- shutting in LiI-involved Li-O2 battery. As corroborated by experimental characterizations and theoretical calculations, the abundant -OH terminal groups on the MXene surface functioned as effective binding sites for suppressing the migration of I3-, while the 3D porous structure ensured the fast transfer of lithium ions. As a result, the Li-O2 battery with the MXene-modified separator showed no sign of redox shuttling compared with its counterparts in the full discharge/charge tests. In the meantime, the MXene-modified separator based-cell exhibited a stable cycle life up to 100 cycles, which is 3 times longer than the control samples. We believe that this work could provide insights into the development of separator modification for Li-O2 batteries with RMs.

Ti3C2Tx MXene Interface Layer Driving Ultra-Stable Lithium-Iodine Batteries with Both High Iodine Content and Mass Loading.

Lithium-iodine (Li-I2) batteries are promising candidates for next-generation electrochemical energy storage systems due to their high energy density and the excellent kinetic rates of I2 cathodes. However, dissolution of iodine and iodide has hindered their widespread adoption for practical applications. Herein, a Ti3C2Tx MXene foam with a three-dimensional hierarchical porous architecture is proposed as a cathode-electrolyte interface layer in Li-I2 batteries, enabling high-rate and ultrastable cycling performance at a high iodine content and loading mass. Theoretical calculations and empirical characterizations indicate that Ti3C2Tx MXene sheets with high metallic conductivity not only provide strong chemical binding with iodine species to suppress the shuttle effect but also facilitate fast redox reactions during cell cycling. As a result, the Li-I2 battery using a cathode with 70 wt % I2 cycled stably for over 1000 cycles at a rate of 2 C, even at an ultrahigh loading mass of 5.2 mg cm-2. To the best of the authors' knowledge, this is the highest reported loading at such a high iodine content. This work suggests that using a Ti3C2Tx MXene interface layer can enable the design and application of high-energy Li-I2 batteries.

Co-Fe Mixed Metal Phosphide Nanocubes with Highly Interconnected-Pore Architecture as an Efficient Polysulfide Mediator for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have been regarded as one of the most promising candidates for next-generation energy storage owing to their high energy density and low cost. However, the practical deployment of Li-S batteries has been largely impeded by the low conductivity of sulfur, the shuttle effect of polysulfides, and the low areal sulfur loading. Herein, we report the synthesis of uniform Co-Fe mixed metal phosphide (Co-Fe-P) nanocubes with highly interconnected-pore architecture to overcome the main bottlenecks of Li-S batteries. With the highly interconnected-pore architecture, inherently metallic conductivity, and polar characteristic, the Co-Fe-P nanocubes not only offer sufficient electrical contact to the insulating sulfur for high sulfur utilization and fast redox reaction kinetics but also provide abundant adsorption sites for trapping and catalyzing the conversion of lithium polysulfides to suppress the shuttle effect, which is verified by both the comprehensive experiments and density functional theory calculations. As a result, the sulfur-loaded Co-Fe-P (S@Co-Fe-P) nanocubes delivered a high discharge capacity of 1243 mAh g-1 at 0.1 C and excellent cycling stability for 500 cycles with an average capacity decay rate of only 0.043% per cycle at 1 C. Furthermore, the S@Co-Fe-P electrode showed a high areal capacity of 4.6 mAh cm-2 with superior stability when the sulfur loading was increased to 5.5 mg cm-2. More impressively, the prototype soft-package Li-S batteries based on S@Co-Fe-P cathodes also exhibited superior cycling stability with great flexibility, demonstrating their great potential for practical applications.

Rapid separation of bacteria from blood-review and outlook.

The high morbidity and mortality rate of bloodstream infections involving antibiotic-resistant bacteria necessitate a rapid identification of the infectious organism and its resistance profile. Traditional methods based on culturing the blood typically require at least 24 h, and genetic amplification by PCR in the presence of blood components has been problematic. The rapid separation of bacteria from blood would facilitate their genetic identification by PCR or other methods so that the proper antibiotic regimen can quickly be selected for the septic patient. Microfluidic systems that separate bacteria from whole blood have been developed, but these are designed to process only microliter quantities of whole blood or only highly diluted blood. However, symptoms of clinical blood infections can be manifest with bacterial burdens perhaps as low as 10 CFU/mL, and thus milliliter quantities of blood must be processed to collect enough bacteria for reliable genetic analysis. This review considers the advantages and shortcomings of various methods to separate bacteria from blood, with emphasis on techniques that can be done in less than 10 min on milliliter-quantities of whole blood. These techniques include filtration, screening, centrifugation, sedimentation, hydrodynamic focusing, chemical capture on surfaces or beads, field-flow fractionation, and dielectrophoresis. Techniques with the most promise include screening, sedimentation, and magnetic bead capture, as they allow large quantities of blood to be processed quickly. Some microfluidic techniques can be scaled up. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:823-839, 2016.

Two mechanisms of oral malodor inhibition by zinc ions

Abstract Objectives The aim of this study was to reveal the mechanisms by which zinc ions inhibit oral malodor. Material and Methods The direct binding of zinc ions to gaseous hydrogen sulfide (H2S) was assessed in comparison with other metal ions. Nine metal chlorides and six metal acetates were examined. To understand the strength of H2S volatilization inhibition, the minimum concentration needed to inhibit H2S volatilization was determined using serial dilution methods. Subsequently, the inhibitory activities of zinc ions on the growth of six oral bacterial strains related to volatile sulfur compound (VSC) production and three strains not related to VSC production were evaluated. Results Aqueous solutions of ZnCl2, CdCl2, CuCl2, (CH3COO)2Zn, (CH3COO)2Cd, (CH3COO)2Cu, and CH3COOAg inhibited H2S volatilization almost entirely. The strengths of H2S volatilization inhibition were in the order Ag+ > Cd2+ > Cu2+ > Zn2+. The effect of zinc ions on the growth of oral bacteria was strain-dependent. Fusobacterium nucleatum ATCC 25586 was the most sensitive, as it was suppressed by medium containing 0.001% zinc ions. Conclusions Zinc ions have an inhibitory effect on oral malodor involving the two mechanisms of direct binding with gaseous H2S and suppressing the growth of VSC-producing oral bacteria.