Sensitive detection of streptomycin in milk using a hybrid signal enhancement strategy of MOF-based bio-bar code and target recycling

A MOF-based bio-bar code material was synthesized and firstly applied to develop an electrochemical streptomycin (STR) aptasensor. By using MOF-based bio-bar code and enzyme-assisted target recycling for dual-signal amplification, highly sensitive detection of STR was achieved. The sensing surface was simply fabricated by immobilizing a mixed monolayer of thiolated cDNA/aptamer duplexes (dsDNA) and 6-mercapto-1-hexanol (MCH) on the gold nanoparticle modified screen printed carbon electrode (Au/SPCE). The presence of target STR caused highly efficient removal of the aptamers from dsDNA assisted by Exo I enzyme. Then MOF-based bio-bar codes were backfilled to achieve the adsorption of electroactive Ru(NH₃)₆³⁺ (RuHex) on electrode surface. The electrochemical signal of the surface-confined RuHex was used for quantitation. The analytical performance for STR was satisfactory with a wide linear range of 0.005-150 ng mL^-1, a low detection limit of 2.6 pg mL^-1 and a good selectivity towards other three antibiotics. Moreover, the application of this aptasensor for determination of STR in real milk samples was also realized. With these merits, this dual-signal amplification assay might provide one of the effective ways for food safety monitoring.

Ultraselective antibiotic sensing with complementary strand DNA assisted aptamer/MoS2 field-effect transistors

Although aptamer has been demonstrated as an important probe for antibiotic determination, the selective sensing of different antibiotics is still a challenge due to their structure similarities and wide folding degrees of aptamer. Herein, a field-effect transistor using MoS₂ nanosheet as the channel and an aptamer DNA (APT) with its configuration shaped by a complementary strand DNA (CS) is employed for kanamycin (KAN) determination. This probe structure contributes to an enhanced selectivity and reliability with reduced device-to-device variations. This MoS₂/APT/CS sensor shows time-dependent performance in antibiotic sensing. Prolonged detection time (20 s-300 s) leads to an enhanced sensitivity (1.85-4.43 M^-1) and a lower limit of detection (1.06-0.66 nM), while a shorter detection time leads to a broader linear working range. A new sensing mechanism relying on charge release from probe is proposed, which is based on the "replacement reaction" between KAN and APT-CS. This sensor exhibits an extremely high selectivity (selectivity coefficient of 12.8) to kanamycin over other antibiotics including streptomycin, tobramycin, amoxicillin, ciprofloxacin and chloramphenicol. This work demonstrates the merits of probe engineering in label-free antibiotic detection with FET sensor, which presents significant promises in sensitive and selective chemical and biological sensing.

Synthesis and characterization of polyaniline-drug conjugates as effective antituberculosis agents

Polyaniline (PANI) and its drug composites with some drugs like Neomycin (NM), Trimethoprim (TMP) and Streptomycin (ST) have been prepared by oxidative polymerization of aniline using hydrochloric acid (HA) and ammonium persulfate (APS) as a dopant and as an oxidant, respectively. The structures of PANI and PANI-drug composites were elucidated by FTIR and NMR spectroscopy, which confirmed the presence of benzenoid and quinoid rings in the synthesized compound. Molecular weight and thermal stability were determined by gel permeation chromatography (GPC) and thermogarvimetric analysis, respectively. From the GPC, PDI values of PANI-NM, PANI-TMP and PANI-ST were found to be 1.37, 1.23 and 1.56, respectively. For the study of antibacterial behavior of the synthesized PANI and PANI-drug composites, different micro-organisms, namely, four Gram positive (S. aureus MTCC 96, B. subtilis MTCC 441, S. pyogenes MTCC 442 and S. mutans MTCC 890) and four Gram negative (S. typhi MTCC 98, KL. pneumoniae MTCC 109, E. coli MTCC 443 and P. aeruginosa MTCC 1688) bacteria were selected due to their pharmacological importance. Some of the PANI-drug composites were found to show excellent results as compared to components polyaniline and drugs used for composite formation. Antituberculosis activity of the PANI and its drug composites against Mycobacterium tuberculosisH₃₇RV (acid fast Bacilli) was determined. MIC values for PANI-NM and PANI-TMP were found to be 0.12 and 0.20 µg/mL, respectively. Results suggested that some of the drug composites may be tried as potential candidates for use as an antituberculoid agent to reduce TB transmission.

Self-Assembled Microgels for Sensitive and Low-Fouling Detection of Streptomycin in Complex Media

In terms of detection of antibiotics within complex media, the nonspecific adsorption is an enormous challenge and antifouling sensing interfaces capable of reducing the nonspecific adsorption from complex biological samples are highly desirable. In this work, a novel antifouling electrochemical immunosensor was explored based on the self-assembly of two kinds of poly( N-isopropylacrylamide) microgels on the surface of graphene oxide for sensitive detection of streptomycin (STR). The microgels modified with glycidyl methacrylate (GMA) and zwitterionic liquid 1-propyl-3-vinylimidazole sulfonate (PVIS) were prepared. The microgels with GMA were used by combining specific recognition of anti-STR. The rapid specific binding of antigen and anti-STR resulted in a decrease of current density to generate electrochemical responsive signals. Zwitterionic liquid-modified microgels were used for antifouling, which can form stronger hydration and show excellent antifouling ability. As a result, we achieved efficient and sensitive detection of STR in the complex sample with evidently resisted nonspecific adsorption effect, the wide linear range toward STR was from 0.05 to 100 ng mL^-1, with a detection limit down to 1.7 pg mL^-1. The immunosensor based on the surface functionalization of microgels showed promising applications for the detection of antibiotics in complex media.

Comparison of in vitro antibacterial activity of streptomycin-diclofenac loaded composite biomaterial dressings with commercial silver based antimicrobial wound dressings

Infected chronic wounds heal slowly, exhibiting prolonged inflammation, biofilm formation, bacterial resistance, high exudate and ineffectiveness of systemic antimicrobials. Composite dressings (films and wafers) comprising polyox/carrageenan (POL-CAR) and polyox/sodium alginate (POL-SA), loaded with diclofenac (DLF) and streptomycin (STP) were formulated and tested for antibacterial activity against 2 × 10⁵ CFU/mL of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus representing infected chronic wounds and compared with marketed silver dressings. Minimum inhibitory concentration (MIC) showed higher values for DLF than STP due to non-conventional antibacterial activity of DLF. The DLF and STP loaded dressings were highly effective against E. coli, P. aeruginosa and S. aureus. POL-SA dressings were more effective against the three types of bacteria compared to POL-CAR formulations, while the DLF and STP loaded dressings showed greater antibacterial activity than the silver-based dressings. The films, showed greater antibacterial efficacy than both wafers and silver dressings. STP and DLF can act synergistically not only to kill the bacteria but also prevent their resistance and biofilm formation compared to silver dressings, while reducing chronic inflammation associated with infection.

Drug Partitioning in Micellar Media and Its Implications in Rational Drug Design: Insights with Streptomycin

Oral bioavailability of a drug molecule requires its effective delivery to the target site. In general, majority of synthetically developed molecular entities have high hydrophobic nature as well as low bioavailability, therefore the need for suitable delivery vehicles arises. Self-assembled structures such as micelles, niosomes, and liposomes have been used as effective delivery vehicles and studied extensively. However, the information available in literature is mostly qualitative in nature. We have quantitatively investigated the partitioning of antibiotic drug streptomycin into cationic, nonionic, and a mixture of cationic and nonionic surfactant micelles and its interaction with the transport protein serum albumin upon subsequent delivery. A combination of calorimetry and spectroscopy has been used to obtain the thermodynamic signatures associated with partitioning and interaction with the protein and the resulting conformational changes in the latter. The results have been correlated with other class of drugs of different nature to understand the role of molecular features in the partitioning process. These studies are oriented toward understanding the physical chemistry of partitioning of a variety of drug molecules into suitable delivery vehicles and hence establishing structure-property-energetics relationships. Such studies provide general guidelines toward a broader goal of rational drug design.

Disassembly/reassembly strategy for the production of highly pure GroEL, a tetradecameric supramolecular machine, suitable for quantitative NMR, EPR and mutational studies

GroEL, a prototypical member of the chaperonin class of chaperones, is a large supramocular machine that assists protein folding and plays an important role in proteostasis. GroEL comprises two heptameric rings, each of which encloses a large cavity that provides a folding chamber for protein substrates. Many questions remain regarding the mechanistic details of GroEL facilitated protein folding. Thus, data at atomic resolution of the type provided by NMR and EPR are invaluable. Such studies often require complete deuteration of GroEL, uniform or residue specific ¹³C and ¹⁵N isotope labeling, and the introduction of selective cysteine mutations for site-specific spin labeling. In addition, high purity GroEL is essential for detailed studies of substrate-GroEL interactions as quantitative interpretation is impossible if the cavities are already occupied and blocked by other protein substrates present in the bacterial expression system. Here we present a new purification protocol designed to provide highly pure GroEL devoid of non-specific protein substrate contamination.

Drug loaded microbeads entrapped electrospun mat for wound dressing application

A new design of antibiotic loaded wound dressing and its initial in vitro evaluation is described. Chitosan microbeads loaded with ampicillin were sandwiched within polycaprolactone electrospun mat (MbAPPCL). The morphology was analyzed by scanning electron microscopy and surface chemistry was characterized by Fourier Transform Infrared Spectroscopy. In vitro cytotoxicity using L-929 fibroblast cells by direct contact test and elution assay revealed non-cytotoxic nature of MbAPPCL. The cell adhesion and viability analysis further confirmed the cytocompatibility of MbAPPCL as a wound dressing material. Percentage hemolysis and platelet adhesion on the mat exposed to blood substantiated the hemocompatibility. The antibiotic susceptibility test analyzed on Staphylococcus aureus by agar plate method confirmed the drug release and antimicrobial property. The proposed wound dressing model explained with ampicillin as a candidate drug has the potential to include microbeads with different antibiotics for multi drug treatment.

Degradation of streptomycin in aquatic environment: kinetics, pathway, and antibacterial activity analysis

Streptomycin used in human and veterinary medicine is released into the environment mainly through excretions. As such, its elimination in water should be investigated to control pollution. In this study, the degradation of streptomycin in water was studied, and the influence of variables, including light exposure, solution pH, temperature, ionic strength, dissolved organic matter (DOM), and coexisting surfactants, on degradation was investigated. Streptomycin degradation was consistent with the first-order model in aquatic environments. Its degradation rate under light exposure was 2.6-fold faster than that in the dark. Streptomycin was stable under neutral conditions, but it was easily decomposed in acidic and basic environments. Streptomycin degradation was enhanced by high temperature, and its half-life decreased from 103.4 days at 15 °C to 30.9 days at 40 °C. This process was also accelerated by the presence of Ca²⁺ and slightly improved by the addition of HA. Streptomycin degradation was suppressed by high levels of the cationic surfactant cetyltri- methylammonium bromide (CTAB), but was promoted by the anionic surfactant sodium dodecyl benzene sulfonate (SDBS). The main degradation intermediates/products were identified through liquid chromatography-mass spectrometry, and the possible degradation pathway was proposed. The antibacterial activity of streptomycin solution was also determined during degradation. Results showed that STR degradation generated intermediates/products with weaker antibacterial activity than the parent compound.

Historical and hygienic aspects on roles of quality requirements for antibiotic products in Japan: Part 5 - Introduction of technology and knowledge on streptomycin production from the United States of Americat

In order to investigate the roles of quality requirements for antibiotics products in Japan, from historical and hygienic aspects, we examined how technology and knowledge in the production and quality control of streptomycin were introduced from the United States of America. In this study, through detailed investigations and analyses, it was confirmed that the introduction of technology and knowledge on streptomycin was strongly supported by Brigadier General CRAWFORD SAms, the chief of the Public Health and Welfare Section (PHW) of the Supreme Commander for Allied Powers/General Headquarters, via the Ministry of Welfare in Japan. Dr. SELMAN WAKSMAN, the discoverer of streptomycin, along with scientists of Merck & Co., also helped Japanese industries extensively, via PHW, by providing the original streptomycin-producing strains and transferring expertise in streptomycin production. With the technology and knowledge being introduced from the USA, domestic production of streptomycin preparations increased very rapidly. As noted in our previous report, domestic production reached amounts enough to satisfy national demand within three years. Japanese people have a racial tendency to be highly susceptible to tuberculosis known as an incurable national disease. Thanks to streptomycin therapy, the tuberculosis mortality rate (per 100,000 population) had fallen dramatically within only five years from 187.2 in 1947 to 82.2 in 1952.

Growth in Egg Yolk Enhances Salmonella Enteritidis Colonization and Virulence in a Mouse Model of Human Colitis

Salmonella Enteritidis (SE) is one of the most common causes of bacterial food-borne illnesses in the world. Despite the SE's ability to colonize and infect a wide-range of host, the most common source of infection continues to be the consumption of contaminated shell eggs and egg-based products. To date, the role of the source of SE infection has not been studied as it relates to SE pathogenesis and resulting disease. Using a streptomycin-treated mouse model of human colitis, this study examined the virulence of SE grown in egg yolk and Luria Bertani (LB) broth, and mouse feces collected from mice experimentally infected with SEE1 (SEE1 passed through mice). Primary observations revealed that the mice infected with SE grown in egg yolk displayed greater illness and disease markers than those infected with SE passed through mice or grown in LB broth. Furthermore, the SE grown in egg yolk achieved higher rates of colonization in the mouse intestines and extra-intestinal organs of infected mice than the SE from LB broth or mouse feces. Our results here indicate that the source of SE infection may contribute to the overall pathogenesis of SE in a second host. These results also suggest that reservoir-pathogen dynamics may be critical for SE's ability to establish colonization and priming for virulence potential.

A novel electrochemical aptasensor based on arch-shape structure of aptamer-complimentary strand conjugate and exonuclease I for sensitive detection of streptomycin

Detection and quantitation of antibiotic residues in blood serum and animal foodstuffs are of great significance. In this study, an electrochemical aptasensor was developed for sensitive and selective detection of streptomycin, based on exonuclease I (Exo I), complimentary strand of aptamer (CS), Arch-shape structure of aptamer (Apt)-CS conjugate and gold electrode. The designed aptasensor inherits characteristics of gold including large surface area and high electrochemical conductivity, as well as high sensitivity and selectivity of aptamer toward its target, property of Arch-shape structure of Apt-CS conjugate to act as a gate and barrier for the access of redox probe to the surface of electrode and the function of Exo I as an enzyme which selectively digests the 3'-end of single stranded DNA (ssDNA). In the absence of streptomycin the gate remains closed. Thus, the electrochemical signal is weak. Upon addition of streptomycin, the Apt leaves the CS and binds to streptomycin and the Arch-shape structure is disassembled. Then, Exo I addition leads to a strong electrochemical signal. The designed electrochemical aptasensor exhibited high selectivity toward streptomycin with a limit of detection (LOD) as low as 11.4nM. Moreover, the developed electrochemical aptasensor was successfully used to detect streptomycin in milk and serum with LODs of 14.1 and 15.3nM, respectively.

Streptomycin Induced Stress Response in Salmonella enterica Serovar Typhimurium Shows Distinct Colony Scatter Signature

We investigated the streptomycin-induced stress response in Salmonella enterica serovars with a laser optical sensor, BARDOT (bacterial rapid detection using optical scattering technology). Initially, the top 20 S. enterica serovars were screened for their response to streptomycin at 100 μg/mL. All, but four S. enterica serovars were resistant to streptomycin. The MIC of streptomycin-sensitive serovars (Enteritidis, Muenchen, Mississippi, and Schwarzengrund) varied from 12.5 to 50 μg/mL, while streptomycin-resistant serovar (Typhimurium) from 125–250 μg/mL. Two streptomycin-sensitive serovars (Enteritidis and Mississippi) were grown on brain heart infusion (BHI) agar plates containing sub-inhibitory concentration of streptomycin (1.25–5 μg/mL) and a streptomycin-resistant serovar (Typhimurium) was grown on BHI containing 25–50 μg/mL of streptomycin and the colonies (1.2 ± 0.1 mm diameter) were scanned using BARDOT. Data show substantial qualitative and quantitative differences in the colony scatter patterns of Salmonella grown in the presence of streptomycin than the colonies grown in absence of antibiotic. Mass-spectrometry identified overexpression of chaperonin GroEL, which possibly contributed to the observed differences in the colony scatter patterns. Quantitative RT-PCR and immunoassay confirmed streptomycin-induced GroEL expression while, aminoglycoside adenylyltransferase (aadA), aminoglycoside efflux pump (aep), multidrug resistance subunit acrA, and ribosomal protein S12 (rpsL), involved in streptomycin resistance, were unaltered. The study highlights suitability of the BARDOT as a non-invasive, label-free tool for investigating stress response in Salmonella in conjunction with the molecular and immunoassay methods.

Fabrication and Characterization of Antimicrobial Ethyl Cellulose Nanofibers Using Electrospinning Techniques

Ethyl cellulose nanofibers were fabricated by electrospinning techniques using ethyl cellulose solution having concentrations of 150 g/l, using different volume ratios of a binary THF (tetrahydrofuran): DMAc (N,N dimethylacetamide) solvent system. The influence of the composition of the binary solvent system on the surface morphology of ethyl cellulose nanofibers with or without adhered antibiotics was investigated using field emission scanning electron microscope (FE-SEM). To assess the effectiveness of drug release from the nanofibers and their antibacterial activities toward S. aureus, streptomycin was selected as the antibiotic. Disc diffusion and optical density tests were used for the assessment. The antibiotic release from ethyl cellulose fibers was best when the THF to DMAc volume ratio was 3 to 2 (v/v). The optical density test showed the antibacterial effective time of the streptomycin antibiotics loaded in nanofibers was longer than that of the bulk antibiotics against S. aureus bacteria.

Establishment and characterization of a gonad cell line from half-smooth tongue sole Cynoglossus semilaevis pseudomale

A new cell line was established from half-smooth tongue sole Cynoglossus semilaevis pseudomale gonad (CSPMG). Primary culture was initiated from gonad tissues pieces, and the CSPMG cells were cultured at 24 °C in Dulbecco's modified Eagle medium/F12 medium (1:1) (pH7.0), supplemented with 20 % fetal bovine serum, basic fibroblast growth factor, epidermal growth factor, insulin-like growth factor-I, 2-mercaptoethanol, penicillin and streptomycin. The cultured CSPMG cells, in fibroblast shape, proliferated to 100 % confluency 10 days later and had been subcultured to passage 109. Chromosome analyses indicated that the CSPMG cells exhibited chromosomal aneuploidy with a modal chromosome number of 42, which displayed the normal diploid karyotype of half-smooth tongue sole (2n = 42t, NF = 42). Reverse transcription polymerase chain reaction revealed CSPMG cells could express gonad somatic cell functional genes Sox9a, Wt1a and weakly germ cell marker gene Vasa, but not male specific gene Dmrt1. Transfection experiment demonstrated that CSPMG cells transfected with pEGFP-N3 plasmid and small RNA could express green and red fluorescence signals with high transfection efficiency. In conclusion, a continuous CSPMG cell line has been established successfully. The cell line might serve as a valuable tool for studies on the mechanism of sex determination, sex reversal and gonad development in flatfish.

A selective fluorescent and colorimetric dual-responses chemosensor for streptomycin based on polythiophene derivative

A colorimetric and fluorescent dual-responses chemosensor (PT3, a water-soluble polythiophene) for streptomycin was designed and synthesized. The structure of PT3 was characterized by using infrared spectroscopy, (1)H NMR and gel-permeation chromatography analyses. The conformational change of PT3 induced by streptomycin resulted in the red shift of absorption spectra and fluorescent quenching. Moreover, PT3 showed excellent selectivity for streptomycin over other antibiotics and biomolecules. PT3 could quantificationally detect streptomycin in the range of 2-70 μM with a detection limit of 0.2 μM (116 ppb), which is lower than the maximum residue limit defined by World Health Organization (200 ppb).

Streptomycin hydrazone derivatives: synthesis and molecular recognition in aqueous solution

Five hydrazone derivatives of streptomycin were synthetized (D0h, D1ph, D2bt, D3dctf, D4ag) and characterized by IR, 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. Protonation constants were determined by potentiometry for all derivatives. D1ph and D2bt derivatives were investigated as receptors of dicarboxylates and adenine nucleotides in aqueous solution by potentiometric and 1H NMR titrations. D1ph and D2bt derivatives have the highest affinity with AMP and ATP, respectively, which shows that electrostatic forces are not always the dominant factor in binding of streptomycin derivatives with nucleotides, but the conformational fit between them. Calculated structures at the DFT level of the D1ph derivative bonded with either AMP or ADP showed that the complexes are stabilized by the formation of multiple interactions with the receptors. The antibiotic activity of the derivatives was explored and compared with native streptomycin.

Protein coronas on gold nanorods passivated with amphiphilic ligands affect cytotoxicity and cellular response to penicillin/streptomycin

We probe how amphiphilic ligands (ALs) of four different types affect the formation of protein coronas on gold nanorods (NRs) and their impact on cellular response. NRs coated with cetyltrimethylammonium bromide were ligand exchanged with polyoxyethylene[10]cetyl ether, oligofectamine, and phosphatidylserine (PS). Protein coronas from equine serum (ES) were formed on these NR-ALs, and their colloidal stability, as well as cell uptake, proliferation, oxidative stress, and gene expression, were examined. We find that the protein corona that forms and its colloidal stability are affected by AL type and that the cellular response to these NR-AL-coronas (NR-AL-ES) is both ligand and corona dependent. We also find that the presence of common cell culture supplement penicillin/streptomycin can impact the colloidal stability and cellular response of NR-AL and NR-AL-ES, showing that the cell response is not necessarily inert to pen/strep when in the presence of nanoparticles. Although the protein corona is what the cells see, the underlying surface ligands evidently play an important role in shaping and defining the physical characteristics of the corona, which ultimately impacts the cellular response. Further, the results of this study suggest that the cellular behavior toward NR-AL is mediated by not only the type of AL and the protein corona it forms but also its resulting colloidal stability and interaction with cell culture supplements.

Chemiluminescence determination of streptomycin in pharmaceutical preparation and its application to pharmacokinetic study by a flow injection analysis assembly

A novel and rapid method for the determination of streptomycin has been established by chemiluminescence (CL) based on significant intensity enhancement of streptomycin on the weak CL of N-bromosuccinimide (NBS) and eosin in alkaline medium. The method is simple, rapid and effective to determine streptomycin in the range of 8.0×10(-9)-1.0×10(-6)gmL(-1) with a determination limit of 2.25×10(-9)gmL(-1). The relative standard deviation is 1.95% for the determination of 2.0×10(-7)gmL(-1) streptomycin (n=11). The pharmacokinetics of streptomycin in plasma of rat coincides with the two-compartment open model. The T1/2α, T1/2β, CL/F, AUC(0-t), MRT, Tmax and Cmax were 18.83±1.24min, 82.14±3.07min, 0.0026±0.0011Lkg(-1)min(-1), 36044.50±105.02mgmin(-1)L(-1), 92.29±8.21min, 21.63±1.26min and 375.61±8.50μgmL(-1), respectively. There was no significant difference between the results obtained by CL and HPLC. The FI-CL method can be used to determine streptomycin in pharmaceutical preparation and biological samples. The established method is simple, rapid and sensitive without expensive instruments. The possible enhancement mechanism was also investigated.

In situ-ATR-FTIR analysis on the uptake and release of streptomycin from polyelectrolyte complex layers

In-situ ATR-FTIR spectroscopy and line shape analysis of the diagnostic spectral region was used to quantify the bound amount and release of the antibiotic streptomycin (STRP) at polyelectrolyte (PEL) multilayers (PEM) of poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAA) or PEI and sodium alginate (ALG). Unlike common concepts based on the drug enrichment of the release medium, this analytical concept allowed to measure quantitatively the drug depletion in the delivery matrix. The measured kinetic in situ ATR-FTIR data were analysed by a modified Korsmeyer-Peppas equation based on two characteristic release parameters k and n. As main experimental parameters the number of PEL layers (adsorption steps) z and the STRP/PEL ratio were varied. For z=8 the STRP/PEL ratio showed the most significant influence on release kinetics, whereby for STRP/PEL=1:25 slowest (n=0.77) and lowest (k=21.4%) and for STRP/PEL=1:5 most rapid (n=0.30) and highest (k=58.6%) drug releases were found. PEM-PEI/ALG-8 (STRP/PEL=1:5) revealed slower release rates (n=0.58) and lower released STRP amounts (k=17.1%) compared to PEI/PAA. UV-VIS data on time dependent STRP enrichment of the release medium showed a similar trend compared to respective ATR-FTIR data on STRP depletion in PEM. Released amounts of around 1-2mg from the herein introduced PEM films could be determined. The introduced analytical concept will be used as screening tool for other drugs, drug eluting films and bone substituting materials.

Electrically controlled drug release from nanostructured polypyrrole coated on titanium

Previous studies have demonstrated that multi-walled carbon nanotubes grown out of anodized nanotubular titanium (MWNT-Ti) can be used as a sensing electrode for various biomedical applications; such sensors detected the redox reactions of certain molecules, specifically proteins deposited by osteoblasts during extracellular matrix bone formation. Since it is known that polypyrrole (PPy) can release drugs upon electrical stimulation, in this study antibiotics (penicillin/streptomycin, P/S) or an anti-inflammatory drug (dexamethasone, Dex), termed PPy[P/S] or PPy[Dex], respectively, were electrodeposited in PPy on titanium. The objective of the present study was to determine if such drugs can be released from PPy on demand and (by applying a voltage) control cellular behavior important for orthopedic applications. Results showed that PPy films possessed nanometer-scale roughness as analyzed by atomic force microscopy. X-ray photoelectron spectroscopy confirmed the presence of P/S and Dex encapsulated within the PPy films. Results from cyclic voltammetry showed that 80% of the drugs were released on demand when sweep voltages were applied for five cycles at a scan rate of 0.1 V s(-1). Furthermore, osteoblast (bone-forming cells) and fibroblast (fibrous tissue-forming cells) adhesion were determined on the PPy films. Results showed that PPy[Dex] enhanced osteoblast adhesion after 4 h of culture compared to plain Ti. PPy-Ti (with or without anionic drug doping) inhibited fibroblast adhesion compared to plain Ti. These in vitro results confirmed that electrodeposited PPy[P/S] and PPy[Dex] can release drugs on demand to potentially fight bacterial infection, reduce inflammation, promote bone growth or reduce fibroblast functions, further implicating the use of such materials as implant sensors.

Comparing the sensitivity of algal, cyanobacterial and bacterial bioassays to different groups of antibiotics

Antibiotics may affect both primary producers and decomposers, potentially disrupting ecosystem processes. Hence, it is essential to assess the impact of antibiotics on aquatic ecosystems. The aim of the present study was therefore to evaluate the potential of a recently developed test for detecting antibiotics in animal tissue, the Nouws Antibiotic Test (NAT), as a sensitive bioassay to assess the effects of antibiotics in water. To this purpose, we determined the toxicity of sulphamethoxazole, trimethoprim, flumequine, tylosin, streptomycin, and oxytetracycline, using the NAT adapted for water exposure. The sensitivity of the NAT was compared to that of bioassays with bacteria (Microtox), cyanobacteria and green algae. In the Microtox test with Vibrio fischeri as test organism, no effects were observed for any of the test compounds. For three of the six antibiotics tested, the cyanobacteria were more vulnerable than the green algae when using photosynthetic efficiency as an endpoint. The lowest EC50 values for four out of six tested antibiotics were obtained using the NAT bacterial bioassay. The bacterial plate system responded to antibiotics at concentrations in the microgL(-1) and lower mgL(-1) range and, moreover, each plate proved to be specifically sensitive to the antibiotics group it was designed for. It is concluded that the NAT bioassay adapted for water exposure is a sensitive test to determine the presence of antibiotics in water. The ability of this test to distinguish five major antibiotic groups is a very strong additional value.

Fluorescently labeled ribosomes as a tool for analyzing antibiotic binding

Measuring the binding of antibiotics and other small-molecular-weight ligands to the 2.5 MDa ribosome often presents formidable challenges. Here, we describe a general method for studying binding of ligands to ribosomes that carry a site-specific fluorescent label covalently attached to one of the ribosomal proteins. As a proof of principle, an environment-sensitive fluorescent group was placed at several specific sites within the ribosomal protein S12. Small ribosomal subunits were reconstituted from native 16S rRNA, individually purified small subunit proteins, and fluorescently labeled S12. The fluorescence characteristics of the reconstituted subunits were affected by several antibiotics, including streptomycin and neomycin, which bind in the vicinity of protein S12. The equilibrium dissociation constants of the drugs obtained using a conventional fluorometer were in good agreement with those observed using previously published methods and with measurements based on the use of radiolabeled streptomycin. The newly developed method is rapid and sensitive, and can be used for determining thermodynamic and kinetic binding characteristics of antibiotics and other small ribosomal ligands. The method can readily be adapted for use in high-throughput screening assays.

Plant agricultural streptomycin formulations do not carry antibiotic resistance genes

Streptomycin is used in plant agriculture for bacterial disease control, particularly against fire blight in pome fruit orchards. Concerns that this may increase environmental antibiotic resistance have led to bans or restrictions on use. Experience with antibiotic use in animal feeds raises the possible influence of formulation-delivered resistance genes. We demonstrate that agricultural streptomycin formulations do not carry producer organism resistance genes. By using an optimized extraction procedure, Streptomyces 16S rRNA genes and the streptomycin resistance gene strA were not detected in agricultural streptomycin formulations. This diminishes the likelihood for one potential factor in resistance development due to streptomycin use.

Reliability of muramic acid as a bacterial biomarker is influenced by methodological artifacts from streptomycin

The muramic acid (MurA) assay is a powerful tool for the detection and quantification of bacteria with no need to enrich samples by culturing. However, the analysis of MurA in mixed biological and environmental matrices is potentially more complex than analysis in isolated bacterial cells. In this study, we employed one commonly used procedure for extraction of MurA from environmental samples and found that the presence of streptomycin interfered with the determination of MurA by creating chemical species that coeluted with the aldononitrile derivative of MurA prepared in this method. On a molar basis, streptomycin yields a signal that is approximately 0.67 times that of MurA. Mass spectrometry analysis confirmed that the interference from hydrolyzed streptomycin is not actually by MurA, but rather is likely to be N-methyl glucosamine. Because streptomycin is widely applied for selective growth of eukaryotes both in situ and in vitro, our findings may have implications for the significance of results from MurA assays. We conclude that MurA remains an effectual bacterial biomarker due to its unique bacterial origin, but care must be applied in interpreting results from the assay when performed in the presence of streptomycin.

Analysis of impurities in streptomycin and dihydrostreptomycin by hydrophilic interaction chromatography/electrospray ionization quadrupole ion trap/time-of-flight mass spectrometry

Impurities in streptomycin (STR) and dihydrostreptomycin (DHS) were investigated by hydrophilic interaction chromatography/electrospray ionization quadrupole ion trap/time-of-flight mass spectrometry (HILIC/ESI-QIT/TOFMS). Samples were separated on a fused-core silica column (100 mmx2.1 mm i.d., particle size: 2.7 microm) with isocratic elution using 200 mM ammonium formate buffer (pH 4.5) and acetonitrile as mobile phase. Constant neutral loss survey in accurate mass measurement was carried out by QIT/TOFMS. Formulae, chemical structures of impurities in an STR sample were suggested with supporting results on the probable pathways of STR biosynthesis by Streptomyces griseus.

[Establishment of an assay for PrP(Sc) detection based on streptomycin precipitation]

To establish a new Western blotting assay for PrP(Sc) detection, we optimized the Western blotting assay with a precipitation procedure of streptomycin sulfate. After digestion with PK, 10% scrapie infected hamster brain homogenates were incubated with 60 mmol/L streptomycin and the precipitated PrP(Sc) was recovered by centrifugation. The enrichment of PrP(Sc) by streptomycin sulfate precipitation was evaluated using Western blotting assay. The results showed streptomycin could bind to PK-treated PrP(Sc), forming high molecular masses, but not influence the glycosylated patterns on SDS-PAGE. Western blot assay revealed that the detective sensitivity of the streptomycin-precipitation PrP(Sc) was remarkably improved. As a sensitive, specific, rapid and flexible protocol for PrP(Sc), the protocol in this study has the potential utility, alone or combined with other techniques, for the detection of low level PrP(Sc) in the specimens from central nerve system, or from peripheral organs or body fluids.

Tuberculosis: drug resistance, fitness, and strategies for global control

Directly observed standardized short-course chemotherapy (DOTS) regimes are an effective treatment for drug susceptible tuberculosis disease. Surprisingly, DOTS has been reported to reduce the transmission of multi-drug resistant tuberculosis, and standardized short-course chemotherapy regimens with first-line agents have been found to be adequate treatments for some patients with drug resistant tuberculosis, including multi-drug resistance. These paradoxical observations and the apparent heterogeneity in treatment outcome of multi-drug resistant tuberculosis when using standard regimens may be due in part to limitations of in vitro drug susceptibility testing based on unique but mistakenly used techniques in diagnostic mycobacteriology. Experimental data and mathematical models indicate that the fitness cost conferred by a resistance determinant is the single most important parameter which determines the spread of drug resistance. Chromosomal alterations that result in resistance to first-line antituberculosis agents, e.g. isoniazid, rifampicin, streptomycin, may or may not be associated with a fitness cost. Based on work in experimental models and from observations in clinical drug resistant isolates a picture emerges in which, among the various resistance mutations that appear with similar rates, those associated with the least fitness cost are selected in the population.

Sensitive detection of PrPSc by Western blot assay based on streptomycin sulphate precipitation

Transmissible spongiform encephalopathies, also termed prion diseases, are fatal neurodegenerative disorders that affect both humans and animals, which are characterized by presences of protease-resistance disease-associated prion protein (PrP(Sc)) in brains. In the present study, we optimized the Western blot assay for PrP(Sc) with a precipitation procedure of streptomycin sulphate. After incubated with suitable amount of streptomycin sulphate, the detective sensitivity for PrP(Sc) was remarkably improved. The precipitation of PrP(Sc) was obviously influenced by pH value in the solution. Employs of PrP(Sc) stock sample into various mimic specimens, including normal hamster brain homogenate, human cerebrospinal fluid and urine, demonstrated that streptomycin precipitation markedly increased the detective sensitivity of PrP(Sc), regardless in low concentration or in large volume. In addition, the PrP(Sc) from a human brain tissue of familiar Creutzfeldt-Jakob disease (fCJD) was efficiently precipitated with streptomycin sulphate. As a sensitive, specific, rapid and flexible protocol for PrP(Sc), the protocol in this study has the potential, alone or combined with other techniques, to detect low levels of PrP(Sc) in the specimens not only from central nerve system, but also from peripheral organs or fluids.

Isolation of specific RNA-binding proteins using the streptomycin-binding RNA aptamer

Here we report a simple and cheap one-step affinity purification protocol for isolating RNAs or proteins that interact with selected functional RNAs. The streptomycin-binding aptamer, termed 'StreptoTag,' is embedded in or fused to either end of any RNA of interest. The resulting hybrid RNA can then be immobilized on a streptomycin affinity matrix. When a complex protein mixture or total cellular lysate is applied to the matrix, subsequent elution with free streptomycin allows efficient recovery of specific ribonucleoprotein or RNA-RNA complexes. The method was successfully used to purify yeast and phage RNA-binding proteins and group II intron, viral and bacterial noncoding RNA (ncRNA)-binding proteins. The selective enrichment of bacterial mRNAs that bind ncRNAs has also been demonstrated. Once the affinity matrix, the RNA construct and the protein extracts have been prepared, the experimental procedure can be performed in 1-2 h.

A practical approach to isolate 48S complexes: affinity purification and analyses

In vitro assembly of eukaryotic translation initiation complexes requires purification of ribosomal subunits, eukaryotic initiation factors, and initiator tRNA from natural sources and therefore yields only limited material for functional and structural studies. In this chapter, we describe a robust, affinity chromatography-based method for the isolation of eukaryotic 48S initiation complexes from rabbit reticulocyte lysate (RRL). Both canonical and internal ribosome entry site (IRES)-containing mRNAs labeled with a streptomycin aptamer sequence at the 3' end can be used to purify milligram quantities of 48S particles in a simple, two-step procedure. The 48S complexes purified with this method are properly assembled at the initiation codon, contain the expected RNA and protein components in a 1:1 stoichiometry, and are functional intermediates along the initiation pathway.

Use of streptomycin for precipitation and detection of proteinase K resistant prion protein (PrPsc) in biological samples

The ability of streptomycin to form multimolecular aggregates with pathogenic prion proteins and their recovery by precipitation via a low-speed centrifugation step has been demonstrated; these novel properties of streptomycin make it a useful substance that increases the sensitivity of laboratory diagnostic techniques for prion infections in man and animals.

Molecular Recognition of Aminoglycoside Antibiotics by Bacterial Defence Proteins: NMR Study of the Structural and Conformational Features of Streptomycin Inactivation byBacillus subtilis Aminoglycoside-6-adenyl Transferase

The molecular recognition of streptomycin by Bacillus subtilis aminoglycoside-6-adenyl transferase has been analysed by a combination of NMR techniques and molecular dynamic simulations. This protein inactivates streptomycin by transferring an adenyl group to position six of the streptidine moiety. Our combined approach provides valuable information about the bioactive conformation for both the antibiotic and ATP and shows that the molecular recognition process for streptomycin involves a conformational selection phenomenon. The binding epitope for both ligands has also been analysed by 1D-STD experiments. Finally, the specificity of the recognition process with respect to the aminoglycoside and to the nucleotide has been studied.

GAPDH enhances group II intron splicing in vitro

Group II introns are autocatalytic RNAs which self-splice in vitro. However, in vivo additional protein factors might be involved in the splicing process. We used an affinity chromatography method called 'StreptoTag' to identify group II intron binding proteins from Saccharomyces cerevisiae. This method uses a hybrid RNA consisting of a streptomycin-binding affinity tag and the RNA of interest, which is bound to a streptomycin column and incubated with yeast protein extract. After several washing steps the bound RNPs are eluted by addition of streptomycin. The eluted RNPs are separated and the proteins identified by mass-spectrometric analysis. Using crude extract from yeast in combination with a substructure of the bl1 group II intron (domains IV-VI) we were able to identify four glycolytic enzymes; glucose-6-phosphate isomerase (GPI), 3-phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and triosephosphate isomerase (TPI). From these proteins GAPDH increases in vitro splicing of the bl1 group II intron by up to three times. However, in vivo GAPDH is not a group II intron-splicing factor, since it is not localised in yeast mitochondria. Therefore, the observed activity reflects an unexpected property of GAPDH. Band shift experiments and UV cross linking demonstrated the interaction of GAPDH with the group II intron RNA. This novel activity expands the reaction repertoire of GAPDH to a new RNA species.

A minimum structure of aminoglycosides that causes an initiation shift of trans-translation

Trans-translation is an unusual translation in which transfer-messenger RNA plays a dual function--as a tRNA and an mRNA--to relieve the stalled translation on the ribosome. It has been shown that paromomycin, a typical member of a 4,5-disubstituted class of aminoglycosides, causes a shift of the translation-resuming point on the tmRNA by -1 during trans-translation. To address the molecular basis of this novel effect, we examined the effects of various aminoglycosides that can bind around the A site of the small subunit of the ribosome on trans-translation in vitro. Tobramycin and gentamicin, belonging to the 4,6-disubstituted class of aminoglycosides having rings I and II similar to those in the 4,5-disubstituted class, possess similar effects. Neamine, which has only rings I and II, a common structure shared by 4,5- and 4,6-disubstituted classes of aminoglycosides, was sufficient to cause an initiation shift of trans-translation. In contrast, streptomycin or hygromycin B, lacking ring I, did not cause an initiation shift. The effect of each aminoglycoside on trans-translation coincides with that on conformational change in the A site of the small subunit of the ribosome revealed by recent structural studies: paromomycin, tobramycin and geneticin which is categorized into the gentamicin subclass, but not streptomycin and hygromycin B, flip out two conserved adenine bases at 1492 and 1493 from the A site helix. The pattern of initiation shifts by paromomycin fluctuates with variation of mutations introduced into a region upstream of the initiation point.

Polycomplexes of poly(acrylic acid) with streptomycin sulfate and their antibacterial activity

Complex formation between streptomycin sulfate and poly(acrylic acid) has been studied in aqueous solutions by turbidimetric, potentiometric and viscometric methods as well as by FTIR spectroscopy. It was shown that these polycomplexes are stabilized by electrostatic interactions. The solubility of polycomplexes was examined as a function of pH and it was found that at pH values below 3.1 the polycomplexes undergo complete dissociation or dissolution. The antimicrobial activity of the drug and its polycomplex was evaluated using Sarcina sp. as a model organism. It was demonstrated that the polycomplexes have an antimicrobial activity on the same level as the free drug.

Encapsulating streptomycin within a small 40-mer RNA

We describe a 2.9 A X-ray structure of a complex between the aminocyclitol antibiotic streptomycin and an in vitro selected RNA aptamer, solved using the anomalous diffraction properties of Ba cations. The RNA aptamer, which contains two asymmetric internal loops, adopts a distinct cation-stabilized fold involving a series of S-shaped backbone turns anchored by canonical and noncanonical pairs and triples. The streptomycin streptose ring is encapsulated by stacked arrays of bases from both loops at the elbow of the L-shaped RNA architecture. Specificity is defined by direct hydrogen bonds between all streptose functional groups and base edges that line the inner walls of the cylindrical binding pocket. By contrast, the majority of intermolecular interactions involve contacts to backbone phosphates in the published structure of streptomycin bound to the 16S rRNA.

Streptomycin revisited: molecular action in the microbial cell

The key event for antimicrobial action begins when streptomycin binds to the 30S subunit (S12 protein) of a ribosome. Lysine 42 and lysine 87 are involved. It is proposed that antagonism of acetyl coenzyme A carboxylase by streptomycin results in faulty fatty acids, lipids and derivatives marked exclusively for cell membrane synthesis. Streptomycin-sensitive growing cells are fatally wounded when defective membranes leak K(+) ions, then amino acids, nucleotides, oligonucleotides and proteins as increasing amounts of streptomycin enter the cell.

Functional insights from the structure of the 30S ribosomal subunit and its interactions with antibiotics

The 30S ribosomal subunit has two primary functions in protein synthesis. It discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding. Also, it works with the 50S subunit to move the tRNAs and associated mRNA by precisely one codon, in a process called translocation. Here we describe the functional implications of the high-resolution 30S crystal structure presented in the accompanying paper, and infer details of the interactions between the 30S subunit and its tRNA and mRNA ligands. We also describe the crystal structure of the 30S subunit complexed with the antibiotics paromomycin, streptomycin and spectinomycin, which interfere with decoding and translocation. This work reveals the structural basis for the action of these antibiotics, and leads to a model for the role of the universally conserved 16S RNA residues A1492 and A1493 in the decoding process.

A new stabilizer used in microencapsulation

In this communication, a new microencapsulation method is reported to entrap solid drug powder in an aqueous system. A hydrophobically modified, random polyacrylamide derivative was used as a stabilizer: with a hydrophilic back bone and hydrophobic side chain, it showed good dispersing and stabilizing effects in the preparation of microcapsules. The preparation of streptomycin microcapsules, using poly(lactide) and poly(caprolactone), showed the successful entrapment of streptomycin powder which is readily soluble in water (solubility larger than 20 mg/ml). In addition, a low concentration of stabilizer (0.25%) is used and a short preparation process is also an advantage of the method.

In vitro selection and characterization of streptomycin-binding RNAs: recognition discrimination between antibiotics

As pathogens continue to evade therapeutical drugs, a better understanding of the mode of action of antibiotics continues to have high importance. A growing body of evidence points to RNA as a crucial target for antibacterial and antiviral drugs. For example, the aminocyclitol antibiotic streptomycin interacts with the 16S ribosomal RNA and, in addition, inhibits group I intron splicing. To understand the mode of binding of streptomycin to RNA, we isolated small, streptomycin-binding RNA aptamers via in vitro selection. In addition, bluensomycin, a streptomycin analogue that does not inhibit splicing, was used in a counter-selection to obtain RNAs that bind streptomycin with high affinity and specificity. Although an RNA from the normal selection (motif 2) bound both antibiotics, an RNA from the counter-selection (motif 1) discriminated between streptomycin and bluensomycin by four orders of magnitude. The binding site of streptomycin on the RNAs was determined via chemical probing with dimethylsulfate and kethoxal. The minimal size required for drug binding was a 46- and a 41-mer RNA for motifs 1 and 2, respectively. Using Pb2+ cleavage in the presence and absence of streptomycin, a conformational change spanning the entire mapped sequence length of motif 1 was observed only when both streptomycin and Mg2+ were present. Both RNAs require Mg2+ for binding streptomycin.

Coordination compounds derived from the interaction of streptomycin and cobalt, nickel, copper, and calcium salts characterized by 13C NMR and spectroscopic studies. Structure and bonding properties of the streptidine fraction

The coordination compounds of streptomycin (St), Co2(St)Cl4.13H2O (2), Co2(St)(NO3)4.7H2O (3), Ni2(St)Cl4.14H2O (4), Ni2(St)(NO3)4.14H2O (5), Cu2(St)Cl4.6H2O (6), and Ca(St)Cl2.8H2O (7) have been synthesized by the reaction of streptomycin sulfate (1) with three equivalents of the corresponding inorganic salt. The compounds (2)-(7) were characterized by electronic spectroscopy (in the solid state and in solution) by conductivity measurements and by 13C NMR in solution. The reaction of streptomycin with CuCl2 in water hydrolyzed the molecule giving the copper complex of the streptidine fraction (Std), Cu(Std)Cl.H2O (8). This compound was characterized by the same techniques. Detailed x-ray diffraction and 13C NMR studies of streptidine sulfate (9) were carried out.