(Un)suitability of the use of pH buffers in biological, biochemical and environmental studies and their interaction with metal ions ��� a review

The use of buffers to maintain the pH within a desired range is a very common practice in chemical, biochemical and biological studies. Among them, zwitterionic N-substituted aminosulfonic acids, usually known as Good���s buffers, although widely used, can complex metals and interact with biological systems. The present work reviews, discusses and updates the metal complexation characteristics of thirty one commercially available buffers. In addition, their impact on biological systems is also presented. The influences of these buffers on the results obtained in biological, biochemical and environmental studies, with special focus on their interaction with metal ions, are highlighted and critically reviewed. Using chemical speciation simulations, based on the current knowledge of the metal���buffer stability constants, a proposal of the most adequate buffer to employ for a given metal ion is presented.

New ionic liquids and salts derived from ��-Lactam antibiotics

In recent years ionic liquids (ILs) have been increasing the popularity and the number of applications. Ionic liquids were used mainly as solvent in organic synthesis, but in recent years they are also used in analytical chemistry, separation chemistry and material science. Additional to significant developments in their chemical properties and applications, ionic liquids are now bringing unexpected opportunities at the interface of chemistry with the life sciences. Ionic liquids (ILs) are currently defined as salts that are composed solely of cations and anions which melt below 100��C. Our goal in this work is to explore the dual activity of the ionic liquids, due to the presence of two different ions, an anion with bacterial activity as ��-lactam antibiotics and different kinds of cations. In this work the anions of ILs and salts were derived from three different antibiotics: ampicillin, penicillin and amoxicillin. The cations were derived from substituted ammonium, phosphonium pyridinium and methylimidazolium salts, such as: tetraethyl ammonium, trihexiltetradecilphosphonium, cetylpyridinium, choline (an essential nutrient), 1-ethyl-3-methylimidazolium, and 1-ethanol-3-methyl imidazolium structures. Commercial ammonium and phosponium halogen salts were first transformed into hydroxides on ionic exchange column (Amberlite IRA-400) in methanol. The prepared hydroxides were then neutralized with ��-lactam antibiotics. After crystallization we obtained pure ILs and salts containing ��-lactam antibiotics. This work presents a novel method for preparation of new salts of antibiotics with low melting point and their chemistry and microbiological characterization.

Preparation and characterization of beta-lactam antibiotic as Ionic liquids and salts

With the increase of bacterial resistance a large number of therapeutic strategies have been used to fight different kind of infections. In recent years ionic liquids (ILs) have been increasing the popularity and the number of applications. First ionic liquids were used mainly as solvent in organic synthesis, but now they are used in analytical chemistry, separation chemistry and material science among others. Additional to significant developments in their chemical properties and applications, ionic liquids are now bringing unexpected opportunities at the interface of chemistry with the life sciences Ionic liquids (ILs) are currently defined as salts that are composed solely of cations and anions which melt below 100��C. Our goal in this work is to explore the dual activity of the ionic liquids, due to the presence of two different ions, an ion with bacterial activity as a beta-lactam antibiotic and different kinds of cations. In this work the anions of ILs and salts were derived from three different antibiotics: ampicillin, penicillin and amoxicillin. The cations were derived from substituted ammonium, phosphonium pyridinium and methylimidazolium salts, such as: tetraethyl ammonium, trihexiltetradecilphosphonium, cetylpyridinium, choline (an essential nutrient), 1-ethyl-3-methylimidazolium, and 1-ethanol-3-methyl imidazolium structures. Commercial ammonium and phosponium halogen salts were first transformed into hydroxides. on ionic exchange column (Amberlite IRA-400) in methanol. The prepared hydroxides were then neutralized with beta-lactam antibiotics. After crystallization we obtained pure ILs and salts containing beta-lactam antibiotics. This work presents a novel method for preparation of new salts of antibiotics with low melting point and their characterization.

Development and biological evaluation of API-ILs based on anti-bacterial and anti-fungal drugs

In recent years Ionic Liquids (ILs) are being applied in life sciences. ILs are being produce with active pharmaceutical drugs (API) as they can reduce polymorphism and drug solubility problems [1] Also ILs are being applied as a drug delivery device in innovative therapies What is appealing in ILs is the ILs building up platform, the counter-ion can be carefully chosen in order to avoid undesirable side effects or to give innovative therapies in which two active ions are paired. This work shows ILs based on ampicillin (an anti-bacterial agent) and ILs based on Amphotericin B. Also we show studies that indicate that ILs based on Ampicillin could reverse resistance in some bacteria. The ILs produced in this work were synthetized by the neutralization method described in Ferraz et. al. [2] Ampicillin anion was combined with the following organic cations 1-ethyl-3-methylimidazolium, [EMIM]; 1-hydroxy-ethyl-3-methylimidazolium, [C2OHMIM]; choline, [cholin]; tetraethylammonium, [TEA]; cetylpyridinium, [C16pyr] and trihexyltetradecylphosphonium, [P6,6,6,14]. Amphotericin B was combined with [C16pyr], [cholin] and 1-metohyethyl-3-methylimidazolium, [C3OMIM]. The ILs-APIs based on ampicillin[2] were tested against sensitive Gram-negative bacteria Escherichia coli ATCC 25922 and Klebsiella pneumonia (clinical isolated), as well as on Gram positive Staphylococcus Aureus ATCC 25923, Staphylococcus epidermidis and Enterococcus faecalis. The arising resistance developed by bacteria to antibiotics is a serious public health threat and needs new and urgent measures. We study the bacterial activity of these compounds against a panel of resistant bacteria (clinical isolated strains): E. coli CTX M9, E. coli TEM CTX M9, E. coli TEM1, E. coli CTX M2, E. coli AmpC Mox2. In this work we demonstrate that is possible to produce ILs from anti-bacterial and anti-fungal compounds. We show here that the new ILs can reverse the bacteria resistance. With the careful choice of the organic cation, it is possible to create important biological and physic-chemical properties. This work also shows that the ion-pair is fundamental in ampicillin mechanism of action.

Remo����o de metais usando casca de amendoim

Mestrado em Engenharia Qu��mica

Determina����o preliminar de par��metros construtivos de barreiras reactivas perme��veis com recurso a colunas para remedia����o de cr��mio com ferro zerovalente

Um dos principais problemas com que se deparam as sociedades actuais, e que �� consequ��ncia da sua forma de se organizar prende-se com a mudan��a das caracter��sticas originais dos locais onde habitam e dos seus componentes como resultado das actividades humanas que transformam solos e ��guas em dep��sitos de res��duos. Entre as subst��ncias que s��o depositadas no meio f��sico, que requerem especial aten����o, encontra-se o grupo dos metais pesados, uma vez que s��o considerados como perigosos pela sua toxicidade e potencial cancer��geno quando em contacto com popula����es ou ecossistemas. Destes metais, o cr��mio �� um dos metais que requer especial aten����o devido a sua relativa abund��ncia como contaminante, e �� periculosidade dos seus i��es, em especial o Cr6+. Este trabalho pretende contribuir para o conhecimento dos fen��menos geoambientais associados �� remedia����o de ��guas contaminadas com Cr6+ recorrendo ao ferro monovalente de forma a estabelecer par��metros de aplicabilidade atrav��s de estudos laboratoriais baseados em ensaios em colunas.

Voltammetric immunosensor for the diagnosis of celiac disease based on the quantification of anti-gliadin antibodies

Antibodies against gliadin are used to detect celiac disease (CD) in patients. An electrochemical immunosensor for the voltammetric detection of human anti-gliadin antibodies (AGA) IgA and AGA IgG in real serum samples is proposed. The transducer surface consists of screen-printed carbon electrodes modified with a carbon nanotube/gold nanoparticle hybrid system, which provides a very useful surface for the amplification of the immunological interactions. The immunosensing strategy is based on the immobilization of gliadin, the antigen for the autoantibodies of interest, onto the nanostructured surface. The antigen���antibody interaction is recorded using alkaline phosphatase labeled anti-human antibodies and a mixture of 3-indoxyl phosphate with silver ions (3-IP/Ag+) was used as the substrate. The analytical signal is based on the anodic redissolution of the enzymatically generated silver by cyclic voltammetry. The electrochemical behavior of this immunosensor was carefully evaluated assessing aspects as sensitivity, non-specific binding and matrix effects, and repeatability and reproducibility. The results were supported with a commercial ELISA test.

Electrochemical immunosensor for multiplexed detection of food-borne pathogens using nanocrystal bioconjugates and MWCNT screen-printed electrode

Bacterial food poisoning is an ever-present threat that can be prevented with proper care and handling of food products. A disposable electrochemical immunosensor for the simultaneous measurements of common food pathogenic bacteria namely Escherichia coli O157:H7 (E. coli), campylobacter and salmonella were developed. The immunosensor was fabricated by immobilizing the mixture of anti-E. coli, anticampylobacter and anti-salmonella antibodies with a ratio of 1:1:1 on the surface of the multiwall carbon nanotube-polyallylamine modified screen printed electrode (MWCNT-PAH/SPE). Bacteria suspension became attached to the immobilized antibodies when the immunosensor was incubated in liquid samples. The sandwich immunoassay was performed with three antibodies conjugated with specific nanocrystal ( -E. coli-CdS, -campylobacter-PbS and -salmonella-CuS) which has releasable metal ions for electrochemical measurements. The square wave anodic stripping voltammetry (SWASV) was employed to measure released metal ions from bound antibody nanocrystal conjugates. The calibration curves for three selected bacteria were found in the range of 1 �� 103 ��� 5 �� 105 cells mL���1 with the limit of detection (LOD) 400 cells mL���1 for salmonella, 400 cells mL���1 for campylobacter and 800 cells mL���1 for E. coli. The precision and sensitivity of this method show the feasibility of multiplexed determination of bacteria in milk samples.

Layer-by-layer immobilization of carbon dots fluorescent nanomaterials on single optical fiber

We report within this paper the development of a fiber-optic based sensor for Hg(II) ions. Fluorescent carbon nanoparticles were synthesized by laser ablation and functionalized with PEG200 and N-acetyl-l-cysteine so they can be anionic in nature. This characteristic facilitated their deposition by the layer-by-layer assembly method into thin alternating films along with a cationic polyelectrolyte, poly(ethyleneimine). Such films could be immobilized onto the tip of a glass optical fiber, allowing the construction of an optical fluorescence sensor. When immobilized on the fiber-optic tip, the resultant sensor was capable of selectively detecting sub-micromolar concentrations of Hg(II) with an increased sensitivity compared to carbon dot solutions. The fluorescence of the carbon dots was quenched by up to 44% by Hg(II) ions and interference from other metal ions was minimal.

Mixed extractant systems for metal recovery

Hoje em dia, a preven����o dos res��duos de metais �� uma quest��o muito importante para um grande n��mero de empresas, pois necessitam optimizar o seu sistema de tratamento de ��guas residuais a fim de alcan��arem os limites legais dos teores em i��es met��licos e poderem efectuar a descarga das ��guas residuais no dom��nio h��drico p��blico. Devido a esta problem��tica foram efectuados estudos inovadores relacionados com a remo����o de i��es met��licos de ��guas residuais, verificando-se que as tecnologias de membrana oferecem uma s��rie de vantagens para o efeito. Uma dessas tecnologias, referida como Membrana L��quida de Suporte (SLM), �� baseada num mecanismo de extrac����o. A membrana hidrof��bica, impregnada com uma solu����o extractora, funciona como barreira entre a ��gua residual e uma solu����o, geralmente ��cida. A diferen��a de pH entre a ��gua residual e a solu����o actua como for��a motriz para o transporte de i��es met��licos da ��gua residual para a referida solu����o. Poder�� ocorrer um problema de falta de estabilidade, resultante da poss��vel fuga da solu����o extractora para fora dos poros das membranas. Estudos anteriores mostraram que os ��cidos alquilfosf��ricos ou ��cidos fosf��nicos, como os reagentes D2EHPA e CYANEX e hidroxioximas como o LIX 860-I podem ser muito ��teis para a extra����o de i��es met��licos como ferro, cobre, n��quel, zinco e outros. A cl��ssica extrac����o l��quido-l��quido tamb��m tem mostrado que a mistura de diferentes extractores pode ter um efeito sinerg��tico. No entanto, n��o �� claro que haja um efeito ��ptimo da raz��o de extractor ou que tipo de complexo �� formado durante o processo de extrac����o. O objectivo deste projecto �� investigar este comportamento sinerg��tico e as complexas forma����es por meio de um m��todo espectrofotom��trico, o ���Job���s method��� e ���Mole-ratio method���. Estes m��todos s��o utilizados para estimar a estequiometria dos v��rios complexos entre dois solutos, a partir da varia����o de absorv��ncia dos complexos quando comparado com a absorv��ncia do soluto. Com este projecto, o Job���s method e mole-ratio method ser��o aplicados a um sistema de tr��s componentes, para conseguir mais informa����es sobre a complexa����o de n��quel (II) e a fim de determinar a raz��o extractor: metal dos complexos formados durante a aplica����o de mistura de extractores D2EHPA e LIX 860-I. Segundo Job���s method a elavada absorv��ncia situa-se na regi��o de 0,015-0,040 M de LIX 860-I e uma baixa concentra����o de D2EHPA. Quando as diferentes experi��ncias s��o encontradas num conjunto experimental foram avaliadas de acordo com o m��todo de trabalho, o valor m��ximo do gr��fico foi encontrado para uma baixa fra����o molar do i��o met��lico e uma maior concentra����o de D2EHPA. Esta mudan��a foi encontrado de 0,50 at�� 0,30, que poderia apontar para a dire����o da forma����o de diferentes complexos. Para o Mole-Ratio method, a estequiometria dos complexos metal pode ser determinada a partir do ponto de intersec����o das linhas tangente do gr��fico da absorb��ncia versus a concentra����o do ligante. Em todos os casos, o m��ximo foi obtido em torno de uma concentra����o total de 0,010 M. Quando D2EHPA foi aplicado sozinho, absorv��ncias muito baixos foram obtidas.

New biomimetic sensors for the determination of tetracycline in biological samples: batch and flow mode operations

New potentiometric membrane sensors with cylindrical configuration for tetracycline (TC) are described based on the use of a newly designed molecularly imprinted polymer (MIP) material consisting of 2-vinylpyridine as a functional monomer in a plasticized PVC membrane. The sensor exhibited significantly enhanced response towards TC over the concentration range 1.59 10 5���1.0 10 3 mol L 1 at pH 3���5 with a lower detection limit of 1.29 10 5 mol L 1. The response was near-Nernstian, with average slopes of 63.9 mV decade 1. The effect of lipophilic salts and various foreign common ions were tested and were found to be negligible. The possibility of applying the proposed sensor to TC determination in spiked biological fluid samples was demonstrated.

Removal of Cd(II), Zn(II) and Pb(II) from aqueous solutions by brown marine macro algae: kinetic modelling

Specific marine macro algae species abundant at the Portuguese coast (Laminaria hyperborea, Bifurcaria bifurcata, Sargassum muticum and Fucus spiralis) were shown to be effective for removing toxic metals (Cd(II), Zn(II) and Pb(II)) from aqueous solutions. The initial metal concentrations in solution were about 75���100 mg L���1. The observed biosorption capacities for cadmium, zinc and lead ions were in the ranges of 23.9���39.5, 18.6���32.0 and 32.3���50.4 mg g���1, respectively. Kinetic studies revealed that the metal uptake rate was rather fast, with 75% of the total amount occurring in the first 10 min for all algal species. Experimental data were well fitted by a pseudo-second order rate equation. The contribution of internal diffusion mechanism was significant only to the initial biosorption stage. Results indicate that all the studied macro algae species can provide an efficient and cost-effective technology for eliminating heavy metals from industrial effluents.

Multiplexed electrochemical immunosensor for detection of celiac disease serological markers

Celiac disease (CD) is a gluten-induced autoimmune enteropathy characterized by the presence of antibodies against gliadin (AGA) and anti-tissue transglutaminase (anti-tTG) antibodies. A disposable electrochemical dual immunosensor for the simultaneous detection of IgA and IgG type AGA and antitTG antibodies in real patient���s samples is presented. The proposed immunosensor is based on a dual screen-printed carbon electrode, with two working electrodes, nanostructured with a carbon���metal hybrid system that worked as the transducer surface. The immunosensing strategy consisted of the immobilization of gliadin and tTG (i.e. CD specific antigens) on the nanostructured electrode surface. The electrochemical detection of the human antibodies present in the assayed serum samples was carried out through the antigen���antibody interaction and recorded using alkaline phosphatase labelled anti-human antibodies and a mixture of 3-indoxyl phosphate with silver ions was used as the substrate. The analytical signal was based on the anodic redissolution of enzymatically generated silver by cyclic voltammetry. The results obtained were corroborated with commercial ELISA kits indicating that the developed sensor can be a good alternative to the traditional methods allowing a decentralization of the analyses towards a point-of-care strategy.

Alternative chelating agents: Evaluation of the ready biodegradability and complexation properties

The ready biodegradability of four chelating agents, N,N -(S,S)-bis[1-carboxy-2-(imidazol-4-yl)ethyl]ethylenediamine (BCIEE), N - ethylenedi-L-cysteine (EC), N,N -bis (4-imidazolymethyl)ethylenediamine (EMI) and 2,6-pyridine dicarboxylic acid (PDA), was tested according to the OECD guideline for testing of chemicals. PDA proved to be a readily biodegradable substance. However, none of the other three compounds were degraded during the 28 days of the test. Chemical simulations were performed for the four compounds in order to understand their ability to complex with some metal ions (Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb, Zn) and discuss possible applications of these chelating agents. Two different conditions were simulated: (i) in the presence of the chelating agent and one metal ion, and (ii) in the simultaneous presence of the chelating agent and all metal ions with an excess of Ca. For those compounds that were revealed not to be readily biodegradable (BCIEE, EC and EMI), applications were evaluated where this property was not fundamental or even not required. Chemical simulations pointed out that possible applications for these chelating agents are: food fortification, food process, fertilizers, biocides, soil remediation and treatment of metal poisoning. Additionally, chemical simulations also predicted that PDA is an efficient chelating agent for Ca incrustations removal, detergents and for pulp metal ions removal process.

Bioatividade de L��quidos I��nicos derivados do ��cido Valpr��ico em bact��rias Gram-negativa

Os L��quidos I��nicos (LIs) s��o sais org��nicos constitu��dos exclusivamente por i��es e possuem pontos de fus��o inferiores a 100��C. As suas propriedades ��nicas e o facto de ser poss��vel ajustar as suas propriedades f��sicas, qu��micas e biol��gicas, de acordo com o objetivo pretendido, tornam esta classe de compostos, um grande objeto de estudo de in��meros investigadores. Desde os in��cios da sua aplica����o at�� �� atualidade, a investiga����o nesta ��rea expandiu o seu raio de a����o, estando j�� descrito o seu potencial como agentes antimicrobianos e, mais recentemente, como compostos farmac��uticos ativos. Atualmente muitas das suas aplica����es s��o baseadas nas suas propriedades biol��gicas. Esta Tese teve como objetivo avaliar a influ��ncia que os LIs podem exercer a n��vel do crescimento bacteriano e estudar alternativas de combater a resist��ncia bacteriana. Todos os LIs utilizados neste trabalho tinham como ani��o o ��cido valpr��ico, sendo utilizados cati��es org��nicos de am��nio e de imidaz��lio. Foram utilizadas 4 bact��rias e avaliou-se a atividade biol��gica e a respetiva taxa de crescimento. O estudo da sua atividade biol��gica foi feito atrav��s da determina����o da Concentra����o M��nima Inibit��ria (CMI) e a an��lise das suas curvas de crescimentos na presen��a e aus��ncia de composto. Com este trabalho foi poss��vel verificar que dentro dos compostos em estudo, LIs derivados do valproato, o Valproato com o cetilperid��nio [valp] [cetylpir] foi o que influenciou o crescimento de todas as bact��rias estudadas. Este estudo demonstrou o potencial antibacteriano de alguns compostos, podendo desta forma vir a ser utilizados para fins farmac��uticos