Palladium Biosensor

Bioactive glasses incorporating less-common ions to improve biological and physical properties

Bioactive glasses (BGs) have been a focus of research for over five decades for several biomedical applications. Although their use in bone substitution and bone tissue regeneration has gained important attention, recent developments have also seen the expansion of BG applications to the field of soft tissue engineering. Hard and soft tissue repair therapies can benefit from the biological activity of metallic ions released from BGs. These metallic ions are incorporated in the BG network not only for their biological therapeutic effects but also in many cases for influencing the structure and processability of the glass and to impart extra functional properties. The "classical" elements in silicate BG compositions are silicon (Si), phosphorous (P), calcium (Ca), sodium (Na), and potassium (K). In addition, other well-recognized biologically active ions have been incorporated in BGs to provide osteogenic, angiogenic, anti-inflammatory, and antibacterial effects such as zinc (Zn), magnesium (Mg), silver (Ag), strontium (Sr), gallium (Ga), fluorine (F), iron (Fe), cobalt (Co), boron (B), lithium (Li), titanium (Ti), and copper (Cu). More recently, rare earth and other elements considered less common or, some of them, even "exotic" for biomedical applications, have found room as doping elements in BGs to enhance their biological and physical properties. For example, barium (Ba), bismuth (Bi), chlorine (Cl), chromium (Cr), dysprosium (Dy), europium (Eu), gadolinium (Gd), ytterbium (Yb), thulium (Tm), germanium (Ge), gold (Au), holmium (Ho), iodine (I), lanthanum (La), manganese (Mn), molybdenum (Mo), nickel (Ni), niobium (Nb), nitrogen (N), palladium (Pd), rubidium (Rb), samarium (Sm), selenium (Se), tantalum (Ta), tellurium (Te), terbium (Tb), erbium (Er), tin (Sn), tungsten (W), vanadium (V), yttrium (Y) as well as zirconium (Zr) have been included in BGs. These ions have been found to be particularly interesting for enhancing the biological performance of doped BGs in novel compositions for tissue repair (both hard and soft tissue) and for providing, in some cases, extra functionalities to the BG, for example fluorescence, luminescence, radiation shielding, anti-inflammatory, and antibacterial properties. This review summarizes the influence of incorporating such less-common elements in BGs with focus on tissue engineering applications, usually exploiting the bioactivity of the BG in combination with other functional properties imparted by the presence of the added elements.

Observation of Surface Ligands-Controlled Etching of Palladium Nanocrystals

Selective adsorption of ligands on nanocrystal surfaces can affect oxidative etching. Here, we report the etching of palladium nanocrystals imaged using liquid cell transmission electron microscopy. The adsorption of surface ligands (i.e., iron acetylacetonate and its derivatives) and their role as inhibitor molecules on the etching process were investigated. Our observations revealed that the etching was dominated by the interplay between palladium facets and ligands and that the etching exhibited different pathways at different concentrations of ligands. At a low concentration of iron acetylacetonate (0.1 mM), rapid etching primarily at {100} facets led to a concave structure. At a high concentration (1.0 mM), the etch rate was decreased owing to a protective film of iron acetylacetonate on the {100} facets and a round nanoparticle was achieved. Ab initio calculations showed that the differences in adsorption energy of inhibitor molecules on palladium facets were responsible for the etching behavior.

V-shaped bis-coumarin based fluorescent probe for detecting palladium in natural waters

A catalytic fluorescent probe based on V-shaped bis-coumarin has been designed and synthesized for detection of palladium (Pd). The detection mechanism of the probe is based on palladium-catalyzed Tsuji‒Trost reaction process and photoinduced electron transfer (PET), which can distinguish and detect palladium (0, +2/+4) in different valence states under different conditions. The fluorescence intensity of the probe enhances after adding the palladium in about 10 min at room temperature. The limit of detection (LOD) of the probe is as low as 40.0 nM (4.2 ng/g), and it has good selectivity and high sensitivity. Apart from that, it has been successfully applied to detection of palladium in environmental waters.

The Application of Curve Fitting on the Voltammograms of Various Isoforms of Metallothioneins-Metal Complexes

The translation of metallothioneins (MTs) is one of the defense strategies by which organisms protect themselves from metal-induced toxicity. MTs belong to a family of proteins comprising MT-1, MT-2, MT-3, and MT-4 classes, with multiple isoforms within each class. The main aim of this study was to determine the behavior of MT in dependence on various externally modelled environments, using electrochemistry. In our study, the mass distribution of MTs was characterized using MALDI-TOF. After that, adsorptive transfer stripping technique with differential pulse voltammetry was selected for optimization of electrochemical detection of MTs with regard to accumulation time and pH effects. Our results show that utilization of 0.5 M NaCl, pH 6.4, as the supporting electrolyte provides a highly complicated fingerprint, showing a number of non-resolved voltammograms. Hence, we further resolved the voltammograms exhibiting the broad and overlapping signals using curve fitting. The separated signals were assigned to the electrochemical responses of several MT complexes with zinc(II), cadmium(II), and copper(II), respectively. Our results show that electrochemistry could serve as a great tool for metalloproteomic applications to determine the ratio of metal ion bonds within the target protein structure, however, it provides highly complicated signals, which require further resolution using a proper statistical method, such as curve fitting.

A gold nanohole array based surface-enhanced Raman scattering biosensor for detection of silver(I) and mercury(II) in human saliva

A surface-enhanced Raman scattering (SERS) biosensor has been developed by incorporating a gold nanohole array with a SERS probe (a gold nanostar@Raman-reporter@silica sandwich structure) into a single detection platform via DNA hybridization, which circumvents the nanoparticle aggregation and the inefficient Raman scattering issues. Strong plasmonic coupling between the Au nanostar and the Au nanohole array results in a large enhancement of the electromagnetic field, leading to amplification of the SERS signal. The SERS sensor has been used to detect Ag(I) and Hg(II) ions in human saliva because both the metal ions could be released from dental amalgam fillings. The developed SERS sensor can be adapted as a general detection platform for non-invasive measurements of a wide range of analytes such as metal ions, small molecules, DNA and proteins in body fluids.

Fate of platinum metals in the environment

For many years now automotive exhaust catalysts have been used to reduce the significant amounts of harmful chemical substances generated by car engines, such as carbon monoxide, nitrogen oxides, and aromatic hydrocarbons. Although they considerably decrease environmental contamination with the above-mentioned compounds, it is known that catalysts contribute to the environmental load of platinum metals (essential components of catalysts), which are released with exhaust fumes. Contamination with platinum metals stems mainly from automotive exhaust converters, but other major sources also exist. Since platinum group elements (PGEs): platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and iridium (Ir) seem to spread in the environment and accumulate in living organisms, they may pose a threat to animals and humans. This paper discusses the modes and forms of PGE emission as well as their impact on the environment and living organisms.

Interaction of Heavy Metal Ions with Carbon and Iron Based Particles

Due to the rapid development of industry and associated production of toxic waste, especially heavy metals, there is a great interest in creating and upgrading new sorption materials to remove these pollutants from the environment. This study aims to determine the effectiveness of different carbon forms (graphene, expanded carbon, multi-wall nanotubes) and paramagnetic particles (Fe₂O₃) for adsorption of cadmium(II), lead(II), and copper(II) on its surface, with different interaction time from 1 min to 24 h. The main attention is paid to the detection of these metals using differential pulse voltammetry. Based on the obtained results, graphene and Fe₂O₃ are found to be good candidates for removal of heavy metals from the environment.

The effects on soil/water/plant/animal systems by platinum group elements

Emissions of toxic substances such as oxides of carbon, nitrogen, sulphur, and, in addition, aromatic hydrocarbons, aldehydes and heavy metals are the most serious problem of road traffic affecting landscape. Platinum group elements (PGE), which are the main component of the catalyst, are one of the main sources of heavy metals in the environment. Here, we review the way by which emissions and forms of the emitted PGE end up in the environment especially to the soil-water-plant-animal system. The major points discussed are the following: 1) the main sources of PGE emission are automobile exhaust catalysts; 2) hospitals, where platinum is widely used to treat malignant neoplasm, and urban waste water belonging to other important sources of PGE in the environment; 3) soil is one of the most important components of the environment that may be contaminated with platinum metals; 4) phytotoxicity of PGE depends on the following conditions: the concentration of metals in the soil, time of exposure, the chemical form of metal, the chemical composition of exposed soil and plant species; 5) animals are also endangered by the increasing concentration of PGE in the environment. Moreover, we pay our attention to thiol-based mechanisms of how an organism protects itself against platinum group elements.

Mammalian metallothioneins: properties and functions

Metallothioneins (MT) are a family of ubiquitous proteins, whose role is still discussed in numerous papers, but their affinity to some metal ions is undisputable. These cysteine-rich proteins are connected with antioxidant activity and protective effects on biomolecules against free radicals, especially reactive oxygen species. In this review, the connection between zinc(II) ions, reactive oxygen species, heavy metal ions and metallothioneins is demonstrated with respect to effect of these proteins on cell proliferation and a possible negative role in resistance to heavy metal-based and non-heavy metal-based drugs.

Bio-sensing of cadmium(II) ions using Staphylococcus aureus

Cadmium, as a hazardous pollutant commonly present in the living environment, represents an important risk to human health due to its undesirable effects (oxidative stress, changes in activities of many enzymes, interactions with biomolecules including DNA and RNA) and consequent potential risk, making its detection very important. New and unique technological and biotechnological approaches for solving this problems are intensely sought. In this study, we used the commonly occurring potential pathogenic microorganism Staphylococcus aureus for the determination of markers which could be used for sensing of cadmium(II) ions. We were focused on monitoring the effects of different cadmium(II) ion concentrations (0, 1.25, 2.5, 5, 10, 15, 25 and 50 μg mL(-1)) on the growth and energetic metabolism of Staphylococcus aureus. Highly significant changes have been detected in the metabolism of thiol compounds-specifically the protein metallothionein (0.79-26.82 mmol/mg of protein), the enzyme glutathione S-transferase (190-5,827 μmol/min/mg of protein), and sulfhydryl groups (9.6-274.3 μmol cysteine/mg of protein). The ratio of reduced and oxidized glutathione indicated marked oxidative stress. In addition, dramatic changes in urease activity, which is connected with resistance of bacteria, were determined. Further, the effects of cadmium(II) ions on the metabolic pathways of arginine, β-glucosidase, phosphatase, N-acetyl β-d-glucosamine, sucrose, trehalose, mannitol, maltose, lactose, fructose and total proteins were demonstrated. A metabolomic profile of Staphylococcus aureus under cadmium(II) ion treatment conditions was completed seeking data about the possibility of cadmium(II) ion accumulation in cells. The results demonstrate potential in the application of microorganisms as modern biosensor systems based on biological components.

An adsorptive transfer technique coupled with brdicka reaction to reveal the importance of metallothionein in chemotherapy with platinum based cytostatics

The drugs based on platinum metals represent one of the oldest, but also one of the most effective groups of chemotherapeutic agents. Thanks to many clinical studies it is known that resistance of tumor cells to drugs is a frequent cause of chemotherapy failure. With regard to platinum based drugs, multidrug resistance can also be connected with increased expression of low-molecular weight protein metallothionein (MT). This study aimed at investigating the interactions of MT with cisplatin or carboplatin, using the adsorptive transfer technique coupled with differential pulse voltammetry Brdicka reaction (AdTS DPV Brdicka reaction), and a comparison of in vitro results with results obtained in vivo. The results obtained from the in vitro study show a strong affinity between platinum based drugs and MT. Further, we analyzed extracts of neuroblastoma cell lines treated with cisplatin or carboplatin. It is clear that neuroblastoma UKF-NB-4 cisplatin-resistant and cisplatin-sensitive cell lines unlikely respond to the presence of the platinum-based cytostatics cisplatin and carboplatin. Finally, we determined the level of MT in samples from rabbits treated with carboplatin and patients with retinoblastoma treated with the same drug.

Electrochemical microsensors for the detection of cadmium(II) and lead(II) ions in plants

Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for easy-to-use and sensitive determination of cadmium(II) and lead(II) ions. The lowest detection limits (hundreds of pM) for both metals was achieved by using of the standard potentiostat, followed by the miniaturized potentiostat (tens of nM) and the homemade instrument (hundreds of nM). Nevertheless, all potentiostats were sensitive enough to evaluate contamination of the environment, because the environmental limits for both metals are higher than detection limits of the instruments. Further, we tested all used potentiostats and working electrodes on analysis of environmental samples (rainwater, flour and plant extract) with artificially added cadmium(II) and lead(II). Based on the similar results obtained for all potentiostats we choose a homemade instrument with a carbon tip working electrode for our subsequent environmental experiments, in which we analyzed maize and sunflower seedlings and rainwater obtained from various sites in the Czech Republic.

Protein-based electrochemical biosensor for detection of silver(I) ions

Silver(I) ions are extremely toxic to aquatic animals. Hence, monitoring of these ions in the environment is needed. The aim of the present study was to suggest a simple biosensor for silver(I) ions detection. The suggested biosensor is based on the modification of a hanging mercury drop electrode (HMDE) by the heavy metal binding protein metallothionein (MT) for silver(I) ions detection. Metallothionein accumulated for 120 s onto the HMDE surface. After rinsing the electrode, the biosensor (MT modified HMDE) was prepared prior to detection of silver(I) ions. The biosensor was immersed in a solution containing silver(I) ions. These ions were bound to the MT structure. Furthermore, the electrode was rinsed and transferred to a pure supporting electrolyte solution, in which no interference was present. Under these experimental conditions, other signals relating to heavy metals naturally occurring in MT were not detected. This phenomenon confirms the strong affinity of silver(I) ions for MT. The suggested biosensor responded well to higher silver(I) ion concentrations. The relative standard deviation for measurements of concentrations higher than 50 microM was approximately 2% (n = 8). In the case of concentrations lower than 10 microM, the relative standard deviation increased to 10% (n = 8). The detection limit (3 signal/noise) for silver(I) ions was estimated as 500 nM.

Sunflower Plants as Bioindicators of Environmental Pollution with Lead (II) Ions

In this study, the influence of lead (II) ions on sunflower growth and biochemistry was investigated from various points of view. Sunflower plants were treated with 0, 10, 50, 100 and/or 500 μM Pb-EDTA for eight days. We observed alterations in growth in all experimental groups compared with non-treated control plants. Further we determined total content of proteins by a Bradford protein assay. By the eighth day of the experiment, total protein contents in all treated plants were much lower compared to control. Particularly noticeable was the loss of approx. 8 μg/mL or 15 μg/mL in shoots or roots of plants treated with 100 mM Pb-EDTA. We also focused our attention on the activity of alanine transaminase (ALT), aspartate transaminase (AST) and urease. Activity of the enzymes increased with increasing length of the treatment and applied concentration of lead (II) ions. This increase corresponds well with a higher metabolic activity of treated plants. Contents of cysteine, reduced glutathione (GSH), oxidized glutathione (GSSG) and phytochelatin 2 (PC2) were determined by high performance liquid chromatography with electrochemical detection. Cysteine content declined in roots of plants with the increasing time of treatment of plants with Pb-EDTA and the concentration of toxic substance. Moreover, we observed ten times higher content of cysteine in roots in comparison with shoots. The observed reduction of cysteine content probably relates with its utilization for biosynthesis of GSH and phytochelatins, because the content of GSH and PC2 was similar in roots and shoots and increased with increased treatment time and concentration of Pb-EDTA. Moreover, we observed oxidative stress caused by Pb-EDTA in roots where the GSSG/GSH ratio was about 0.66. In shoots, the oxidative stress was less distinctive, with a GSSG/GSH ratio 0.14. We also estimated the rate of phytochelatin biosynthesis from the slope of linear equations plotted with data measured in the particular experimental group. The highest rate was detected in roots treated with 100 μM of Pb-EDTA. To determine heavy metal ions many analytical instruments can be used, however, most of them are only able to quantify total content of the metals. This problem can be overcome using laser induced breakdown spectroscopy, because it is able to provide a high spatial-distribution of metal ions in different types of materials, including plant tissues. Data obtained were used to assemble 3D maps of Pb and Mg distribution. Distribution of these elements is concentrated around main vascular bundle of leaf, which means around midrib.

Study of Interactions between Metallothionein and Cisplatin by using Differential Pulse Voltammetry Brdickás reaction and Quartz Crystal Microbalance

Treatment strategies for tumour diseases are progressively focusing on personalization of medicine. However, this focus requires methods revealing the early general biological mechanisms, including the formation anti-cancer drugs’ resistance. The low molecular mass protein metallothionein is thought to be the crucial for the formation of resistance in tumour treatment based on the platinum-cytostatics. The interactions between metallothionein (MT) and cisplatin were determined by the adsorptive transfer stripping technique coupled with the differential pulse votlammetry Brdickás reaction. The signals related to the MT-cisplatin complex appeared at −0.9 V. The formation of this complex depended on the time of interaction between cisplatin and MT. The complex formation was consequently confirmed by quartz crystal microbalance analyses. The formation of this complex was detectable even after a 20 s long interaction. Moreover, we detected presence of MT-cisplatin complex in the blood of male rats treated with this drug.

Amperometric Sensor for Detection of Chloride Ions

Chloride ion sensing is important in many fields such as clinical diagnosis, environmental monitoring and industrial applications. We have measured chloride ions at a carbon paste electrode (CPE) and at a CPE modified with solid AgNO₃, a solution of AgNO₃ and/or solid silver particles. Detection limits (3 S/N) for chloride ions were 100 μM, 100 μM and 10 μM for solid AgNO₃, solution of AgNO₃ and/or solid silver particles, respectively. The CPE modified with silver particles is the most sensitive to the presence chloride ions. After that we approached to the miniaturization of the whole electrochemical instrument. Measurements were carried out on miniaturized instrument consisting of a potentiostat with dimensions 35 × 166 × 125 mm, screen printed electrodes, a peristaltic pump and a PC with control software. Under the most suitable experimental conditions (Britton-Robinson buffer, pH 1.8 and working electrode potential 550 mV) we estimated the limit of detection (3 S/N) as 500 nM.

An Electrochemical Detection of Metallothioneins at the Zeptomole Level in Nanolitre Volumes

An Electrochemical Detection of Metallothioneins at the Zeptomole Level in Nanolitre VolumesWe report on improvement of the adsorptive transfer stripping technique (AdTS) coupled with the differential pulse voltammetry Brdicka reaction to determine a thiol-protein. The current technique has been unable to generate reproducible results when analyzing very low sample volumes (nanolitres). This obstacle can be overcome technically by modifying the current transfer technique including cooling step of the adsorbed analyte. We tested the technique on determination of a promising tumour disease marker protein called metallothionein (MT). The detection limit (3 S/N) of MT was evaluated as 500 zeptomoles per 500 nL (1 pM) and the quantification limit (10 S/N) as 1,500 zeptomoles per 500 nL (3 pM). Further, the improved AdTS technique was utilized to analyze blood serum samples from patients with breast cancer. Based on the results obtained it can be concluded that the improved technique can be used to detect a thiolprotein in very low sample volumes and can also prevent interferences during the washing and transferring step.

Lactoferrin Isolation Using Monolithic Column Coupled with Spectrometric or Micro-Amperometric Detector

Lactoferrin is a multifunctional protein with antimicrobial activity and others tohealth beneficial properties. The main aim of this work was to propose easy to usetechnique for lactoferrin isolation from cow colostrum samples. Primarily we utilizedsodium dodecyl sulphate - polyacrylamide gel electrophoresis for isolation of lactoferrinfrom the real samples. Moreover we tested automated microfluidic Experionelectrophoresis system to isolate lactoferrin from the collostrum sample. The welldeveloped signal of lactoferrin was determined with detection limit (3 S/N) of 20 ng/ml. Inspite of the fact that Experion is faster than SDS-PAGE both separation techniques cannotbe used in routine analysis. Therefore we have tested third separation technique, ionexchange chromatography, using monolithic column coupled with UV-VIS detector (LCUV-VIS). We optimized wave length (280 nm), ionic strength of the elution solution (1.5M NaCl) and flow rate of the retention and elution solutions (0.25 ml/min and 0.75 ml/min.respectively). Under the optimal conditions the detection limit was estimated as 0.1 μg/mlof lactoferrin measured. Using LC-UV-VIS we determined that lactoferrin concentrationvaried from 0.5 g/l to 1.1 g/l in cow colostrums collected in the certain time interval up to 72 hours after birth. Further we focused on miniaturization of detection device. We testedamperometric detection at carbon electrode. The results encouraged us to attempt tominiaturise whole detection system and to test it on analysis of real samples of humanfaeces, because lactoferrin level in faeces is closely associated with the inflammations ofintestine mucous membrane. For the purpose of miniaturization we employed thetechnology of printed electrodes. The detection limit of lactoferrin was estimated as 10μg/ml measured by the screen-printed electrodes fabricated by us. The fabricatedelectrodes were compared with commercially available ones. It follows from the obtainedresults that the responses measured by commercial electrodes are app. ten times highercompared with those measured by the electrodes fabricated by us. This phenomenonrelates with smaller working electrode surface area of the electrodes fabricated by us(about 50 %) compared to the commercial ones. The screen-printed electrodes fabricatedby us were utilized for determination of lactoferrin faeces. Regarding to fact that sample offaeces was obtained from young and healthy man the amount of lactoferrin in sample wasunder the limit of detection of this method.

Shapes of Differential Pulse Voltammograms and Level of Metallothionein at Different Animal Species

Metallothioneins play a key role in maintaining homeostasis of essential metals and in protecting of cells against metal toxicity as well as oxidative damaging. Excepting humans, blood levels of metallothionein have not yet been reported from any animal species. Blood plasma samples of 9 animal species were analysed by the adsorptive transfer stripping technique to obtain species specific voltammograms. Quite distinct records were obtained from the Takin (Budorcas taxicolor), while other interesting records were observed in samples from the European Bison (Bison bonasus bonasus) and the Red-eared Slider (Trachemys scripta elegans). To quantify metallothionein the catalytic peak Cat2 was used, well developed in the Domestic Fowl (Gallus gallus f. domestica) and showing a very low signal in the Red Deer (Cervus elaphus). The highest levels of metallothionein reaching over 20 µM were found in the Domestic Fowl. High levels of MT were also found in the Bearded Dragon (Pogona vitticeps) and the Grey Wolf (Canis lupus lupus). The lowest values of about 1-3 µM were determined in the Red-eared Slider, Takin and Red Deer. Employing a simple electrochemical detection it was possible to examine variation in blood metallothionein in different species of vertebrates.