Aqueous Phosphate Buffer Solution Research Articles

Insights into the surface and redox properties of single-walled carbon nanotube—cobalt(II) tetra-aminophthalocyanine self-assembled on gold electrode

This paper describes for the first time the electrochemical properties of redox-active self-assembled films of single-walled carbon nanotubes (SWCNTs) coordinated to cobalt(II)tetra-aminophthalocyanine (CoTAPc) by sequential self-assembly onto a preformed aminoethanethiol (AET) self-assembled monolayer (SAM) on a gold electrode. Both redox-active SAMs (Au-AET-SWCNT and Au-AET-SWCNT-CoTAPc) exhibited reversible electrochemistry in aqueous (phosphate buffer) solution. X-ray photoelectron spectroscopy (XPS) confirmed the appearance on the gold surface of the various elements found on the SAMs. Atomic force microscopy (AFM) images prove, corroborating the estimated electrochemical surface concentrations, that these SAMs lie normal to the gold surface. Electrochemical impedance spectroscopy (EIS) analyses in the presence of [Fe(CN) 6] 3−/4− as a redox probe revealed that the Au-AET-SWCNT-CoTAPc showed much lower (∼10 times) electron-transfer resistance ( R et) and much higher (∼10 times) apparent electron-transfer rate constant ( k app) compared to the Au-AET-SWCNT SAM. Interestingly, a preliminary electrocatalytic investigation showed that both SAMs exhibit comparable electrocatalytic responses towards the detection of dopamine in pH 7.4 phosphate buffer solutions (PBS). The electrochemical studies (cyclic voltammetry (CV) and EIS) prove that SWCNT greatly improves the electronic communication between CoTAPc and the Au electrode surface.

Electrochemical membrane reactor for the reduction of carbondioxide to formate

An electrochemical reactor with anode and cathode chambers separated by a composite perfluoro polymer cation exchange membrane was designed, fabricated and used for the reduction of dissolved carbon dioxide under ambient conditions to formate. The flow reactor enhanced the mass transfer of carbon dioxide compared to the batch reactor and maximum current efficiency of 93% for formate formation was obtained. A formate concentration of 1.5 × 10−2 mol dm−3 was obtained. Experiments were conducted using two different perfluoro polymer membranes – Nafion 961 and Nafion 430. Optimum values of flow rate and current density were evaluated for the energy efficient formation of formate in aqueous phosphate buffer solutions.

The effects of conductivity and electrochemical doping on the reduction of methemoglobin immobilized in nanoparticulate TiO 2 films

Methemoglobin (bovine) is immobilized from aqueous phosphate buffer (pH 5.5) solution into thin porous TiO 2 (anatase) films at ITO electrode surfaces. Films of TiO 2 are produced in a deposition process employing 40 nm diameter TiO 2 nanoparticles suspended in dry methanol followed by calcination. The pore size in these films is sufficient for methemoglobin (ca. 6 nm diameter) to diffuse into the porous structure (over several hours) and to remain immobilized in electrochemically active form. The electrochemical reduction of methemoglobin immobilized in TiO 2 and immersed in aqueous phosphate buffer at pH 5.5 is observed in two steps with (i) a small quasi-reversible voltammetric response at − 0.16 V vs. SCE (Process 1) and (ii) an irreversible reduction peak at ca. − 0.5 V vs. SCE (Process 2). The irreversible response is recovered only after slow chemical re-oxidation of hemoglobin to methemoglobin. At sufficiently negative applied potential “electrochemical doping” of the TiO 2 host is observed to lead to a considerably enhanced reduction Process 1. TiO 2 can be temporarily switched from a non-conducting (irreversible electron transfer) into a conducting (reversible electron transfer) state.

Antibody purification using porous metal–chelated monolithic columns

AbstractA novel monolithic material was developed to obtain efficient and cost‐effective purification of IgG from human plasma. The porous monolith was obtained by bulk polymerization in a glass tube of 2‐hydroxyethyl methacrylate (HEMA) and N‐methacryloyl‐(L)‐histidine methyl ester (MAH). The poly(HEMA‐MAH) monolith had a specific surface area of 214.6 m2/g and was characterized by swelling studies, porosity measurement, FTIR, scanning electron microscopy, and elemental analysis. Then the monolith was loaded with Cu2+ ions to form the metal chelate. Poly(HEMA‐MAH) monolith with a swelling ratio of 74% and containing 20.9 μmol MAH/g was used in the adsorption/desorption of IgG from aqueous solutions and human plasma. The maximum adsorption of IgG from an aqueous solution in phosphate buffer was 10.8 mg/g at pH 7.0. Higher adsorption was obtained from human plasma (up to 104.2 mg/g), with a purity of 94.1%. It was observed that IgG could be repeatedly adsorbed and desorbed with the poly(HEMA‐MAH) monolith without significant loss of adsorption capacity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 395–404, 2006

Selective Binding Thermodynamics of Bile Acids by Oligo (ethylenediamino)-β-Cyclodextrins and Their Copper (II) Complexes

Complex stability constants (KS), standard molar enthalpy changes (DH) and entropy changes (TDS) for the inclusion complexation of native b-cyclodextrin (b-CD) (1) and some modified b-CDs, i.e., mono(6-ethylenediamino-6-deoxy)-b-CD (3), mono[6-diethylenetriamino-6-deoxy]-b-CD (4) and their corresponding copper complexes 5 and 6, with four representative bile acid guests, i.e., cholate (CA), deoxycholate (DCA), glycocholate (GCA) and taurocholate (TCA), were determined at 25 C in aqueous phosphate buffer solution (pH 7.20) by means of isothermal titration microcalorimetry (ITC). The stoichiometry of resulting inclusion complexes between CDs and bile acids was demonstrated by UV and conductivity as well as ITC experiments, showing 1:1 binding model upon all inclusion complexation except for metal-mediated dimer 5. The complex stability constants for modified b-CD 2-4 are dramatically magnified with the extended length of amino tether. As compared with 3 and 4, copper(II) complexes 5 and 6 significantly enhance not only binding ability but also molecular selectivity toward bile guest molecule CA through multipoint recognition, but decreased complexes stability toward TCA could be attributed to the decreased hydrophobic microenvironment of CDs cavity due to the introduction of copper(II) coordination center. Thermodynamically, the resulting complexes between hosts and bile guests are driven absolutely by enthalpy, accompanied by entropy gain or loss. Using the present data and those previously reported for mono(6-amino-6-deoxy)-b-CD (2), thermodynamic behavior and enhanced molecular selectivity could be discussed from the viewpoint of hydrophobic interactions, electrostatic cooperation and van der Waals between the hosts and guests.

Design and characterization of a lactate biosensor based on immobilized lactate oxidase onto gold surfaces

The design and characterization of a lactate biosensor and its application to the determination of this analyte in wine and beer are described. The biosensor is developed through the immobilization of lactate oxidase (LOx) using two different strategies including direct adsorption and covalent binding. The characterization of the resulting lactate oxidase monolayers was performed in aqueous phosphate buffer solutions using atomic force microscopy (AFM) and quartz crystal microbalance (QCM) techniques. In presence of lactate and using hydroxymethylferrocene as a redox mediator, biosensors obtained by either direct adsorption or by covalent binding exhibit a clear electrocatalytic activity, and lactate could be determined amperometrically at 300 mV versus SSCE. Results obtained under these conditions give a linear current response versus lactate concentration up to 0.3 mM, with a detection limit of 10 μM of lactate and a sensitivity of 0.77 ± 0.08 μA mM −1. Finally, biosensors were applied to the determination of lactate in wine and beer. The results obtained are in good agreement with those obtained by a well-established enzymatic-spectrophotometric assay kit.

Porous poly(hydroxyethyl methacrylate) based monolith as a new adsorbent for affinity chromatography

A new approach was developed to obtain an efficient and cost effective purification of IgG from human plasma. Porous monoliths were obtained by the bulk polymerization of 2-hydroxyethyl methacrylate (HEMA) and N-methacryloyl-( l)-histidinemethylester (MAH) conducted in a glass tube. Poly(HEMA-MAH) monolith had a specific surface area of 145.8 m 2/g. Poly(HEMA-MAH) monolith was characterized by swelling studies, FTIR, scanning electron microscopy and elemental analysis. Poly(HEMA-MAH) monolith with a swelling ratio of 68%, and containing 47.8 μmol MAH/g were used in the adsorption/desorption of IgG from aqueous solutions and human plasma. The maximum amount of IgG adsorption from aqueous solution in phosphate buffer was 9.8 mg/g at pH 7.4. A higher adsorption value was obtained from human plasma (up to 96.5 mg/g) with a purity of 95.3%. It was observed that IgG could be repeatedly adsorbed and desorbed with Poly(HEMA-MAH) monolith without significant loss in the adsorption capacity.

Nitric Oxide Detection with Glassy Carbon Electrodes Coated with Charge-different Polymer Films

Trace amounts of nitric oxide (NO) have been determined in aqueous phosphate buffersolutions (pH=7.4) by using a glassy carbon electrode coated with three charge-different polymerfilms. The glassy carbon electrode was coated first with negatively charged Nafion film containingtetrakis(pentafluorophenylporphyrin) iron(III) chloride (Fe(III)TPFPP) as the NO oxidation catalyst,and then with positively charged poly(acrylamide-co-diallyldimethylammonium chloride) (PADDA)and with neutral poly(dimethylsiloxane) (silicone) at the outermost layer. This polymer-coatedelectrode showed an excellent selectivity towards NO against possible concomitants in blood such asnitrite, ascorbic acid, uric acid, and dopamine. All current ratios between each concomitant and NOat the cyclic voltammogram was in 10-3 ~ 10-4. This type of electrode showed a detection limit of80 nM for NO. It was speculated from the electrochemical study in methanol that high-valent oxoiron(IV) of Fe(TPFPP) participated in the catalytic oxidation of NO.

Effect of AOT on enzymatic activity of the organic solvent resistant tyrosinase from Streptomyces sp. REN-21 in aqueous solutions and water-in-oil microemulsions

The effect of AOT (sodium-bis(2-ethylhexyl sulfosuccinate)) on enzymatic activity of the organic solvent resistant tyrosinase (OSRT) in aqueous phosphate buffer solutions and in water-in-oil microemulsions of the water/AOT/isooctane system has been investigated. In contrast to mushroom tyrosinase, AOT does not activate OSRT in aqueous solutions, altering its activity very little at concentrations lower than 2 mM. Increasing contents of AOT in isooctane reduce the observed initial reaction rates of oxidation of t-butylcatechol (tBC) and 4-methylcatechol (4-MC). Similarly to mushroom tyrosinase, the effect has been described using an equation based on preferential binding of the substrates by surfactant interface layers. The apparent Michaelis–Menten substrate binding constants increase linearly with AOT concentration (with slopes of 0.12 ± 0.02 and 0.051 ± 0.006 for tBC and 4-MC, respectively), and the effective enzyme turnover number in the microemulsions remains practically constant.

Molecular recognition thermodynamics and structural elucidation of interactions between steroids and bridged bis(beta-cyclodextrin)s.

A series of bridged bis(beta-cyclodextrin(CD))s (2-7) were synthesized, i.e., bridged bis(beta-CD)s 2 and 3 bearing binaphthyl or biquinoline tethers and bridged bis(beta-CD)s 4-7 possessing dithiobis(benzoyl) tether, and their complex stability constants (KS), enthalpy (DeltaH degrees), and entropy changes (DeltaS degrees) for the 1:2 inclusion complexation with representative steroids, deoxycholate, cholate, glycocholate, and taurocholate, have been determined in an aqueous phosphate buffer solution of pH 7.20 at 298.15 K by means of titration microcalorimetry. The original conformations of bridged bis(beta-cyclodextrin)s were investigated by circular dichroism and 1H ROESY spectroscopy. Structures of the inclusion complexes between steroids and bridged bis(beta-CD)s in solution were elucidated by 2D NMR experiments, indicating that anionic groups of two steroid molecules penetrate, respectively, into the two hydrophobic CD cavities in one 6,6'-bridged bis(beta-CD) molecule from the secondary rim to give a 1:2 binding mode upon inclusion complexation. The results obtained from titration microcalorimetry and 2D NMR experiments jointly demonstrate that bridged bis(beta-CD)s 2, 3 and 5-7 tethered by protonated amino group possessing different substituted groups can enhance not only the molecular binding ability toward steroids by electrostatic interaction but also molecular selectivity. Thermodynamically, the resulting 1:2 bis(beta-CD)-steroid complexes are formed by an enthalpy-driven process, accompanied by smaller entropy loss. The increased complex stability mainly results from enthalpy gain, accompanied by large conformational change and extensive desolvation effects for the 1:2 inclusion complexation between bis(beta-CD)s and steroids.

Poly(ethylene dimethacrylate-glycidyl methacrylate) Monolith as a Stationary Phase in Dye-Affinity Chromatography

Porous monolith was obtained by the bulk polymerization of ethylene dimethacrylate (EDMA) and glycidyl methacrylate (GMA) conducted in a glass tube. Poly(EDMA-GMA) monolith had a specific surface area of 98.7 m2/g. Poly(EDMA-GMA) monolith was characterized by swelling studies, FTIR, scanning electron microscopy, and elemental analysis. Poly(EDMA-GMA) monolith with a swelling ratio of 48%, and containing 45.7 μmol Cibacron Blue F3GA/g, were used in the adsorption/desorption of human serum albumin (HSA) from aqueous solutions and human plasma. The nonspecific adsorption of HSA was very low (0.8 mg/g). The maximum amount of HSA adsorption from aqueous solution in phosphate buffer was 22 mg/g at pH 5.0. Higher HSA adsorption value was obtained from human plasma (up to 53.2 mg/g) with a purity of 92%. Desorption of HSA from Cibacron Blue F3GA-attached poly(EDMA-GMA) monolith was obtained using 0.1 M Tris/HCl buffer containing 0.5 M NaCl. It was observed that HSA could be repeatedly adsorbed and desorbed with poly(EDMA-GMA) monolith without significant loss in the adsorption capacity.

Characteristics of polyaniline synthesized in phosphate buffer solution

Polyaniline (PAni) was synthesized from aqueous phosphate buffer solution (1.7 ⩽ pH ⩽ 2.2) containing 0.1 mol l −1 aniline, electrochemically on a platinum electrode and chemically using ammonium persulfate as oxidant agent. The polymers obtained were characterized by electrochemical response, UV–vis and IR spectrocopies, conductivity measurements and morphological analysis. In general, the polymer growth rate and the characteristics of the polymeric materials are similar to those prepared in sulfuric acid medium. However, phosphate medium presents as advantage the formation of phosphate layers interpenetrated with PAni on active metallic surfaces like steels, aluminum and aluminum alloys, with a wide range of application in corrosion protection.

Improvement of alternariol monomethyl ether detection at gold electrodes modified with a dodecanethiol self-assembled monolayer

The electro-oxidation of alternariol monomethyl ether (AME), one of the main metabolites of the Alternaria genus mycotoxins, is studied at 1-dodecanethiol (DDT)-modified gold electrodes, in acetonitrile (ACN) – aqueous phosphate buffer solutions of different pH values, by using cyclic (CV) and square-wave (SWV) voltammetries. The AME voltammetric response at the bare electrode suffers from two drawbacks: it appears at potentials close to the onset of gold oxide formation, and it is hampered by a fouling of the electrode surface due to the accumulation of oxidized products. These shortcomings are circumvented by the use of DDT-coated electrodes, since the intervening monolayer inhibits gold oxide formation and surface passivation by the electrochemical products, without affecting the oxidation kinetics of AME significantly. Diagnostic criteria based on the voltammetric peak parameters show that the electrochemical behavior of AME at the modified electrode is mainly controlled by reactant diffusion from solution, with a weak adsorption of both the mycotoxin and its oxidation products at monolayer defects. Calibration curves were constructed from the AME square-wave voltammetric response and a detection limit of 9.1 × 10 −8 mol dm −3 was determined, which is about three times smaller than a previous estimate at platinum and glassy carbon electrodes, and about fifty times smaller than the limit derived from measurements carried out at a polyphenol oxidase-modified carbon paste electrode.

Gelatin–alpha olefin sulfonate interactions studied by dynamic light scattering

Dynamic light scattering (DLS) measurements were performed to study the binding of anionic surfactant alpha olefin sulfonate (AOS) to gelatin chains at various NaCl concentrations at 30 °C in aqueous sodium phosphate buffer (pH=6.8) solutions. The surfactant concentration was varied from 0 to 80 mM and the NaCl concentrations chosen were 0.025, 0.05, and 0.1 M. AOS exhibited electrostatic binding to the positively charged sites of the polypeptide chain resulting in considerable reduction in its hydrodynamic radius up to critical micellar concentration (cmc=8 mM for no salt, 0.01 and 0.025 M, and 5 mM for 0.05 M and 2 mM for 0.1 M solutions). The correlation function revealed the presence of two types of structures above cmc; namely the micelles of AOS and gelatin–AOS micelle complexes. The micellar radii ( R m), the effective gelatin–surfactant complex radii ( R c), have been determined as a function of salt concentration. No critical aggregation concentration (cac) was observed. The inter-gelatin–surfactant complex ( k D 1 ) and inter-micellar interactions ( k D 2 ), were determined by fitting the concentration dependence of R m and R c to a virial expansion in reduced concentration ( c−cmc), which are compared. While k D 1 showed strong ionic strength dependence, k D 2 remained invariant of the same. The protein to surfactant binding ratio was found to be smaller than normal. Results have been discussed within the framework of the necklace-bead model of polymer–surfactant interactions.

Cooperative molecular recognition of dyes by dyad and triad cyclodextrin-crown ether conjugates.

Three beta-cyclodextrin (beta-CyD) derivatives with crown ether units, that is N-(4'-benzo-15-crown-5)-6-imino-6-deoxy-beta-CyD (2), 6,6'-[N-(4,4'-dibenzo-18-crown-6)-imino]-bridged bis(beta-CyD)(3), and 2,2'-[O-(4',5'-benzo-15-crown-5)-ethyl]-bridged bis (beta-CyD)(5), were synthesized as cooperative recognition receptor models. Their molecular binding behavior with four representative fluorescent dyes, i.e., ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium-6-toluidino-2-naphthalene-sulfonate (TNS), Acridine Red (AR) and Rhodamine B (RhB), was investigated in buffer solutions (pH = 7.20) at 25 degreesC by means of circular dichroism, NMR and fluorescence spectroscopy. 2D-ROESY experiments showed that dyad host 2 and triad host 3 adopted a CyD-guest-crown ether binding mode, while triad host 5 adopted a CyD-guest-CyD binding mode, upon inclusion complexation with guest molecules. Therefore, hosts 2 and 3 showed high molecular recognition ability towards charged guests, giving an enhanced binding ability up to 115 times for ANS by 3 and fairly high molecular selectivity up to 1450 times for the ANS/AR pair by 2 as compared with native beta-CyD in an aqueous phosphate buffer solution. On the other hand, host 5 was found to be able to effectively recognize the shape of a guest molecule, showing significantly higher binding ability towards linear guests. The binding affinities and molecular recognition abilities of these CyD-crown ether conjugates towards guest molecules are discussed from the viewpoint of electrostatic and/or hydrophobic interactions, size/shape-fit concept, and multiple recognition mechanism between host and guest.

Synthesis of L-cystine bridged bis(b-cyclodextrin) and its cooperative binding toward guest molecules

A novel p-cyclodextrin derivative, L-cystine bridged bis(β-cyclodextrin) 1 has been synthesized and characterized by 1H NMR, 13C NMR, IR, Raman and combustion analyses. Spectrofluorometric titrations have been performed in aqueous phosphate buffer solution (pH=7.20) at 25℃ to give the complex stability constants (Ks) and Gibbs free energy changes (-△G°) for the stoichiometric 1 : 1 inclusion complexation of 1 with four dyes. The binding abilities and molecular selectivities are discussed from the viewpoint of size/shape-fit and electrostatic interactions between hosts and guests. 2D ROESY investigation for the complexation between host and guest further confirms the cooperative binding of bridged cyclodextrin 1 with guest.

Experimental and Theoretical Study of the Activity of Substituted Metallophthalocyanines for Nitrite Electro-oxidation

The electrocatalytic activity of various metallophthalocyanines (M-Pc) adsorbed on an ordinary pyrolytic graphite electrode for the oxidation of nitrite has been investigated in aqueous phosphate buffer solution (pH 7.3). A comparison of Pcs of different metals, shows that the activity is influenced by the nature of the central metal but not very significantly. However, the effect of substituents on the periphery of the Pc ligand is more pronounced. Electron-donor substituents of the Pc ligand enhance this activity. At a density functional theoretical level, we found that the calculated condensed Fukui function, associated to a nucleophilic attack, gives a reasonable explanation for the location of the reaction site in the case of the set of M-Pcs. Indeed, for Cr-Pc, Mn-Pc, Fe-Pc, and Co-Pc, the Fukui function predicts that the preferred reactive sites are located on the central metal whereas for Ni-Pc, Cu-Pc, and Zn-Pc it predicts that the reactive sites are located on the ligand, in agreement with the experimental trends observed. © 2003 The Electrochemical Society. All rights reserved.

Molecular Recognition and Cooperative Binding Ability of Fluorescent Dyes by Bridged Bisβ-cyclodextrin)s Tethered with Aromatic Diamine

A novel bridged bis(β-cyclodextrin),m-phenylenediimino-bridged bis(6-imino-6-deoxy-β-cyclodextrin) (2), was synthesized by the reaction of m-phenylenediamine and 6-deoxy-6-formyl-β-cyclodextrin. The inclusion complexation behavior of the novel bridged bis(β-cyclodextrin) 2,as well as native β-cyclodextrin (1),p-phenylenediamino-bridged bis(6-amino-6-deoxy-β-cyclodextrin) (3) and 4,4'-bianilino-bridged bis(6-amino-6-deoxy-β-cyclodextrin) (4) with representative fluorescent dye molecules, i.e., acridine red (AR), neutral red (NR), Rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonate (ANS) and sodium 6-toluidino-2-naphthalenesulfonate (TNS), was investigated at 25 °C in aqueous phosphate buffer solution (pH 7.20) by means of fluorescence, and circular dichroism, as well as 2D NMR spectrometry. The spectrofluorometric titrations have been performed to calculate the complex stability constants (KS) and Gibbs free energy changes (Δ G°) for the stoichiometric 1 : 1 inclusion complexation of 1–4 with fluorescent dye molecules. The results obtained demonstrated that bis(β-cyclodextrin)s 2–4 showed much higher affinities toward these guest dyesthan native β-cyclodextrin 1. Typically, dimer 2 displayed the highest binding ability upon inclusion complexation with ANS, affording 35 times higher KS value than native β-cyclodextrin. The significantlyenhanced binding abilities of these bis(β-cyclodextrin)s are discussed from thebinding mode and viewpoints of size/shape-fit concept and multiple recognition mechanism.

Preparation of photo-patterned polymer–hydroxyapatite composites

A polymer–hydroxyapatite (HAp) composite is useful as hard tissue engineering scaffold materials for bone and teeth, particularly. It is necessary to control the form of the composites precisely, because form of bone and teeth is unique and specific. We demonstrated that the shape of a base polymer film was controlled by a photo-pattering technique. Hybridization of the photo-patterned polymer film and HAp was performed by alternative soaking of the film into calcium chloride aqueous solution and phosphate buffer solution. Poly(vinyl alcohol) bearing trans-cinnamate moieties as chromophoric groups (P(VA-VCI)) was spin-coated on various substrates, glass, metals such as titanium, aluminum, stainless steel. The spin-coated film was covered with a patterned photo-mask, exposed by using UV lamp and finally developed by dipping into mixed organic solvent. The patterned P(VA-VCI) film was processed by the alternate soaking process for preparation of P(VA-VCI)–HAp composites. We confirmed that formation of HAp in the P(VA-VCI) film by infrared spectroscopy and X-ray diffraction technique. Microscopic observations of the photo-patterned P(VA-VCI)–HAp composites were also performed. The border line between the polymer–HAp composite film and the substrate is clearly observed even after the alternative soaking process. This method is a method for being very useful for producing the polymer–HAp composite with the form of thought way.

XPS and AFM Characterization of Oligonucleotides Immobilized on Gold Substrates

The adsorption processes of oligonucleotides onto gold substrates have been investigated in aqueous phosphate buffer solutions using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) in conjunction with the quartz crystal microbalance. The hybridization of a thiol-modified, single-stranded oligonucleotide (HS-polyA), anchored to a gold surface via the thiol group, with its complementary sequence (polyT) has been observed and characterized via XPS and AFM techniques, which provide semiquantitative information about the amount of the material deposited and its surface morphology, making possible the monitoring of the hybridization process. The use of these techniques represents a complementary approach to those generally employed, such as spectrophotometry and surface plasmon resonance.