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Benavides T, Guerra J, Garcia C. Dielectric Spectroscopy can Predict the Effect of External AC Fields on the Dynamic Adsorption of Lysozyme. Chemphyschem 2022; 23:e202100914. [PMID: 35226788 PMCID: PMC9311058 DOI: 10.1002/cphc.202100914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 02/25/2022] [Indexed: 11/08/2022]
Abstract
This report describes the application of dielectric spectroscopy as a simple and fast way to guide protein adsorption experiments. Specifically, the polarization behavior of a layer of adsorbed lysozyme was investigated using a triangular‐wave signal with frequencies varying from 0.5 to 2 Hz. The basic experiment, which can be performed in less than 5 min and with a single sample, not only allowed confirming the susceptibility of the selected protein towards the electric signal but also identified that this protein would respond more efficiently to signals with lower frequencies. To verify the validity of these observations, the adsorption behavior of lysozyme onto optically transparent carbon electrodes was also investigated under the influence of an applied alternating potential. In these experiments, the applied signal was defined by a sinusoidal wave with an amplitude of 100 mV and superimposed to +800 mV (applied as a working potential) and varying the frequency in the 0.1–10000 Hz range. The experimental data showed that the greatest adsorbed amounts of lysozyme were obtained at the lowest tested frequencies (0.1–1.0 Hz), results that are in line with the corresponding dielectric features of the protein.
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Affiliation(s)
- Tomas Benavides
- Universidad Nacional de Córdoba: Universidad Nacional de Cordoba, Physical-Chemistry, ARGENTINA
| | - Jose Guerra
- Federal University of Uberlandia: Universidade Federal de Uberlandia, physics, BRAZIL
| | - Carlos Garcia
- Clemson University, Chemistry, 211 S. Palmetto Blvd, 29634, Clemson, UNITED STATES
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2
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Lefebvre G, Bruckert F, Filipe V, Huille S, Weidenhaupt M. Adsorption rate constants of therapeutic proteins and surfactants for material surfaces. Colloids Surf B Biointerfaces 2021; 203:111722. [PMID: 33839475 DOI: 10.1016/j.colsurfb.2021.111722] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 03/01/2021] [Accepted: 03/23/2021] [Indexed: 12/20/2022]
Abstract
Adsorption of therapeutic proteins to material surfaces can be a pivotal issue in drug development, especially for low concentration products. Surfactants are used to limit adsorption losses. For each formulation component, surface adsorption is the result of a combination of its diffusion and surface adsorption rates. The latter are difficult to measure accurately because a depletion layer forms rapidly in the bulk solution above a bare surface, slowing down adsorption. Adapting flow conditions and local surface chemistry, we are able to minimize depletion limitations and measure apparent adsorption rate constants of three monoclonal antibodies, other proteins and surfactants with a hydrophobic surface. We show that surface adsorption rates scale with the molecular mass of the molecule, with polysorbates therefore showing thousand times slower rates than antibodies. Moreover, we observed that the desorption dynamic of polysorbates from a given hydrophobic surface depends on surface coverage, whereas this is not the case for Poloxamer 188. These novel contributions to surface adsorption dynamics enable a new perspective on the evaluation of drug surface compatibility and can, together with diffusion rates, be used to predict the protective potential of surfactants in given conditions.
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Affiliation(s)
- Guillaume Lefebvre
- Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000, Grenoble, France(1); Sanofi, 94400, Vitry-sur-Seine, France
| | - Franz Bruckert
- Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000, Grenoble, France(1)
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3
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Alipoormazandarani N, Fokkink R, Fatehi P. Deposition behavior of lignin on solid surfaces assessed by stagnation point adsorption reflectometry. RSC Adv 2021; 11:16980-16988. [PMID: 35479723 PMCID: PMC9032271 DOI: 10.1039/d1ra02248b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 04/22/2021] [Indexed: 11/28/2022] Open
Abstract
The deposition behavior of lignin on a solid surface was studied using stagnation point adsorption reflectometry (SPAR) comprehensively. In this study, the light absorption coefficient of lignin (τ = 20 476 m−1) at 633 nm wavelength was considered to define a new imaginary refractive index (k) used in the SPAR technique for adsorption analysis. The inclusion of k in the adsorption model yielded an adsorbed amount (Γ) of 1.11 mg m−2, leading to the quality factor (Qf) of 31.71 mg m−2. At a lower concentration, the deposition of lignin on the surface was increased, and it generated a maximum sticking coefficient of β = 0.71 at 25 mg L−1 on the surface. At the concentration range of 35 and 45 mg L−1, lignin formed clusters and its deposition dropped. The use of Quartz crystal microbalance (QCM) and SPAR techniques also confirmed that the proportion of water in the deposited lignin adlayer was greater when a lower concentration (5–25 mg L−1) of lignin solution was used for adsorption. The findings of this study revealed the potential use of the SPAR technique for evaluating the deposition performance of lignin-based materials on varied surfaces, which would facilitate the development of coating and composite applications for lignin. The deposition of lignin on a solid surface (i.e., SiO2 made wafer) was fundamentally studied using Stagnation Point Adsorption Reflectometry (SPAR).![]()
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Affiliation(s)
| | - Remco Fokkink
- Laboratory of Physical Chemistry and Soft Matter
- Wageningen University & Research
- The Netherlands
| | - Pedram Fatehi
- Chemical Engineering Department
- Lakehead University
- Thunder Bay
- Canada
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4
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Benavidez TE, Garcia CD. Spectroscopic ellipsometry as a complementary tool to characterize coatings on PDMS for CE applications. Electrophoresis 2016; 37:2509-2516. [DOI: 10.1002/elps.201600143] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/20/2016] [Accepted: 05/20/2016] [Indexed: 11/11/2022]
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5
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Benavidez TE, Wechsler ME, Farrer MM, Bizios R, Garcia CD. Electrochemically Preadsorbed Collagen Promotes Adult Human Mesenchymal Stem Cell Adhesion. Tissue Eng Part C Methods 2015; 22:69-75. [PMID: 26549607 DOI: 10.1089/ten.tec.2015.0315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The present article reports on the effect of electric potential on the adsorption of collagen type I (the most abundant component of the organic phase of bone) onto optically transparent carbon electrodes (OTCE) and its mediation on subsequent adhesion of adult, human, mesenchymal stem cells (hMSCs). For this purpose, adsorption of collagen type I was investigated as a function of the protein concentration (0.01, 0.1, and 0.25 mg/mL) and applied potential (open circuit potential [OCP; control], +400, +800, and +1500 mV). The resulting substrate surfaces were characterized using spectroscopic ellipsometry, atomic force microscopy, and cyclic voltammetry. Adsorption of collagen type I onto OTCE was affected by the potential applied to the sorbent surface and the concentration of protein. The higher the applied potential and protein concentration, the higher the adsorbed amount (Γcollagen). It was also observed that the application of potential values higher than +800 mV resulted in the oxidation of the adsorbed protein. Subsequent adhesion of hMSCs on the OTCEs (precoated with the collagen type I films) under standard cell culture conditions for 2 h was affected by the extent of collagen preadsorbed onto the OTCE substrates. Specifically, enhanced hMSCs adhesion was observed when the Γcollagen was the highest. When the collagen type I was oxidized (under applied potential equal to +1500 mV), however, hMSCs adhesion was decreased. These results provide the first correlation between the effects of electric potential on protein adsorption and subsequent modulation of anchorage-dependent cell adhesion.
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Affiliation(s)
- Tomás E Benavidez
- 1 Department of Chemistry, Clemson University , Clemson, South Carolina
| | - Marissa E Wechsler
- 2 Department of Biomedical Engineering, The University of Texas at San Antonio , San Antonio, Texas
| | - Madeleine M Farrer
- 2 Department of Biomedical Engineering, The University of Texas at San Antonio , San Antonio, Texas
| | - Rena Bizios
- 2 Department of Biomedical Engineering, The University of Texas at San Antonio , San Antonio, Texas
| | - Carlos D Garcia
- 1 Department of Chemistry, Clemson University , Clemson, South Carolina
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Bhakta SA, Evans E, Benavidez TE, Garcia CD. Protein adsorption onto nanomaterials for the development of biosensors and analytical devices: a review. Anal Chim Acta 2015; 872:7-25. [PMID: 25892065 PMCID: PMC4405630 DOI: 10.1016/j.aca.2014.10.031] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/25/2014] [Accepted: 10/21/2014] [Indexed: 12/11/2022]
Abstract
An important consideration for the development of biosensors is the adsorption of the biorecognition element to the surface of a substrate. As the first step in the immobilization process, adsorption affects most immobilization routes and much attention is given into the research of this process to maximize the overall activity of the biosensor. The use of nanomaterials, specifically nanoparticles and nanostructured films, offers advantageous properties that can be fine-tuned to maximize interactions with specific proteins to maximize activity, minimize structural changes, and enhance the catalytic step. In the biosensor field, protein-nanomaterial interactions are an emerging trend that span across many disciplines. This review addresses recent publications about the proteins most frequently used, their most relevant characteristics, and the conditions required to adsorb them to nanomaterials. When relevant and available, subsequent analytical figures of merits are discussed for selected biosensors. The general trend amongst the research papers allows concluding that the use of nanomaterials has already provided significant improvements in the analytical performance of many biosensors and that this research field will continue to grow.
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Affiliation(s)
- Samir A Bhakta
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
| | - Elizabeth Evans
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
| | - Tomás E Benavidez
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
| | - Carlos D Garcia
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA.
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Benavidez TE, Torrente D, Marucho M, Garcia CD. Adsorption of soft and hard proteins onto OTCEs under the influence of an external electric field. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2455-62. [PMID: 25658387 PMCID: PMC4433030 DOI: 10.1021/la504890v] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The adsorption behavior of hard and soft proteins under the effect of an external electric field was investigated by a combination of spectroscopic ellipsometry and molecular dynamics (MD) simulations. Optically transparent carbon electrodes (OTCE) were used as conductive, sorbent substrates. Lysozyme (LSZ) and ribonuclease A (RNase A) were selected as representative hard proteins, whereas myoglobin (Mb), α-lactalbumin (α-LAC), bovine serum albumin (BSA), glucose oxidase (GOx), and immunoglobulin G (IgG) were selected to represent soft proteins. In line with recent publications from our group, the experimental results revealed that while the adsorption of all investigated proteins can be enhanced by the potential applied to the electrode, the effect is more pronounced for hard proteins. In contrast with the incomplete monolayers formed at open-circuit potential, the application of +800 mV to the sorbent surface induced the formation of multiple layers of protein. These results suggest that this effect can be related to the intrinsic polarizability of the protein (induction of dipoles), the resulting surface accessible solvent area (SASA), and structural rearrangements induced upon the incorporation on the protein layer. The described experiments are critical to understand the relationship between the structure of proteins and their tendency to form (under electric stimulation) layers with thicknesses that greatly surpass those obtained at open-circuit conditions.
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Affiliation(s)
- Tomás E. Benavidez
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
| | - Daniel Torrente
- Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
| | - Marcelo Marucho
- Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
| | - Carlos D. Garcia
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
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8
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Evans E, Gabriel EFM, Benavidez TE, Tomazelli Coltro WK, Garcia CD. Modification of microfluidic paper-based devices with silica nanoparticles. Analyst 2014; 139:5560-7. [PMID: 25204446 PMCID: PMC4180781 DOI: 10.1039/c4an01147c] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This paper describes a silica nanoparticle-modified microfluidic paper-based analytical device (μPAD) with improved color intensity and uniformity for three different enzymatic reactions with clinical relevance (lactate, glucose, and glutamate). The μPADs were produced on a Whatman grade 1 filter paper and using a CO2 laser engraver. Silica nanoparticles modified with 3-aminopropyltriethoxysilane were then added to the paper devices to facilitate the adsorption of selected enzymes and prevent the washing away effect that creates color gradients in the colorimetric measurements. According to the results herein described, the addition of silica nanoparticles yielded significant improvements in color intensity and uniformity. The resulting μPADs allowed for the detection of the three analytes in clinically relevant concentration ranges with limits of detection (LODs) of 0.63 mM, 0.50 mM, and 0.25 mM for lactate, glucose, and glutamate, respectively. An example of an analytical application has been demonstrated for the semi-quantitative detection of all three analytes in artificial urine. The results demonstrate the potential of silica nanoparticles to avoid the washing away effect and improve the color uniformity and intensity in colorimetric bioassays performed on μPADs.
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Affiliation(s)
- Elizabeth Evans
- Department of Chemistry, The University of Texas at San Antonio, San Antonio, TX 78249, USA.
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9
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Adsorption and catalytic activity of glucose oxidase accumulated on OTCE upon the application of external potential. J Colloid Interface Sci 2014; 435:164-70. [PMID: 25261840 DOI: 10.1016/j.jcis.2014.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 08/04/2014] [Accepted: 08/06/2014] [Indexed: 11/21/2022]
Abstract
This article describes the adsorption of glucose oxidase (GOx) onto optically transparent carbon electrodes (OTCE) under the effect of applied potential and the analysis of the enzymatic activity of the resulting GOx/OTCE substrates. In order to avoid electrochemical interferences with the enzyme redox center, control electrochemical experiments were performed using flavin adenine dinucleotide (FAD) and GOx/OTCE substrates. Then, the enzyme adsorption experiments were carried out as a function of the potential applied (ranged from the open circuit potential to +950mV), the pH solution, the concentration of enzyme, and the ionic strength on the environment. The experimental results demonstrated that an increase in the adsorbed amount of GOx on the OTCE can be achieved when the potential was applied. Although the increase in the adsorbed amount was examined as a function of the potential, a maximum enzymatic activity was observed in the GOx/OTCE substrate achieved at +800mV. These experiments suggest that although an increase in the amount of enzyme adsorbed can be obtained by the application of an external potential to the electrode, the magnitude of such potential can produce detrimental effects in the conformation of the adsorbed protein and should be carefully considered. As such, the article describes a simple and rational approach to increase the amount of enzyme adsorbed on a surface and can be applied to improve the sensitivity of a variety of biosensors.
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Bhakta SA, Benavidez TE, Garcia CD. Immobilization of glucose oxidase to nanostructured films of polystyrene-block-poly(2-vinylpyridine). J Colloid Interface Sci 2014; 430:351-6. [PMID: 24980481 DOI: 10.1016/j.jcis.2014.05.067] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 05/29/2014] [Accepted: 05/31/2014] [Indexed: 12/31/2022]
Abstract
A critical step for the development of biosensors is the immobilization of the biorecognition element to the surface of a substrate. Among other materials that can be used as substrates, block copolymers have the untapped potential to provide significant advantages for the immobilization of proteins. To explore such possibility, this manuscript describes the fabrication and characterization of thin-films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP). These films were then used to investigate the immobilization of glucose oxidase, a model enzyme for the development of biosensors. According to the results presented, the nanoporous films can provide significant increases in surface area of the substrate and the immobilization of larger amounts of active enzyme. The characterization of the substrate-enzyme interface discussed in the manuscript aims to provide critical information about relationship between the surface (material, geometry, and density of pores), the protein structure, and the immobilization conditions (pH, and protein concentration) required to improve the catalytic activity and stability of the enzymes. A maximum normalized activity of 3300±700 U m(-2) was achieved for the nanoporous film of PS-b-P2VP.
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Affiliation(s)
- Samir A Bhakta
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
| | - Tomas E Benavidez
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
| | - Carlos D Garcia
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA.
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11
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Benavidez TE, Garcia CD. Potential-assisted adsorption of bovine serum albumin onto optically transparent carbon electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14154-14162. [PMID: 24156567 PMCID: PMC3867293 DOI: 10.1021/la4029657] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
This article describes the effect of the applied potential on the adsorption of bovine serum albumin (BSA) to optically transparent carbon electrodes (OTCE). To decouple the effect of the applied potential from the high affinity of the protein for the bare surface, the surface of the OTCE was initially saturated with a layer of BSA. Experiments described in the article show that potential values higher than +500 mV induced a secondary adsorption process (not observed at open-circuit potential), yielding significant changes in the thickness (and adsorbed amount) of the BSA layer obtained. Although the process showed a significant dependence on the experimental conditions selected, the application of higher potentials, selection of pH values around the isoelectric point (IEP) of the protein, high concentrations of protein, and low ionic strengths yielded faster kinetics and the accumulation of larger amounts of protein on the substrate. These experiments, obtained around the IEP of the protein, contrast with the traditional hypothesis that enhanced electrostatic interactions between the polarized substrate and the (oppositely charged) protein are solely responsible for the enhanced adsorption. These results suggest that the potential applied to the electrode is able to polarize the adsorbed layer and induce dipole-dipole interactions between the adsorbed and the incoming protein. This mechanism could be responsible for the potential-dependent oversaturation of the surface and could bolster to the development of surfaces with enhanced catalytic activity and implants with improved biocompatibility.
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Affiliation(s)
| | - Carlos D. Garcia
- To whom correspondence should be addressed. One UTSA Circle, San Antonio, TX 78249, USA. Ph: (210) 458-5774, Fax: (210) 458-7428,
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12
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Benavidez TE, Garcia CD. Spectroscopic and electrochemical characterization of nanostructured optically transparent carbon electrodes. Electrophoresis 2013; 34:1998-2006. [PMID: 23595607 PMCID: PMC3860877 DOI: 10.1002/elps.201300022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 02/15/2013] [Accepted: 03/03/2013] [Indexed: 12/15/2022]
Abstract
The present paper describes the results related to the optical and electrochemical characterization of thin carbon films fabricated by spin coating and pyrolysis of AZ P4330-RS photoresist. The goal of this paper is to provide comprehensive information allowing for the rational selection of the conditions to fabricate optically transparent carbon electrodes (OTCE) with specific electrooptical properties. According to our results, these electrodes could be appropriate choices as electrochemical transducers to monitor electrophoretic separations. At the core of this manuscript is the development and critical evaluation of a new optical model to calculate the thickness of the OTCE by variable angle spectroscopic ellipsometry. Such data were complemented with topography and roughness (obtained by atomic force microscopy), electrochemical properties (obtained by cyclic voltammetry), electrical properties (obtained by electrochemical impedance spectroscopy), and structural composition (obtained by Raman spectroscopy). Although the described OTCE were used as substrates to investigate the effect of electrode potential on the real-time adsorption of proteins by ellipsometry, these results could enable the development of other biosensors that can be then integrated into various CE platforms.
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Affiliation(s)
- Tomas E. Benavidez
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
| | - Carlos D. Garcia
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
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13
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Szott LM, Horbett TA. Protein interactions with surfaces: cellular responses, complement activation, and newer methods. Curr Opin Chem Biol 2011; 15:677-82. [DOI: 10.1016/j.cbpa.2011.04.021] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Accepted: 04/07/2011] [Indexed: 10/18/2022]
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Toccafondi C, Prato M, Maidecchi G, Penco A, Bisio F, Cavalleri O, Canepa M. Optical properties of Yeast Cytochrome c monolayer on gold: an in situ spectroscopic ellipsometry investigation. J Colloid Interface Sci 2011; 364:125-32. [PMID: 21920531 DOI: 10.1016/j.jcis.2011.07.097] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 07/29/2011] [Accepted: 07/30/2011] [Indexed: 11/18/2022]
Abstract
The adsorption of Yeast Cytochrome c (YCC) on well defined, flat gold substrates has been studied by Spectroscopic Ellipsometry (SE) in the 245-1000 nm wavelength range. The investigation has been performed in aqueous ambient at room temperature, focusing on monolayer-thick films. In situ δΨ and δΔ difference spectra have shown reproducibly well-defined features related to molecular optical absorptions typical of the so-called heme group. The data have been reproduced quantitatively by a simple isotropic optical model, accounting for the molecular absorption spectrum and film-substrate interface effects. The simulations allowed a reliable estimate of the film thickness and the determination of the position and the shape of the so-called Soret absorption peak that, within the experimental uncertainty, is the same found for molecules in liquid. These findings suggest that YCC preserves its native structure upon adsorption. The same optical model was able to reproduce also ex situ results on rinsed and dried samples, dominated by the spectral features associated to the polypeptide chain that tend to overwhelm the heme absorption features.
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Affiliation(s)
- Chiara Toccafondi
- CNISM and Dipartimento di Fisica, Universitá di Genova, Via Dodecaneso 33, 16146 Genova, Italy
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15
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Nejadnik MR, Deepak FL, Garcia CD. Adsorption of Glucose Oxidase to 3-D Scaffolds of Carbon Nanotubes: Analytical Applications. ELECTROANAL 2011; 23:1462-1469. [PMID: 22735356 PMCID: PMC3380380 DOI: 10.1002/elan.201000758] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 02/07/2011] [Indexed: 01/21/2023]
Abstract
This study is the first to focus on the potential use of carbon nanotube (CNT) scaffolds as enzyme immobilization substrates for analytical purposes. Besides all the well-known advantages of CNT, three-dimensional scaffolds can significantly increase the amount of enzymes adsorbed per unit area, preserve the catalytic activity of the adsorbed molecules, and allow effective exposure to substrates present in the adjacent medium. Additionally, our results indicate that the sensitivity of analytical probes based on enzyme-loaded CNT scaffolds is proportional to the thickness of the scaffold providing 3-fold sensitivity improvements with respect to the control surfaces.
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Affiliation(s)
- M. Reza Nejadnik
- Department of Chemistry University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249 USA
| | - Francis L. Deepak
- Department of Physics and Astronomy University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249 USA
| | - Carlos D. Garcia
- Department of Chemistry University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249 USA
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16
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Chumbimuni-Torres KY, Coronado RE, Mfuh AM, Castro-Guerrero C, Silva MF, Negrete GR, Bizios R, Garcia CD. Adsorption of Proteins to Thin-Films of PDMS and Its Effect on the Adhesion of Human Endothelial Cells. RSC Adv 2011; 1:706-714. [PMID: 25068038 DOI: 10.1039/c1ra00198a] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This paper describes a simple and inexpensive procedure to produce thin-films of poly(dimethylsiloxane). Such films were characterized by a variety of techniques (ellipsometry, nuclear magnetic resonance, atomic force microscopy, and goniometry) and used to investigate the adsorption kinetics of three model proteins (fibrinogen, collagen type-I, and bovine serum albumin) under different conditions. The information collected from the protein adsorption studies was then used to investigate the adhesion of human dermal microvascular endothelial cells. The results of these studies suggest that these films can be used to model the surface properties of microdevices fabricated with commercial PDMS. Moreover, the paper provides guidelines to efficiently attach cells in BioMEMS devices.
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Affiliation(s)
| | - Ramon E Coronado
- Department of Biomedical Engineering, The University of Texas at San Antonio
| | - Adelphe M Mfuh
- Department of Chemistry, The University of Texas at San Antonio
| | | | - Maria Fernanda Silva
- School of Agronomic Sciences - IBAM-CONICET, National University of Cuyo, Mendoza, Argentina
| | | | - Rena Bizios
- Department of Biomedical Engineering, The University of Texas at San Antonio
| | - Carlos D Garcia
- Department of Chemistry, The University of Texas at San Antonio
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17
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Felhofer JL, Caranto JD, Garcia CD. Adsorption kinetics of catalase to thin films of carbon nanotubes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:17178-83. [PMID: 20945910 PMCID: PMC3033603 DOI: 10.1021/la103035n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The adsorption conditions used to immobilize catalase onto thin films of carbon nanotubes were investigated to elucidate the conditions that produced films with maximum amounts of active catalase. The adsorption kinetics were monitored by spectroscopic ellipsometry, and the immobilized catalase films were then assayed for catalytic activity. The development of a volumetric optical model used to interpret the ellipsometric data is discussed. According to the results herein discussed, not only the adsorbed amount but also the initial adsorption rates determine the final catalytic activity of the adsorbed layer. The results described in this paper have direct implications on the rational design and analytical performance of enzymatic biosensors.
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Affiliation(s)
- Jessica L. Felhofer
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
| | - Jonathan D. Caranto
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
| | - Carlos D. Garcia
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle, San Antonio, TX 78249, USA
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Nejadnik MR, Garcia CD. Staining proteins: a simple method to increase the sensitivity of ellipsometric measurements in adsorption studies. Colloids Surf B Biointerfaces 2010; 82:253-7. [PMID: 20833003 DOI: 10.1016/j.colsurfb.2010.08.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Accepted: 08/16/2010] [Indexed: 10/19/2022]
Abstract
This communication describes a simple way to improve the sensitivity of spectroscopic ellipsometry, when applied to monitor the adsorption of proteins to solid surfaces. The method described herein is based on the reaction of a commercially available dye (Coomassie brilliant blue G) with the adsorbed proteins and the subsequent analysis by spectroscopic ellipsometry. In order to demonstrate the potential advantages of this method, the adsorption of bovine serum albumin to an antifouling coating was also investigated. According to our results, the modification with the dye significantly affects the optical properties of the adsorbed protein layer, which can be represented using a simple optical model (Lorentz). In general, the proposed modification increases the sensitivity of the detection by 2.5 ± 0.4-fold and enables the analysis of thin layers of adsorbed protein not obtainable by conventional methods. These results particularly reveal the importance of the proposed modification for the evaluation of low adsorbing substrates and antifouling coatings.
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Affiliation(s)
- M Reza Nejadnik
- Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
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