Adsorption Kinetics Of Bovine Serum Albumin Research Articles

Insight into the interactions of albumin with TiO2 nanomaterials and calcium phosphate-based biomaterials by kinetic adsorption and spectroscopic studies

Among key factors determining the fate of biomaterials in vivo are their interactions with blood serum proteins, which can lead to either successful integration or rejection/encapsulation. Although there are a number of studies investigating the interactions between proteins and bioimplants, comparable data for different types of biomaterials are lacking. To fill this gap, the adsorption kinetics and binding interactions of bovine serum albumin (BSA) with calcium phosphates (CaPs), namely hydroxyapatite (HA) and calcium deficient apatite (CaDHA), different TiO2 nanomaterials (TiNMs) presenting various morphologies such as nanoparticles (TiNPs), nanoplatelets (TiNPls), nanotubes (TiNTs) and nanowires (TiNWs), as well as their composites with CaDHA (CaDHA/TiNMs) were investigated. The kinetics of BSA adsorption on all studied materials was best described by pseudo-second order kinetics. The rate coefficient values obtained for the composites were lower than those for CaDHA and the corresponding TiNMs, while the adsorption density was higher for the composites than for CaDHA, except for the composites with TiNTs. Adsorption on TiNWs, CaDHA and all composites involved intraparticle diffusion, which was the rate-limiting step only for CaDHA/TiNTs. Fluorimetric titration experiments revealed that the number of binding sites was in larger than 1, except for TiNTs and TiNWs, indicating positive binding cooperativity. Interestingly, the values of the binding constants were lower for the TiNMs with a higher adsorption rate coefficient. Overall, BSA adsorption on the studied materials proved to be a complex process, which depended on the different surface properties of the adsorbents. Which property had a dominant role depended on the chemical identity of the adsorbent. The obtained comparable data for different types of materials point to the way of modifying their protein adsorption and binding properties.

UHMWPE-MWCNT-nHA based hybrid trilayer nanobiocomposite: Processing approach, physical properties, stem/bone cell functionality, and blood compatibility.

The development of polymeric nanocomposites for biomedical applications remains a major challenge in terms of tailored addition of nanoparticles to realize the simultaneous enhancement of fracture resistance and cell/blood compatibility. To address this, the present work has been planned to determine whether small addition of surface functionalized multiwalled-carbon-nanotube, MWCNT (<1.5 wt%) and egg-shell derived nanosized hydroxyapatite, nHA (<10 wt%) to ultrahigh-molecular-weight-polyethylene (UHMWPE) can significantly improve the physical properties as well as biocompatibility. The difference in mouse osteoblast and human mesenchymal stem cell (hMSc) proliferation has been validated using both the monolithic composite and a trilayered composite with two different UHMWPE nanocomposites on either face with pure polymer at the middle. The combination of rheology and micro-CT with fractography reveals the homogeneous dispersion of nanofillers, leading to mechanical property enhancement. The quantitative analysis of cell viability and cell spreading by immunocytochemistry method, using vinculin and vimentin expression, establish significant cytocompatibility with hMSc and osteoblast cells onto the trilayer hybrid nanobiocomposite substrates. The hemocompatibility of the investigated composites under the controlled flow of rabbit blood in a microfluidic device reveals the signature of reduced thrombogenesis with reduction of platelet activation on UHMWPE nanocomposite w.r.t. unreinforced UHMWPE. An attempt has been made to discuss the blood compatibility results in the backdrop of the bovine serum albumin adsorption kinetics. Summarizing, the present study establishes that the twin requirement of mechanical property and cyto/hemo-compatibility can be potentially realized in developing trilayer composites in UHMWPE-nHA-MWCNT system.

Green synthesis of hydrophilic protein-imprinted resin with specific recognition of bovine serum albumin in aqueous matrix

The synthesis of biomacromolecule imprinted materials is a challenge with the bulkiness and instability of macromolecule, such as protein. A green strategy to prepare hydrophilic protein-imprinted resin (HPIR) was firstly developed using resorcinol and melamine as double functional monomers, hexamethylenetetramine instead of formaldehyde as crosslinker, water as solvent, and bovine serum albumin (BSA) as a dual-function template. BSA as dual-function template could not only act as template but also porogen in the preparation of HPIR. According to the adsorption experiments, the adsorption kinetics of BSA on HPIR obeyed pseudo-second-order adsorption kinetics and the equilibrium data were best described by Langmuir isotherm model. The adsorption capability was 44.3459 mg g−1 (25 °C), and the imprinted factor for binding BSA is 5.78. HPIR showed high adsorption capacity, fast mass transfer rate, and specific selectivity towards BSA in aqueous solvent. More importantly, HPIR can be applied to selectively adsorb target protein BSA in urine without the matrix interference of biological matrix, therefore, it is promising for HPIR to be applied to proteomics, diagnostics, and pharmaceutics.

Changing the activities and structures of bovine serum albumin bound to graphene oxide

To elucidate the binding mechanism of graphene oxide (GO) with bovine serum albumin (BSA) at molecular level, it is urgent to investigate their interactions in this work. The results indicated that multi noncovalent forces including hydrophobic force, hydrogen bonds, van der Waals and π-π* stacking interactions were involved in the adsorption forces of BSA on GO surface. The kinetics of BSA adsorption onto GO follows the pseudo-second-order kinetic model and was a fast process with high adsorption capacity. Some structure and functions of BSA were changed by GO binding. The decrease of melting temperature (Tm) and enthalpy changes (ΔHm) implied that BSA on GO surface is more prone towards thermal denaturation. Drug competition experimental results showed that the binding affinities of BSA with 1-anilinonaphthalene-8-sulfonic acid (ANS) and ofloxacin (OFLX) were decreased to some extent. The esterase-like activity of BSA was obviously increased and BSA became more glycosylated in the presence of GO. Interestingly it was found that presence of GO significantly induced the conformation and activity changes of BSA. This work should help readers to understand and develop ideas for bio-related applications and to discuss the toxicological effects of graphene materials.

Evaluation of agarose-entrapped magnetic nanoparticles influence on protein adsorption isotherm and kinetics using nickel-iminodiacetic acid ligand

Abstract Employing magnetic beads for immobilized metal affinity chromatography application was studied with the approach of magnetic effects investigation. Hence, fabricated magnetic nanoparticles-carrying beads were functionalized with Ni(II)-iminodiacetic acid (IDA). BET-BJH results showed that nanoparticles affected pore sizes lower than 10 nm. Therefore, the pore blockage by protein molecules is considered as an outcome of the new pore diameter in magnetic beads. In accordance, bovine serum albumin (BSA) adsorption isotherms revealed a significant difference between magnetic and nonmagnetic beaded matrices. For nonmagnetic beads, adsorption isotherm followed Langmuir model. However, one step increase in adsorption isotherm for initial BSA concentration from 0.5 mg/ml to 0.8 mg/ml was observed on magnetic beads due to pore blockage by proteins. BSA Adsorption kinetics on beads was found to follow the assumptions of an intraparticle diffusion-controlled pseudo-second order mechanism, with higher adsorption rate constants at lower adsorbate concentrations. Furthermore, though the same IDA density on both non/magnetic beads, presence of magnetic nanoparticles reduced the required equilibrium time (up to 60 min), the saturation path of BSA adsorption breakthrough curves, dynamic binding capacity and the number of theoretical plates. It is concluded that magnetic characteristic of composite agarose adsorbent carrying Fe 3 O 4 nanoparticles affects protein’s conformation. Thus, BSA travel toward ligand is enhanced and sped up.

Structure of bovine serum albumin adsorbed on silica investigated by quartz crystal microbalance

Abstract Adsorption of bovine serum albumin (BSA) on the surface of SiO 2 was investigated mainly using quartz crystal microbalance (QCM) with energy dissipation mode. BSA adsorption kinetics and coverage were determined as a function of pH of the solution with the ionic strength of 1 × 10 −2 M. The maximum coverage was obtained in the pH range 4.5–5.4, near the protein isoelectric point. For pH larger than 5.4 and smaller than 4.5 a monotonic decrease of the adsorbed mass was observed. The images obtained using atomic force microscopy (AFM) method revealed various BSA structures depending on the pH at which they were adsorbed. The identified conformations were assigned to the compact triangular form with an effective length L ef = 8.3 nm and the elongated one with length L ef = 26.7 nm. The dependence between the structure of the protein layers formed on the surface and BSA conformations in solution was additionally followed by contact angle (CA) measurements. It turned out that CA values are very sensitive to the structure of BSA monolayers formed on the silica surface. Comparison of QCM and AFM data with those obtained by other indirect methods (CA) additionally enabled interpretation of the dependence of BSA adsorption on the pH of the solution. The obtained results confirmed the significant role of the highly anisotropic surface charge distribution of BSA molecules on the process of their adsorption.

A comparative PM-IRRAS and ellipsometry study of the adsorptive behaviour of bovine serum albumin on a gold surface

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and ellipsometry were used ex situ to investigate adsorption of bovine serum albumin (BSA) on a gold surface, in terms of the adsorption equilibrium and kinetics. The aim of the work was to examine if the two different techniques give similar/complementary results under the same experimental conditions employing the same protein/surface system, and thus validate the use of the techniques for the investigation of protein/surface interactions under the applied experimental conditions, in general. It was found that the adsorption of BSA on gold follows Type I isotherm, which can be described by the Freundlich isotherm. The initial BSA adsorption kinetics was found to be very fast, and the results were modelled using a two-step kinetic model. The first step represents reversible BSA adsorption that yields BSA adsorbed in a native configuration (θ1) that is not thermodynamically stable. The second step represents the irreversible transformation of this protein configuration into a thermodynamically stable surface-adsorbed configuration (θ2). It was found that the θ2/θ1 ratio increased with time. Finally, the comparison of the results obtained by the two techniques showed a very good agreement.

Plasma Polymerized Pyrrole Films for Biological Applications: Correlation Between Protein Adsorption Properties and Characteristics

AbstractThe present work describes the fabrication, characterization, and optimization of plasma polymerized pyrrole films, PPpy, prepared by continuous wave for application as the adhesion layers of bovine serum albumin (BSA). Plasma conditions used throughout the work produced significant differences in the chemical, physical, and electrochemical properties of the resultant PPpy films. Structural analysis and property characterizations of PPpy were carried out using Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and electrochemical workstation. Surface plasmon resonance spectroscopy was used to investigate the adsorption kinetics of BSA onto PPpy films. Moreover, when immersed in solutions or after BSA adsorption, the differences of electron transfer at the interfaces between the PPpy and the electrolyte solutions were determined by electro impedance spectroscopy. While there is a clear dependence of the protein adsorption affinity on the plasma polymerization condition employed during the film preparation. The relationship between film structure, electrochemical properties, polymer stability in aqueous buffer, and protein binding affinities are discussed.magnified image

Protein adsorption materials based on conducting polymers: polypyrrole modified with ω‐(N‐pyrrolyl)‐octylthiol

AbstractIn order to fabricate a new polymer matrix for application in biochips and to understand the mechanism of adsorption of proteins on conducting polymers, we prepared polypyrrole (PPy) functionalized with ω‐(N‐pyrrolyl)‐octylthiol moieties. The chemical structure of the polymer could be controlled by varying the concentration of pyrrole added as the monomer. Initially, ω‐(N‐pyrrolyl)‐octylthiol was self‐assembled into a monolayer on a gold surface. Thereafter, a layer of uniform and smooth PPy was obtained by the chemical copolymerization of pyrrole and the ω‐(N‐pyrrolyl)‐octylthiol. Bovine serum albumin (BSA) adsorption on the polymer was investigated using surface plasmon resonance spectroscopy and cyclic voltammograms. The chemical structure and monomer components of the as‐prepared films were characterized using Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Water contact angle measurements were used to assess the surface wettability of the films throughout the preparative procedure. The kinetics of BSA adsorption onto the polymer could be controlled by varying the copolymer thickness and the pH value of the buffer solutions used. Moreover, the electroactivity was changed upon BSA binding. The results suggest that the new conducting polymer may potentially be applied as a more sensitive and reliable matrix in protein sensors. Copyright © 2011 Society of Chemical Industry

Adsorption of Bovine Serum Albumin onto Metal Oxides: Adsorption Equilibrium and Kinetics onto Alumina and Zirconia

In this study, the equilibrium and the kinetics of Bovine Serum Albumin (BSA) adsorption onto metal oxides such as alumina (Al2O3) and zirconia (ZrO2) were investigated in a batch reactor. The effects of pH and temperature to adsorption rate and the equilibrium were studied. The equilibrium process was described by the Langmuir or the Freundlich isotherm models. The maximum adsorption capacity (Q0) was found as 81.6 mg/g at pH 5 and 20°C for Al2O3 and 26 mg/g at pH 4 and 40°C for ZrO2, respectively. The protein adsorption capacity for ZrO2 increased with increasing pH and temperature, while the protein adsorption capacity of Al2O3 increased with increasing pH and decreasing temperature. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The rate kinetics of BSA adsorption onto Al2O3 and ZrO2 at all pH and temperatures were best fitted with the pseudo-first-order kinetic model. The electrostatic interactions of BSA with the metal oxide surface were found to be higher at pH 5 for Al2O3 and pH 4 for ZrO2.

Quartz Crystal Microbalance Study of Protein Adsorption on Chitosan, Chitosan/Poly(vinyl pyrrolidone) Blends and Chitosan-graft-Poly(vinyl pyrrolidone) Surfaces

Adsorption behaviour of bovine serum albumin (BSA) onto chitosan (CS), chitosan/poly(vinyl pyrrolidone) blends (CS/PVP blends), and chitosan- graft-poly(vinyl pyrrolidone) (CS- graft-PVP) surfaces were investigated using quartz crystal microbalance (QCM). The adsorbed quantities of protein on the three surfaces were examined and were found to decrease in the following order: CS &gt; CS/PVP blends &gt; CS- graft-PVP. The kinetics of BSA adsorption in the early stage was analysed. The Langmuir isotherm model was used to describe the BSA adsorption behaviour on CS and its derivates. The attachment, detachment rate constants, and the association constants ( Ka ) were of the same order of magnitude, whereas the Ka for BSA on CS- graft-PVP surface was the lowest of the three surfaces. The adsorbed protein layer structure was also estimated. For CS- graft -PVP, most of the proteins adsorbed on the surface were of side-on structure, whereas for CS only about 40% of the proteins were of side-on structure.

Adsorption of BSA on passivated chromium studied by a flow-cell EQCM and XPS

The adsorption of bovine serum albumin (BSA) on a passivated chromium surface in deaerated pH 4 sulphate solution was studied in situ using a switch-flow cell in combination with an electrochemical quartz crystal microbalance (EQCM) and ex situ by X-ray photoelectron spectroscopy (XPS). EQCM measurements showed that the kinetics of BSA adsorption was fast, and that a steady-state was reached about 10 min after introducing the protein. They also showed that BSA adsorption was an irreversible process, or that the kinetics of desorption was very slow. The equivalent thicknesses of the adsorbed BSA layer estimated in situ by EQCM and ex situ by XPS are in excellent agreement, and are equal to 3.5 ± 0.7 nm, which corresponds to one horizontally orientated monolayer.

Adsorption of bovine serum albumin (BSA) onto lecithin studied by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy

The adsorption of bovine serum albumin (BSA) to lecithin was investigated by ATR-FTIR spectroscopy. Lecithin films were prepared by casting aliquots of 3.2 μg lecithin in methanol onto ZnSe ATR prisms. Surface morphology and the thickness of the films were investigated by laser scanning confocal electron microscopy and scanning electron microscopy and the thickness of the films used for adsorption studies was estimated to be 40 Å. The dependency of the C O peak area on the lecithin mass in the calibration curve confirms that the thickness of the film is below the penetration depth of the infrared evanescent wave. Size exclusion HPLC and fluorescence spectroscopy show that BSA conformation in up to 1 M NaCl and CaCl 2 solutions is similar to that in water with no aggregation or changes in protein conformation seen over 4 h. The kinetics of BSA adsorption on the lecithin film from water, NaCl and CaCl 2 solutions demonstrates that ions promote the protein adsorption. BSA bound more in the presence of NaCl compared to CaCl 2 at equivalent concentrations. The adsorption appeared greatest at a 0.1 M concentration for both NaCl and CaCl 2. The results are explained in terms of absorptive reactivity of BSA and lecithin surfaces upon salt addition.

Predictive modeling of protein adsorption along the bed height by taking into account the axial nonuniform liquid dispersion and particle classification in expanded beds

Expanded bed adsorption (EBA) is a special chromatography technique with perfect classification of adsorbent particles in the column, thus the performance of protein adsorption in expanded beds is particular, obviously nonuniform and complex along the column. Detailed description of the complex adsorption kinetics of proteins in expanded bed is essential for better analyzing of adsorptive mechanisms, the design of chromatographic processes and the optimization of operation parameters of EBA processes. In this work, a theoretical model for the prediction of protein adsorption kinetics in expanded beds was developed by taking into account the classified distribution of adsorbent particles along the bed height, the nonuniform behaviors of axial liquid dispersion, the axial variation of local bed voidage as well as the axial changes of target component mass transfer. The model was solved using the implicit finite difference scheme combining with the orthogonal collocation method, and then applied to predict the breakthrough behaviors of bovine serum albumin (BSA) on Streamline DEAE and lysozyme on Streamline SP along the bed height in expanded beds under various conditions. In addition, the experiments of front adsorption of BSA on Streamline DEAE at different axial column positions were carried out to reveal the adsorption kinetics of BSA along the bed height in a 20 mm I.D. expanded bed, and the influences of liquid velocity and feed concentration on the breakthrough behaviors were also analyzed. The breakthrough behaviors predicted by the present model were compared with the experimental data obtained in this work and in the literature published. The agreement between the prediction and the experimental breakthrough curves is satisfied.

Effect of Albumin on Underpotential Lead Deposition and Stripping on Ag‐RDE

AbstractThe effects of adsorption of bovine serum albumin (BSA) on the electrodeposition and stripping of Pb‐adatoms at a Ag‐RDE in acetate buffer solutions have been studied. The adsorbed BSA molecules have been found to inhibit the lead adsorption process. A decrease in the apparent charge transfer coefficient α for Pb‐adatom desorption from 0.39 to 0.34 in the presence of adsorbed BSA molecules has been attributed to the electric field screening by multiply charged BSA in the adsorption film, since no major lateral interactions between Pb and BSA have been observed. The kinetics of BSA adsorption on a Ag‐RDE was followed by Pb‐adatom probe technique in the range of low BSA coverage, 0&lt;θBSA&lt;0.4. The adsorption (k1) and desorption (k−1) rate constants were determined as follows: k1=2.42×10−4 cm/s, k−1=1.12×10−14 mol cm−2 s−1. The equilibrium constant for BSA adsorption on Ag electrode from 3×10−8 M BSA solution, also determined from the Pb‐adatom probe method, was: Kads=2.17×107 L/mol and the corresponding Gibbs free energy of adsorption: ΔG°ads=−9.99 kcal/mol (−41.85 kJ/mol). The formation of BSA films on Ag electrodes has been confirmed by EQCN mass transients and AFM imaging. It follows from these experiments that BSA molecules adsorb in horizontal orientation and form a film on Ag with 4 nm thickness.

Macroporous chitosan layer coated on non-porous silica gel as a support for metal chelate affinity chromatographic adsorbent

A new immobilized metal affinity chromatography (IMAC) matrix was prepared by coordinating Cu 2+ with cross-linked chitosan coated on non-porous silica gel (Cu–CTS–SiO 2). Macroporous structure could be formed on the coated layer by imprinting polyethylene glycol (PEG) in chitosan film. The surface morphology changes on Cu–CTS–SiO 2 bead prepared in different condition were confirmed by scanning electron microscopy (SEM). Effects of chitosan and PEG content in coating solution, the molecular mass of PEG on the surface macropore formation and adsorption capacity of bovine serum albumin (BSA) were investigated. Results indicated that coating solution with 2% chitosan and 10% PEG 20000 was optimal. Batch experiments were also conducted for elucidating the optimal pH, the adsorption isotherm and adsorption kinetics of BSA. Adsorption isotherm of trypsin on the same adsorbent was also performed. Results showed that the support itself had low non-specific interaction with both BSA and trypsin. The maximum adsorption capacity for BSA and trypsin on the prepared IMAC adsorbent could reach 192 mg and 5000 IU, respectively calculated by every gram of chitosan. The binding and eluting condition for BSA were tested on column filled with the adsorbent. Crude BSA sample could be purified on the IMAC column.

Adsorption kinetics of BSA at air–sugar solution interfaces as affected by sugar type and concentration

The influence of glucose, sucrose and fructose at concentrations ranging from 0 to 40 wt.% on the adsorption kinetics of bovine serum albumin (BSA) at air–aqueous solution interfaces at 20 °C was measured using drop shape analysis. The rate of adsorption of proteins decreased in the presence of sugars. The diffusion coefficient of BSA in 40 wt.% sucrose solutions, calculated from the initial period of protein adsorption, was two orders of magnitude lower than the diffusion coefficient of BSA dissolved in pure water. The decrease of the diffusion coefficient with sugar concentration (δ D eff/δ c sugar) was appreciably higher at low sugar concentrations (<10 wt.%). Diffusion coefficients in the presence of sucrose were smaller than in the presence of glucose or fructose. Results were attributed to an increase in solution viscosity, preferential interactions of sugars with protein surfaces and an increased hydrophilicity of protein surfaces due to preferential hydration.

Analysis of diffusion models for protein adsorption to porous anion-exchange adsorbent

The ion-exchange adsorption kinetics of bovine serum albumin (BSA) and γ-globulin to an anion exchanger, DEAE Spherodex M, has been studied by batch adsorption experiments. Various diffusion models, that is, pore diffusion, surface diffusion, homogeneous diffusion and parallel diffusion models, are analyzed for their suitabilities to depict the adsorption kinetics. Protein diffusivities are estimated by matching the models with the experimental data. The dependence of the diffusivities on initial protein concentration is observed and discussed. The adsorption isotherm of BSA is nearly rectangular, so there is little surface diffusion. As a result, the surface and homogenous diffusion models do not fit to the kinetic data of BSA adsorption. The adsorption isotherm of γ-globulin is less favorable, and the surface diffusion contributes greatly to the mass transport. Consequently, both the surface and homogenous diffusion models fit to the kinetic data of γ-globulin well. The adsorption kinetics of BSA and γ-globulin can be very well fitted by parallel diffusion model, because the model reflects correctly the intraparticle mass transfer mechanism. In addition, for both the favorably bound proteins, the pore diffusion model fits the adsorption kinetics reasonably well. The results here indicate that the pore diffusion model can be used as a good approximate to depict protein adsorption kinetics for protein adsorption systems from rectangular to linear isotherms.

Heteroenergetics of Bovine Serum Albumin Adsorption from Good Solvents Related to Crystallization Conditions

Total internal reflection fluorescence (TIRF) was applied to study adsorption of bovine serum albumin (BSA) from a thermodynamically good solvent commonly used as a buffer for BSA crystallization. BSA adsorption is shown to exhibit heteroenergetics, which is possibly a general property of protein interfacial behavior. For example, BSA adsorption on quartz, SnO2, and alkyl-modified surfaces demonstrates broad continuous distributions of energies of adsorption activation and protein-surface binding. For heteroenergetic adsorption, the type of the isotherm and kinetics depends on the type of the energy distribution functions and the type of correlation between the energies. In the case of BSA adsorption on quartz and SnO2surfaces, protein interfacial behavior is consistent with a model suggesting rectangular distributions both of activation energies of adsorption and energies of protein–surface binding. In the case of an alkyl-modified surface, BSA adsorption kinetics is interpreted in terms of a heteroenergetic model suggesting initial adsorption at selected adsorption sites with maximum rate constants. The model also suggests that lateral diffusion quickly redistributes the molecules from the initial adsorption sites to the sites with higher binding energies. The combination of TIRF spectroscopy with an electrochemical system was used to study the effect of surface charge on protein adsorption on a transparent SnO2electrode. BSA behavior on the SnO2electrode was found to correlate with surface hydrophobicity and indifferent to charges both of the surface and the protein. Hydrophobic interactions seem to be the principal driving force in determining the behavior of BSA at the solid–liquid interface and likely plays an important role in protein crystallogenesis.

Dilatational Properties of Adsorbed Poly(D,L-lactide) and Bovine Serum Albumin Monolayers at the Dichloromethane/Water Interface

The use of the dynamic pendant drop method has permitted the accumulation of information in real time on the kinetic and rheological processes that accompany the adsorption of bovine serum albumin (BSA) at the dichloromethane (DCM)/water interface in the presence and in the absence of poly(D,L-lactide) (PLA50). These results have been compared with those obtained at the air/water interface. The study of the adsorption kinetics of BSA at the DCM/water and air/water interfaces has shown that the adsorption process was diffusion controlled in both cases for relatively low concentrations of protein (0.005 g/L). In the presence of PLA50, the adsorption of BSA at the DCM/water interface led to a mixed interfacial layer. The mechanism of the formation of this mixed interface involves the penetration of BSA into the saturated layer of PLA50 with the displacement and condensation of the PLA50 segments. In all cases, rheological results indicated a pure elastic behavior for the mixed BSA/PLA50 interfacial layers. The absence of relaxation upon the application of dilatational stress was attributed to the instantaneous displacement of the PLA50 segments and the nonexpulsion of the BSA segments. These results are interpreted with respect to the preparation of biodegradable PLA50 microparticles related to an emulsion-based process