Increasing Bovine Serum Albumin Concentration Research Articles

Clarifying the role of carboxyl functionality in squaraines towards aggregation and self-assembly through photophysical characterization and BSA interactions

The demand for near-infrared (NIR) probes with robust and stable fluorescence signals has surged, driven by their applications in optical sensing and bioimaging. Squraine dyes as NIR fluorescent probes have gained significant traction. However, understanding their behavior in aqueous media is important for their successful application. Herein we report the synthesis and photophysical characterization of carboxy-functionalized unsymmetrical squaraine dyes capable of light absorption and emission in the near-infrared (NIR) wavelength region. Structural variations in alkyl chain length, and spacer chain length between the primary chromophore and –COOH group were systematically introduced to investigate their impact on self-assembly in aqueous media leading to dye aggregation and their differential interactions with Bovine Serum Albumin (BSA) as a model protein. In phosphate buffer (PB) the absorption intensity decreased drastically along with pronounced shoulders due to dye aggregation leading to complete fluorescence quenching. However, in the presence of BSA, the intensity of shoulder bands reduced coupled with a sharp increase in the absorption associated with monomeric dye with the increasing concentration of BSA, indicating the prevention of dye aggregation owing to dye-BSA interactions. The prevention of dye aggregation due to dye-BSA interaction also led to a tremendous increase in the fluorescence intensities as a function of the increasing BSA concentrations. Site-selective study off BSA showed that these dyes bind preferably at Site-II using hydrophilic interactions. Thus, these dyes show great potential as FRET or fluorescent on/off probes for biosensing, non-covalent labeling of proteins, and fluorescent probes for bioimaging.

Photophysical Characterization and Biointeractions of NIR Squaraine Dyes for in Vitro and in Vivo Bioimaging.

The increasing demand for reliable near-infrared (NIR) probes exhibiting enduring fluorescence in living systems and facile compatibility with biomolecules such as peptides, antibodies or proteins is driven by the increasing use of NIR imaging in clinical diagnostics. To address this demand, a series of carboxy-functionalized unsymmetrical squaraine dyes (SQ-27, SQ-212, and SQ-215) along with non-carboxy-functionalized SQ-218 absorbing and emitting in the NIR wavelength range were designed and synthesized followed by photophysical characterization. This study focused on the impact of structural variations in the alkyl chain length, carboxy functionality positioning, and spacer chain length on dye aggregation and interaction with bovine serum albumin (BSA) as a model protein. In phosphate buffer (PB), the absorption intensity of the dyes markedly decreased accompanied by pronounced shoulders indicative of dye aggregation, and complete fluorescence quenching was seen in contrast to organic solvents. However, in the presence of BSA in PB, there was a enhancement in absorption intensity while regaining the fluorescence coupled with a remarkable increase in the intensity with increasing BSA concentrations, signifying the impact of dye-BSA interactions on preventing aggregation. Further analysis of Job's plot unveiled a 2:1 interaction ratio between BSA and all dyes, while the binding studies revealed a robust binding affinity (Ka) in the order of 107/mol. SQ-212 and SQ-215 were further tested for their in vitro and in vivo imaging capabilities. Notably, SQ-212 demonstrated nonpermeability to cells, while SQ-215 exhibited easy penetration and prominent cytoplasmic localization in in vitro studies. Injection of the dyes into laboratory mice showcased their efficacy in visualization, displaying stable and intense fluorescence in tissues without toxicity, organ damage, or behavioral changes. Thus, SQ-212 and SQ-215 are promising candidates for imaging applications, holding potential for noninvasive cellular and diagnostic imaging as well as biomarker detection when coupled with specific vectors in living systems.

Design and Synthesis of Novel Squaraine Dye with Highly Enhanced Far‐Red Fluorescence and its Interaction with a Model Protein

Novel amine‐functionalized symmetrical squaraine (SQ)‐dye and fluorescein isothiocyanate (FITC)–SQ–FITC dye conjugate are designed and successfully synthesized, followed by their structural and photophysical characterizations. Symmetrical SQ dye exhibits complete fluorescence quenching in polar solvents, which is explained by considering photoinduced electron transfer (PET) as a dominant quenching pathway. In contrast, FITC–SQ–FITC dye conjugate results in a decrease in an aggregation of both SQ and FITC units and about 47 times enhancement in the far‐red fluorescence appearing at 674 nm. This profound enhancement in the far‐red fluorescence is explained by the synergistic influence of suppression of aggregation‐induced quenching (ACQ) and PET. This newly designed FITC–SQ–FITC dye conjugate shows complete quenching of the far‐red fluorescence in phosphate buffer saline (PBS) owing to very strong dye aggregation, as confirmed by spectral absorption investigation. In PBS, it strongly interacts with bovine serum albumin (BSA) (Ka = 1.1 × 104 m−1) used as a model protein breaking the dye aggregation by BSA and increasing far‐red fluorescence associated with SQ as a function of increasing BSA concentration. A profound 117 times increase in fluorescence at 674 nm with 25 times of BSA concentration suggests that the designed FITC–SQ–FITC is an excellent far‐red probe for dye‐protein interaction.

The effect of buffer concentration on the dynamic/equilibrium surface tension of bovine serum albumin solution

The effect of phosphate buffer (Na2HPO4 and NaH2PO4) concentration on the dynamic and equilibrium surface tension (ST) of bovine serum albumin (BSA) solutions was examined in this study. A pendant bubble tensiometer was utilized for measuring the ST relaxation of BSA solutions in varying buffer concentration (0, 0.01–300 mM). The data showed: (i) an initial increase in buffer concentration (Cbuff < 0.3 mM) resulted in a slower ST relaxation and a notable rise in the equilibrium ST; (ii) a further rise in buffer concentration (Cbuff > 0.3 mM) resulted in a faster ST relaxation and a progressive decrease in the equilibrium ST; and (iii) despite an increase in BSA concentration from 2 to 15 (10−10 mol/cm3), the dynamic ST of BSA solutions always relaxed the slowest at Cbuff = 0.3 mM. The equilibrium ST of BSA solutions in 10 and 44 mM buffer [C = 0.1–15 (10−10 mol/cm3)] was also obtained and the data confirmed the near-constant equilibrium ST of purely aqueous BSA solutions [Le et al., J.Mol.Liq (2022) 118305] to not be an anomalous behavior but, observable irrespective of the solvent formulation.

Preparation, Characterization, and Biological Properties of Hydroxyapatite from Bigeye Snapper (Priancanthus tayenus) Bone.

The optimum condition of acid hydrolysis for hydroxyapatite extraction from bigeye snapper (Priancanthus tayenus) bone and the effects of extraction time (10-60 min) and HCl concentration (2.0-5.0% w/v) on yield and hydroxyapatite properties were determined. The optimum extracted condition was found using 5% HCl for 60 min, which was 13.4% yield; 19.8 g/100 g Ca content; 9.6 g/100 g P content; 2.1 Ca/P ratio; L*, a*, b*; and ΔE as 84.5, 2.8, 16.5, and 15.6, respectively. The using of 5% NaOH solution was optimum for hydroxyapatite precipitation from the extracted solution. The characteristic and biological properties of the obtained hydroxyapatite were studied. Fourier transform infrared spectroscopy and X-ray diffraction results showed a good comparison between the extracted and commercial hydroxyapatite. The microstructure of the extracted hydroxyapatite from a scanning electron microscope showed an irregular and flat-plate shape, large surface area, and roughness. The extracted hydroxyapatite was non- and low-cytotoxicity at a concentration of 50 and 100-400 µg/mL, respectively. Bovine serum albumin (BSA) adsorption and desorption of hydroxyapatite was studied. An increasing BSA concentration, hydroxyapatite amount, and adsorption time significantly increased protein adsorption on hydroxyapatite. Protein desorption from BSA-loaded hydroxyapatite showed an increase of release initially in the first 4 days and became a steady release rate until 14 days.

Triphenylphosphonium-functionalized BODIPY derivatives for mitochondria-targeted cell imaging and fluorescence turn-on sensing with protein selectivity

Triphenylphosphonium (TPP) cations endow fluorophores with improved hydrophilicities and mitochondria targeting abilities. Evidently, the number of cationic moieties can influence the behavior of fluorophores in different environments. Two water-soluble BODIPY fluorophores, 3TPP and 5TPP, were constructed with three and five TPP groups, respectively, in their structure. Both showed maximum absorption and emission at 640–700 nm wavelengths; however, 5TPP showed a fluorescence quantum yield 10 times higher than that of 3TPP in an aqueous medium, highlighting the beneficial effect of two additional TPP groups on the photophysical properties. While both fluorophores showed excellent stabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells, 5TPP permeated into the mitochondria better than 3TPP. Interestingly, 5TPP demonstrated a 90-fold increase in “turn-on” fluorescence in the presence of bovine serum albumin (BSA) in relation to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). Notably, the fluorescence intensity of 5TPP increased with increasing BSA concentration. The present work is the first report on BODIPY sensors with multiple bulky cationic moieties and provides insights on the applicability of 5TPP as a novel biomaterial for mitochondrion tracking and light-up fluorescence protein sensing.

Effects of Different Concentrations of BSA on In Vitro Corrosion Behavior of Pure Zinc in Artificial Plasma

When medical metallic materials are implanted in the body and come into contact with the body fluid environment, proteins will be rapidly adsorbed on the surface and affect the corrosion process of the material. Currently, there is no uniform understanding of the effect of protein adsorption on the corrosion behavior of materials due to the limitations of the nature of metal materials, protein concentrations, and different media environments. The effect of various bovine serum albumin (BSA) concentrations in artificial plasma (AP) on the corrosion behavior of pure Zn during 14 days of immersion was investigated in this research. The corrosion rate of pure Zn was slowed down by the addition of BSA, and the decelerating effect of lower protein concentration on the corrosion rate of Zn was more significant in the initial stage of immersion. With prolonging the immersion time, the corrosion rate of pure Zn in different media slowed down and stabilized, and the corrosion rates of pure Zn showed a decreasing trend with an increase of BSA concentration. Furthermore, the Langmuir adsorption isotherm model was utilized to study the relationship between the BSA concentration and corrosion behavior of pure Zn and to analyze the role of proteins in the degradation mechanism of pure Zn. This work could be useful for further exploration of potential clinical applications of zinc alloys.

Ultra-Fast Oxygen Monitoring During Proton FLASH Delivery Using the Phosphorescence Quenching Method and Soluble Oxyphor Probes

<h3>Purpose/Objective(s)</h3> FLASH is a promising form of radiation therapy due to its reported ability to spare normal tissues while being equipotent in tumor control. The mechanism underlying this tissue sparing effect is currently unknown, however the depletion of tissue oxygen at FLASH dose rates has been proposed as a potential source. To date, the oxygen depletion hypothesis has only been supported by analytical or numerical modeling studies, primarily due to the difficulty of measuring oxygen concentration on millisecond time scales during irradiation. In this project, we use the phosphorescence quenching method to probe oxygen depletion during proton delivery at both conventional (∼1Gy/sec) and FLASH (∼100 Gy/sec) dose rates. <h3>Materials/Methods</h3> Oxygen concentration was measured at rates of up to 3kHz using a phosphorescent probe, Oxyphor PtG4, and a time-domain OxyLED phosphorometer modified for ultra-fast operation. Sealed glass vials, containing the experimental solution and probe, were placed such that they were exposed to a uniform dose rate where the proton beam entered the vial. Radiation was delivered at conventional (conv) (∼1 Gy/s) and FLASH (∼100 Gy/s) dose rates. The g-value of oxygen depletion was measured as a function of dose rate, total dose, oxygen concentration, biomolecule concentration, and in the presence or absence of oxygen scavengers. Biomolecule relevant experiments were carried out using either 20mM phosphate buffer containing 1, 2, and 5% bovine serum albumin (BSA) or a solution designed to emulate the intracellular environment, containing 5mM glucose, 1M glycerol, 5mM glutathione, and 10 mM HEPES (Buffer 3G). Oxygen concentration was continuously monitored before, during, and after irradiation for all experiments. <h3>Results</h3> We found that FLASH dose rates resulted in lower g-values for oxygen depletion when compared to conventional dose rates by ∼15% (range: 7.2 to 22.5%) for each of the solutions tested. For example, in Buffer 3G, for a 30Gy dose, the g-value was 16% lower at FLASH dose rates (g_conv = 0.72 ± 0.02 μM/Gy, g_FLASH = 0.63 ± 0.02 μM/Gy) (all values listed are mean ± S.E.M.). The g-value increased with increasing BSA concentration (values for 1% and 5% BSA listed) at both conventional and FLASH dose rates (g_conv = 0.45 ± 0.05 and 0.58 ± 0.03 μM/Gy respectively, g_FLASH = 0.37 ± 0.01 and 0.62 ± 0.01 μM/Gy respectively). The g-value was higher for Buffer 3G than for the BSA solutions (g_conv = 0.72 ± 0.02 and 0.58 ± 0.03 μM/Gy respectively, g_FLASH = 0.63 ± 0.02 and 0.54 ± 0.01 μM/Gy respectively). An "after FLASH" period of gradual oxygen depletion which persisted for ∼0.5s and depleted an additional 32.1% oxygen was observed for Buffer 3G. <h3>Conclusion</h3> We have demonstrated a method for ultra-fast measurements of oxygen concentration during the delivery of proton radiation. Furthermore, we found that the g-value of oxygen depletion at FLASH dose rates is lower than that of conventional dose rates by approximately 15%.

Micellization, interaction and thermodynamics behavior of BSA + SDS mixture in aqua-organic mixed solvent: Influences of temperature and solvent composition

The interaction of bovine serum albumin (BSA) with sodium dodecyl sulphate (SDS) in aqueous medium as well as aqua-organic mixed media has been performed using the conductivity measurement technique at several temperatures. The experiments were performed in the temperature ranges of 298.15–313.15 K with a gap of 5 K. The critical micelle concentration (CMC) and the degree of micelle ionization (α) have been computed from the specific conductivity versus the surfactant concentration plot. The CMC values achieved in the present study are dependent on the concentration of BSA, composition of the mixed solvent, and a variation of experimental temperature. For SDS + BSA mixture, an increase of BSA concentration causes a decrease in the values of CMC. Also, the values of CMC of SDS + BSA system in water-organic solvents were found to follow the order: CMCwater-DMF > CMCwater-AN > CMCwater-DMSO > CMCwater. In every case examined, the association of SDS + BSA mixture was spontaneous (negative ΔG0m). On the basis of observed ΔH0m and ΔS0m values for the SDS + BSA mixed system, it is expected that an electrostatic, hydrophobic, and ion–dipole interactions are in effect between SDS and BSA species, whereas the hydrophobic interaction is believed to be the main driving force for the aggregation process. In each of the case thoroughly detected, a linear relationship between ΔH0m and ΔS0m values was viewed, which is a strong indication in favor of the presence of enthalpy–entropy compensation phenomenon in the overall interaction process.

Refractive index modulation in magnetophoresis of bioreaction induced self-assembled magnetic fluid.

We explore the refractive index (RI) modulation of bioreaction induced self-assembled magnetic fluid (SAMF) so as to facilitate the design of sensitive biosensors. Bovine serum albumin (BSA) is taken as a model protein to induce self-assembly of carboxylated magnetic nanoparticles (MNPs). A bidirectional magnetophoresis (BDMP) system is designed to generate uniform and large RI modulation to SAMF. A robust Mach-Zehnder interferometer compatible to the BDMP system is used for the RI detection. It is found that BDMP has greater ability in modulating the RI of magnetic fluid than the alignment of MNPs in a uniform magnetic field. The modulation depth of the RI increases with the increase of BSA concentration when applying a certain external magnetic field for a period of time. A larger magnetic field has greater ability to modulate the RI of SAMF. However, it may generate an over-modulation.

Influence of bovine serum albumin on biodegradation behavior of pure Zn.

Zinc is emerging as a promising biodegradable metal for temporary implant applications. In this work, we investigate the influence of bovine serum albumin (BSA)-the most abundant blood protein in simulated body fluid (SBF) on degradation of pure Zn via electrochemical measurements and long-term immersion. Electrochemical experiments indicate a decrease of the corrosion rate of bare Zn with increasing BSA concentration in solution for short-term exposures. Samples were characterized with scanning electron microscope (SEM) (including energy dispersive spectroscopy [EDS], X-ray photoelectron spectroscopy [XPS], Fourier transform infrared spectroscopy [FTIR], and time-of-flight secondary ion mass spectrometry [TOF-SIMS]) after immersion up to 21 days. Presence of BSA in the electrolyte, decrease the amount of Ca-phosphate precipitation on Zn surface. However, a more compact surface layer formed in the presence of BSA in solution. Most noteworthy, in long-term exposures, BSA enhances localized corrosion of Zn-such detrimental localized attack was not observed in BSA-free solution. We suggest that a sealed space forming between the Zn substrate and a protein adsorption layer restricts mass transport, thus triggering localized corrosion of Zn.

Signal Amplification in an Optical and Dielectric Biosensor Employing Liquid Crystal-Photopolymer Composite as the Sensing Medium.

An optical and dielectric biosensor based on a liquid crystal (LC)–photopolymer composite was established in this study for the detection and quantitation of bovine serum albumin (BSA). When the nematic LC E7 was doped with 4-wt.% NOA65, a photo-curable prepolymer, and photopolymerized by UV irradiation at 20 mW/cm2 for 300 s, the limit of detection determined by image analysis of the LC optical texture and dielectric spectroscopic measurements was 3400 and 88 pg/mL for BSA, respectively, which were lower than those detected with E7 alone (10 μg/mL BSA). The photopolymerized NOA65, but not the prepolymer prior to UV exposure, contributed to the enhanced optical signal, and UV irradiation of pristine E7 in the absence of NOA65 had no effect on the optical texture. The effective tilt angle θ, calculated from the real-part dielectric constant ε’, decreased with increasing BSA concentration, providing strong evidence for the correlation of photopolymerized NOA65 to the intensified disruption in the vertically oriented LC molecules to enhance the optical and dielectric signals of BSA. The optical and dielectric anisotropy of LCs and the photo-curable dopant facilitate novel quantitative and signal amplification approaches to potential development of LC-based biosensors.

An Investigation of the Membrane Fouling Behaviors in Constant Flux Mode

Studying the effect of different operation conditions (bovine serum albumin (BSA) concentration, flux and stirring speed) on the membrane fouling behaviors (the variation of transmembrane pressure (TMP), cake resistance (Rc), pore blocking resistance (Rc ) and available membrane area ratio (A/A0 ) is of paramount importance in the membrane bioreactor (MBR) process. The constant flux filtration experiment was conducted to investigate the fouling behaviors of BSA solution, which provides a guidance for controlling the membrane fouling. The intermediate blocking-cake combined model was established and it was described mathematically with good results. The results showed that the influence sequence of operating conditions on the TMP was obtained as flux > concentration > stirring speed. Meanwhile, Rc decreased with the increase of stirring speed, and the A/A0 decreased with the increase of BSA concentration and the flux.

The effect of albumin in photostabilization of riboflavin: A kinetic study

This investigation involves a study of the photochemical interaction of riboflavin (RF) and bovine serum albumin (BSA) in aqueous solution and the evaluation of this effect on the photostabilization of RF. RF solution (5 × 10–5 M) were irradiated with visible light in the presence of BSA (4.0–6.0 × 10–5 M) at pH 7.4 (0.005 M, phosphate buffer saline) and the apparent first–order rate constants for the photolysis of RF were found to be in the range of 3.92–9.26 × 10–3 min–1. The rate of RF photolysis is inhibited with an increase in the concentration of BSA. The second–order rate constant for the photochemical interaction of RF and BSA at pH 7.4 is 1.22 M–1 min–1. There is a gradual loss of RF fluorescence with an increase in BSA concentration due to the formation of a non–fluorescent complex between the two molecules. The value of Stern-Volmer quenching constant has been determined as 2.673 × 103 M–1. A two-component spectrometric method with correction for irrelevant absorption caused by BSA components has been used to determine RF and its photoproduct, lumichrome (LC), in photolyzed solutions. The mode of photochemical interaction of RF and BSA has been discussed.

Bovine Serum Albumin Enhances Silver Nanoparticle Dissolution Kinetics in a Size- and Concentration-Dependent Manner.

The dissolution of silver nanoparticles (AgNPs) to release Ag(I)(aq) is an important mechanism in potentiating AgNP cytotoxicity and imparting their antibacterial properties. However, AgNPs can undergo other simultaneous biophysicochemical transformations, such as protein adsorption, which can mediate AgNP dissolution behaviors. We report the comprehensive analysis of AgNP dissolution and protein adsorption behaviors with monolayer surface coverage of AgNPs by bovine serum albumin (BSA). AgNP dissolution rate constants, kdissolution, were quantified over several particle sizes (10, 20, and 40 nm) and BSA concentrations (0-2 nM) using linear sweep stripping voltammetry. Across all particle sizes, the dissolution rate constant increased with increasing BSA concentrations. However, protein-enhanced dissolution behaviors were most pronounced for 10 nm AgNPs, which exhibited 3.6-fold and 7.7-fold relative enhancement when compared to 20 and 40 nm AgNPs, respectively. Changes to AgNP surface properties upon interaction with BSA were monitored using dynamic light scattering and zeta potential measurements, while BSA-AgNP complex formation was evaluated using UV-vis spectroscopy and circular dichroism spectroscopy. A subtle increase in the BSA-AgNP association constant was observed with an increase in the AgNP size. Together, these results suggest that the AgNP size dependence of BSA-enhanced dissolution of AgNPs is possibly mediated through both displacement of Ag(I)(aq)-loaded BSA by excess protein in the bulk solution and minimized accessibility of the AgNP surface because of BSA adsorption.

The effect of humic acid and bovine serum albumin on the adsorption and stability of ZnO nanoparticles on powdered activated carbon

Abstract Natural organic matter (NOM) can influence the properties and behavior of metal nanoparticles (MNPs) in aquatic environments. Thus, understanding the effect of NOM on MNPs’ physiochemical properties is critical for identifying an effective water treatment processes, and controlling the potential risk they pose to ecological and human health. In this study, adsorption and leaching experiments were performed with powder activated carbon (PAC), to investigate the effect of humic acid (HA) and bovine serum albumin (BSA) on the removal of ZnO nanoparticles (ZnONPs) from an aqueous environment and their stability on the adsorbed PAC. The different ZnONPs forms— particulate, colloidal, and dissolved Zn fractions, were respectively considered. The adsorption experiments demonstrated that both colloidal and dissolved Zn fractions can adsorb on the PAC’s surface. As the HA concentration increased from 0 to 20 mg/L, the colloidal Zn fraction’s adsorption efficiency decreased from 74.49% to 61.24%. However, BSA did not significantly influence the colloidal Zn fraction’s adsorption. The leaching experiments showed that the colloidal Zn fraction would release from the PAC’s surface, and most of them transferred to the dissolved Zn fraction. As the HA concentration increased from 0 to 20 mg/L, the Zn concentration leached from the PAC adsorbed ZnONPs reduced from 0.956 to 0.694 mg/g. Comparatively, the leached Zn concentration varied only slightly with an equal increase in BSA concentration.

Influence of Proteins on Transport of Ferrihydrite Particles Formed during Recharge of Groundwater Containing Fe with Reclaimed Water

When reclaimed water was recharged into groundwater containing a low content of ferrous iron, Fe-rich particles were generated and started to transport into the porous medium. X-ray powder diffraction and Mössbauer spectroscopy analysis showed that the generated Fe-rich particles were in a poorly crystallized ferrihydrite phase. After the formation of ferrihydrite particles, the mass loss of contaminants was calculated, which was 88.2% for Al, 93.3% for Zn, and 41.6% for chemical oxygen demand (COD). Protein-like compounds were predominant in the removed COD. Bovine serum albumin (BSA) was used as a model to investigate the effect of proteins on the transport of ferrihydrite particles in porous medium. Results showed that the attachment efficiency of ferrihydrite particles on the porous medium decreased from 100% to 75% with the increase of BSA concentration from 10 mg/L to 100 mg/L. BSA was attached to the surface of ferrihydrite particles via electrostatic adsorption. Thus, the zeta potential of ferrihydrite particles changed from positive to negative, and the particles became less aggregated, thereby enhancing particle mobility. This observation provided evidence that protein residues in reclaimed water enhance the transport of Fe-rich particles in saturated porous medium.

Micellization and aggregation behavior of crocin with bovine serum albumin: A biophysical study

The interaction of bovine serum albumin (BSA) with a naturally occurring surfactant (trans-crocetin di-(β-D-gentiobiosyl) ester, crocin) was studied under biophysical conditions by using various techniques such as surface tensiometry, UV–visible spectrophotometery and fluorescence. Upon the addition of a small amount of BSA, the λmax of a crocin dispersion in water shifted to lower wavelengths, indicating either a ground state complex formation between BSA and crocin or solubilization of BSA into the micelles of crocin. The critical micelle concentration (cmc) of crocin decreases in the presence of increasing BSA concentrations. The complex formation constant (KC), surface pressure πcmc, maximum surface excess (Γmax), the minimum surface area per molecule (Amin), enthalpy (ΔH0), entropy (ΔS0), and Gibbs free energy change (ΔG0) were calculated for the BSA-crocin interactions. BSA fluorescence was quenched in the presence of crocin. The fluorescence data were used for determining the apparent association constant (Kapp), the Stern-Volmer constant (KSV), the bimolecular rate constant of the quenching process (kq) and the thermodynamic parameters.

Ultrasensitive, highly selective, and real-time detection of protein using functionalized CNTs as MIP platform for FOSPR-based biosensor

A facile approach is presented for the detection of bovine serum albumin (BSA), based on fiber optic surface plasmon resonance (FOSPR) combined with molecular imprinting (MI). The probe is fabricated by exploiting the plasmonic property of silver thin film and vinyl-functionalised carbon nanotube-based MIP platform. BSA template molecules are imprinted on the MIP layer coated over multi-walled carbon nanotubes to ensure high specificity of the probe in the interfering environments. In addition, FOSPR endorses the sensor capability of real-time and remote sensing along with very high sensitivity due to the use of nanostructured MI platform. The response of the probe is considered in terms of the absorbance spectrum recorded for various concentrations of BSA. The sensor shows a wide dynamic range of 0–350 ng l−1 with a considerably linear response up to 100 ng l−1 in the peak absorbance wavelength with BSA concentration. A highest sensitivity of 0.862 nm per ng l−1 is achieved for the lowest concentration of BSA and it decreases with the increase in BSA concentration. The performance of the present sensor is compared with those reported in the literature in terms of the limit of detection. It is found that the probe possesses a lowest LOD of 0.386 ng l−1 in addition to other advantages such as real-time online monitoring, high sensitivity, high specificity, and remote sensing.

Effect of surface energy of solid surfaces on the micro- and macroscopic properties of adsorbed BSA and lysozyme

The surface energy, a macroscopic property, depends on the chemical functionality and micro- and macroscopic roughness of the surface. The adsorption of two widely used proteins bovine serum albumin (BSA) and lysozyme on surfaces of four different chemical functionalities were done to find out the interrelation between macroscopic and microscopic properties. We have observed the secondary structure of protein after its adsorption. In addition, we observed the variation of surface energy of proteins due to variation in adsorption time, change in protein concentration and effect of a mixture of proteins.Surfaces of three different chemical functionalities namely, amine, hydroxyl and octyl were obtained through self-assembled monolayer on silica surfaces and were tested for responses towards adsorption of lysozyme and BSA. The adsorbed lysozyme has higher surface energy than the adsorbed BSA on amine and octyl surfaces. On hydroxyl functional surface, the surface energy due to the adsorbed lysozyme or BSA increases slowly with time.The surface energy of the adsorbed protein increases gradually with increasing protein concentration on hydrophobic surfaces. On hydrophilic surfaces, with increasing BSA concentration in bulk solution, the surface energy of the adsorbed protein on GPTMS and amine surfaces is maximum at 1μM concentration. During the adsorption from a mixture of BSA and lysozyme on octyl surface, first lysozyme adsorbs and subsequent BSA adsorption leads to a high surface energy.