Bovine serum albumin adsorption onto immobilized organotrichlorosilane surface: influence of the phase separation on protein adsorption patterns

The influence of charge on the translation of the sandwich ELISA approach to electronic biosensors

The sandwich approach, whereby an antigen is captured by a primary antibody and detected by a secondary antibody, is commonly used to improve the selectivity and sensitivity of enzyme-linked immunosorbent assays (ELISA). This work details the experimental factors that impact the reliable translation of this sandwich approach to two commonly used electronic biosensors, namely potentiometric and impedimetric biosensors. Previous studies have demonstrated the Debye screening limitations associated with potentiometric biosensors. However, the correlation between the ionic strength of the measurement buffer and the impedimetric biosensing response has not been studied. Potentiometric biosensors were able to successfully detect the primary antibody and the target antigen by decreasing the ionic strength of the phosphate buffered saline (PBS) measurement buffer from 1x PBS to 0.01x PBS. However, the secondary antibody used for the selective signal amplification was not reliably detected. Therefore, the sandwich approach is not viable for potentiometric sensing at biologically relevant ionic strengths, due to the Debye screening effect. Alternatively, decreasing the ionic strength of the measurement buffer allowed for the successful translation of the sandwich approach to impedimetric biosensors. Impedimetric biosensing literature typically attributes a measured increase in the charge transfer resistance to an increase in the thickness of the immobilized biolayer. However, this work highlights the influence that both the charge and thickness of the biolayer have on the transport of the redox couple. Decreasing the ionic strength of the measurement buffer lowers the molecular charge screening effect. This permits the transport of a positively charged redox probe through a negatively charged immobilized biolayer via migration and diffusion. The results demonstrate that the use of a buffer at a lower, yet biologically relevant ionic strength allows for the successful translation of the sandwich approach to impedimetric biosensors.

Fabrication of bovine serum albumin nanofibrils: Physicochemical characteristics, emulsifying and foaming activities

Bovine serum albumin nanofibrils (BSNs) were fabricated under thermal treatment (85 °C) at acidic condition (pH 2.0) and the incubation time on the structural, and physicochemical characteristics were probed. The formation and development of BSNs have been detected and confirmed by Thioflavin T (ThT) fluorescence and circular dichroism (CD) measurements. The structural alterations of bovine serum albumin (BSA) have also been investigated using intrinsic fluorescence and Congo red (CGR) UV-vis spectroscopy. Atomic force microscopy (AFM) outcomes displayed the morphologies of BSNs at varied time, with a diameter of about 3 nm and a contour length of about 200 nm at 24 h. The apparent viscosities of BSNs at three different pH were in the following order: pH 3.0 > pH 5.0 > pH 7.0. Emulsifying and foaming properties of BSA were pronouncedly enhanced through fibrillation, which was highly correlated with the interfacial properties and structural characteristics. Highest EAI 54.2 m2/g was attained at 48 h and no pronounced alterations were observed for EAI at 24 h and 48 h. Maximum value of FC was obtained at 48 h for BSA. This study will provide some useful information in understanding the formation of BSNs and broaden their application in food systems as functional food ingredients.

Micro-flow imaging multi-instrument evaluation for sub-visible particle detection

Sub-visible particles (SVPs) in pharmaceutical products are a critical quality attribute, and therefore should be monitored during development. Although light obscuration (LO) and microscopic particle count tests are the primary pharmacopeial methods used to quantify SVPs, flow imaging methods like Micro-Flow Imaging (MFI™) appear to overcome shortcomings of LO such as limited sensitivity concerning smaller translucent SVPs in the size range < 10 µm. Nowadays, MFI™ is routinely utilized during development of biologicals. Oftentimes multiple devices are distributed across several laboratories and departments. This poses challenges in data interpretation and consistency as well as in the use of multiple devices for one purpose. In this study, we systematically evaluated seven MFI™ instruments concerning their counting and size precision and accuracy, using an inter-comparable approach to mimic daily working routine. Therefore, we investigated three different types of particles (i) NIST certified counting standards, (ii) protein-coated particles, and (iii) stress-induced particles from a monoclonal antibody. We compared the results to alternative particle detection methods: LO and Backgrounded Membrane Imaging (BMI). Our results showed that the precision and accuracy of particle count and size, as well as the comparability of instruments, depended on the particle source and its material properties. The various MFI™ instruments investigated showed high precision (<15 %) and data generated on different instruments were of the same order of magnitude within pharmacopeial relevant size ranges for NIST certified counting standards. However, we found limitations in the upper and lower detection limits, contrary to the limits claimed by the manufacturer. In addition, proteinaceous and protein-containing particles showed statistically significant differences in particle counts, while the measured particle diameters of all sizes were quite consistent.

Non-toxic Polymeric Dots with the Strong Protein-Driven Enhancement of One- and Two-Photon Excited Emission for Sensitive and Non-destructive Albumin Sensing

The need for efficient probing, sensing, and control of the bioactivity of biomolecules (e.g., albumins) has led to the engineering of new fluorescent albumins' markers fulfilling very specific chemical, physical, and biological requirements. Here, we explore acetone-derived polymer dots (PDs) as promising candidates for albumin probes, with special attention paid to their cytocompatibility, two-photon absorption properties, and strong ability to non-destructively interact with serum albumins. The PDs show no cytotoxicity and exhibit high photostability. Their pronounced green fluorescence is observed upon both one-photon excitation (OPE) and two-photon excitation (TPE). Our studies show that both OPE and TPE emission responses of PDs are proteinaceous environment-sensitive. The proteins appear to constitute a matrix for the dispersion of fluorescent PDs, limiting both their aggregation and interactions with the aqueous environment. It results in a large enhancement of PD fluorescence. Meanwhile, the PDs do not interfere with the secondary protein structures of albumins, nor do they induce their aggregation, enabling the PD candidates to be good nanomarkers for non-destructive probing and sensing of albumins.

Safe magnetic resonance imaging on biocompatible nanoformulations

Magnetic resonance imaging (MRI) holds promise for the early clinical diagnosis of various diseases, but most clinical MR techniques require the use of a contrast medium. Several nanomaterial (NM) mediated contrast agents (CAs) are widely used as T1- and T2-based MR contrast agents for clinical and non-clinical applications. Unfortunately, most NM-based CAs are toxic or non-biocompatible, restricting their practical/clinical applications. Therefore, the development of nontoxic and biocompatible CAs for clinical MRI diagnosis is highly desired. To this end, several biocompatible and biomimetic strategies have been developed to offer long blood circulation time, significant biocompatibility, in vivo biodistribution and high contrast ability for efficient imaging. However, detailed review reports on biocompatible NMs, specifically for MR imaging have not yet been summarized. Thus, in the present review we summarize  various surface coating strategies (such as polymers, proteins, cell membranes, etc.) to achieve biocompatible NPs, providing a detailed discussion of advances and future prospects for safe MRI imaging.

Spectral image contrast-based flow digital nanoplasmon-metry for ultrasensitive antibody detection

Background

Gold nanoparticles (AuNPs) have been widely used in local surface plasmon resonance (LSPR) immunoassays for biomolecule sensing, which is primarily based on two conventional methods: absorption spectra analysis and colorimetry. The low figure of merit (FoM) of the LSPR and high-concentration AuNP requirement restrict their limit of detection (LOD), which is approximately ng to μg mL⁻¹ in antibody detection if there is no other signal or analyte amplification. Improvements in sensitivity have been slow in recent for a long time, and pushing the boundary of the current LOD is a great challenge of current LSPR immunoassays in biosensing.

Results

In this work, we developed spectral image contrast-based flow digital nanoplasmon-metry (Flow DiNM) to push the LOD boundary. Comparing the scattering image brightness of AuNPs in two neighboring wavelength bands near the LSPR peak, the peak shift signal is strongly amplified and quickly detected. Introducing digital analysis, the Flow DiNM provides an ultrahigh signal-to-noise ratio and has a lower sample volume requirement. Compared to the conventional analog LSPR immunoassay, Flow DiNM for anti-BSA detection in pure samples has an LOD as low as 1 pg mL⁻¹ within only a 15-min detection time and 500 μL sample volume. Antibody assays against spike proteins of SARS-CoV-2 in artificial saliva that contained various proteins were also conducted to validate the detection of Flow DiNM in complicated samples. Flow DiNM shows significant discrimination in detection with an LOD of 10 pg mL⁻¹ and a broad dynamic detection range of five orders of magnitude.

Conclusion

Together with the quick readout time and simple operation, this work clearly demonstrated the high sensitivity and selectivity of the developed Flow DiNM in rapid antibody detection. Spectral image contrast and digital analysis further provide a new generation of LSPR immunoassay with AuNPs.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01188-6.

The albumin-based nanoparticle formation in relation to protein aggregation

Albumin is an attractive protein for the preparation of nanoparticle with possible therapeutic applications, due to its biodegradable, nontoxic, non-immunogenic, and metabolizable properties. Many studies have investigated the formation of albumin nanoparticles, generally by the desolvation or coacervation approaches. One of the most important parameters that should be considered in the formation of nanoparticles is their morphology (size and shape). There are many proposals to control the nanoparticle size, but it remains a challenge for researchers yet. In this study, we showed that control of BSA-based nanoparticles/microparticles size could be achieved by varying the temperature and pH and therefore controlling the rate of aggregation. The aggregation behavior was monitored by UV-Vis spectroscopy, SEM, and dye-binding assay. Our results provide more options for the size and shape control of BSA-based nanoparticle in natural buffer systems. The aggregation of BSA at different temperatures within the range of 50-80 °C were studied under the effect of different pHs in the range of 4.7-6.2. In this research, we found that protein aggregation under extreme conditions of pH and temperature, or at the pH near to pI appears to be amorphous, and at the pH above the pI seems to be the amyloid fibril structure. In some instances where the aggregation is neither too fast nor too slow, in the initial phase of the aggregation process, nanoparticle structures can be identified and separated by mechanistic approaches. This observation suggests that the best condition for monitoring the formation of albumin-based nanoparticles could be pH 5.7, 70 °C. Satisfactory rationalization of all aspects of our experimental observation requires further and more detailed study.

Diffusion of Protein Molecules through Microporous Nanofibrous Polyacrylonitrile Membranes

Porous nanofibrous membranes have ultrahigh specific surface areas and could be broadly employed in protein purification, enzyme immobilization, and biosensors with enhanced selectivity, sensitivity, and efficiency. However, large biomolecules, such as proteins, have hindered diffusion behavior in the micro-porous media, significantly reducing the benefits provided by the nanofibrous membranes. The study of protein diffusion in polyacrylonitrile (PAN) nanofibrous membranes produced under varied humidity and polymer concentration of electrospinning revealed that heterogeneous structures of the nanofibrous membranes possess much smaller effective pore sizes than the measured pore sizes, which significantly affects the diffusion of large molecules through the system though sizes of proteins and pH conditions also have great impacts. Only when the measured membrane pore size is at least 1000 times higher than the protein size, the diffusion behavior of the protein is predictable in the system. The results provide insights into the design and applications of proper nanofibrous materials for improved applications in protein purification and immobilizations.

On the control of dispersion interactions between biological membranes and protein coated biointerfaces

HYPOTHESIS

Interaction of cellular membranes with biointerfaces is of vital importance for a number of medical devices and implants. Adhesiveness of these surfaces and cells is often regulated by depositing a layer of bovine serum albumin (BSA) or other protein coatings. However, anomalously large separations between phospholipid membranes and the biointerfaces in various conditions and buffers have been observed, which could not be understood using available theoretical arguments.

METHODS

Using the Lifshitz theory, we here evaluate the distance-dependent Hamaker coefficient describing the dispersion interaction between a biointerface and a membrane to understand the relative positioning of two surfaces. Our theoretical modeling is supported by experiments where the biointerface is represented by a glass substrate with deposited BSA and protein layers. These biointerfaces are allowed to interact with giant unilamellar vesicles decorated with polyethylene glycol (PEG) using PEG lipids to mimic cellular membranes and their pericellular coat.

RESULTS

We demonstrate that careful treatment of the van der Waals interactions is critical for explaining the lack of adhesiveness of the membranes with protein-decorated biointerfaces. We show that BSA alone indeed passivates the glass, but depositing an additional protein layer on the surface BSA, or producing multiple layers of proteins and BSA results in repulsive dispersion forces responsible for 100 nm large equilibrium separations between the two surfaces.

Nanostructure of bioactive glass affects bone cell attachment via protein restructuring upon adsorption

The nanostructure of engineered bioscaffolds has a profound impact on cell response, yet its understanding remains incomplete as cells interact with a highly complex interfacial layer rather than the material itself. For bioactive glass scaffolds, this layer comprises of silica gel, hydroxyapatite (HA)/carbonated hydroxyapatite (CHA), and absorbed proteins—all in varying micro/nano structure, composition, and concentration. Here, we examined the response of MC3T3-E1 pre-osteoblast cells to 30 mol% CaO–70 mol% SiO₂ porous bioactive glass monoliths that differed only in nanopore size (6–44 nm) yet resulted in the formation of HA/CHA layers with significantly different microstructures. We report that cell response, as quantified by cell attachment and morphology, does not correlate with nanopore size, nor HA/CHO layer micro/nano morphology, or absorbed protein amount (bovine serum albumin, BSA), but with BSA’s secondary conformation as indicated by its β-sheet/α-helix ratio. Our results suggest that the β-sheet structure in BSA interacts electrostatically with the HA/CHA interfacial layer and activates the RGD sequence of absorbed adhesion proteins, such as fibronectin and vitronectin, thus significantly enhancing the attachment of cells. These findings provide new insight into the interaction of cells with the scaffolds’ interfacial layer, which is vital for the continued development of engineered tissue scaffolds.

Near-Infrared-Triggered Photothermal Aggregation of Polymer-Grafted Gold Nanorods in a Simulated Blood Fluid

Gold nanorods were decorated with thermoresponsive copolymers of tailored architecture and constructed from N-isopropyl acrylamide and acrylamide. The copolymers were prepared via reversible addition-fragmentation chain transfer polymerization (RAFT) and immobilized on the gold nanorod surface taking advantage of the aurophilicity of its inherently formed trithiocarbonate groups. The topology as well as the average molecular weight of the copolymers was altered using either a monofunctional or 3-arm star RAFT agent. Two-dimensional arrays of the self-assembled core-shell nanostructures were fabricated by drop-casting showing tunable interparticle spacings. In a simulated blood fluid, the lower critical solution temperature of the nanohybrids could be modified over a significant temperature range around body temperature by adjusting the copolymer composition, the architecture, and/or the size of the polymer. The intrinsic photothermal properties of the gold nanorods were utilized to trigger particle aggregation by irradiation at 808 nm in the optical window of human tissues. In effect, a new nanohybrid system with remotely controllable aggregation via an external NIR-light stimulus for nanomedical applications was developed.

In vitro evaluation of drug delivery behavior for inhalable amorphous nanoparticle formulations in a human lung epithelial cell model

Respiratory tract infections caused by multidrug-resistant (MDR) Gram-negative bacteria such as Pseudomonas aeruginosa are serious burdens to public health, especially in cystic fibrosis patients. The combination of colistin, a cationic polypeptide antibiotic, and ivacaftor, a cystic fibrosis transmembrane regulator (CFTR) protein modulator, displays a synergistic antibacterial effect against P. aeruginosa. The primary aim of the present study is to investigate the transport, accumulation and toxicity of a novel nanoparticle formulation containing colistin and ivacaftor in lung epithelial Calu-3 cells. The cell viability results demonstrated that ivacaftor alone or in combination with colistin in the physical mixture showed significant toxicity at an ivacaftor concentration of 10 μg/mL or higher. However, the cellular toxicity was significantly reduced in the nanoparticle formulation. Ivacaftor transport into the cells reached a plateau rapidly as compared to colistin. Colistin transport across the Calu-3 cell monolayer was less than ivacaftor. A substantial amount (46-83%) of ivacaftor, independent of dose, was accumulated in the cell monolayer following transport from the apical into the basal chamber, whereas the intracellular accumulation of colistin was relatively low (2-15%). The nanoparticle formulation significantly reduced the toxicity of colistin and ivacaftor to Calu-3 cells by reducing the accumulation of both drugs in the cell and potential protective effects by bovine serum albumin (BSA), which could be a promising safer option for the treatment of respiratory infections caused by MDR P. aeruginosa.

Fluorescence correlation spectroscopy to unravel the interactions between macromolecules in wine

In this work, the interaction of wine macromolecules with a bovine serum albumin (BSA) was investigated using fluorescence correlation spectroscopy (FCS). FCS offers the opportunity to study molecular and macromolecular aggregation without disturbing the wine by introducing only very small amounts of fluorescently labelled molecules to the system. It was observed that the diffusion coefficient of fluorescently labelled BSA varies with the addition of wine macromolecules, indicating changes in the protein conformation and the formation of complexes and aggregates. The addition of a wine polysaccharide rhamnogalacturonan II-enriched fraction led to aggregation, while addition of a mannoprotein-enriched fraction exhibited a protective effect on protein aggregation. Proteins strongly interacted with tannins, leading to the precipitation of protein-tannin complexes, while the presence of polysaccharides prevented this precipitation. Finally, the application of FCS was demonstrated in real wines, to investigate the problem of protein haze formation through live monitoring of heat-induced aggregation in wine.

Effects of Surface Protein Adsorption on the Distribution and Retention of Intratumorally Administered Gold Nanoparticles

The heterogeneous distribution of delivery or treatment modalities within the tumor mass is a crucial limiting factor for a vast range of theranostic applications. Understanding the interactions between a nanomaterial and the tumor microenvironment will help to overcome challenges associated with tumor heterogeneity, as well as the clinical translation of nanotheranostic materials. This study aims to evaluate the influence of protein surface adsorption on gold nanoparticle (GNP) biodistribution using high-resolution computed tomography (CT) preclinical imaging in C57BL/6 mice harboring Lewis lung carcinoma (LLC) tumors. LLC provides a valuable model for study due to its highly heterogenous nature, which makes drug delivery to the tumor challenging. By controlling the adsorption of proteins on the GNP surface, we hypothesize that we can influence the intratumoral distribution pattern and particle retention. We performed an in vitro study to evaluate the uptake of GNPs by LLC cells and an in vivo study to assess and quantify the GNP biodistribution by injecting concentrated GNPs citrate-stabilized or passivated with bovine serum albumin (BSA) intratumorally into LLC solid tumors. Quantitative CT and inductively coupled plasma optical emission spectrometry (ICP-OES) results both confirm the presence of particles in the tumor 9 days post-injection (n = 8 mice/group). A significant difference is highlighted between citrate-GNP and BSA-GNP groups (** p < 0.005, Tukey's multiple comparisons test), confirming that the protein corona of GNPs modifies intratumoral distribution and retention of the particles. In conclusion, our investigations show that the surface passivation of GNPs influences the mechanism of cellular uptake and intratumoral distribution in vivo, highlighting the spatial heterogeneity of the solid tumor.

Adsorption behaviors of salivary pellicle proteins onto denture base metals using 27-MHz quartz crystal microbalance

BACKGROUND

The adsorption of salivary pellicle proteins onto the material surface is key for denture plaque formation.

OBJECTIVE

We aimed to investigate the adsorption of bovine serum albumin (BSA) and mucin (MCN) onto denture base metal materials using a 27-MHz quartz crystal microbalance (QCM) method.

METHODS

A gold (Au), titanium (Ti), and cobalt chromium alloy (Co-Cr) sensors were employed for QCM measurements. Adsorbed amounts of BSA or MCN were calculated by observing the frequency decrease, and the apparent reaction rate, kobs, was obtained by the curve fitting of the frequency shift against the adsorption time.

RESULTS

The adsorbed amounts of BSA on Ti were significantly lower than those on Au and Co-Cr. For MCN adsorption, Au showed significantly greater amounts of adsorption than Co-Cr. The kobs of Ti for BSA adsorption was significantly smaller than for the Co-Cr. The kobs of Ti, and Co-Cr for MCN adsorption were significantly smaller than for the Au. A clear correlation was not determined between adsorbed amounts of BSA or MCN onto each sensor and the surface topography or contact angles.

CONCLUSIONS

The difference of denture base metals and the difference of salivary proteins influences the adsorption behavior of salivary proteins.

Salting Up and Salting Down of Bovine Serum Albumin Layers at the Air-Water Interface

The surface adsorption of bovine serum albumin in pure water and salted aqueous solutions was studied by neutron reflection. With the contrast match technique, the surface excess in null reflecting water as a function of the protein concentration was revealed. It is found that, in a concentration range from 1 ppm (parts per million, mg/L) to 1000 ppm, without salts, the surface excess shows a profound peak at around 20 ppm; with salts, the surface excess increases steadily with the protein concentration. When the surface excess at a specific protein concentration is viewed, the introduction of sodium chloride causes either a salting down effect (surface adsorption decline) or a salting up effect (surface adsorption increase), depending upon the protein concentration. The salting up effect is observed at the low (∼1 ppm) and high (∼1000 ppm) concentrations, and the salting down effect dominates the intermediate concentration range. The change in solution pH relative to the isoelectric point (PI) can act as a simple indicator for the salting up or salting down behavior. When the solution pH is shifted toward the PI by adding salts, surface adsorption enhances; when the solution pH is shifted away from the PI by adding salts, surface adsorption declines.

Imaging GPCR internalization using near-infrared Nebraska red-based reagents

Internalization of G protein-coupled receptor (GPCRs) represents a nearly universal pathway for receptor downregulation. Imaging this process provides a means for the identification of pharmaceutical agents as well as potential ligands for orphan receptors. However, there is a need for the further development of near-infrared (NIR) probes capable of monitoring internalization in order to enable multiplexing with existing green fluorescent GPCR activity assays. Our laboratory has recently described a series of near-infrared (NIR) fluorophores in which a phosphinate functionality is inserted at the bridging position of the xanthene scaffold. These fluorophores, termed Nebraska Red (NR) dyes, provide attractive reagents for imaging protein localization. Herein, we disclose the development of NR-based HaloTag ligands for imaging membrane proteins on living cells. These new probes are utilized to image membrane pools of the human orexin type 2 receptor, an established target for the treatment of insomnia. We demonstrate the ability of fetal bovine serum (FBS) to noncovalently associate with a spirolactonized NR probe, enabling no-wash imaging with a 45-fold enhancement of fluorescence. Furthermore, we characterize the utility of NR-based HaloTag ligands for real-time monitoring of receptor internalization upon agonist stimulation. These new reagents enable potential multiplexing with existing GPCR activity assays in order to identify new modulators of GPCR activity as well as ligands for orphan receptors.

Role of carboxylic group pattern on protein surface in the recognition of iron oxide nanoparticles: A key for protein corona formation

The knowledge of protein-nanoparticle interplay is of crucial importance to predict the fate of nanomaterials in biological environments. Indeed, protein corona on nanomaterials is responsible for the physiological response of the organism, influencing cell processes, from transport to accumulation and toxicity. Herein, a comparison using four different proteins reveals the existence of patterned regions of carboxylic groups acting as recognition sites for naked iron oxide nanoparticles. Readily interacting proteins display a distinctive surface distribution of carboxylic groups, recalling the geometric shape of an ellipse. This is morphologically complementary to nanoparticles curvature and compatible with the topography of exposed Fe^III sites laying on the nanomaterial surface. The recognition site, absent in non-interacting proteins, promotes the nanoparticle harboring and allows the formation of functional protein coronas. The present work envisages the possibility of predicting the composition and the biological properties of protein corona on metal oxide nanoparticles.

Investigation on Secondary Structure Alterations of Protein Drugs as an Indicator of Their Biological Activity Upon Thermal Exposure

Protein drugs are important therapeutic agents however; they may degrade during formulation processing. The objective of this study was to investigate the correlation between secondary structure alterations and the retentions of biological activity of protein upon the application of thermal stress. Catalase, horseradish peroxidase and α- chymotrypsin were employed as model proteins. Each protein was heated in a solid and solution state at a temperature of 70 °C for 1 h. Attenuated total reflectance Fourier transform infrared spectroscopy, size-exclusion chromatography and biological activity assay were performed. Results showed that heat-exposure of protein solids at 70 °C caused minimum changes in secondary structure and biological activity was almost retained. However, thermal exposure of protein aqueous solution induced significant changes in the secondary structure indicated by area overlap values and caused considerable reduction in the biological activity. The changes in secondary structures were found to be in full alignment with the loss of biological activity for both protein solids as well as aqueous solutions. Catalase lost entire biological activity upon heating in the solution state. In conclusion, the findings of the present study indicate a direct correlation between protein secondary structure alterations and the retention of biological activity which can be taken into account during the development and delivery of protein drugs formulations.

Proteolysis of Iron Oxide-Associated Bovine Serum Albumin

Proteins are a substantial nitrogen source in soils provided that they can be hydrolyzed into bioavailable small peptides or amino acids. However, the strong associations between proteins and soil minerals restrict such proteolytic reactions. This study focused on how an extracellular fungal protease (Rhizopus sp.) hydrolyzed iron oxide-associated bovine serum albumin (BSA) and the factors that affected the proteolysis. We combined batch experiments with size-exclusion and reversed phase liquid chromatography and in situ infrared spectroscopic measurements to monitor the generation of proteolytic products in solution as well as the real-time changes of the adsorbed BSA during 24 h. Results showed that protease hydrolyzed the iron oxide-associated BSA directly at the surface without an initial desorption of BSA. Concurrently, the protease was adsorbed to vacant surface sites at the iron oxides, which significantly slowed down the rate of proteolysis. This inhibiting effect was counteracted by the presence of preadsorbed phosphate or by increasing the BSA coverage, which prevented protease adsorption. Fast initial rates of iron oxide-associated BSA proteolysis, comparable to proteolysis of BSA in solution, and very slow rates at prolonged proteolysis suggest a large variability in mineral-associated proteins as a nitrogen source in soils and that only a fraction of the protein is bioavailable.

Ultrabright fluorescent nanoscale labels for the femtomolar detection of analytes with standard bioassays

The detection and quantification of low-abundance molecular biomarkers in biological samples is challenging. Here, we show that a plasmonic nanoscale construct serving as an ‘add-on’ label for a broad range of bioassays improves their signal-to-noise ratio and dynamic range without altering their workflow and read-out devices. The plasmonic construct consists of a bovine-serum-albumin scaffold with approximately 210 IRDye 800CW fluorophores (with fluorescence intensity approximately 6700-fold that of a single 800CW fluorophore), a polymer-coated gold nanorod acting as a plasmonic antenna, and biotin as a high-affinity biorecognition element. Its emission wavelength can be tuned over the visible and near-infrared spectral regions by modifying its size, shape and composition. It is compatible with multiplexed bead-based immunoassays (it improves the limit of detection by up to 4,750-fold in fluorescence-linked immunosorbent assays), immuno-microarrays, flow-cytometry and immunocytochemistry methods, and it shortens overall assay times and lowers sample volumes, as shown for the detection of a pro-inflammatory cytokine in mouse interstitial fluid and of urinary biomarkers in patient samples.

Synthesis of gold-silica core-shell nanoparticles by pulsed laser ablation in liquid and their physico-chemical properties towards photothermal cancer therapy

Due to the increasing scientific and biomedical interest in various nanoparticles (NPs) with excellent properties and the onset of their commercial use, a convenient and adjustable physical method for improved efficiency needs to be used for enabling their tech-scale production. Recently, great progress has been made in the large-scale production of NPs with a simple structure by pulsed laser ablation in liquid (PLAL). In this work, we synthesized gold-silica core-shell NPs by improved PLAL and provided a guide on how to investigate their physico-chemical properties and association with biological effects towards cancer photothermal therapy (PTT). By means of this method, reproducible and scalable liquid phase NPs with less toxicity and good stability can be realized for tech-scale production based on its further adjustment and modification. Moreover, a more complete investigation of the associations between the physico-chemical properties of functional NPs with complex structure and their biological effects may enable more targeted NPs towards specific requirements of biomedical applications.

Developing hyaluronic acid microgels for sustained delivery of platelet lysate for tissue engineering applications

Platelet lysate (PL), a blood product that contains high concentrations of growth factors (GFs), can be considered as a cost-effective source of multiple GFs. In this study, hyaluronic acid (HA) based microgels were developed for delivery of PL proteins. Spherical microgel were prepared using a water in oil emulsion method. First, hyaluronic acid was grafted with tyramine groups, after which prepared microdroplets were crosslinked via an enzymatic reaction in the presence of hydrogen peroxide and horseradish peroxidase. Because of electrostatic interactions, these microgels are promising carriers for positively charged proteins entrapment like most of the GFs. When microgels are incubated in PL solution, protein loading takes place which is mainly governed by nonspecific adsorption of plasma proteins. Although this hampered loading efficiency, loading could be increased by repeated washing and incubation steps. The loaded microgels presented a sustained release of PL growth factors for a period of two weeks. When PL enriched microgels were embedded in a HA bulk hydrogel, cell proliferation was higher compared to constructs without microgels. These findings suggest that the developed microgels are a potential candidate for sustained delivery of PL growth factors and present a solution to the issue of their short half-lives in vivo.

A near-infrared light-controlled smart nanocarrier with reversible polypeptide-engineered valve for targeted fluorescence-photoacoustic bimodal imaging-guided chemo-photothermal therapy

Despite burgeoning development of nanoplatform made in the past few years, it remains a challenge to produce drug nanocarrier that enables requested on/off drug release. Thus, this study aimed to develop an ideal near-infrared light-triggered smart nanocarrier for targeted imaging-guided treatment of cancer that tactfully integrated photothermal therapy with chemotherapy to accurately control drug release time and dosage. Methods: This delivery system was composed of Ag₂S QD coating with dendritic mesoporous silica (DMSN), which acted as nanocarrier of doxorubicin localized inside pores. To provide the nanocarrier with controlled release capability, a polypeptide-engineered that structure was reversible to photothermal effect of Ag₂S QD, was covalently grafted to the external surface of drug-loaded DMSN. Results: This nanocarrier with the size of 40~60 nm had satisfactory biocompatibility and photothermal conversion efficiency up to 28.35%. Due to acidity-triggered charge reversal of polypeptide, which significantly extended circulation time and improved targeting ability, fluorescence and photoacoustic signals were still obvious at tumor site post-24 h by tail vein injection and chemo-photothermal synergistic therapy obviously enhanced antitumor efficacy. Mild PTT with multiple short-term exposures not only reduced the side effect of overdose drug but also avoided skin damage caused by long-term irradiation. Conclusion: By adjusting irradiation time and on/off cycle, multiple small amount local drug release reduced the side effect of overdose drug and skin damage. This novel approach provided an ideal near-infrared light-triggered nanocarrier with accurate control of area, time, and especially dosage.

Development of a multiplex immunochromatographic strip test and ultrasensitive electrochemical immunosensor for hepatitis B virus screening

This research proposes two methods for hepatitis B diagnosis including rapid testing and electrochemical assay. For the first method, a multiplex hepatitis B test strip was fabricated to serve as a rapid test for hepatitis B screening. It was developed to simultaneously test three essential serological markers of hepatitis B virus infection including hepatitis B surface antigen (HBsAg), hepatitis B surface antibody (Anti-HBs) and hepatitis B core antibody (Anti-HBc). Gold nanoparticles (GNPs) were used as the signal generator on the test strip. Furthermore, a part of a paper network was incorporated on the strip for the gold-silver enhancement process. This paper network helped in decreasing the analysis time of enhancement and makes the enhancement process easier for rapid testing. The developed test strip was specific for each serological marker. The detection limits of HBsAg, Anti-HBs and Anti-HBc were obtained at 0.5, 0.3 and 0.1 μg mL^-1, respectively. For the second method, electrochemical impedance spectroscopy (EIS) was applied for HBsAg detection. This method was proposed for quantitative hepatitis B detection. Anti-HBs antibodies were immobilized on a carbon screen printed electrode (SPCE) via the N-ethyl-N'-(3-(dimethylamino)propyl)carbo-diimide/N-hydroxy succinimide (EDC/NHS) couple reaction which reacted with the carboxyl group of the BSA cross-linked film on the electrode. The electrode modification process was characterized by EIS. A linear relationship between delta charge transfer resistance (ΔRct) and HBsAg concentration was obtained in the range of 5-3000 ng mL^-1 with a detection limit of 2.1 ng mL^-1. This work is appropriate for quantitative analysis because it is a simple and low-cost method to implement as the SPCE is disposable. Therefore, we hope that this research will be useful to improve hepatitis B detection in the future.

Cancer cell targeting and therapeutic delivery of silver nanoparticles by mesoporous silica nanocarriers: insights into the action mechanisms using quantitative proteomics

An approach for safely delivering AgNPs to cancer cells and the evaluation of the affected cellular mechanism are presented. The use of mesoporous silica nanoparticles (MSNs) as nanovehicles decorated with transferrin (Tf, targeting agent) provides a nanoplatform for the nucleation and immobilization of AgNPs (MSNs-Tf-AgNPs). We performed the physico-chemical characterization of the nanosystems and evaluated their therapeutic potential using bioanalytical strategies to estimate the efficiency of the targeting, the degree of cellular internalization in two cell lines with different TfR expression, and the cytotoxic effects of the delivered AgNPs. In addition, cellular localization of the nanosystems in cells has been evaluated by a transmission electron microscopy analysis of ultrathin sections of human hepatocarcinoma (HepG2) cells exposed to MSNs-Tf-AgNPs. The in vitro assays demonstrate that only the nanosystem functionalized with Tf is able to transport the AgNPs inside the cells which overexpress transferrin receptors. Therefore, this novel nanosystem is able to deliver AgNPs specifically to cancer cells overexpressing Tf receptors and offers the possibility of a targeted therapy using reduced doses of silver nanoparticles as cytotoxic agents. Then, a quantitative proteomic experiment validated through the analysis of gene expression has been performed to identify the molecular mechanisms of action associated with the chemotherapeutic potential of the MSNs-Tf-AgNP nanocarriers.

Avidin Adsorption to Silk Fibroin Films as a Facile Method for Functionalization

Silk fibroin biomaterials are highly versatile in terms of materials formation and functionalization, with applications in tissue engineering and drug delivery, but necessitate modifications for optimized biological activity. Herein, a facile, avidin-based technique is developed to noncovalently functionalize silk materials with bioactive molecules. The ability to adsorb avidin to silk surfaces and subsequently couple biotinylated macromolecules via avidin-biotin interaction is described. This method better preserved functionality than standard covalent coupling techniques using carbodiimide cross-linking chemistry. The controlled release of avidin from the silk surface was demonstrated by altering the adsorption parameters. Application of this technique to culturing human foreskin fibroblasts (hFFs) and human mesenchymal stem cells (hMSCs) on arginine-glycine-aspartic-acid-modified (RGD-modified) silk showed increased cell growth over a seven-day period. This technique provides a facile method for the versatile functionalization of silk materials for biomedical applications including tissue engineering, drug delivery, and biological sensing.

19F NMR as a Tool for Monitoring Individual Differentially Labeled Proteins in Complex Mixtures

The ability to monitor the behavior of individual proteins in complex mixtures has many potential uses, ranging from analysis of protein interactions in highly concentrated solutions, modeling biological fluids or the intracellular environment, to optimizing biopharmaceutical co-formulations. Differential labeling NMR approaches, which traditionally use ¹⁵N or ¹³C isotope incorporation during recombinant expression, are not always practical in cases when endogenous proteins are obtained from an organism, or where the expression system does not allow for efficient labeling, especially for larger proteins. This study proposes differential labeling of proteins by covalent attachment of ¹⁹F groups with distinct chemical shifts, giving each protein a unique spectral signature which can be monitored by ¹⁹F NMR without signal overlap, even in complex mixtures, and without any interfering signals from the buffer or other unlabeled components. Parameters, such as signal intensities, translational diffusion coefficients, and transverse relaxation rates, which report on the behavior of individual proteins in the mixture, can be recorded even for proteins as large as antibodies at a wide range of concentrations.

Effects of hydrogenated TiO2 nanotube arrays on protein adsorption and compatibility with osteoblast-like cells

Background

Modified titanium (Ti) substrates with titanium dioxide (TiO₂) nanotubes have broad usage as implant surface treatments and as drug delivery systems.

Methods

To improve drug-loading capacity and accelerate bone integration with titanium, in this study, we hydrogenated anodized titanium dioxide nanotubes (TNTs) by a thermal treatment. Three groups were examined, namely: hydrogenated TNTs (H₂-TNTs, test), unmodified TNTs (air-TNTs, control), and Ti substrates (Ti, control).

Results

Our results showed that oxygen vacancies were present in all the nanotubes. The quantity of -OH groups greatly increased after hydrogenation. Furthermore, the protein adsorption and loading capacity of the H₂-TNTs were considerably enhanced as compared with the properties of the air-TNTs (P<0.05). Additionally, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate the interactions of TNTs with proteins. During the protein-loading process, the H₂-TNTs not only enabled rapid protein adsorption, but also decreased the rate of protein elution compared with that of the air-TNTs. We found that the H₂-TNTs exhibited better biocompatibility than the air-TNT and Ti groups. Both cell adhesion activity and alkaline phosphatase activity were significantly improved toward MG-63 human osteoblast-like cells as compared with the control groups (P<0.05).

Conclusion

We conclude that hydrogenated TNTs could greatly improve the loading capacity of bioactive molecules and MG-63 cell proliferation.

Tunable degradation of acetalated dextran microparticles enables controlled vaccine adjuvant and antigen delivery to modulate adaptive immune responses

Subunit vaccines are often poorly immunogenic, and adjuvants and/or delivery vehicles, such as polymeric microparticles (MPs), can be used to enhance immune responses. MPs can also be used to understand cell activation kinetics and the significant impact antigen and adjuvant release has on adaptive immune responses. By controlling antigen and adjuvant release, we can determine if it is important to have precise temporal control over release of these elements to optimize the peak and duration of protective immunity and improve vaccine safety profiles. In order to study the effect of tunable adjuvant or antigen delivery on generation of adaptive immunity, we used acetalated dextran (Ace-DEX) MPs. Ace-DEX MPs were used because their tunable degradation can be controlled based on polymer cyclic acetal coverage (CAC). Ace-DEX MPs of varying degradation profiles were used to deliver murabutide or ovalbumin (OVA) as a model adjuvant or antigen, respectively. When murabutide was encapsulated within Ace-DEX MPs to test for controlled adjuvant delivery, fast-degrading MPs exhibited higher humoral and cellular responses in vivo at earlier time points, while slow-degrading MPs resulted in stronger responses at later time points. When OVA was encapsulated within Ace-DEX MPs to test for controlled antigen delivery, fast-degrading MPs induced greater antibody and cytokine production throughout the length of the experiment. This differential response suggests the need for distinct, flexible control over adjuvant or antigen delivery and its impact on immune response modulation.

Protein-mediated anti-adhesion surface against oral bacteria

Biomedical materials, such as orthopedic biomaterials, have a great impact on improving life quality and self-esteem of human beings. However, the usage of fixed appliances during dental treatment often increases the difficulty of oral cleaning and enlarges the adhesion opportunity of oral bacteria. Furthermore, the existing anti-adhesion coatings, such as polyethylene glycol derivatives and zwitterionic polymers, have not been universally accepted in the oral environment due to their intrinsic problems. Herein, inspired by the anti-adhesion capability of bovine serum albumin, we report a facile protein-based anti-bacterial surface, showing excellent anti-adhesion performance toward oral bacteria. This protein-mediated anti-adhesion strategy may provide a promising clue for developing new anti-bacterial biomaterials, such as dental fixed appliances, restorative materials and medical mouthwashes.

Smart functional polymer coatings for paper with anti-fouling properties

Preparation of functionalized cellulose films on SiO₂ to introduce protein repellent properties evaluated by spectroscopic in situ ellipsometry.

Sustained release of multicomponent platelet-rich plasma proteins from hydrolytically degradable PEG hydrogels

Platelet-rich plasma (PRP), an autologous blood derived product is a concentrated mix of multiple growth factors and cytokines. Direct injections of PRP are clinically used for treatment of various musculoskeletal disorders and in wound healing. However, PRP therapy has met with limited clinical success possibly due to unpredictable and premature bolus delivery of PRP growth factors. The objective of this study was to predictably control the bioavailability of PRP growth factors using a hydrolytically degradable polyethylene glycol (PEG) hydrogel. We used a step-growth polymerization based on a Michael-type addition reaction between a 6-arm PEG-acrylate and a dithiol crosslinker, which led to the formation of a homogenous hydrogel network under mild, physiologically relevant conditions. Specifically, to model the release of multicomponent PRP through PEG hydrogels, we examined bulk diffusion of PRP as well as model proteins in a size range corresponding to that of growth factors found in PRP. Our results indicated that protein size and hydrogel degradation controlled diffusion of all proteins and that secondary structure of proteins encapsulated during gelation remained unaffected post-release. Analysis of specific PRP proteins released from the hydrogel showed sustained release until complete hydrogel degradation. PRP released from hydrogels promoted proliferation of human dermal fibroblast, indicating retained bioactivity upon encapsulation and release. The versatile hydrogel system holds clinical potential as a therapeutic drug delivery depot of multicomponent mixtures like PRP. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3304-3314, 2017.