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

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.

Electrostatic-Driven Exfoliation and Hybridization of 2D Nanomaterials

Here, direct and effective electrostatic-driven exfoliation of tungsten trioxide (WO₃ ) powder into atomically thin WO₃ nanosheets is demonstrated for the first time. Experimental evidence together with theoretical simulations clearly reveal that the strong binding of bovine serum albumin (BSA) on the surface of WO₃ via the protonation of NH₂ groups in acidic conditions leads to the effective exfoliation of WO₃ nanosheets under sonication. The exfoliated WO₃ nanosheets have a greatly improved dispersity and stability due to surface-protective function of BSA, and exhibit a better performance and unique advantages in applications such as visible-light-driven photocatalysis, high-capacity adsorption, and fast electrochromics. Further, simultaneous exfoliation and hybridization of WO₃ and MoS₂ nanosheets are demonstrated to form hybrid WO₃ /MoS₂ nanosheets through respective electrostatic and hydrophobic interaction processes. In addition, this electrostatic-driven exfoliation strategy is applied to exfoliate ultrathin black-phosphorus nanosheets from its bulk to exhibit a greatly improved stability due to the surface protection by BSA. Overall, the work presented not only presents a facile and effective route to fabricate 2D materials but also brings more opportunities to exploit unusual exotic and synergistic properties in resulting hybrid 2D materials for novel applications.

Control of nacre biomineralization by Pif80 in pearl oyster

Molluscan nacre is a fascinating biomineral consisting of a highly organized calcium carbonate composite that provides unique fracture toughness and an iridescent color. Organisms elaborately control biomineralization using organic macromolecules. We propose the involvement of the matrix protein Pif80 from the pearl oyster Pinctada fucata in the development of the inorganic phase during nacre biomineralization, based on experiments using the recombinant form of Pif80. Through interactions with calcium ions, Pif80 participates in the formation of polymer-induced liquid precursor-like amorphous calcium carbonate granules and stabilizes these granules by forming calcium ion-induced coacervates. At the calcification site, the disruption of Pif80 coacervates destabilizes the amorphous mineral precursors, resulting in the growth of a crystalline structure. The redissolved Pif80 controls the growth of aragonite on the polysaccharide substrate, which contributes to the formation of polygonal tablet structure of nacre. Our findings provide insight into the use of organic macromolecules by living organisms in biomineralization.

Direct measurement of interaction forces between bovine serum albumin and poly(ethylene oxide) in water and electrolyte solutions

The net interaction between a probe tip coated with bovine serum albumin (BSA) protein and a flat substrate coated with poly(ethylene oxide) (PEO) polymer was measured directly on approach in water and electrolyte solutions using AFM. The approach force curve between the two surfaces was monotonically repulsive in water and in electrolyte solutions. At pH ~5, slightly above the isoelectric point (pI) of BSA, and at large distances, the force was dominated by electrostatic repulsion between the oxygen atoms of the incoming protein with those belonging to the ether groups of PEO. Such repulsive force and range decreased in NaCl. Under physiological conditions, pH 6, BSA is definitely charged and the electrostatic repulsion with ether groups in PEO appears at larger separation distances. Interestingly, at pH 4, below the pI of BSA, the repulsion decreased because of an attractive, although weak, electrostatic force that appeared between the ether groups in PEO and the positively charged amino groups of BSA. However, for all solution conditions, once compression of PEO begun, the net repulsion was always dominated by short-range polymeric steric repulsion and repulsive enthalpy penalties for breaking PEO-water bonds. Results suggest that PEO in mushroom conformation may also be effective in reducing biofouling.

In Vitro and in Vivo Visualization and Trapping of Fluorescent Magnetic Microcapsules in a Bloodstream

Remote navigation and targeted delivery of biologically active compounds is one of the current challenges in the development of drug delivery systems. Modern methods of micro- and nanofabrication give us new opportunities to produce particles and capsules bearing cargo to deploy and possess magnetic properties to be externally navigated. In this work we explore multilayer composite magnetic microcapsules as targeted delivery systems in vitro and in vivo studies under natural conditions of living organism. Herein, we demonstrate magnetic addressing of fluorescent composite microcapsules with embedded magnetite nanoparticles in blood flow environment. First, the visualization and capture of the capsules at the defined blood flow by the magnetic field are shown in vitro in an artificial glass capillary employing a wide-field fluorescence microscope. Afterward, the capsules are visualized and successfully trapped in vivo into externally exposed rat mesentery microvessels. Histological analysis shows that capsules infiltrate small mesenteric vessels whereas large vessels preserve the blood microcirculation. The effect of the magnetic field on capsule preferential localization in bifurcation areas of vasculature, including capsule retention at the site once external magnet is switched off is discussed. The research outcome demonstrates that microcapsules can be effectively addressed in a blood flow, which makes them a promising delivery system with remote navigation by the magnetic field.

Preparation of Multifunctional Liposomes as a Stable Vaccine Delivery-Adjuvant System by Procedure of Emulsification-Lyophilization

Liposomes have been proven to be useful carriers for vaccine antigens and can be modified as a versatile vaccine adjuvant-delivery system (VADS). To fulfill efficiently both functions of adjuvant and delivery, the liposomes are often modified with different functional molecules, such as lipoidal immunopotentiators, APC (antigen-presenting cell) targeting ligands, steric stabilization polymers, and charged lipids. Also, to overcome the weakness of instability, vaccines are often lyophilized as a dry product. In this chapter the procedure of emulsification-lyophilization (PEL) is introduced as an efficient method for preparing a stable anhydrous precursor to the multifunctional liposomes which bear dual modifications with APC targeting molecule of the mannosylated cholesterol and the adjuvant material of monophosphoryl lipid A. The techniques and procedures for synthesis of APC targeting molecule, i.e., the mannosylated cholesterol, and for characterization of the multifunctional liposomes are also described.

Measuring the Surface-Surface Interactions Induced by Serum Proteins in a Physiological Environment

In this work, we applied total internal reflection microscopy (TIRM) to directly measure the interactions between three different kinds of macroscopic surfaces: namely bare polystyrene (PS) particle and bare silica surface (bare-PS/bare-silica), PS particle and silica surfaces both coated with bovine serum albumin (BSA) (BSA-PS/BSA-silica), and PS particle and silica surfaces both modified with polyethylene glycol (PEG) (PEG-PS/PEG-silica) polymers, in phosphate buffer solution (PBS) and fetal bovine serum (FBS). Our results showed that in PBS, all the bare-PS, BSA-PS, and PEG-PS particles were irreversibly deposited onto the bare silica surface or surfaces coated either with BSA or PEG. However, in FBS, the interaction potentials between the particle and surface exhibited both free-diffusing particle and stuck particle profiles. Dynamic light scattering (DLS) and elliposmeter measurements indicated that there was a layer of serum proteins adsorbed on the PS particle and silica surface. TIRM measurement revealed that such adsorbed serum proteins can mediate the surface-surface interactions by providing additional stabilization under certain conditions, but also promoting bridging effect between the two surfaces. The measured potential profile of the stuck particle in FBS thus was much wider than in PBS. These quantitative measurements provide insights that serum proteins adsorbed onto surfaces can regulate surface-surface interactions, thus leading to unique moving behavior and stability of colloidal particles in the serum environment.

Ultrasensitive microarray bioassays using cyanine5 dye-doped silica nanoparticles

Herein we report the use of high brightness Cyanine5-doped silica nanoparticles (NPs) for the detection of antibodies or DNA in microarray bioassays. NP labels showed negligible non-specific binding, greater sensitivity and lower limits of detection when compared to free dye-labelled biomolecules. Moreover, the spotted microarrays used in this study required low NP and antibody concentrations to generate large data sets with improved statistical accuracy. These NPs have significant potential for use in biosensing for disease detection.

Biokinetics of food additive silica nanoparticles and their interactions with food components

Nanomaterials have been widely utilized in the food industry in production, packaging, sensors, nutrient delivery systems, and food additives. However, research on the interactions between food-grade nanoparticles and biomolecules as well as their potential toxicity is limited. In the present study, the in vivo solubility, oral absorption, tissue distribution, and excretion kinetics of one of the most extensively used food additives, silica (SiO₂) were evaluated with respect to particle size (nano vs bulk) following single-dose oral administration to rats. Intestinal transport mechanism was investigated using a 3D culture system, in vitro model of human intestinal follicle-associated epithelium (FAE). The effect of the presence of food components, such as sugar and protein, on the oral absorption of nanoparticles was also evaluated with focus on their interactions. The results obtained demonstrated that the oral absorption of nanoparticles (3.94±0.38%) was greater than that of bulk materials (2.95±0.37%), possibly due to intestinal transport by microfold (M) cells. On the other hand, particle size was found to have no significant effect on in vivo dissolution property, biodistribution, or excretion kinetics. Oral absorption profile of silica nanoparticles was highly dependent on the presence of sugar or protein, showing rapid absorption rate in glucose, presumably due to their surface interaction on nanoparticles. These findings will be useful for predicting the potential toxicity of food-grade nanoparticles and for understanding biological interactions.

Elution Is a Critical Step for Recovering Human Adenovirus 40 from Tap Water and Surface Water by Cross-Flow Ultrafiltration

This paper examines the recovery of the enteric adenovirus human adenovirus 40 (HAdV 40) by cross-flow ultrafiltration and interprets recovery values in terms of physicochemical interactions of virions during sample concentration. Prior to ultrafiltration, membranes were either blocked by exposure to calf serum (CS) or coated with a polyelectrolyte multilayer (PEM). HAdV 40 is a hydrophobic virus with a point of zero charge between pH 4.0 and pH 4.3. In accordance with predictions from the extended Derjaguin-Landau-Verwey-Overbeek theory, the preelution recovery of HAdV (rpre) from deionized water was higher with PEM-coated membranes (rpre (PEM) = 74.8% ± 9.7%) than with CS-blocked membranes (rpre (CS) = 54.1% ± 6.2%). With either membrane type, the total virion recovery after elution (rpost) was high for both deionized water (rpost (PEM) = 99.5% ± 6.6% and rpost (CS) = 98.8% ± 7.7%) and tap water (rpost (PEM) = 89% ± 15% and rpost (CS) = 93.7% ± 6.9%). The nearly 100% recoveries suggest that the polyanion (sodium polyphosphate) and surfactant (Tween 80) in the eluent disrupt electrostatic and hydrophobic interactions between the virion and the membrane. Addition of EDTA to the eluent greatly improved the elution efficacy (rpost (CS) = 88.6% ± 4.3% and rpost (PEM) = 87.0% ± 6.9%) with surface water, even when the organic carbon concentration in the water was high (9.4 ± 0.1 mg/liter). EDTA likely disrupts cation bridging between virions and particles in the feed water matrix or the fouling layer on the membrane surface. For complex water matrices, the eluent composition is the most important factor for achieving high virion recovery.

IMPORTANCE

Herein we present the results of a comprehensive physicochemical characterization of HAdV 40, an important human pathogen. The data on HAdV 40 surface properties enabled rigorous modeling to gain an understanding of the energetics of virion-virion and virion-filter interactions. Cross-flow filtration for concentration and recovery of HAdV 40 was evaluated, with postelution recoveries from ultrapure water (99%), tap water (∼91%), and high-carbon-content surface water (∼84%) being demonstrated. These results are significant because of the very low adenovirus recoveries that have been reported, to date, for other methods. The recovery data were interpreted in terms of specific interactions, and the eluent composition was designed accordingly to maximize HAdV 40 recovery.

Hydrodynamic Radii of Ranibizumab, Aflibercept and Bevacizumab Measured by Time-Resolved Phosphorescence Anisotropy

PURPOSE

To measure the hydrodynamic radii of intravitreal anti-VEGF drugs ranibizumab, aflibercept and bevacizumab with μs time-resolved phosphorescence anisotropy.

METHODS

Ruthenium-based dye Ru(bpy)2(mcbpy - O - Su - ester)(PF6)2, whose lifetime of several hundred nanoseconds is comparable to the rotational correlation time of these drugs in buffer, was used as a label. The hydrodynamic radii were calculated from the rotational correlation times of the Ru(bpy)2(mcbpy - O - Su - ester)(PF6)2-labelled drugs obtained with time-resolved phosphorescence anisotropy measurements in buffer/glycerol solutions of varying viscosity.

RESULTS

The measured radii of 2.76±0.04 nm for ranibizumab, 3.70±0.03 nm for aflibercept and 4.58±0.01 nm for bevacizumab agree with calculations based on molecular weight and other experimental measurements.

CONCLUSIONS

Time-resolved phosphorescence anisotropy is a relatively simple and straightforward method that allows experimental measurement of the hydrodynamic radius of individual proteins, and is superior to theoretical calculations which cannot give the required accuracy for a particular protein.

Semiconductor Electronic Label-Free Assay for Predictive Toxicology

While animal experimentations have spearheaded numerous breakthroughs in biomedicine, they also have spawned many logistical concerns in providing toxicity screening for copious new materials. Their prioritization is premised on performing cellular-level screening in vitro. Among the screening assays, secretomic assay with high sensitivity, analytical throughput, and simplicity is of prime importance. Here, we build on the over 3-decade-long progress on transistor biosensing and develop the holistic assay platform and procedure called semiconductor electronic label-free assay (SELFA). We demonstrate that SELFA, which incorporates an amplifying nanowire field-effect transistor biosensor, is able to offer superior sensitivity, similar selectivity, and shorter turnaround time compared to standard enzyme-linked immunosorbent assay (ELISA). We deploy SELFA secretomics to predict the inflammatory potential of eleven engineered nanomaterials in vitro, and validate the results with confocal microscopy in vitro and confirmatory animal experiment in vivo. This work provides a foundation for high-sensitivity label-free assay utility in predictive toxicology.

Bovine Serum Albumin-Conjugated Ferrimagnetic Iron Oxide Nanoparticles to Enhance the Biocompatibility and Magnetic Hyperthermia Performance

ABSTRACT

Magnetic hyperthermia is a fast emerging, non-invasive cancer treatment method which is used synergistically with the existing cancer therapeutics. We have attempted to address the current challenges in clinical magnetic hyperthermia-improved biocompatibility and enhanced heating characteristics, through a single combinatorial approach. Both superparamagnetic iron oxide nanoparticles (SPIONs) of size 10 nm and ferrimagnetic iron oxide nanoparticles (FIONs) of size 30 nm were synthesized by thermal decomposition method for comparison studies. Two different surface modifying agents, viz, Cetyl Trimethyl Ammonium Bromide and 3-Aminopropyltrimethoxysilane, were used to conjugate Bovine Serum Albumin (BSA) over the iron oxide nanoparticles via two different methods-surface charge adsorption and covalent amide bonding, respectively. The preliminary haemolysis and cell viability experiments show that BSA conjugation mitigates the haemolytic effect of the iron oxide nanoparticles on erythrocytes and is non-cytotoxic to the healthy Baby Hamster Kidney cells. It was observed from the results that due to better colloidal stability, the SAR value of the BSA-iron oxide nanoparticles is higher than the iron oxide nanoparticles without BSA, irrespective of the size of the iron oxide nanoparticles and method of conjugation. The BSA-FIONs seem to show improved biocompatibility, as the haemolytic index is less than 2 % and cell viability is up to 120 %, when normalized with the control. The SAR value of BSA-FIONs is 2300 W g^-1 when compared to 1700 W g^-1 of FIONs without BSA conjugation. Thus, we report here that BSA conjugation over FIONs (with a high saturation magnetization of 87 emu g^-1) provide a single combinatorial approach to improve the biocompatibility and enhance the SAR value for magnetic hyperthermia, thus addressing both the current challenges of the same.

Comparative study of antibody immobilization mediated by lipid and polymer fibers

Antibody immobilization and function retention are important to a variety of applications, including proteomics, drug discovery, diagnostics, and biosensors. The present study investigates antibody immobilization mediated by cholesteryl succinyl silane (CSS) fibers, in comparison to hydrophobic polycaprolactone (PCL) fibers and hydrophilic plasma-treated PCL fibers. When incubated with a model protein, the formation of protein aggregates is observed on hydrophobic PCL fibers but not on the more hydrophobic CSS fibers, indicating that CSS fibers immobilize proteins through mechanisms other than hydrophobic interaction. When exposed to a limited amount of antibody, CSS fibers immobilize more antibodies than plasma-treated PCL fibers and no fewer antibodies than PCL fibers. The function retention of antibodies immobilized on the fibers is analyzed using a cell-capture assay, which shows that the antibody-functionalized CSS fibrous matrices capture 6- or 7-fold more cells than the antibody-functionalized PCL or plasma-treated PCL fibrous matrices, respectively. Data collected from the study show that the lipid fiber-mediated immobilization of antibody not only maintains the advantages of physical immobilization such as easiness and rapidness of operation but also improves function retention.

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAH layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance-voltage and constant-capacitance measurements. In addition, the surface morphology of the PAH layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event.

Biological Effect of Ultraviolet Photocatalysis on Nanoscale Titanium with a Focus on Physicochemical Mechanism

Physicochemical properties, regulated by various surface modifications, influence the biological performance of materials. The interaction between surface charge and biomolecules is key to understanding the mechanism of surface-tissue integration. The objective of this study was to evaluate the biological response to a nanoscale titanium surface after ultraviolet (UVC, λ = 250 ± 20 nm) irradiation and to analyze the effects via a physicochemical mechanism. The surface characteristics were evaluated by field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, surface profilometry, and contact angle assay. In addition, we applied the zeta-potential, a direct method to measure the electrostatic charge on UV-treated and UV-untreated titanium nanotube surfaces. The effect of the Ti surface after UV treatment on the biological process was determined by analyzing bovine serum albumin (BSA) adsorption and osteoblast-like MG-63 early adhesion, morphology, cytoskeletal arrangement, proliferation, and focal adhesion. Compared to an anodized titanium nanotube coating, UV irradiation altered the contact angles on the control surface from 51.5° to 6.2° without changing the surface topography or roughness. Furthermore, titanium nanotubes after UV treatment showed a significant reduction in the content of acidic hydroxyl groups and held less negative charge than the anodized coating. With regard to the biological response, along with an enhanced capability to adsorb BSA, osteoblasts exhibited higher colonization and viability on the UV-treated material. The results suggest that UV treatment enhances the biocompatibility by reducing the electrostatic repulsion between biomaterials and biomolecules.

Binding Interactions of Keratin-Based Hair Fiber Extract to Gold, Keratin, and BMP-2

Hair-derived keratin biomaterials composed mostly of reduced keratin proteins (kerateines) have demonstrated their utility as carriers of biologics and drugs for tissue engineering. Electrostatic forces between negatively-charged keratins and biologic macromolecules allow for effective drug retention; attraction to positively-charged growth factors like bone morphogenetic protein 2 (BMP-2) has been used as a strategy for osteoinduction. In this study, the intermolecular surface and bulk interaction properties of kerateines were investigated. Thiol-rich kerateines were chemisorbed onto gold substrates to form an irreversible 2-nm rigid layer for surface plasmon resonance analysis. Kerateine-to-kerateine cohesion was observed in pH-neutral water with an equilibrium dissociation constant (KD) of 1.8 × 10(-4) M, indicating that non-coulombic attractive forces (i.e. hydrophobic and van der Waals) were at work. The association of BMP-2 to kerateine was found to be greater (KD = 1.1 × 10(-7) M), within the range of specific binding. Addition of salts (phosphate-buffered saline; PBS) shortened the Debye length or the electrostatic field influence which weakened the kerateine-BMP-2 binding (KD = 3.2 × 10(-5) M). BMP-2 in bulk kerateine gels provided a limited release in PBS (~ 10% dissociation in 4 weeks), suggesting that electrostatic intermolecular attraction was significant to retain BMP-2 within the keratin matrix. Complete dissociation between kerateine and BMP-2 occurred when the PBS pH was lowered (to 4.5), below the keratin isoelectric point of 5.3. This phenomenon can be attributed to the protonation of keratin at a lower pH, leading to positive-positive repulsion. Therefore, the dynamics of kerateine-BMP-2 binding is highly dependent on pH and salt concentration, as well as on BMP-2 solubility at different pH and molarity. The study findings may contribute to our understanding of the release kinetics of drugs from keratin biomaterials and allow for the development of better, more clinically relevant BMP-2-conjugated systems for bone repair and regeneration.

Extraction and stability of bovine serum albumin (BSA) using cholinium-based Good's buffers ionic liquids

Good's buffers ionic liquids (GB-ILs), composed of cholinium-based cations and Good's buffers anions, display self-buffering characteristics in the biological pH range, and their polarity and hydrophobicity can be easily tuned by a proper manipulation of their ions chemical structures. In this work, the extraction ability for bovine serum albumin (BSA) of aqueous biphasic systems (ABS) formed by polypropylene glycol 400 (PPG 400) and several GB-ILs was evaluated. ABS formed by PPG 400 and cholinium chloride ([Ch]Cl), GBs, and sucrose were also investigated for comparison purposes. It is shown that BSA preferentially migrates for the GB-IL-rich phase, with extraction efficiencies of 100%, achieved in a single-step. Dynamic light scattering, and circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopies were employed to evaluate the effect of the investigated cholinium-based GB-ILs on the BSA stability, and compared with results obtained for the respective GBs precursors, [Ch]Cl and sucrose, a well-known protein stabilizer. Molecular docking studies were also carried out to investigate on the binding sites of GB-IL ions to BSA. The experimental results confirm that BSA has a higher stability in GB-ILs than in any of the other compounds investigated.

Selective glycoprotein detection through covalent templating and allosteric click-imprinting

A hierarchical bottom-up route exploiting reversible covalent interactions with boronic acids and so-called click chemistry for selective glycoprotein detection is described. The self-assembled and imprinted surfaces confer high binding affinities, nanomolar sensitivity, exceptional glycoprotein specificity and selectivity.

Many glycoproteins are intimately linked to the onset and progression of numerous heritable or acquired diseases of humans, including cancer. Indeed the recognition of specific glycoproteins remains a significant challenge in analytical method and diagnostic development. Herein, a hierarchical bottom-up route exploiting reversible covalent interactions with boronic acids and so-called click chemistry for the fabrication of glycoprotein selective surfaces that surmount current antibody constraints is described. The self-assembled and imprinted surfaces, containing specific glycoprotein molecular recognition nanocavities, confer high binding affinities, nanomolar sensitivity, exceptional glycoprotein specificity and selectivity with as high as 30 fold selectivity for prostate specific antigen (PSA) over other glycoproteins. This synthetic, robust and highly selective recognition platform can be used in complex biological media and be recycled multiple times with no performance decrement.

Enhanced extraction of proteins using cholinium-based ionic liquids as phase-forming components of aqueous biphasic systems

Aqueous biphasic systems (ABS) composed of ionic liquids (ILs) are promising platforms for the extraction and purification of proteins. In this work, a series of alternative and biocompatible ABS composed of cholinium-based ILs and polypropylene glycol were investigated. The respective ternary phase diagrams, tie-lines, tie-line lengths and critical points were determined at 25°C. The extraction performance of these systems for commercial bovine serum albumin (BSA) was then evaluated. The stability of BSA at the IL-rich phase was ascertained by size exclusion high-performance liquid chromatography and Fourier transform infrared spectroscopy. Appropriate ILs lead to the complete extraction of BSA for the IL-rich phase, in a single step, while maintaining the protein's native conformation. Furthermore, to evaluate the performance of these systems when applied to real matrices, the extraction of BSA from bovine serum was additionally carried out, revealing that the complete extraction of BSA was maintained and achieved in a single step. The remarkable extraction efficiencies obtained are far superior to those observed with typical polymer-based ABS. Therefore, the proposed ABS may be envisaged as a more effective and biocompatible approach for the separation and purification of other value-added proteins.

Multifunctional liposomes constituting microneedles induced robust systemic and mucosal immunoresponses against the loaded antigens via oral mucosal vaccination

To develop effective, convenient and stable mucosal vaccines, mannose-PEG-cholesterol (MPC)/lipid A-liposomes (MLLs) entrapping model antigen bovine serum albumin (BSA) were prepared by the procedure of emulsification-lyophilization and used to constitute microneedles, forming the proMLL-filled microneedle arrays (proMMAs). The proMMAs were rather stable and hard enough to pierce porcine skin and, upon rehydration, dissolved rapidly recovering the MLLs without size and entrapment change. The proMMAs given to mice via oral mucosal (o.m.) route, rather than routine intradermal administration, elicited robust systemic and mucosal immunoresponses against the loaded antigens as evidenced by high levels of BSA-specific IgG in the sera and IgA in the salivary, intestinal and vaginal secretions of mice. Enhanced levels of IgG2a and IFN-γ in treated mice revealed that proMMAs induced a mixed Th1/Th2 immunoresponse. Moreover, a significant increase in CD8(+) T cells confirmed that strong cellular immunity had also been established by the immunization of the proMMAs. Thus, the proMMAs can be immunized via o.m. route to set up an effective multiple defense against pathogen invasion and may be an effective vaccine adjuvant-delivery system (VADS) applicable in the controlled temperature chain.

Measurements of long-range interactions between protein-functionalized surfaces by total internal reflection microscopy

Understanding the interaction between protein-functionalized surfaces is an important subject in a variety of protein-related processes, ranging from coatings for biomedical implants to targeted drug carriers and biosensors. In this work, utilizing a total internal reflection microscope (TIRM), we have directly measured the interactions between micron-sized particles decorated with three types of common proteins concanavalin A (ConA), bovine serum albumin (BSA), lysozyme (LYZ), and glass surface coated with soy proteins (SP). Our results show that the protein adsorption greatly affects the charge property of the surfaces, and the interactions between those protein-functionalized surfaces depend on solution pH values. At pH 7.5-10.0, all these three protein-functionalized particles are highly negatively charged, and they move freely above the negatively charged SP-functionalized surface. The net interaction between protein-functionalized surfaces captured by TIRM was found as a long-range, nonspecific double-layer repulsion. When pH was decreased to 5.0, both protein-functionalized surfaces became neutral and double-layer repulsion was greatly reduced, resulting in adhesion of all three protein-functionalized particles to the SP-functionalized surface due to the hydrophobic attraction. The situation is very different at pH = 4.0: BSA-decorated particles, which are highly charged, can move freely above the SP-functionalized surfaces, while ConA- and LYZ-decorated particles can only move restrictively in a limited range. Our results quantify these nonspecific kT-scale interactions between protein-functionalized surfaces, which will enable the design of surfaces for use in biomedical applications and study of biomolecular interactions.

Protein Precipitation Behavior of Condensed Tannins from Lotus pedunculatus and Trifolium repens with Different Mean Degrees of Polymerization

The precipitation of bovine serum albumin (BSA), lysozyme (LYS), and alfalfa leaf protein (ALF) by two large- and two medium-sized condensed tannin (CT) fractions of similar flavan-3-ol subunit composition is described. CT fractions isolated from white clover flowers and big trefoil leaves exhibited high-purity profiles by 1D/2D NMR and purities >90% (determined by thiolysis). At pH 6.5, large CTs with a mean degree of polymerization (mDP) of ∼18 exhibited similar protein precipitation behaviors and were significantly more effective than medium CTs (mDP ∼9). Medium CTs exhibited similar capacities to precipitate ALF or BSA, but showed small but significant differences in their capacity to precipitate LYS. All CTs precipitated ALF more effectively than BSA or LYS. Aggregation of CT-protein complexes likely aided precipitation of ALF and BSA, but not LYS. This study, one of the first to use CTs of confirmed high purity, demonstrates that the mDP of CTs influences protein precipitation efficacy.

Polypyrrole-supported membrane proteins for bio-inspired ion channels

Biomedical platforms constructed by immobilizing membrane proteins in matrixes made of synthetic organic polymers is a challenge because the structure and function of these proteins are affected by environmental conditions. In this work, an operative composite that regulates the diffusion of alkali ions has been prepared by functionalizing a supporting matrix made of poly(N-methylpyrrole) (PNMPy) with a β-barrel membrane protein (Omp2a) that forms channels and pores. The protein has been unequivocally identified in the composite, and its structure has been shown to remain unaltered. The PNMPy-Omp2a platform fulfills properties typically associated with functional bio-interfaces with biomedical applications (e.g., biocompatibility, biodegrabadility, and hydrophilicity). The functionality of the immobilized protein has been examined by studying the passive ion transport response in the presence of electrolytic solutions with Na(+) and K(+) concentrations close to those found in blood. Although the behavior of PNMPy and PNMPy-Omp2a is very similar for solutions with very low concentration, the resistance of the latter decreases drastically when the concentration of ions increases to ∼100 mM. This reduction reflects an enhanced ion exchange between the biocomposite and the electrolytic medium, which is not observed in PNMPy, evidencing that PNMPy-Omp2a is particularly well suited to prepare bioinspired channels and smart biosensors.

Controlling colloidal stability of silica nanoparticles during bioconjugation reactions with proteins and improving their longer-term stability, handling and storage

Robust protocols for antibody-nanoparticle (Ab-NP) conjugation, and improved method for long-term stability and storage of Ab-NPs using cryoprotectants.

Straightforward phase-transfer route to colloidal iron oxide nanoparticles for protein immobilization

Removal of hydrophobic ligand enables a convenient phase-transfer route to aqueous magnetic nanocolloid that shows excellent protein immobilization capability.

Fickian-Based Empirical Approach for Diffusivity Determination in Hollow Alginate-Based Microfibers Using 2D Fluorescence Microscopy and Comparison with Theoretical Predictions

Hollow alginate microfibers (od = 1.3 mm, id = 0.9 mm, th = 400 µm, L = 3.5 cm) comprised of 2% (w/v) medium molecular weight alginate cross-linked with 0.9 M CaCl₂ were fabricated to model outward diffusion capture by 2D fluorescent microscopy. A two-fold comparison of diffusivity determination based on real-time diffusion of Fluorescein isothiocyanate molecular weight (FITC MW) markers was conducted using a proposed Fickian-based approach in conjunction with a previously established numerical model developed based on spectrophotometric data. Computed empirical/numerical (D_empiricial/D_numerical) diffusivities characterized by small standard deviations for the 4-, 70- and 500-kDa markers expressed in m²/s are (1.06 × 10⁻⁹ ± 1.96 × 10⁻¹⁰)/(2.03 × 10⁻¹¹), (5.89 × 10⁻¹¹ ± 2.83 × 10⁻¹²)/(4.6 × 10⁻¹²) and (4.89 × 10⁻¹² ± 3.94 × 10⁻¹³)/(1.27 × 10⁻¹²), respectively, with the discrimination between the computation techniques narrowing down as a function of MW. The use of the numerical approach is recommended for fluorescence-based measurements as the standard computational method for effective diffusivity determination until capture rates (minimum 12 fps for the 4-kDa marker) and the use of linear instead of polynomial interpolating functions to model temporal intensity gradients have been proven to minimize the extent of systematic errors associated with the proposed empirical method.

In situ generation of tunable porosity gradients in hydrogel-based scaffolds for microfluidic cell culture

Compared with preformed anisotropic matrices, an anisotropic matrix that allows users to alter its properties and structure in situ after synthesis offers the important advantage of being able to mimic dynamic in vivo microenvironments, such as in tissues undergoing morphogenesis or in wounds undergoing tissue repair. In this study, porous gradients are generated in situ in a hydrogel comprising enzymatically crosslinked gelatin hydroxyphenylpropionic acid (GTN-HPA) conjugate and carboxylmethyl cellulose tyramine (CMC-TYR) conjugate. The GTN-HPA component acts as the backbone of the hydrogel, while CMC-TYR acts as a biocompatible sacrificial polymer. The hydrogel is then used to immobilize HT1080 human fibrosarcoma cells in a microfluidic chamber. After diffusion of a biocompatible cellulase enzyme through the hydrogel in a spatially controlled manner, selective digestion of the CMC component of the hydrogel by the cellulase gives rise to a porosity gradient in situ instead of requiring its formation during hydrogel synthesis as with other methods. The influence of this in situ tunable porosity gradient on the chemotactic response of cancer cells is subsequently studied both in the absence and presence of chemoattractant. This platform illustrates the potential of hydrogel-based microfluidics to mimic the 3D in vivo microenvironment for tissue engineering and diagnostic applications.

Microretroreflector-sedimentation immunoassays for pathogen detection

Point-of-care detection of pathogens is medically valuable but poses challenging trade-offs between instrument complexity and clinical and analytical sensitivity. Here we introduce a diagnostic platform utilizing lithographically fabricated micron-scale forms of cubic retroreflectors, arguably one of the most optically detectable human artifacts, as reporter labels for use in sensitive immunoassays. We demonstrate the applicability of this novel optical label in a simple assay format in which retroreflector cubes are first mixed with the sample. The cubes are then allowed to settle onto an immuno-capture surface, followed by inversion for gravity-driven removal of nonspecifically bound cubes. Cubes bridged to the capture surface by the analyte are detected using inexpensive, low-numerical aperture optics. For model bacterial and viral pathogens, sensitivity in 10% human serum was found to be 10⁴ bacterial cells/mL and 10⁴ virus particles/mL, consistent with clinical utility.