High Protein Adsorption Capacity Research Articles

Activated carbon from sugarcane bagasse as support for lipase immobilization by physical adsorption technique

Lipases are recognized as the most important group of catalysts in biotechnology. However, utilization of free enzymes is often hampered by the need for more operational stability, high cost, and non-reusability. Most of these obstacles can be solved by lipase immobilization. This work's objective was to evaluate the performance of the activated carbon obtained from sugarcane straw (SAC) as a support for lipase immobilization. Two lipases were immobilized by physical adsorption on SAC: Aspergillus niger 11T53A14 lipase and CalB (lipase B from Candida antarctica, Novozymes). Results revealed that the lipase had been anchored on the activated carbon with the lipase binding efficiency of 89 % (A. niger lipase) and 100 % (CalB) at the optimum experimental conditions (initial protein concentration 0.1 mg mL-1, 0.15 g of SAC, 25 °C, and 120 min). Langmuir isotherm fitted the adsorption equilibrium data of the lipases on SAC. SAC presents a high surface area and protein adsorption capacity. These results show that activated carbon synthesized from the sugarcane straw is a promising support for enzyme immobilization.

Injectable Hydrated Calcium Phosphate Bone-like Paste: Synthesis, In Vitro, and In Vivo Biocompatibility Assessment

The injectable hydrated calcium phosphate bone-like paste (hCPP) was developed with suitable rheological characteristics, enabling unhindered injection through standard 23G needles. In vitro assays showed the cytocompatibility of hCPP with mesenchymal embryonic C3H10T1/2 cell cultures. The hCPP was composed of aggregated micro-sized particles with sphere-like shapes and low crystallinity. The ability of hCPP particles to adsorb serum proteins (FBS) was investigated. The hCPP demonstrated high protein adsorption capacity, indicating its potential in various biomedical applications. The results of the in vivo assay upon subcutaneous injection in Wistar rats indicated nontoxicity and biocompatibility of experimental hCPP, as well as gradual resorption of hCPP, comparable to the period of bone regeneration. The data obtained are of great interest for the development of commercial highly effective osteoplastic materials for bone tissue regeneration and augmentation.

Development of porous calcite structure from industrial waste for efficient adsorbent for protein

AbstractPorous adsorbent (PA) with high specific surface area and calcite surface was prepared from an industrial waste, electric arc furnace oxidizing slag (EOS). As the EOS is composed of silica and metal oxide nanoparticle like CaO, MgO, and so on, the metal oxide parts were selectively dissolved by acid treatment. The remained silica part exhibited porous structure due to the assembly of nanoparticles. Then, calcite was developed on the silica surface by simply titrating the silica framework with carbonate under basic condition. According to the x‐ray diffraction pattern and scanning electron microscopy, we could hypothesize that the EOS had dense texture of amorphous nanoparticles. On the other hand, the PA had well‐crystallized calcite particles with sufficient interparticle pores. The zeta potential of EOS shifted to positive region upon transformation to PA, possibly due to the change in surface‐exposed moiety from silica to calcite. The albumin adsorption profiled exhibited that the PA had very high protein adsorption capacity up to 3.33 mg‐protein/mg‐adsorbent at 5 mg/L of protein concentration, while the EOS itself did not show meaningful adsorption.

Molecularly imprinted hydrogel sensor for proteins

The approach toward the molecular imprinting of hydrogel with different proteins erects the template-size cavities inside the matrix. The cavities provide the binding sites to adsorb the protein perfectly in the hydrogel. To intensify the adsorption efficiency of protein bovine serum albumin (BSA), cobalt ions (Co) play an essential role. In contrast, 2-(Dimethylamino) ethyl methacrylate (DMAEMA) provides pH sustainability as an assistant monomer. Results elucidate that incorporating Co in preparation can enhance the hydrogel’s imprinting effect or adsorption efficiency compared to others due to the development of coordinated covalent bonding. Hydrogel adsorption capacity is an essential factor in this study. In this research, the obtained BSA-imprinted hydrogel also observed a high protein adsorption capacity. The Co concentration and pH of the hydrogel system are the main factors affecting proteins’ adsorption efficiency. Their optimizations are the main concerns, and their successful implementations are confirmed by UV/Vis spectroscopy. The imprinted BSA protein was removed by using 500 mmol/L NaCl solution. The two and three-parameter isothermal models were implemented to predict the mechanism of the adsorption process.

Effects of glycation methods on the interfacial behavior and emulsifying performance of soy protein isolate-gum Arabic conjugates

Glycated conjugation of plant protein such as soy protein isolate (SPI) with saccharides is one popular strategy to modify the physicochemical characteristics of these plant protein resources, which may be affected by the glycation methods including dry-heating and wet-heating. In this study, the impact of these two glycation methods on the rheological and emulsifying properties of a binary system made by SPI-gum Arabic (GA) was studied. The results indicated that dry-heating conjugates had higher viscosity and more elastic characteristics than those wet-heating conjugates. The emulsifying properties of SPI-GA conjugates by different preparation routes were evaluated by various oil phases including eugenol, cinnamaldehyde and soybean oil. Overall, emulsions stabilized by dry-heating conjugates showed lower zeta-potential value than those with wet heating conjugates. The interfacial properties of these conjugates were compared using soybean oil emulsion as a model. Higher emulsifying ability and stability were obtained by emulsions with dry-heating conjugates, which was attributed to their more compact structures, higher protein adsorption capacity and thicker viscoelastic films formed at the interface, and therefore enhanced electrostatic repulsion between droplets. The findings in this study are useful for fabrication and utilization of protein-polysaccharide glycation conjugates as emulsifiers in functional foods.

Negatively Charged Composite Nanofibrous Hydrogel Membranes for High-Performance Protein Adsorption.

Nanofibrous materials are considered as promising candidates for fabricating high-efficiency chromatography media, which are urgently needed in protein pharmaceuticals purification and biological research, yet still face several bottlenecks. Herein, novel negatively charged composite nanofibrous hydrogel membranes (NHMs) are obtained by a facile combination of electrospinning and surface coating modification. The resulting NHMs exhibit controllable morphologies and chemical structures. Benefitting from the combined effect of the stable framework of silicon dioxide (SiO2) nanofiber and the function layer of negatively charged hydrogel, as well as good pore connectivity among nanofibers, NHMs exhibit a high protein adsorption capacity of around 1000 mg g−1, and are superior to the commercial cellulose fibrous adsorbent (Sartobind®) and the reported nanofibrous membranous adsorbents. Moreover, due to their relatively stable physicochemical and mechanical properties, NHMs possess comprehensive adsorption performance, favorable resistance to acid and solvents, good selectivity, and excellent regenerability. The designed NHMs composite adsorbents are expected to supply a new protein chromatography platform for effective protein purification in biopharmaceuticals and biochemical reagents.

Microwave Treatment of Calcium Phosphate/Titanium Dioxide Composite to Improve Protein Adsorption.

Calcium phosphate has attracted enormous attention as a bone regenerative material in biomedical fields. In this study, we investigated the effect of microwave treatment on calcium phosphate deposited TiO2 nanoflower to improve protein adsorption. Hierarchical rutile TiO2 nanoflowers (TiNF) fabricated by a hydrothermal method were soaked in modified simulated body fluid for 3 days to induce calcium phosphate (CAP) formation, followed by exposure to microwave radiation (MW). Coating the dental implants with CAP/TiNF provides a means of improving the biological properties, as the structure, morphology, and thickness of the composites can be controlled. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), field emission transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR), respectively. The composites were identified to be composed of aggregated nano-sized particles with sphere-like shapes, and the calcium phosphate demonstrated low crystallinity. The ability of bovine serum albumin (BSA) to adsorb on MW-treated CAP/TiNF composites was studied as a function of BSA concentration. The Sips isotherm was used to analyze the BSA adsorption on MW-treated CAP/TiNF composites. The MW-treated samples showed high protein adsorption capacity, thereby indicating their potential in various biomedical applications.

Highly bioactive bone cement microspheres based on α-tricalcium phosphate microparticles/mesoporous bioactive glass nanoparticles: Formulation, physico-chemical characterization and in vivo bone regeneration

Calcium phosphate cement (CPC) is a self-setting, biocompatible and osteoconductive bone cement, however its use as a bone substitute is still limited owing to its low bioactivity (i.e. its slow in vivo resorption and slow new bone formation rate) which is a challenging issue to be addressed. Herein, we report for the first time highly bioactive bone cement microspheres formulated from a cement paste containing α-tricalcium phosphate microparticles (α-TCP) and mesoporous calcium silicate bioactive glass nanoparticles (mesoporous BGn) using a water-in-oil emulsion method. Indeed, bioactive microspheres possess high potential as bone defect fillers for bone regeneration. The α-TCP microparticles were prepared by a solid state synthesis at 1400 ºC while mesoporous BGn were synthesized by template-assissted ultrasound-mediated sol-gel method. The particle size distribution of as-prepared cement microspheres was in the range of 200 – 450 µm with a sphericity index in the range of 0.92 – 0.94. The surface morphology of α-TCP microspheres revealed α-TCP micoparticles with smooth surfaces whereas α-TCP/BGn microspheres unveiled nano-roughened α-TCP microparticles. The as-prepared α-TCP/BGn cement microspheres exhibited larger specific surface area ca 18.6 m2/g, sustained release of soluble silicate (SiO44-) ions (118 ppm within a week) and high protein adsorption capacity (252 mg/g). Notably, the α-TCP/BGn cement microspheres showed excellent in vitro surface bioactivity via formation of massive amounts of bone-like hydroxyapatite spherules and aggregates on their surfaces after soaking in simulated body fluid. Importantly, the in vivo implantation of as-prepared α-TCP/BGn cement microspheres in rat calvarial critical size bone defects for 6 weeks unveiled high in vivo bioactivity in terms of substantial new bone ingrowth and significant new bone formation within the bone defect as evidenced by histological analyses, X-ray radiography and micro-computed tomography evaluations.

The comparative biological properties of Mg+ or Ca+ implanted Cu–TiN nanocomposite coatings on titanium alloys

In this paper, Cu–TiN nanocomposite coatings on titanium alloys were prepared by multi-target co-sputtering system. On this basis, Mg or Ca ions at the same doses were then implanted into the Cu–TiN coatings respectively via plasma immersion ion implantation system (PIII) to further improve their biological properties. The corrosion resistances, protein adhesion rates, in vitro cell proliferation and bacterial inhibition capabilities of Mg + implanted Cu–TiN and Ca+ implanted Cu–TiN were also compared. The results showed that the Mg+ implanted Cu–TiN showed (i) improved corrosion behavior, (ii) higher protein adsorption capacity, (iii) ideal cell proliferation and adhesion, (iv) better antimicrobial properties. The research results showed that compared with Ca, Mg and Cu–TiN combined better in osteogenetic and antibacterial activities, which could provide a good choice for the surface modification of medical materials.

Nano/micro-structured poly(ϵ-caprolactone)/gelatin nanofibers with biomimetically-grown hydroxyapatite spherules: High protein adsorption, controlled protein delivery and sustained bioactive ions release designed as a multifunctional bone regenerative membrane

Bioactive and biodegradable fibrous membranes are highly attractive for periodontal bone regeneration. Herein, we demonstrate a new approach for fabrication of a novel nano/micro-structured fibrous membrane made of biodegradable poly(ϵ-caprolactone)/gelatin (PCL/GEL) nanofibers and biomemtically-grown hydroxyapatite spherules (HAs). The proposed approach includes electrospinning fabrication of PCL/GEL nanofibers containing nanobioglass (NBG) agglomerates and their biomimetic transformation into HAs. The NBG agglomerates (~1.9 μm in diameter) enabled the growth of biomimetic HAs (~4 μm in diameter) around the PCL/GEL nanofibers and generated a unique nano/micro-structure. Interestingly, the biomimetically-grown HAs imparted the PCL/GEL-HAs nanofibrous membrane with several remarkable properties including nano/micro-topography, bone-mimetic composition (Ca/P = 1.60), large specific surface area (~31 m2/g), high protein adsorption capacity (~157 μg protein/mg membrane) and controlled protein delivery with zero-order release kinetics; along with sustained release of therapeutic ions (Ca2+ ~ 37 ppm, PO43− ~ 24 ppm, and SiO44− ~ 61 ppm). Furthermore, the PCL/GEL-HAs membrane exhibited enhanced wettability, good biodegradability and adequate mechanical properties. Collectively, the PCL/GEL-HAs demonstrated unique properties and it can be considered as a novel multifunctional bioactive/biodegradable membrane for periodontal bone regeneration.

Soy/whey protein isolates: interfacial properties and effects on the stability of oil-in-water emulsions.

The adsorption of proteins at oil/water interfaces can reduce interfacial tension and increase emulsion stability. However, emulsions stabilized by soy protein isolate (SPI) are not sufficiently stable. Using SPI as a control, a theoretical basis for the adsorption behavior of mixed SPI and whey protein isolate (WPI) at the oil/water interface was established and the effects of the protein ratio and content on the emulsion stability were studied. Compared to SPI solution, SPI-WPI mixed solutions were found to reduce the size distribution of emulsion droplets and significantly improve the emulsion stability. Among the studied protein contents and ratios, the protein content of 0.2 g kg-1 and SPI/WPI mass ratio of 1:9 offered the lowest creaming stability index (15%), the smallest droplet size (278 nm), and the largest absolute value ζ-potential (35 mV), i.e. the emulsion stability was excellent. The largest dilatational modulus (10.08 mN m-1 ), dilatational elasticity (10.01 mN m-1 ), and dilatational viscosity (1.18 mN m-1 ), were observed with a protein content of 0.15 g kg-1 (SPI/WPI ratio of 1:9), along with a high interfacial protein adsorption capacity (47.33%). SPI-WPI complexes form a thick adsorption layer around oil droplets, resulting in an increase of the expansion modulus of the interfacial layer. SPI-WPI complexes can form a thick adsorption layer around oil droplets, resulting in increased expansion modulus of the interfacial layer, which improves emulsion stability. © 2020 Society of Chemical Industry.

Phenethylamine@Pillar[5]arene Biointerface for Highly Enantioselective Adsorption of Protein.

In the life system, the biointerface plays an important role in cell adsorption, platelet adsorption and activation. Therefore, the study of protein adsorption on the biointerface is of great significance for understanding life phenomena and treatment in vitro. In this paper, a chiral biointerface was constructed by the virtue of host-guest interaction between a water-soluble pillar[5]arene (WP5) and phenethylamine (PEA) over a gold surface for adsorption of lysozyme proteins. From the experimental results it was identified that the host-guest biointerface has a high adsorption capacity and strong chiral selectivity. Furthermotre, it was identified that the host-guest interaction plays the decisive role in the enhancement of chirality of the interface, which was much beneficial for increasing protein adsorption and amplifying the capacity of chiral discrimination. Therefore, this work provides a new idea for the construction of biointerface materials with high protein adsorption capacity and high chiral selectivity through supramolecular interaction, which will have potential applications in the fields of biosensors, biocatalysts, biomaterials.

Implications from the grafting density and ionic capacity effects on protein adsorption to poly (N,N-dimethylaminopropyl acrylamide)-grafted sepharose FF

Our previous study reported a novel protein ion-exchanger, N,N-dimethylaminopropyl acrylamide (DMAPAA)-grafted Sepharose FF, of very high protein adsorption capacity and uptake rate. To gain new insight into the polymer grafting effects on protein adsorption and chromatography, 18 DMAPAA-grafted anion exchangers of four grafting densities and various chain lengths (i.e., ionic capacities, ICs) were prepared and named as FF-Brx-pDMAPAAn (x represents grafting density and n stands for IC in mmol/L). It was found that an optimal IC existed at each grafting density to present a maximal capacity. Of the four optimal-IC resins, FF-Br3-pDMAPAA587 showed the highest capacity (377 mg/mL), but the protein uptake rate, defined as the ratio of effective pore diffusivity to free diffusivity (De/D0), was smaller than the resin of a similar ionic capacity but lower grafting density (FF-Br2-pDMAPAA592). Consequently, the dynamic binding capacity (DBC) of FF-Br2-pDMAPAA592 was higher than that of FF-Br3-pDMAPAA587 at flow velocities higher than 450 cm/h. Moreover, FF-Br3-pDMAPAA587 showed higher adsorption capacity than FF-Br2-pDMAPAA592 at 0−150 mmol/L NaCl, leading to its higher DBC values as compared to FF-Br2-pDMAPAA592 in the same salt concentration range. Taken together, DMAPAA-grafted resins of different grafting densities would be useful for purifying feedstocks of different ionic strengths.

Mesoporous Silica-Coated β-TCP Granules Prepared Using Alginate and <i>In vitro</i> Evaluation

β-Tricalcium phosphate (β-TCP) is widely used, along with bone-derived growth factor, due to its poor osteogenic ability. Mesoporous silica (MPS)-coated β-tricalcium phosphate (β-TCP) granules were prepared to improve protein loading capability, and in vitro evaluations of this material were carried out. β-TCP powder containing 2 wt% Al2O3 and 6 wt% SiO2 was prepared via mechanochemical synthesis. A sodium alginate solution containing β-TCP powder was transferred into a calcium chloride solution, and the obtained spherical beads were heated at 1100 to 1300°C to produce TCP granules. The X-ray diffraction (XRD) profile of the β-TCP granules containing 2 wt% Al2O3 and 6 wt% SiO2 was identical to that of the single β-TCP phase when heated to 1300°C. The compressive strengths of the TCP granules prepared using alginate were remarkably improved compared with those of TCP granules prepared using a pan-type granulator. A silica interlayer was formed on the β-TCP granules containing 2 wt% Al2O3 and 6 wt% SiO2 via magnetron sputtering prior to the coating of the MPS. MPS coatings on β-TCP granules containing 2 wt% Al2O3 and 6 wt% SiO2 was carried out by a dip-coating method after silica interlayer coatings, and the β-TCP granules containing 2 wt% Al2O3 and 6 wt% SiO2 were covered by the MPS particles. A silica interlayer may offer bonding between the β-TCP granules and MPS coating. The Alamar blue assay of the MPS-coated TCP granules exhibited excellent cell viability as well as a high protein-adsorption capacity.

Protein cation exchangers derived by charge reversal from poly(ethylenimine)-Sepharose FF: Comparisons between two derivatization routes

It has been known that anion exchangers prepared by grafting poly(ethyleneimine) (PEI) onto Sepharose FF (PEI-Sepharose) at ionic capacities (IC) over 600 mmol/L show both high protein adsorption capacity and uptake kinetics, and charge reversal of PEI-Sepharose by modification with succinic anhydride can produce protein cation exchangers of high capacity and uptake rate. Previously, a Charge Reversal-then-Reduction procedure (route A) was studied for preparation of cation exchangers of different IC values from PEI-Sepharose. In this work, we proposed a new route, that is, Charge Reduction-then-Reversal route (route B), to develop cation exchangers of different IC values from PEI-Sepharose FF with an IC of 700 mmol/L (FF-PEI-L700) as the starting resin. The two kinds of cation exchangers (route A, PEI-L700-CRn; route B, PEI-Rm-Cn) are compared for lysozyme (Lys) adsorption and chromatography. The two modification routes result in the difference in the ligand structures that significantly affect protein adsorption equilibrium and kinetics. Route A introduces long electroneutral groups that hinder protein adsorption and reduce equilibrium capacity. Moreover, charge reversal by reaction with succinic anhydride could cause diamide formation, which reduces remaining carboxyl groups or the IC. In the charge-reduced FF-PEI-Rm resins of the lowest IC (394 mmol/L) prepared in route B, the diamide formation was little due to the lack of primary and secondary amine groups, so its charge reversal makes a higher-IC cation exchanger. This makes PEI-Rm-Cn show a higher IC (589 mmol/L) than PEI-L700-CRn (463 mmol/L) in which De/D0 jumps about four times. The differences in the adsorption equilibrium and kinetics make the two kinds of resins behave distinctly in dynamic adsorption and chromatography. Namely, PEI-Rm-Cn resins display obviously higher dynamic binding capacities than PEI-L700-CRn resins in the IC range studied. For instance, the DBC (at 10% breakthrough) of PEI-R590-C680 (192 mg/mL) is 33% higher than that of PEI-L700-CR680 (144 mg/mL). This is proved by the purification of Lys from chicken egg white solution, in which the PEI-R590-C680 column purified Lys with a recovery yield 14% higher than the PEI-L700-CR680 column. This research thus demonstrated that Charge Reduction-then-Reversal route is superior over Charge Reversal-then-Reduction route in fabricating a high-capacity cation exchanger from PEI-Sepharose.

Biomimetic Carbon Fiber Systems Engineering: A Modular Design Strategy To Generate Biofunctional Composites from Graphene and Carbon Nanofibers.

Carbon-based fibrous scaffolds are highly attractive for all biomaterial applications that require electrical conductivity. It is additionally advantageous if such materials resembled the structural and biochemical features of the natural extracellular environment. Here, we show a novel modular design strategy to engineer biomimetic carbon fiber-based scaffolds. Highly porous ceramic zinc oxide (ZnO) microstructures serve as three-dimensional (3D) sacrificial templates and are infiltrated with carbon nanotubes (CNTs) or graphene dispersions. Once the CNTs and graphene coat the ZnO template, the ZnO is either removed by hydrolysis or converted into carbon by chemical vapor deposition. The resulting 3D carbon scaffolds are both hierarchically ordered and free-standing. The properties of the microfibrous scaffolds were tailored with a high porosity (up to 93%), a high Young’s modulus (ca. 0.027–22 MPa), and an electrical conductivity of ca. 0.1–330 S/m, as well as different surface compositions. Cell viability, fibroblast proliferation rate and protein adsorption rate assays have shown that the generated scaffolds are biocompatible and have a high protein adsorption capacity (up to 77.32 ± 6.95 mg/cm3) so that they are able to resemble the extracellular matrix not only structurally but also biochemically. The scaffolds also allow for the successful growth and adhesion of fibroblast cells, showing that we provide a novel, highly scalable modular design strategy to generate biocompatible carbon fiber systems that mimic the extracellular matrix with the additional feature of conductivity.

RF-Magnetron Sputtered Silica Interlayer on β-TCP Granules for Mesoporous Silica Coating

Mesoporous silica (MPS) coatings on β-tricalcium phosphate (β-TCP) granules and their protein adsorptive capabilities were studied. β-TCP granules containing 2 wt% of aluminum oxide and 6 wt% of silicon oxide were prepared using a pan-type granulator and heated at 1200 oC. MPS coatings on β-TCP granules was carried out by a dip-coating method, but the β-TCP granules were not covered by the MPS particles. A silica interlayer was formed on the β-TCP granules via magnetron sputtering prior to the coating of the MPS. The β-TCP granules coated with the silica interlayer were fully covered by the MPS particles. A silica interlayer may offer bonding between the β-TCP granules and MPS coating. The adsorption of protein on the MPS-coated β-TCP granules was evaluated by UV-VIS spectroscopy. The adsorption capacity of protein on the β-TCP granules was improved by the MPS coatings on the β-TCP granules, and that of the β-TCP granules coated with the silica interlayer showed a higher protein adsorption capacity.

Adsorption of Plasma Proteins on Single-Walled Carbon Nanotubes Reduced Cytotoxicity and Modulated Neutrophil Activation.

Proteins in the bloodstream bind to carbon nanotubes (CNTs) through noncovalent interactions to form a protein corona, thereby effectively influencing the biological properties and blood biocompatibility of the CNTs. Here, we investigated the binding of common plasma proteins (i.e., human immunoglobulin G (IgG), human serum albumin (HSA), and fibrinogen (FG)) to carboxylated single-walled CNTs (SWCNTs), and evaluated the effects of these different protein coronas on cytotoxicity to endothelial cells and immune response to neutrophils in the bloodstream. Measurements of adsorption parameters revealed tight binding of proteins to SWCNTs, and the SWCNTs adsorption capacities followed the order FG > HSA > IgG. In addition, the basic residues (Arg, Lys, His) were found to play an important role in the formation of protein-SWCNTs corona complexes and determine their adsorption capacity. Consistent with the higher protein adsorption capacity, FG more significantly reduced the cytotoxicity of CNTs to human umbilical vein endothelial cells than the other two proteins. However, only treatment of SWCNTs with IgG resulted in the enhancement of CNT-induced myeloperoxidase (MPO) release (i.e., neutrophil activation) in neutrophils, while MPO-dependent degradation of CNTs induced less cytotoxicity than initial nanomaterials. Consistent with these effects of protein coronas, the presence of serum attenuated the cytotoxicity of CNTs and CNTs could induce neutrophil activation in human blood plasma. Our study demonstrates the ability of adsorbed plasma proteins to influence cytotoxicity and neutrophil response caused by CNTs in the bloodstream.

Adsorption of Bovine Serum Albumin on Carbon-Based Materials

The protein adsorption plays a very important role in biotechnology, biomolecular engineering and it is one of the main factors determining bio- and hemocompatibility of biomedical materials in medical applications, such as blood purification and wound healing. Here we report adsorption properties of two carbon-based materials, thermally expanded graphite (EGr) and graphene nanoplatelets (GnP), for bovine serum albumin (BSA), the most abundant blood plasma protein. The influence of the surface chemistry of expanded graphite on the mechanism of BSA adsorption was studied by using EGr modified with oxygen or nitrogen functionalities. Having low microporosity and the specific surface area in the range of 5 to 50 m2/g, the expanded graphite exhibits high protein adsorption capacity at high equilibrium concentrations, which makes this material a potential candidate for biomedical applications as a carrier for high molecular weight (HMW) drug delivery or adsorption of HMW metabolites. At low equilibrium concentrations, the effect of specific protein-surface functional groups interaction reveals the differences between the adsorption affinity of different surface modified EGr materials to BSA. The adsorption of BSA on GnP with a specific surface area of 286 m2/g and a developed micro-/mesoporous structure did not follow the same mechanism as seen with EGr materials. At low equilibrium concentration of BSA, GnP exhibits high adsorption efficiency. An important finding is that no release of nanoparticles from expanded graphite adsorbents was observed, which makes them potentially suitable for direct contact with blood and other tissues while very small nanoparticles were noticed in the case of graphene nanoplatelets.

Biologically inspired, catechol-coordinated, hierarchical organization of raspberry-like calcium phosphate nanospheres with high specific surface area.

The elaborate design of calcium phosphates (CaP) with a hierarchical structure for biomedical applications is severely restricted due to their instinctive pertinacious irregular agglomeration. Thus, the development of mesoporous CaP with large internal pores is far from satisfactory. In this study, catechol is selected as a modifier to intervene in the precipitation of CaP. Compared to pure CaP with smooth irregular aggregates with an average size of 110 nm, the catechol-intervened CaP (CaP/Cat) samples are raspberry-like nano-spherical assemblies of ca. 25 nm nanoparticles. The obtained spheres possess a mesoporous structure, large interior pores and high specific surface area, which endow them with a high protein adsorption capacity and high DNA delivery efficacy. Catechol is subjected to oxidative polymerization while CaP precipitation occurs. This simultaneous reaction is supposed to play a crucial role in directing the assembling of the CaP/Cat nanospheres. The flexible catechol moiety is shown to be a novel and promising modifier for manufacturing CaP with tunable structures and properties for various applications.