Measuring binding of protein to gel-bound ligands using magnetic levitation

This paper describes the use of magnetic levitation (MagLev) to measure the association of proteins and ligands. The method starts with diamagnetic gel beads that are functionalized covalently with small molecules (putative ligands). Binding of protein to the ligands within the bead causes a change in the density of the bead. When these beads are suspended in a paramagnetic aqueous buffer and placed between the poles of two NbFeB magnets with like poles facing, the changes in the density of the bead on binding of protein result in changes in the levitation height of the bead that can be used to quantify the amount of protein bound. This paper uses a reaction-diffusion model to examine the physical principles that determine the values of rate and equilibrium constants measured by this system, using the well-defined model system of carbonic anhydrase and aryl sulfonamides. By tuning the experimental protocol, the method is capable of quantifying either the concentration of protein in a solution, or the binding affinities of a protein to several resin-bound small molecules simultaneously. Since this method requires no electricity and only a single piece of inexpensive equipment, it may find use in situations where portability and low cost are important, such as in bioanalysis in resource-limited settings, point-of-care diagnosis, veterinary medicine, and plant pathology. It still has several practical disadvantages. Most notably, the method requires relatively long assay times and cannot be applied to large proteins (>70 kDa), including antibodies. The design and synthesis of beads with improved characteristics (e.g., larger pore size) has the potential to resolve these problems.

Injectable and biodegradable hydrogels: gelation, biodegradation and biomedical applications

Injectable hydrogels with biodegradability have in situ formability which in vitro/in vivo allows an effective and homogeneous encapsulation of drugs/cells, and convenient in vivo surgical operation in a minimally invasive way, causing smaller scar size and less pain for patients. Therefore, they have found a variety of biomedical applications, such as drug delivery, cell encapsulation, and tissue engineering. This critical review systematically summarizes the recent progresses on biodegradable and injectable hydrogels fabricated from natural polymers (chitosan, hyaluronic acid, alginates, gelatin, heparin, chondroitin sulfate, etc.) and biodegradable synthetic polymers (polypeptides, polyesters, polyphosphazenes, etc.). The review includes the novel naturally based hydrogels with high potential for biomedical applications developed in the past five years which integrate the excellent biocompatibility of natural polymers/synthetic polypeptides with structural controllability via chemical modification. The gelation and biodegradation which are two key factors to affect the cell fate or drug delivery are highlighted. A brief outlook on the future of injectable and biodegradable hydrogels is also presented (326 references).

Accelerated identification of proteins by mass spectrometry by employing covalent pre-gel staining with Uniblue A

Background

The identification of proteins by mass spectrometry is a standard method in biopharmaceutical quality control and biochemical research. Prior to identification by mass spectrometry, proteins are usually pre-separated by electrophoresis. However, current protein staining and de-staining protocols are tedious and time consuming, and therefore prolong the sample preparation time for mass spectrometry.

Methodology and Principal Findings

We developed a 1-minute covalent pre-gel staining protocol for proteins, which does not require de-staining before the mass spectrometry analysis. We investigated the electrophoretic properties of derivatized proteins and peptides and studied their behavior in mass spectrometry. Further, we elucidated the preferred reaction of proteins with Uniblue A and demonstrate the integration of the peptide derivatization into typical informatics tools.

Conclusions and Significance

The Uniblue A staining method drastically speeds up the sample preparation for the mass spectrometry based identification of proteins. The application of this chemo-proteomic strategy will be advantageous for routine quality control of proteins and for time-critical tasks in protein analysis.

Stimuli responsive polymers for nanoengineering of biointerfaces

There is an increasing demand on the development of "smart" switchable interfaces since controlling surface topography and chemical functionality on a nanometer scale is crucial for numerous biomedical applications. Those surfaces, which are based on stimuli responsive polymers (SRPs), are able to modify their interactions with cells, biomolecules responding to different physical (e.g., temperature) or chemical (e.g., pH) stimuli. Such behavior may partially mimic complex dynamic properties of natural systems that are regulated by many biological stimuli. This paper reviews major studies and applications of SRPs as biointerfaces in a form of thin polymeric films (gels) and surface tethered polymers (brushes).

Marine microgels

The ocean plays a critical role in global carbon cycling: it handles half of the global primary production, yielding the world's largest stock of reduced organic carbon (ROC) that supports one of the world's largest biomasses. However, the mechanisms whereby ROC becomes mineralized remain unresolved. This review focuses on laboratory and field observations that dissolved organic carbon (DOC) self-assembles, forming self-assembled microgels (SAGs). Self-assembly has approximately10% yield, generating an estimated global seawater SAG budget of approximately 10(16) g C. Transects at depths of 10-4,000 m reveal concentrations of approximately 10(6) to approximately 3 x 10(12) SAG L(-1), respectively, forming an estimated ROC stock larger than the global marine biomass. Because hydrogels have approximately 1% solids (10 g L(-1)), whereas seawater DOC reaches approximately 10(-3) g L(-1), SAGs contain approximately 10(4) more bacterial substrate than seawater. Thus, microgels represent an unsuspected and huge micron-level ocean patchiness that could profoundly influence the passage of DOC through the microbial loop, with ramifications that may scale to global cycles of bioactive elements.

On the crucial importance of the pH for the formation and self-stabilization of protein microgels and strands

Stable suspensions of protein microgels are formed by heating salt-free β-lactoglobulin solutions at concentrations up to about C = 50 g·L(-1) if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g·L(-1) and the average hydrodynamic radius decreases with increasing pH from 200 to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short, curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm.

SOX trio-co-transduced adipose stem cells in fibrin gel to enhance cartilage repair and delay the progression of osteoarthritis in the rat

The aim of this study was to test the hypotheses that retroviral gene transfer of SOX trio enhances the in vitro chondrogenic differentiation of ASCs, and that SOX trio-co-transduced ASCs in fibrin gel promote the healing of osteochondral defects, and arrest the progression of surgically-induced osteoarthritis in a rat model. ASCs isolated from inguinal fat in rats were transduced with SOX trio genes using retrovirus, and further cultured in vitro in pellets for 21 days, then analyzed for gene and protein expression of SOX trio and chondrogenic markers. SOX trio-co-transduced ASCs in fibrin gel were implanted on the osteochondral defect created in the patellar groove of the distal femur, and also injected into the knee joints of rats with surgically-induced osteoarthritis. Rats were sacrificed after 8 weeks, and analyzed grossly and microscopically. After 21 days, ASCs transduced with SOX-5, -6, or -9 had hundreds-fold greater gene expression of each gene compared with the control with the SOX protein expression matching gene expression. SOX trio-co-transduction significantly increased GAG contents as well as type II collagen gene and protein expression. ASCs co-transduced with SOX trio significantly promoted the in vivo cartilage healing in osteochondral defect model, and prevented the progression of degenerative changes in surgically-induced osteoarthritis.

Collagen-agarose co-gels as a model for collagen-matrix interaction in soft tissues subjected to indentation

The mechanical properties of soft tissues depend on the collagen fiber network and the surrounding non-fibrillar matrix. The mechanical role of non-fibrillar material remains poorly understood. Our recent study (Lake and Barocas, Ann Biomed Eng 2011) introduced collagen-agarose co-gels as a simple experimental model system to evaluate the mechanical contribution of non-fibrillar matrix, and evaluated co-gel properties in uniaxial tension. In this study, we utilized similar co-gels to examine collagen-matrix interaction in tissues subjected to incremental stress-relaxation indentation tests. Mechanical testing was performed using two orthogonal custom test devices, and polarized light imaging was used to quantify 3D collagen fiber kinematics under load. The addition of agarose led to concentration-dependent changes in the time-dependent mechanical response and magnitude/spread of collagen fiber reorganization of tissue analogs. Specifically, peak/relaxed loads increased, and relaxation rate decreased, with increasing agarose concentration. In addition, increasing agarose content led to larger magnitude changes in orientation direction and alignment strength that were more localized near the indenter. Results suggest that non-fibrillar material significantly contributes to the behavior of co-gels in indentation, likely by reducing permeability and resisting volume change, thereby providing insight into the properties of artificial and native tissues subjected to non-tensile loading.

Calcium signaling in live cells on elastic gels under mechanical vibration at subcellular levels

A new device was designed to generate a localized mechanical vibration of flexible gels where human umbilical vein endothelial cells (HUVECs) were cultured to mechanically stimulate these cells at subcellular locations. A Fluorescence Resonance Energy Transfer (FRET)-based calcium biosensor (an improved Cameleon) was used to monitor the spatiotemporal distribution of intracellular calcium concentrations in the cells upon this mechanical stimulation. A clear increase in intracellular calcium concentrations over the whole cell body (global) can be observed in the majority of cells under mechanical stimulation. The chelation of extracellular calcium with EGTA or the blockage of stretch-activated calcium channels on the plasma membrane with streptomycin or gadolinium chloride significantly inhibited the calcium responses upon mechanical stimulation. Thapsigargin, an endoplasmic reticulum (ER) calcium pump inhibitor, or U73122, a phospholipase C (PLC) inhibitor, resulted in mainly local calcium responses occurring at regions close to the stimulation site. The disruption of actin filaments with cytochalasin D or inhibition of actomyosin contractility with ML-7 also inhibited the global calcium responses. Therefore, the global calcium response in HUVEC depends on the influx of calcium through membrane stretch-activated channels, followed by the release of inositol trisphosphate (IP3) via PLC activation to trigger the ER calcium release. Our newly developed mechanical stimulation device can also provide a powerful tool for the study of molecular mechanism by which cells perceive the mechanical cues at subcellular levels.

A high-throughput solid phase screening method for identification of lignocellulose-degrading bacteria from environmental isolates

The development of cost-effective biofuels will require improvements in the efficiency of biomass deconstruction, a process typically carried out by lignocellulose-degrading enzymes. Environmental microbes represent an abundant and diverse source of lignocelluloses-degrading enzymes for use in biotechnology. However, identification of microorganisms that possess these enzymes has been slowed by a lack of rapid screening methodologies, particularly those that utilize native lignocellulosic substrates. In this report, we describe a new, solid-phase screening system for the identification of microbes capable of lignocellulose degradation. The critical component of this screening system is the use of acrylamide, instead of agar, as the solidifying agent. Our results show that this screening method allows for the identification of Gram-positive and Gram-negative bacteria that possess cellulose and hemicellulose degrading activities from environmental isolates.

ALK, the key gene for gelatinization temperature, is a modifier gene for gel consistency in rice

Gelatinization temperature (GT) is an important parameter in evaluating the cooking and eating quality of rice. Indeed, the phenotype, biochemistry and inheritance of GT have been widely studied in recent times. Previous map-based cloning revealed that GT was controlled by ALK gene, which encodes a putative soluble starch synthase II-3. Complementation vector and RNAi vector were constructed and transformed into Nipponbare mediated by Agrobacterium. Phenotypic and molecular analyses of transgenic lines provided direct evidence for ALK as a key gene for GT. Meanwhile, amylose content, gel consistency and pasting properties were also affected in transgenic lines. Two of four nonsynonymous single nucleotide polymorphisms in coding sequence of ALK were identified as essential for GT. Based on the single nucleotide polymorphisms (SNPs), two new sets of SNP markers combined with one cleaved amplified polymorphic sequence marker were developed for application in rice quality breeding.

Development and modeling of arsenic-trioxide-loaded thermosensitive liposomes for anticancer drug delivery

In this article, a novel delivery system for the anticancer drug, arsenic trioxide (ATO), is characterized. The release of ATO from DPPC liposomes with MPPC lysolipid incorporated into the bilayer was measured. Upon heating the liposomes to 37°C, there was a 15-25% release over 24 hours. The ATO release from the DPPC and DPPC:MPPC (5%) systems leveled off after 10 hours at 37°C, whereas the DPPC:MPPC (10%) liposomes continue to release ATO over the 24-hour time span. Upon heating the liposomes rapidly to 42°C, the release rate was substantially increased. The systems containing lysolipids exhibited a very rapid release of a significant amount of arsenic in the first hour. In the first hour, the DPPC:MPPC (5%) liposomes released 40% of the arsenic and the DPPC:MPPC (10%) liposomes released 55% of the arsenic. Arsenic release from pure DPPC liposomes was comparable at 37 and 42°C, indicating that the presence of a lysolipid is necessary for a significant enhancement of the release rate. A coarse-grained molecular dynamics (CGMD) model was used to investigate the enhanced permeability of lysolipid-incorporated liposomes and lipid bilayers. The CG liposomes did not form a gel phase when cooled due to the high curvature; however, permeability was still significantly lower below the liquid-to-gel phase-transition temperature. Simulations of flat DPPC:MPPC bilayers revealed that a peak in the permeability did coincide with the phase transition from the gel to LC state when the lysolipid, MPPC, was present. No pores were observed in the simulations, so it is unlikely this was the permeability-enhancing mechanism.

[Biodegradation of methyl tert-butyl ether by stabilized immobilized Methylibium petroleiphilum PM1 cells and its biodegradation kinetics analysis]

Methylibium petroleiphilum PM1, which is capable of degrading methyl tert-butyl ether (MTBE) , was immobilized in calcium alginate gel beads. Several methods were explored to increase the strength of these gel beads. The central composite design analysis indicated that the introduction of 0.2 mol x L(-1) Ca2+ into the crosslinking solution, 1.38 mmol x L(-1) Ca2+ into the growth medium and 0.1% polyethyleneimine (PEI) as the chemical crosslinking agent could increase the stability of the Ca-alginate gel beads with no loss of biodegradation activity. The stabilized immobilized cells could be used 400 h continuously with no breakage and no bioactivity loss. Examination of scanning electron microscope demonstrated that a membrane surrounding the gel beads was formed and the cells could grow and breed well in the stabilized calcium alginate gel beads. Kinetic analysis of the gel bead-degradation indicated that the rate-limiting step was biochemical process instead of intraparticle diffusion process. The diameter of 3 mm affected the biodegradability less while high concentration of PEI induced much more serious mass transfer restraint.

pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli

Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75-133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216-220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe(3+) interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe(3+) cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G') that approach covalently cross-linked gels as well as self-healing properties.

[Culture of human amniotic fluid stem cells in 3D collagen matrix]

Most of the researchers attribute amniotic fluid stem cells (AF SCs) to mesenchymal stem cells (MSCs). However, AF SCs express both mesenchymal and epithelial markers, which distinguishes them from postnatal MSCs. Cultivation in the three-dimensional matrix provides a different look at the nature of these cells. We showed that, in 3D collagen gel, AF SCs form epithelial structures (tubules and cysts). Active contraction of the gel during the first days of cultivation, which is characteristic if mesenchymal cells, does not occur. Electron microscopic study showed that typical to epithelial cell adherent junctions are formed between AF SCs. On the other hand, AF SCs continue to express MSCs markers during cultivation in the gel. Thus, AF SCs may not be true mesenchymal cells because they can display properties of epithelial cells. Perhaps these cells undergo epithelial-mesenchymal transition, the process which actively takes place during embryogenesis.

Non-destructive label-free monitoring of collagen gel remodeling using optical coherence tomography

Matrix remodeling plays a fundamental role in physiological and pathological processes, as well as in tissue engineering applications. In this paper, optical coherence tomography (OCT), a non-destructive optical imaging technology, was used to image collagen gel remodeling by smooth muscle cells (SMCs). The optical scattering properties of collagen-SMC gels were characterized quantitatively by fitting OCT data to a theoretical model. Matrix remodeling over 5 days produced a 10-fold increase in the reflectivity of the collagen gels, corresponding to a decrease in scattering anisotropy from 0.91 to 0.46. The increase in reflectivity was corroborated in confocal mosaic images. Blocking matrix degradation in collagen-SMC gels with doxycycline, a non-specific matrix metalloproteinases (MMPs) inhibitor, impeded the decrease in scattering anisotropy and resulted in few macroscopic signs of remodeling. Causing matrix degradation in acellular gels with a 3 h treatment of MMP-8 (collagenase 2) partially mimicked the decrease in anisotropy measured in collagen-SMC gels after 5 days. These results suggest that the decrease in scattering anisotropy in the collagen-SMC gels was due to MMP activity that degrades collagen fibrils into smaller fragments.

Effect of penetration enhancers on gel formulation of Zidovudine: in vivo and ex vivo studies

To overcome many challenges associated with antiretroviral drug therapy, novel drug delivery systems present an opportunity for formulation scientists to improve the management of patients with HIV/AIDS. The purpose of this study was to prepare a transdermal delivery system for zidovudine using different penetration enhancers incorporated in carbopol 971P gel and to evaluate the same for rheology, percent drug content, drug deposition, in vitro, ex vivo, and in vivo permeation across rat skin. The rheology studies indicated that 1% w/w carbopol gel had a higher linear viscoelastic region, good creep recovery, and desirable viscosity. Among all gel formulations, gel containing cineole and menthol as penetration enhancers attained a steady-state flux of 5.9 mg/cm(2)/h and 5.4 mg/cm(2)/h of zidovudine, respectively, leading to plasma concentration in the therapeutic range. The drug deposition was also found to be highest in the case of gel containing cineole and menthol as penetration enhancers. The results indicated a linear relationship between in vitro flux and in vivo bioavailability of zidovudine transdermal gel.

Factors affecting daughter cells' arrangement during the early bacterial divisions

On agar plates, daughter cells of Escherichia coli mutually slide and align side-by-side in parallel during the first round of binary fission. This phenomenon has been previously attributed to an elastic material that restricts apparently separated bacteria from being in string. We hypothesize that the interaction between bacteria and the underneath substratum may affect the arrangement of the daughter bacteria. To test this hypothesis, bacterial division on hyaluronic acid (HA) gel, as an alternative substratum, was examined. Consistent with our proposition, the HA gel differs from agar by suppressing the typical side-by-side alignments to a rare population. Examination of bacterial surface molecules that may contribute to the daughter cells' arrangement yielded an observation that, with disrupted lpp, the E. coli daughter cells increasingly formed non-typical patterns, i.e. neither sliding side-by-side in parallel nor forming elongated strings. Therefore, our results suggest strongly that the early cell patterning is affected by multiple interaction factors. With oscillatory optical tweezers, we further demonstrated that the interaction force decreased in bacteria without Lpp, a result substantiating our notion that the side-by-side sliding phenomenon directly reflects the strength of in-situ interaction between bacteria and substratum.

Papain-gel degrades intact nonmineralized type I collagen fibrils

Papain-gel has been utilized as a chemo-mechanical material for caries removal due to its ability to preserve underlying sound dentin. However, little is known about the effect of the papain enzyme on intact type I collagen fibrils that compose the dentin matrix. Here we sought to define structural changes that occur in intact type I collagen fibrils after an enzymatic treatment with a papain-gel. Intact and nonmineralized type I collagen fibrils from rat tail were obtained and treated with a papain-gel (Papacarie) for 30 s, rinsed with water and imaged using an atomic force microscope (AFM). Additionally, polished healthy dentin specimens were also treated using the same protocol described above and had their elastic modulus (E) and hardness (H) measured by means of AFM-based nanoindentation. AFM images showed that the papain-gel induced partial degradation of the fibrils surface, yet no rupture of fibrils was noticed. The distinction between gap and overlap zones of fibrils vanished in most regions after treatment, and overlap zones appeared to be generally more affected. Mechanical data suggested a gradual decrease in E and H after treatments. A significant two-fold drop from the values of normal dentin (E=20+/-1.9, H=0.8+/-0.08 GPa) was found after four applications (E=9.7+/-3.2, H=0.24+/-0.1 GPa) (P<0.001), which may be attributed to the degradation of proteoglycans of the matrix. In summary, this study provided novel evidence that intact nonmineralized type I collagen fibrils are partially degraded by a papain-gel.

Characterization of sol-gel-encapsulated proteins using small-angle neutron scattering

Entrapment of biomolecules in silica-derived sol-gels has grown into a vibrant area of research since it was originally demonstrated. However, accessing the consequences of entrapment on biomolecules and the gel structure remains a major challenge in characterizing these biohybrid materials. We present the first demonstration that it is possible with small-angle neutron scattering (SANS) to study the conformation of dilute proteins that are entrapped in transparent and dense sol-gels. Using deuterium-labeled green fluorescent protein (GFP) and SANS with contrast variation, we demonstrate that the scattering signatures of the sol-gel and the protein can be separated. Analysis of the scattering curves of the sol-gels using a mass-fractal model shows that the size of the colloidal silica particles and the fractal dimensions of the gels were similar in the absence and presence of protein, demonstrating that GFP did not influence the reaction pathway for the formation of the gel. The major structural difference in the gels was that the pore size was increased 2-fold in the presence of the protein. At the contrast match point for silica, the scattering signal from GFP inside the gel became distinguishable over a wide q range. Simulated scattering curves representing a monomer, end-to-end dimer, and parallel dimer of the protein were calculated and compared to the experimental data. Our results show that the most likely structure of GFP is that of an end-to-end dimer. This approach can be readily applied and holds great potential for the structural characterization of complex biohybrid and other materials.

Bioactivated collagen-based scaffolds embedding protein-releasing biodegradable microspheres: tuning of protein release kinetics

In tissue engineering, the recapitulation of natural sequences of signaling molecules, such as growth factors, as occurring in the native extracellular matrix (ECM), is fundamental to support the stepwise process of tissue regeneration. Among the manifold of tissue engineering strategies, a promising one is based on the creation of the chrono-programmed presentation of different signaling proteins. This approach is based upon the integration of biodegradable microspheres, loaded with suitable protein molecules, within scaffolds made of collagen and, in case, hyaluronic acid, which are two of the fundamental ECM constituents. However, for the design of bioactivated gel-like scaffolds the determination of release kinetics must be performed directly within the tissue engineering template. In this work, biodegradable poly(lactic-co-glycolic)acid (PLGA) microspheres were produced by the multiple emulsion-solvent evaporation technique and loaded with rhodamine-labelled bovine serum albumin (BSA-Rhod), a fluorescent model protein. The microdevices were dispersed in collagen gels and collagen-hyaluronic acid (HA) semi-interpenetrating networks (semi-IPNs). BSA-Rhod release kinetics were studied directly on single microspheres through confocal laser scanning microscopy (CLSM). To thoroughly investigate the mechanisms governing protein release from PLGA microspheres in gels, BSA-Rhod diffusion in gels was determined by fluorescence correlation spectroscopy (FCS), and water transport through the microsphere bulk was determined by dynamic vapor sorption (DVS). Moreover, the decrease of PLGA molecular weight and glass transition temperature (T(g)) were determined by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC), respectively. Results indicate that protein release kinetics and delivery onset strongly depend on the complex interplay between protein transport through the PLGA matrix and in the collagen-based release media, and water sequestration within the scaffolds, related to the scaffold hydrophilicity, which is dictated by HA content. The proper manipulation of all these features may thus allow the obtainment of a fine control over protein sequential delivery and release kinetics within tissue-engineering scaffolds.

Nitric oxide-releasing S-nitrosothiol-modified xerogels

The synthesis, material characterization, and in vitro biocompatibility of S-nitrosothiol (RSNO)-modified xerogels are described. Thiol-functionalized xerogel films were formed by hydrolysis and co-condensation of 3-mercaptopropyltrimethoxysilane (MPTMS) and methyltrimethoxysilane (MTMOS) sol-gel precursors at varying concentrations. Subsequent thiol nitrosation via acidified nitrite produced RSNO-modified xerogels capable of generating nitric oxide (NO) for up to 2 weeks under physiological conditions. Xerogels also exhibited NO generation upon irradiation with broad-spectrum light or exposure to copper, with NO fluxes proportional to wattage and concentration, respectively. Xerogels were capable of storing up to approximately 1.31 micromol NO mg(-1), and displayed negligible fragmentation over a 2-week period. Platelet and bacterial adhesion to nitrosated films was reduced compared to non-nitrosated controls, confirming the antithrombotic and antibacterial properties of the NO-releasing materials. Fibroblast cell viability was maintained on the xerogel surfaces illustrating the promise of RSNO-modified xerogels as biomedical device coatings.

Maize arabinoxylan gels as protein delivery matrices

The laccase induced gelation of maize bran arabinoxylans at 2.5% (w/v) in the presence of insulin or β-lactoglobulin at 0.1% (w/v) was investigated. Insulin and β-lacto-globulin did not modify either the gel elasticity (9 Pa) or the cross-links content (0.03 and 0.015 μg di- and triferulic acids/mg arabinoxylan, respectively). The protein release capability of the gel was also investigated. The rate of protein release from gels was dependent on the protein molecular weight. The apparent diffusion coefficient was 0.99 × 10^-7 and 0.79 × 10^-7 cm²/s for insulin (5 kDa) and β-lactoglobulin (18 kDa), respectively. The results suggest that maize bran arabinoxylan gels can be potential candidates for the controlled release of proteins.