Adsorption Of Hyaluronic Acid Research Articles

A Study of Hyaluronic Acid's Theoretical Reactivity and of Magnetic Nanoparticles Capped with Hyaluronic Acid.

Hyaluronic acid (HA) has attracted much attention in tumor-targeted drug delivery due to its ability to specifically bind to the CD44 cellular receptor, which is widely expressed on cancer cells. We present HA-capped magnetic nanoparticles (HA-MNPs) obtained via the co-precipitation method, followed by the electrostatic adsorption of HA onto the nanoparticles' surfaces. A theoretical study carried out with the PM3 method evidenced a dipole moment of 3.34 D and negatively charged atom groups able to participate in interactions with nanoparticle surface cations and surrounding water molecules. The ATR-FTIR spectrum evidenced the hyaluronic acid binding to the surface of the ferrophase, ensuring colloidal stability in the water dispersion. To verify the success of the synthesis and stabilization, HA-MNPs were also characterized using other investigation techniques: TEM, EDS, XRD, DSC, TG, NTA, and VSM. The results showed that the HA-MNPs had a mean physical size of 9.05 nm (TEM investigation), a crystallite dimension of about 8.35 nm (XRD investigation), and a magnetic core diameter of about 8.31 nm (VSM investigation). The HA-MNPs exhibited superparamagnetic behavior, with the magnetization curve showing saturation at a high magnetic field and a very small coercive field, corresponding to the net dominance of single-domain magnetic nanoparticles that were not aggregated with reversible magnetizability. These features satisfy the requirement for magnetic nanoparticles with a small size and good dispersibility for long-term stability. We performed some preliminary tests regarding the nanotoxicity in the environment, and some chromosomal aberrations were found to be induced in corn root meristems, especially in the anaphase and metaphase of mitotic cells. Due to their properties, HA-MNPs also seem to be suitable for use in the biomedical field.

Tumor microenvironment-activated, immunomodulatory nanosheets loaded with copper(II) and 5-FU for synergistic chemodynamic therapy and chemotherapy

The tumor microenvironment (TME) has a redox state that differs greatly from normal tissues, as characterized by the overexpression of H2O2 and glutathione (GSH). To address the GSH-related restrictions on chemodynamic therapy (CDT) efficacy, we have developed a Cu(II)-based CDT strategy. In this study, a novel organic–inorganic hybrid drug delivery system (LDH/HA/5-FU) was conceived and prepared by the intercalation of 5-FU into the interlayer of copper–aluminum layered double hydroxide (CuAl-LDH) via ion exchange strategy and the adsorption of hyaluronic acid (HA) on the surface of CuAl-LDH. Taking advantage of the pH-degradable property of CuAl-LDH and the CD44-targeting property of HA, the formed LDH/HA/5-FU nanosheets could specifically target tumor cells' overexpressing CD44 receptor, rapidly release Cu(II) and 5-FU in tumor cells, inducing tumor cell apoptosis and cuproptosis, and long-term intracellular GSH depletion and toxic hydroxyl radicals (·OH) generation could be achieved through the cyclic catalytic reaction of Cu(I)/Cu(II). Meanwhile, peritumoral injection of LDH/HA/5-FU nanosheets might function as an adjuvant to increase the levels of antitumor tumor-associated macrophages (TAMs) and T cells. In vivo experiments further verified that the intelligently designed LDH/HA/5-FU nanosheets successfully promoted the immune systems, with an excellent inhibition efficacy towards tumors by combining Cu-based CDT and chemotherapy, showing promising potential for solid tumor treatments.

Development of In Situ Product Recovery (ISPR) System Using Amberlite IRA67 for Enhanced Biosynthesis of Hyaluronic Acid by Streptococcus zooepidemicus

High broth viscosity due to the accumulation of hyaluronic acid (HA) causes a limited yield of HA. It is a major problem of HA production using Streptococcus zooepidemicus. Extractive fermentation via in situ product recovery (ISPR) was utilized to enhance the HA production. Resins from Amberlite: IRA400 Cl; IRA900 Cl; IRA410 Cl; IRA402 Cl; and IRA67 were tested for the HA adsorption. IRA67 showed high adsorption capacity on HA. The study of the adsorption via a 2 L stirred tank bioreactor of S. zooepidemicus fermentation was investigated to elucidate the adsorption of HA onto IRA67 in dispersed and integrated internal column systems. The application of a dispersed IRA67 improved the HA production compared to the fermentation without resin addition by 1.37-fold. The HA production was further improved by 1.36-fold with an internal column (3.928 g/L) over that obtained with dispersed IRA67. The cultivation with an internal column shows the highest reduction of viscosity value after the addition of IRA67 resin: from 58.8 to 23.7 (mPa·s), suggesting the most effective ISPR of HA. The improved biosynthesis of HA indicated that an extractive fermentation by ISPR adsorption is effective and may streamline the HA purification.

Chitosan/hyaluronic acid polyanion bilayer applied from carbon acid as an advanced coating with intelligent antimicrobial properties for improved biological prosthetic heart valves

The tightly bonded shielding coating on biomatrix significantly enhances the functionality of medical devices, bioprostheses in particular. In our work we have obtained a polyelectrolyte coating on a biomatrix by sequentially depositing chitosan and hyaluronic acid (HA) from solutions in carbonic acid under pressure. This approach makes it possible to obtain hybrid biomatrix with a firmly bonded polymer screen due to the electrostatic bonding of polyions. High-precision analysis using a tritium label shows a 3-fold increase in quantity of HA in carbonic acid under pressure compared to the conventional method. The presence of the chitosan layer increases the HA adsorption by 15–20 % due to electrostatic interaction of differently charged polymers. Antimicrobial results show the possibility of implementing an induced antimicrobial response, due to the lysis of the upper layer of the coating (HA) and the release of antimicrobial agents in the case of growth of pathogens on the bioprosthesis.

Hyaluronic Acid-Stabilized Fe3O4 Nanoparticles for Promoting In Vivo Magnetic Resonance Imaging of Tumors.

The use of iron oxide (Fe3O4) nanoparticles as novel contrast agents for magnetic resonance imaging (MRI) has attracted great interest due to their high r 2 relaxivity. However, both poor colloidal stability and lack of effective targeting ability have impeded their further expansion in the clinics. Here, we reported the creation of hyaluronic acid (HA)-stabilized Fe3O4 nanoparticles prepared by a hydrothermal co-precipitation method and followed by electrostatic adsorption of HA onto the nanoparticle surface. The water-soluble HA functions not only as a stabilizer but also as a targeting ligand with high affinity for the CD44 receptor overexpressed in many tumors. The resulting HA-stabilized Fe3O4 nanoparticles have an estimated size of sub-20 nm as observed by transmission electron microscopy (TEM) imaging and exhibited long-term colloidal stability in aqueous solution. We found that the nanoparticles are hemocompatible and cytocompatible under certain concentrations. As verified by quantifying the cellular uptake, the Fe3O4@HA nanoparticles were able to target a model cell line (HeLa cells) overexpressing the CD44 receptor through an active pathway. In addition, we showed that the nanoparticles can be used as effective contrast agents for MRI both in vitro in HeLa cells and in vivo in a xenografted HeLa tumor model in rodents. We believe that our findings shed important light on the use of active targeting ligands to improve the contrast of lesion for tumor-specific MRI in the nano-based diagnosis systems.

HA/PEI-coated acridine orange-loaded gold-core silica shell nanorods for cancer-targeted photothermal and chemotherapy.

Aims: To develop a tumor-targeted chemo-photothermal nanomedicine through the functionalization of acridine orange (AO)-loaded gold-core mesoporoussilica shell (AuMSS)nanorods withpolyethylenimine (PEI) and hyaluronic acid (HA). Methods: Functionalization of theAuMSS nanorodswas achieved through the chemical linkage of PEI followed by electrostatic adsorption of HA. Results: HA functionalization improved AuMSS'cytocompatibility by decreasing blood hemolysis, and PEI-HAinclusion promoted a controlled and sustained AO release. In vitro assays revealed that HA functionalization increased the internalization ofnanoparticles byhuman negroid cervix epithelioid carcinoma cancer (HeLa)cells, and the combinatorial treatment mediated by AuMSS/PEI/HA_AO nanorods presented an enhanced effect, with >95% ofcellular death. Conclusion: AuMSS/PEI/HA_AO formulations can act as tumor-targeted chemo-photothermal nanomedicines for thecombinatorialtherapy ofcervical cancer.

Hyaluronic acid adsorption on nanodiamonds: Quantitative characteristics and mechanism

Formation of adsorption complex between hyaluronic acid and detonation nanodiamonds was studied. Nanodiamonds that possess negative and positive zeta-potential in an aqueous suspension were used. To determine the direct amount of hyaluronic acid on the nanodiamond surface tritium label was introduced into the polymer by means of tritium thermal activation method. It was found that hyaluronic acid irreversibly adsorbs on both positively and negatively charged nanodiamonds, but in different quantities. Adsorption of hyaluronic acid on nanodiamonds of positive zeta potential leads to the isoelectric point at the surface coverage close to 100 mg/g, while further increase in surface amount of hyaluronic acid results in the formation of negatively charged particles and the increase of its species diameter comparing with the initial material. In the case of negatively charged nanodiamonds adsorption of hyaluronic acid is also observed, but it was as much as 50 times lower than in the case of positively charged nanodiamonds. Even small amounts of hyaluronic acid adsorbed on nanodiamond surface results in the disaggregation of clusters of nanodiamonds that are formed in an aqueous suspension, while zeta potential was from − 50 to − 40 mV that is around of the value for non-modified material. On the basis of the experimental data, we can suggest that the adsorption mechanism of complex formation between hyaluronic acid and nanodiamonds includes both electrostatic interaction and formation of hydrogen bonds between surface functional groups and adsorbed water molecules.

A bioinspired mucoadhesive restores lubrication of degraded cartilage through reestablishment of lamina splendens

Adsorbed lubricious films composed of biomacromolecules are natively present at all articulating interfaces in the human body where they provide ultralow friction and maintain normal physiological function. Biolubrication gets impaired due to diseases such as osteoarthritis, in which cartilage damage results from alterations in synovial fluid and lamina splendens composition. Osteoarthritis is treated with hyaluronic acid (HA) orally or via intra-articular injection, but due to the poor adsorption of HA on the cartilage surface in the absence of adhesive molecules, pain relief is temporary. Here, we describe how natural lubrication on degraded cartilage surface can be restored with the help of a bioinspired mucoadhesive biopolymer chitosan catechol (Chi-C). Quartz crystal microbalance was used to mimic the formation of lamina splendens in vitro, known as synovial fluid conditioning films (SyCF), and colloidal probe atomic force microscopy was used to measure their nanoscale frictional properties. Clear evidence of glycoprotein (PRG4) recruitment by Chi-C increased the softness of SyCF, which also improved nanoscale lubrication in vitro, decreasing the friction coefficient from 0.06 to 0.03. At the macroscale, cartilage damage induced by Chondroitinase ABC increased the coefficient of friction (COF) from 0.07 ± 0.04 (healthy tissue) to 0.15 ± 0.03 (after tissue damage) in the presence of synovial fluid after sliding for 50 min. After Chi-C treatment of damaged cartilage, the COF fell to 0.06 ± 0.03, which is comparable to healthy cartilage. Chi-C did not adversely affect the metabolic activity of human chondrocytes. This study provides new key insight into the potential for restoring biolubrication through the use of muco-adhesive molecules.

Effect of concentration and surface roughness on corrosion behavior of Co–Cr–Mo alloy in hyaluronic acid

The work presented in this paper is based on the study of electrochemical corrosion behavior of Co–Cr–Mo alloy as a function of the concentration of simulated biological fluid (hyaluronic acid), the influence of Cl- on hyaluronic acid (HA) and machining configurations. For the electrochemical tests, electrochemical impedance spectroscopy and potentiodynamic polarization test were undertaken. With the increase in HA concentration, high metal dissolution was observed. Whereas with the addition of NaCl in the solution, the corrosion resistance of the sample was enhanced. Also, an increase in surface roughness of sample surface HA caused a decrease in icorr. This is due to the adhesion property of the HA on the sample surface. X-ray photoelectron spectroscopy was executed to analyze the passive film formed due to HA and NaCl on Co–Cr–Mo. Scanning electron microscope were carried out to analyze the surface morphology. Energy dispersive spectroscopy shows lower Cr at the pit. The study reveals the adsorption of HA on the surface. This adsorbed HA on the surface caused the metal dissolution and hence initiation sites for pitting. When compared with the sample in HA + NaCl solution, better passive film property was observed to cause better corrosion resistance.

Surface functionalization of methotrexate-loaded chitosan nanoparticles with hyaluronic acid/human serum albumin: Comparative characterization and in vitro cytotoxicity

The active tumor targeting ligands, hyaluronic acid (HA) and human serum albumin (HSA), are considered promising targeting moieties of drug carriers for cancer therapy. The chitosan nanoparticles loaded with methotrexate (MTX-CsNPs) were employed as the core for subsequent coating process. HA and HSA coating solutions were used at different concentrations. The effect of different HA Mw (1000, 360, 10kDa) was also investigated. The coated MTX-CsNPs was characterized proving the success of surface functionalization. The antitumor activity of the prepared MTX-CsNPs was evaluated on MCF-7 breast cancer cell lines. Results showed that both 360 and 10kDa HA allowed for successful HA adsorption, while its Mw and concentration determined negative charge density. HSA coating was accompanied by a slight increase in nanoparticles (NPs) size and a final positive surface charge. The in vitro cytotoxicity proved that HA and HSA coated MTX-CsNPs improved the antitumor activity compared to uncoated NPs and free drug.

Characterization of adsorption and lubrication of synovial fluid proteins and HA on DLC joint bearings surface

Adsorption and competitive adsorption behavior of bovine serum albumin (BSA), human γ-globulin (HGG), and hyaluronic acid (HA) molecules on a diamond-like carbon (DLC) film surface were investigated by the means of a quartz crystal microbalance with dissipation (QCM-D), and antigen-antibody reactions. The results showed that a BSA monolayer could be formed on the DLC film surface with side-on orientation and that an HGG monolayer could be formed on the DLC film surface with end-on orientation by using pure BSA or HGG solutions, respectively. HA molecules were hardly adsorbed onto the surface of DLC film or HGG or BSA biomolecular layer. The results of competitive adsorption showed that HGG molecules could displace BSA molecules and that HGG was the dominantly adsorbed molecule on the DLC film surface in a mixture of BSA, HGG, and HA. The frictional behavior of a DLC film sliding against Al2O3 in a mixture of BSA, HGG, and HA, was investigated by means of the friction coefficient and an open circuit potential, which suggested that the HGG molecule was the main component that formed the lubricating film.

Adsorption of hyaluronic acid on solid supports: Role of pH and surface chemistry in thin film self-assembly

Owing to its biocompatibility, resistance to biofouling, and desirable physicochemical and biological properties, hyaluronic acid (HA) has been widely used to modify the surface of various materials. The role of various physicochemical factors in HA adsorption remains, however, to be clarified. Herein, we employed quartz crystal microbalance with dissipation (QCM-D) in order to investigate HA adsorption at different pH conditions onto three substrates—silicon oxide, amine-terminated self-assembled monolayer (SAM) on gold, and carboxylic acid-terminated SAM on gold. The QCM-D experiments indicated specific pH conditions where either strong or weak HA adsorption occurs. The morphology of the adsorbed HA layers was investigated by atomic force microscopy (AFM), and we identified that strong HA adsorption produced a complete, homogenous and smooth HA layer, while weak HA adsorption resulted in rough and inhomogeneous HA layers. The observed specifics of the kinetics of HA adsorption, including a short initial linear phase and subsequent long non-linear phase, were described by using a mean-field kinetic model taking HA diffusion limitations and reconfiguration in the adsorbed state into account. The findings extend the physicochemical background of design strategies for improving the use of passive HA adsorption for surface modification applications.

Hyaluronic acid-coated chitosan nanoparticles: Molecular weight-dependent effects on morphology and hyaluronic acid presentation

Chitosan nanoparticles are popular carriers for the delivery of macromolecular payloads, e.g. nucleic acids. In this study, nanoparticles were prepared via complexation with triphosphate (TPP) anions and were successively coated with hyaluronic acid (HA). Key variables of the preparative process (e.g. chitosan and HA molecular weight) were optimised in view of the maximisation of loading with DNA, of the Zeta potential and of the dimensional stability, and the resulting particles showed excellent storage stability.We have focused on the influence of chitosan molecular weight on nanoparticle properties. Larger molecular weight increased their porosity (=decreased cross-link density), and this caused also larger dimensional changes in response to variations in osmotic pressure or upon drying. The dependency of nanoparticle porosity on chitosan molecular weight had a profound effect on the adsorption of HA on the nanoparticles; HA was apparently able to penetrate deeply into the more porous high molecular weight (684kDa) chitosan nanoparticles, while it formed a corona around those composed of more densely cross-linked low molecular weight (25kDa) chitosan. Atomic Force Microscopy (AFM) allowed not only to highlight the presence of this corona, but also to estimate its apparent thickness to about 20–30nm (in a dry state). The different morphology has a significant effect on the way HA is presented to biomolecules, and this has specific relevance in relation to interactions with HA receptors (e.g. CD44) that influence kinetics and mechanism of nanoparticle uptake.Finally, it is worth to mention that chitosan molecular weight did not appear to greatly affect the efficiency of nanoparticle loading with DNA, but significantly influenced its chitosanase-triggered release, with high molecular chitosan nanoparticles seemingly more prone to degradation by this enzyme.

Separation and purification of hyaluronic acid by embedded glucuronic acid imprinted polymers into cryogel

Hyaluronic acid (HA) has been used in many applications such as pharmaceutical, clinical and cosmetics, so its separation and purification is very important. In this study, firstly d-glucuronic acid imprinted polymers (MIPs) have been synthesized for the separation of HA which has glucuronic acid part in its structure. MIP particles have characterized by elemental analysis, Fourier Transform Infrared Spectroscopy (FT-IR) and swelling tests. Then, synthesized MIP particles have embedded into polyacrylamide based cryogel. Cryogel has prepared by free radical cryogelation process initiated by N,N,N',N'-Tetramethylethylenediamine (TEMED) and ammonium persulfate (APS) as redox initiators. This cryogel material was characterized by FT-IR, swelling tests, scanning electron microscopy (SEM) and surface adsorption analyze including pore size analyzer (BET) method. The adsorption of HA has investigated by spectrophotometric method using MIPs embedded into cryogel columns (GAIPEC) and the maximum HA adsorption capacity was found to be 318mgg(-1). The selectivity of GAIPEC column has estimated using N-acetylglucose amine as interfering agent since this molecule is a part of HA and the results have shown that GAIPEC has been nearly 35 times selective for HA than N-acetylglucose amine. The optimum chromatographic conditions for separation of HA were investigated. pH 7.0 buffer solution for elution and 0.1M of NaCl solution as desorption agent were used at 0.5mLmin(-1) flow rate. Also, recovery of GAIPEC was investigated and the results have shown that GAIPEC could be used many times without decreasing its adsorption capacity significantly. Here in, combining selectivity of MIP particles and mechanical properties of cryogel, a rigid and stable material was prepared for the separation and purification of HA. To point out this, HA has been isolated from fish eye and fermentation of Streptococcus equi RSKK 679 cell culture. After that, it has characterized and Fast Protein Liquid Chromatography (FPLC) applications have been investigated.

Friction coefficients for mechanically damaged bovine articular cartilage

We used a pin-on-disc tribometer to measure the friction coefficient of both pristine and mechanically damaged cartilage samples in the presence of different lubricant solutions. The experimental set up maximizes the lubrication mechanism due to interstitial fluid pressurization. In phosphate buffer solution (PBS), the measured friction coefficient increases with the level of damage. The main result is that when poly(ethylene oxide) (PEO) or hyaluronic acid (HA) are dissolved in PBS, or when synovial fluid (SF) is used as lubricant, the friction coefficients measured for damaged cartilage samples are only slightly larger than those obtained for pristine cartilage samples, indicating that the surface damage is in part alleviated by the presence of the various lubricants. Among the lubricants considered, 100 mg/mL of 100,000 Da MW PEO in PBS appears to be as effective as SF. We attempted to discriminate the lubrication mechanism enhanced by the various compounds. The lubricants viscosity was measured at shear rates comparable to those employed in the friction experiments, and a quartz crystal microbalance with dissipation monitoring was used to study the adsorption of PEO, HA, and SF components on collagen type II adlayers pre-formed on hydroxyapatite. Under the shear rates considered the viscosity of SF is slightly larger than that of PBS, but lower than that of lubricant formulations containing HA or PEO. Neither PEO nor HA showed strong adsorption on collagen adlayers, while evidence of adsorption was found for SF. Combined, these results suggest that synovial fluid is likely to enhance boundary lubrication. It is possible that all three formulations enhance lubrication via the interstitial fluid pressurization mechanism, maximized by the experimental set up adopted in our friction tests.

Extraction of hyaluronic acid (HA) from rooster comb and characterization using flow field‐flow fractionation (FlFFF) coupled with multiangle light scattering (MALS)

Hyaluronic acid (HA) was extracted in a relatively large scale from rooster comb using a method similar to that reported previously. The extraction method was modified to simplify and to reduce time and cost in order to accommodate a large-scale extraction. Five hundred grams of frozen rooster combs yielded about 500 mg of dried HA. Extracted HA was characterized using asymmetrical flow field-flow fractionation (AsFlFFF) coupled online to a multiangle light scattering detector and a refractive index detector to determine the molecular size, molecular weight (MW) distribution, and molecular conformation of HA. For characterization of HA, AsFlFFF was operated by a simplified two-step procedure, instead of the conventional three-step procedure, where the first two steps (sample loading and focusing) were combined into one to avoid the adsorption of viscous HA onto the channel membrane. The simplified two-step AsFlFFF yielded reasonably good separations of HA molecules based on their MWs. The weight average MW (M(w) ) and the average root-mean-square (RMS) radius of HA extracted from rooster comb were 1.20×10(6) and 94.7 nm, respectively. When the sample solution was filtered through a 0.45 μm disposable syringe filter, they were reduced down to 3.8×10(5) and 50.1 nm, respectively.

Nonleaching antimicrobial cotton fibers for hyaluronic acid adsorption

Quaternary ammonium containing compounds (QACs) such as cetylpyridinium chloride (CPC) is commonly employed in hyaluronic acid (HA) production process as an HA precipitating agent. 3-(Trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, a Si containing QAC (Si-QAC) generally used to modify the surface of cotton fibers for the preparation of nonleaching antibacterial textiles, has a chemical structure very similar to CPC. Choline, a natural QAC, can form a deep eutectic solvent with urea and be grafted onto cotton surface when incubating cotton in the deep eutectic solvent. Both of the QAC-modified cottons demonstrated antibacterial activity against Gram (−) Escherichia coli and Gram (+) Bacillus subtilis along with HA adsorption capacity. The HA adsorption isotherm could be well-fitted with Langmuir model with maximum adsorption capacities of 184 mg/g and 351 mg/g for Si-QAC and choline surface-functionalized cotton fibers, respectively. In the presence of high concentration of contaminants, HA could be directly recovered from a B. subtilis culture with a capacity of 15 mg/g by using Si-QAC modified antimicrobial cotton fiber.

Influences of lubricant composition on forming boundary film composed of synovia constituents

In this study, the influences of lubricant composition on adsorption behavior of proteins and stability of protein boundary film were investigated by using total internal reflection fluorescence microscopy (TIRFM). In addition, the adsorption of hyaluronic acid (HA) on rubbed surface was also observed. It was found that the forming of bottom layer of protein boundary film mainly composed of γ-globulin is a key factor to form a stable boundary film and the friction-induced enhancement of forming protein boundary film occurred in appropriate lubricant. In addition, the adsorption of HA on rubbed surface was enhanced by coexistence with γ-globulin and frictional action. It was indicated that a gel-like film is formed due to the introduction of hydrophilic HA molecules into boundary film and it contributes to reduce friction.

Separation and purification of hyaluronic acid by glucuronic acid imprinted microbeads

The purification of hyaluronic acid (HA) is relatively significant to use in biomedical applications. The structure of HA is formed by the repetitive units of glucuronic acid and N-acetyl glucosamine. In this study, glucuronic acid-imprinted microbeads have been supplied for the purification of HA from cell culture ( Streptococcus equi). Histidine-functional monomer, methacryloylamidohistidine (MAH) was chosen as the metal-complexing monomer. The glucuronic acid-imprinted poly(ethyleneglycoldimethacrylate-MAH-Copper(II)) [p(EDMA-MAH-Cu 2+)] microbeads have been synthesized by typical suspension polymerization procedure. The template glucuronic acid has been removed by employing 5 M methanolic KOH solution. p(EDMA-MAH-Cu 2+) microbeads have been characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) images and swelling studies. Moreover, HA adsorption experiments have been performed in a batch experimental set-up. Purification of HA from cell culture supernatant has been also investigated by determining the hyaluronidase activity using purified HA as substrate. The glucuronic acid imprinted p(EDMA-MAH-Cu 2+) particles can be used many times with no significant loss in adsorption capacities. Also, the selectivity of prepared molecular imprinted polymers (MIP) has been examined. Results have showed that MIP particles are 19 times more selective for glucuronic acid than N-acetylglucose amine.

Conformational Mechanics, Adsorption, and Normal Force Interactions of Lubricin and Hyaluronic Acid on Model Surfaces

Glycoproteins, such as lubricin, and hyaluronic acid (HA) play a prominent role in the boundary lubrication mechanism in diarthrodial joints. Although many studies have tried to elucidate the lubrication mechanisms of articular cartilage, the molecular details of how lubricin and HA interact with cartilage surfaces and mediate their interaction still remain poorly understood. Here we used model substrates, functionalized with self-assembled monolayers terminating in hydroxyl or methyl groups, (1) to determine the effect of surface chemistry on lubricin and HA adsorption using surface plasmon resonance (SPR) and (2) to study normal force interactions between these surfaces as a function of lubricin and HA concentration using colloidal probe microscopy. We found that lubricin is amphiphilic and adsorbed strongly onto both methyl- and hydroxyl-terminated surfaces. On hydrophobic surfaces, lubricin likely adopts a compact, looplike conformation in which its hydrophobic domains at the N and C termini serve as surface anchors. On hydrophilic surfaces, lubricin likely adsorbs anywhere along its hydrophilic central domain and adopts, with increasing solution concentration, an extended tail-like conformation. Overall, lubricin develops strong repulsive interactions when compressing two surfaces into contact. Furthermore, upon surface separation, adhesion occurs between the surfaces as a result of molecular bridging and chain disentanglement. This behavior is in contrast to that of HA, which does not adsorb appreciably on either of the model surfaces and does not develop significant repulsive interactions. Adhesive forces, particularly between the hydrophobic surfaces, are large and not appreciably affected by HA. For a mixture of lubricin and HA, we observed slightly larger adsorptions and repulsions than those found for lubricin alone. Our experiments suggest that this interaction depends on unspecific physical rather than chemical interactions between lubricin and HA. We speculate that in mediating interactions at the cartilage surface, an important role of lubricin, possibly in conjunction with HA, is one of providing a protective coating on cartilage surfaces that maintains the contacting surfaces in a sterically repulsive state.