Sulfur Trioxide-pyridine Complex Research Articles

Antiviral effect of oversulfated kappa-carrageenan derivatives against COVID-19 for spray coating application on facemasks

The COVID-19 pandemic caused by SARS-CoV-2 has spurred the urgent need for effective antiviral strategies. In this work, we explored the potential of oversulfated kappa-carrageenan (OSKC) in spray-coated facemasks for SARS-CoV-2 inhibition pathway. The sulfated derivative was synthesized with sulfur trioxide pyridine complex in dimethylformamide solution. The antiviral efficacy of OSKC at different concentrations and spray-coated facemasks was evaluated using betacoronavirus Murine Hepatitis Virus strain 3, revealing a significant reduction in viral load compared to commercial kappa-carrageenan. Furthermore, the characterization techniques assessed the effect of the position of the introduced sulfate groups on the antiviral activity and on the physicochemical characteristics. OSKC is able to bind specific proteins of enveloped viruses, preventing viral attachment into target cells. Overall, this study demonstrates the feasibility and effectiveness of OSKC spray coating for breathable facemasks with antimicrobial properties, offering a promising approach to enhancing personal protective equipment against viral transmission in healthcare and community settings.

Fabrication of curcumin−loaded foxtail millet prolamin−based nanoparticle: Impact of curdlan sulfate on the particle properties

The sulfation of curdlan was achieved by modification of curdlan with sulfur trioxide–pyridine complex. Curcumin−loaded curdlan sulfate−sodium caseinate stabilized foxtail millet prolamin nanoparticles were fabricated using pH-driven method. Under the optimal conditions, two kinds of foxtail millet prolamin−based nanoparticles were fabricated using different preparation processes for the first time. The mean diameters and zeta-potentials of co−assembled foxtail millet prolamin−sodium caseinate−curdlan sulfate nanoparticles and curdlan sulfate coated co−assembled foxtail millet prolamin−sodium caseinate nanoparticles were 84.7 nm, 136.4 nm and − 45.7 mV, − 41.5, respectively. Molecular docking and infrared spectroscopy indicated that the curcumin was retained in the hydrophobic region of foxtail millet prolamin though four hydrogen bonds and ten hydrophobic interactions, and amino residues of proline, arginase, cysteine, glycine, and alanine served as the main binding sites for curcumin. The deposition and co−assembly of curdlan sulfate enhanced the curcumin encapsulation efficiency from 78.3% to 81.8% and 85.9%, respectively, and slightly reduced the release of curcumin under physiological and endosomal pH conditions. Consequently, the intake of curdlan sulfate−sodium caseinate stabilized composite nanoparticles encapsulated−curcumin by MCF-7 cells was lower than that of sodium caseinate stabilized nanoparticles entrapped−curcumin, and increased the IC50 value from 5.3 μg/mL to 10.5 and 9.0 μg/mL, respectively. This study showed that the biopolymeric nanoparticles have the potential to encapsulate hydrophobic bioactives, and the incorporation of curdlan sulfate exhibited a significant effect on the physicochemical properties, encapsulation, and release profile of foxtail millet prolamin particles.

Sulfonation of HwBKP by Sulfur Trioxide Pyridine Complex and Preparation of Anionic Cellulose Beads Using the Same

To expand the applications of cellulose beads, sulfonated cellulose beads were prepared by chemically modifying HwBKP fibers with sulfur trioxide pyridine complex (STP), dissolving in tetraethylammonium hydroxide (TEAOH)/urea solvent, and dropping into acetic acid solution. The effect of the amount of STP added on the properties of sulfonated cellulose solution and cellulose beads was investigated. It was observed that the sulfonated cellulose beads exhibited anionic surface charge in a fairly wide pH range, and the degree of substitution of sulfonic acid groups and the zeta potential of the cellulose beads could be controlled by adjusting the amount of added STP. In addition, as the amount of STP added increased, the crystallinity of the cellulose decreased, the viscosity and surface tension of the sulfonated cellulose/TEAOH/urea solution decreased, and the size of the cellulose beads increased.

Highly stereoselective synthesis of heparin tri- and tetra-saccharide derivatives

<p indent="0mm">Heparin, a naturally highly sulfated glycosaminoglycan, mediates various physiologic and pathophysiologic processes, and is mainly used for the prevention and treatment of venous thrombosis in clinic. Here we report an efficient synthesis of heparin oligosaccharides with different degrees of 6-<italic>O</italic>-sulfonation modification, employing orthogonal protective group strategy. <italic>tert</italic>-Butyldiphenylsilyl (TBDPS) group is used as the protective group of 6-OH of the 2-azide-glucose donors, and highly α-selective construction of the key GlcN-(1→4)-GlcUA glycosidic bond was achieved with the corresponding <italic>N</italic>-phenyl trifluoroacetimidate donors. Thus, tri- and tetra-saccharides are synthesized by the convergent [1 + 2] and [2 + 2] glycosylation. The fully elaborated oligosaccharides have then been successfully transformed into the target heparin oligosaccharides <bold>28</bold>–<bold>34</bold> <italic>via</italic> an optimal sequence of manipulation of the protecting groups. The post-assembly manipulations include desilylation with HF·Py (for removal of TBDPS group), delevulinoylation with hydrazine hydrate (for removal of levulinoyl group), saponification under Zemplén conditions (for removal of methyl ester and benzoyl group), <italic>O</italic>-sulfonation with sulfur trioxide pyridine complex (for hydroxyl groups), reduction and <italic>N</italic>-sulfonation (for azido group), and atmospheric pressure hydrogenation (for removal of benzyl and Cbz groups). The availability of these heparin oligosaccharide derivatives which bear amino linker shall facilitate the preparation of glycan chips for studies on the interaction between heparin oligosaccharides with proteins, such as the heparanase.

Preparation and characterization of sulfated inulin-type fructans from Jerusalem artichoke tubers and their antitumor activity

The modification of polysaccharides is important for enhancing their biological activities. In this study, a pure inulin-type fructan, denoted as Jerusalem artichoke polysaccharide (P-JAP), was purified from Jerusalem artichoke tubers and modified by sulfation via treatment with a sulfur trioxide-pyridine complex to produce its sulfated derivative (S-JAP). Fourier-transform infrared spectroscopic analysis confirmed the successful introduction of sulfate groups. The inhibitory effects of S-JAP on the proliferation of human liver hepatocellular carcinoma (HepG2) cells was evaluated via a CCK-8 assay, and the pro-apoptotic effects were assessed using annexin V-FITC/PI double staining. The inhibition rates of various concentrations of S-JAP on HepG2 cells after 24, 48, and 72 h were significantly higher than those of P-JAP; moreover, S-JAP succeeded in promoting cell apoptosis. Thus, the sulfate-modified polysaccharide extracted from Jerusalem artichoke tubers was shown to exhibit effective antitumor activity with potential for further development.

Green Synthesis of Heteroatom Doped Graphene from Natural and Chemical Precursors for Oxygen Reduction Reaction

In the present work, natural biomass and chemical materials were applied as the heteroatom resources for modifying the Porous Graphene (PG) structure by pyrolysis method at 900 oC. The physical and chemical characterizatons were performed by means of Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), Raman Spectroscopy, N2 Adsorption-Desorption, and X-ray Photo-electron Spectroscopy (XPS). Furthemore, the behavior of the prepared materials was investigated by Cyclic Voltammetry (CV) and Rotating Disk Electrode (RDE). The obtained results indicated that doping of heteroatoms into the graphene framework was possible using a low-cost and environment-friendly biomass material as well as chemical sources. Moreover, one-step quarternary and tersiary co-doped graphene could be acheived using natural biomass. The prepared electrocatalysts using grape leaves and sulfur trioxide pyridine complex exhibit higher electrocatalytic performance as exampled which conducted the electrocatalyst in 4e- pathway and showed high stability in methanol solutions during the process, confirming their considerable potential to Oxygen Reduction Reaction (ORR) as an electro-catalyst. Moreover, the onset potential of Gl300G-900 and GSP 900 (0.93 V vs RHE) is almost equal to the Pt/C 20 wt % (0.99 V vs RHE). These optimal prepared cathodes (Gl300G-900 and GSP 900) in the Microbial Fuel Cell (MFC) test lead to considerable power densities of 31.5 mW m-2 and 30.9.mW m-2, which are close to 38.6 mW m-2 for the Pt/C 20 wt % cathode.

Conformational and rheological properties of bacterial cellulose sulfate

In this study, a water-soluble bacterial cellulose sulfate (BCS) was prepared with sulfur trioxide pyridine complex (SO3· Py) in a lithium chloride (LiCl)/dimethylacetamide (DMAc) homogeneous solution system using bacterial cellulose (BC). The structural study showed that the value for the degrees of substitution of BCS was 1.23. After modification, the C-6 hydroxyl group of BC was completely substituted and the C-2 and C-3 hydroxyl groups were partially substituted. In an aqueous solution, the BCS existed as a linear polymer with irregular coil conformation, which was consistent with the findings observed using atomic force microscopy. The steady-state shear flow and dynamic viscoelasticity were systematically determined over a range of BCS concentrations (1 %–4 %, w/v) and temperature (5 °C–50 °C). Steady-state flow experiments revealed that BCS exhibited shear thinning behavior, which increased with an increase in concentration and a decrease in temperature. These observations were quantitatively demonstrated using the cross model. Moreover, based on the dynamical viscoelastic properties, we confirmed that BCS was a temperature-sensitive and weak elastic gel, which was somewhere between a dilute solution and an elastic gel. Therefore, considering the special synthetic strategy and rheological behavior, BCS might be used as a renewable material in the field of biological tissue engineering, especially in the manufacture of injectable hydrogels, cell scaffolds, and as a drug carrier.

Sulfated modification, characterization and bioactivities of an acidic polysaccharide fraction from an edible mushroom Pleurotus eous (Berk.) Sacc.

The acidic fraction (P3a) of Pleurotus eous was successfully sulfated by sulphur trioxide-pyridine complex method. The effect of sulfate modification (SP3a) on the structure, physicochemical properties and in vitro biological activity of P3 was studied. The structural characteristics were established by UV absorption, FT-IR, HPGPC and GC-MS. Biological studies were carried out, such as in vitro antioxidant, anticoagulant, anti-tumour and antibacterial activities. The sulfation process changed its physicochemical and biological characteristics. Compared with P3a, the molecular weight of SP3a is reduced. P3a and SP3a are composed of galactose, xylose, arabinose with different molar percentages. Sulfated derivatives have strong antioxidant and anticoagulant properties. Compared with P3a, SP3a showed obvious cytotoxicity to Jurkat and HeLa cells. SP3a showed a higher inhibition zone for Gram-positive and Gram-negative bacteria. This article demonstrates that sulfation is an effective way to enhance biological activity, especially SP3a is a promising candidate for bioactive macromolecules and has great potential for industrial and biomedical applications.

Preparation, structural changes and adsorption performance of heavy metal ions on sulfonated cellulose with varying degrees of substitution

Abstract Sulfonated cellulose (SC) with varying degrees of substitution (DS) were prepared with the pyridine sulfur trioxide complex (Py-SO3) as a sulfonation reagent (as a source of sulfur trioxide) in dimethyl formamide (DMF) as a solvent, where the DS was primarily affected by the molar ratio between Py-SO3 and the anhydroglucose (AHG) unit. Sulfonation temperature and residence time have less effect on DS. The ratio of the crystalline domain of SC decreased gradually with incremental DS, and the crystalline cellulose I of SC at DS0.81 nearly disappeared, and the moiety of the paracrystalline SC with high hydrophilicity increased. The thermostability decreased with increasing DS as a consequence of crystalline domain decrement. The adsorption performance of SC to metal ions was enhanced with increasing DS. However, above DS 0.62, the adsorption capacity enhancement is negligible. For an economic adsorption of heavy meatal ions in effluents, the DS of SC must be optimized.

Comparative Study of Various Types of Metal-Free N and S Co-Doped Porous Graphene for High Performance Oxygen Reduction Reaction in Alkaline Solution.

Heteroatom doping into carbon structures is an effective approach to enhance the electrochemical performance of carbon materials. In the work presented here, the electrocatalysts including: nitrogen and co-doped nitrogen and sulfur on porous graphene (PG) were synthesized by different precursors. The physico-chemical properties of the prepared samples were determined using X-ray Diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), N2 sorption-desorption, Transmission electron microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The prepared samples were further applied for oxygen reduction reaction (ORR) and the effects of pyrolysis temperature, precursor type and dose, on the prepared samples structure and their electrochemical performances were investigated. The results revealed that synergistic effect of nitrogen and sulfur co-doped on the graphene structure leads to improvement in catalytic activity and current. Furthermore, S and N co-doped graphene prepared using sulfur trioxide pyridine complex exhibited excellent methanol tolerance and long-term stability.

Amidation Reaction of Carboxylic Acid with Formamide Derivative Using SO3·pyridine

The amidation reaction of carboxylic acid derivatives was developed using sulfur trioxide pyridine complex (SO3·py) as a commercially available and easily handled oxidant. This method could be applied to the reaction of various aromatic and aliphatic carboxylic acids, including optically active ones, with formamide derivatives to afford the corresponding amides in good to high yields.

Antioxidant and anticoagulant activities of mycelia polysaccharides from Catathelasma ventricosum after sulfated modification

Sulfated polysaccharides are known to possess excellent antioxidant and anticoagulant activities. The mycelial polysaccharides from Catathelasma ventricosum (mCVP-1S) was sulfated using sulphur trioxide–pyridine complex. Varying the reaction temperature, time and sulphur trioxide–pyridine complex (SO3·Pyr) dosage altered the yield, degree of sulfation (DS), substitution and chain conformation of sulfated mCVP-1Ss (smCVP-1Ss). The yields and DS of the samples were ranging from 166 to 216mg and from 0.18 to 0.56, respectively. Furthermore, FT-IR and NMR spectra showed that the sulfate groups had successfully introduced into mCVP-1S and mainly substituted in C-6 position. Congo red test revealed that mCVP-1S and most smCVP-1Ss had triple-helical structures. Especially, the smCVP-1S with DS of 0.28 and stable triple-helical structure showed the best antioxidant and anticoagulant abilities. Whereas, excessive substitution might destroy the triple-helical structure, and result in a sharply decrease of antioxidant and anticoagulant abilities. Besides, all smCVP-1Ss exhibited better antioxidant and anticoagulant abilities than native polysaccharides. The results suggest that the sulfated mycelial polysaccharides could be used as an alternative derivative of natural source of anticoagulant and antioxidant for industrial uses.

Synthesis of Four Monoterpene-Derived Organosulfates and Their Quantification in Atmospheric Aerosol Samples.

Monoterpenes, a major class of biogenic volatile organic compounds, are known to produce oxidation products that further react with sulfate to form organosulfates. The accurate quantification of monoterpene-derived organosulfates (OSs) is necessary for quantifying this controllable aerosol source; however, it has been hampered by a lack of authentic standards. Here we report a unified synthesis strategy starting from the respective monoterpene through Upjohn dihydroxylation or Sharpless asymmetric dihydroxylation followed by monosulfation with the sulfur trioxide-pyridine complex. We demonstrate the successful synthesis of four monoterpene-derived OS compounds, including α-pinene OS, β-pinene OS, limonene OS, and limonaketone OS. Quantification of OSs is commonly achieved using liquid chromatography-mass spectrometry (LC-MS) by either monitoring the [M-H]- ion or through multiple reaction monitoring (MRM) of mass transitions between the [M-H]- and m/z 97 ions. Comparison between the synthesized standards and previously adopted quantification surrogates reveals that camphor-10-sulfonic acid is a better quantification surrogate using [M-H]- as the quantification ion, while the highly compound-specific nature of MRM quantification makes it difficult to choose a suitable surrogate. Both could be rationalized in accordance to their respective MS quantification mechanisms. The in-house availability of the authentic standards enables us to discover that β-pinene OS, due to the sulfate group at the primary carbon, partially degrades to a dehydrogenated OS compound during LC/MS analysis and a hydroperoxy OS over a prolonged storage period (>5 month) and forms a regioisomer through intermolecular isomerization. Limonene OS was positively identified for the first time in ambient samples and found to be more abundant than α-/β-pinene OS in the Pearl River Delta, China. This work highlights the critical importance of having authentic standards in advancing our understanding of the interactions between biogenic VOC emissions and anthropogenic sulfur pollution.

Fabrication of sulfated nanofilter membrane based on carboxymethyl cellulose.

The aim of this study is to prepare sulfated carboxymethyl cellulose (SCMC) nanofilter membrane using sulfur trioxide pyridine complex (SO3/pyridine) as sulfating agent and glutaraldehyde (GA) as a crosslinking agent onto polysulfone supporting membrane. The prepared nanofilter was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy and zeta potential. To evaluate the prepared nanofilter, various amounts of SO3/Pyridine were used and efficiency of them was investigated. The results showed that increasing the sulfate groups raised the flux from 13.87 to 29.54 L/(m2·h-1), whereas percentage rejection was increased during the separation of salt aqueous solutions and then decreased. It can be concluded that, SCMC-GA-2 (with molar ratio of SO3/pyridine to CMC of 1) shows high separation efficiency in acidic conditions and improves the hydrophilicity and charge density of the filter.

Synthesis of sulfated brassinosteroids

A number of water soluble sulfates of 24-epibrassinolide including the 2α,3α-disulfate and all possible monosulfates were synthesized. The target compounds were isolated in crystalline form as the corresponding sodium salts. Pyridine–sulfur trioxide complex was used as sulfating agent followed by transformation of the resulting pyridinium salts into the sodium sulfates by treatment with NaOH. The control of the regioselectivity was achieved by an appropriate use of acetyl and benzyl protecting groups.

Balancing osteoblast/osteoclast ratio in vitro by means of chitosan scaffolds either surficial sulfated or modified by hemocyanines and calcium phosphate phases. A co-culture study.

Event Abstract Back to Event Balancing osteoblast/osteoclast ratio in vitro by means of chitosan scaffolds either surficial sulfated or modified by hemocyanines and calcium phosphate phases. A co-culture study. Christiane Heinemann1, Jana Farack1, Susanne Hoehne2, Ronny Bruenler3, Simy Weil4, Dilibaier Aibibu3, Amir Sagi4 and Thomas Hanke1 1 Technische Universitaet Dresden, IfWW - Max-Bergmann-Center of Biomaterials, Germany 2 Leibniz Association, Institute of Polymer Research Dresden, Germany 3 Technische Universitaet Dresden, Institute of Textile Machinery and High Performance Material Technology, Germany 4 Ben Gurion University of the Negev, Department of Life Sciences and the National Institute for Biotechnology in the Negev, Israel Introduction: Bone tissue engineering is still a field of interest. Due to a variety of material properties the natural polysaccharide chitosan is an excellent candidate for a scaffold material[1]. Recently, development focuses on modification for improvement of the impact on the healing process of bone. Main point of application is the ratio of osteoblasts and osteoclasts in the bone multicellular unit. The present study reports on differently sulfated chitosan scaffolds and scaffolds modified by hemocyanines, collagen and calcium phosphate phases. Materials and Methods: (1) Solid-phase sulf­ation was achieved by treating embroidered chitosan scaffolds with sulfur trioxide dimethylformamide complex (DMF/SO3) or chlorethan sulfonic acid (CLESA) or sulphur trioxide pyridine complex (Pyr/SO3)[2]. (2) Net shape nonwoven-(NSN)-chitosan scaffolds were functionalized by collagen coating[3]. The microfibrous scaffolds were coated with bovine type I collagen by dipping the scaffolds into a solution of 2 mg/ml collagen dissolved in 0.1M TRIS buffer solution with pH 7.4. Then the scaffolds were freeze-dried and subsequently chemically cross-linked. (3) For the macroporous scaffolds homogeneous clear solutions of 1 % chitosan in acetic acid were prepared. Chitosan solution was transferred to 48-well plates and freeze-dried. After neutralization with NaOH and several washing steps the scaffolds were lyophilized again. To get mineralized chitosan scaffolds brushite or hydroxyapatite were added to the same weight of chitosan, while it was dissolved acetic acid. Hemocyanin modification was carried out by dip-coating. (4) Single culture experiments with hMSC/ Osteoblasts[4] and Monocytes/ Osteoclasts[1] as well as co-culture experiments[5] were carried out as described in our cited previous studies. Results and Discussion: (1) All sulfation methods resulted in enhanced proliferation and enhanced osteogenic differentiation. During cultivation, Pyr/SO3 scaffolds turned out to provide the best conditions for both. On the contrary, ostoclastogenesis was most effective for CLESA-sulfation. That is a key-result because the use of differently sulfated scaffolds could be a tool to adjust the ratio of bone building and bone resorbing activity. (2) Collagen coating of the NSN scaffolds enhances the adhesion and proliferation of hMSC and their differention to osteoblasts, as well. So, the bone building activity could be supported by NSN chitosan collagen-hybrid scaffolds. (3) Modification of chitosan scaffolds by hemocyanines enhances attachment and proliferation of hMSC/osteoblasts as well as the bioactivity of the scaffold material. Co-culture experiments on special hemocyanine-calcium phosphate-chitosan compositions show the enhancement of osteogenic hMSC differentiation in comparison with the osteoclastogenesis. Conclusion: The in vitro-findings give reason to expect that all three approaches are applicable to the manipulation of the ratio of bone resorption and bone formation during remodeling. Deutsche Forschungsgemeinschaft Grants HA5284/2-1 and HA 5284/4-2; Bundesministerium für Forschung und Technologie Grant 13GW0025

Studies on the sulfation of cellulose α-lipoate and ability of the sulfated product to stabilize colloidal suspensions of gold nanoparticles

A versatile method for the synthesis of cellulose α-lipoate with a low degree of substitution (DS) has been developed using N,N-dimethylacetamide (DMA)/LiCl as a solvent and N,N′-carbonyldiimidazole (CDI) as an esterification reagent. The cellulose α-lipoate with DS of α-lipoate groups of 0.26 was converted with sulfur trioxide–pyridine complex in dimethyl sulfoxide (DMSO) as solvent. The sulfation is accompanied by an unexpected partial oxidation of the disulfide moiety leading to the formation of the corresponding stereoisomers of S-oxides. The resulting mixture of water-soluble cellulose α- and β-lipoate sulfate possesses a DS of sulfuric acid half ester groups of 1.78. This cellulose-α/β-lipoate sulfate derivative can be used as an effective stabilizer and solubilizer for the formation of colloidal suspensions of gold nanoparticles formed in situ in aqueous solution.

Sulfation of citrus pectin by pyridine-sulfurtrioxide complex and its anticoagulant activity

Citrus pectin (CP) was sulfated by the pyridine–sulfur-trioxide complex in dimethyl sulfoxide (DMSO). Monosaccharide composition analysis revealed a decrease in the GalA content after sulfation. A decrease in the average molecular weight (MW) and a fall in particle size of the pectin gave additional proof of pectin degradation during the sulfation reaction. Structural characterization by IR and NMR spectra indicated sulfation occurred mainly at positions C-2, C-3 of the GalA (located in backbone region of the CP). Anticoagulant assays demonstrated that sulfated CP (TBA-3) could prolong activated partial thromboplastin time and thrombin time, with an activity of 51.96 IU/mg and 15.2 IU/mg, respectively. Further investigation on coagulation factors indicated TBA-3 could achieve inactivation of thrombin with both heparin cofactor II and antithrombin. Our results indicated sulfated pectin might be a promising anticoagulant ingredient with excellent activity and simple monosaccharides, and could be a possible substitute for the limited heparin.

Sulphation pattern analysis of chemically sulphated polysaccharide LbGp1 from Lycium barbarum by GC–MS

The polysaccharide LbGp1 from Lycium barbarum L. was sulphated with sulphur trioxide–pyridine complex in DMF, yielding two sulphated polysaccharides, which were LbGp1-OL-SL with 13.7% sulphate content, and LbGp1-OL-SH with 27.4% sulphate content. The sulphation patterns were analysed using a GC–MS strategy. After a series of sequential chemical derivatisations, the sulphated polysaccharides were converted to partially methylated alditol acetates. All the sulphate groups were replaced by acetyl groups, maintaining the positional information of the original sulphation pattern. The number and position of sulphate substitutions were deduced by comparing the relative molar ratio from methylation analysis between native polysaccharide and sulphated derivatives. In LbGp1-OL-SL, 12.65% of sulphation located on C-5 of Ara, only 0.69% and 0.34% of sulphation occurred on C-4 and C-6 Gal, respectively; while in LbGp1-OL-SH, 24.96% of sulphate groups were found at C-5 of Ara, and 0.40% and 2.02% of sulphate groups were found at C-4 and C-6 Gal, respectively.

Chondrocyte Culture in Three Dimensional Alginate Sulfate Hydrogels Promotes Proliferation While Maintaining Expression of Chondrogenic Markers

The loss of expression of chondrogenic markers during monolayer expansion remains a stumbling block for cell-based treatment of cartilage lesions. Here, we introduce sulfated alginate hydrogels as a cartilage biomimetic biomaterial that induces cell proliferation while maintaining the chondrogenic phenotype of encapsulated chondrocytes. Hydroxyl groups of alginate were converted to sulfates by incubation with sulfur trioxide-pyridine complex (SO3/pyridine), yielding a sulfated material cross-linkable with calcium chloride. Passage 3 bovine chondrocytes were encapsulated in alginate and alginate sulfate hydrogels for up to 35 days. Cell proliferation was five-fold higher in alginate sulfate compared with alginate (p=0.038). Blocking beta1 integrins in chondrocytes within alginate sulfate hydrogels significantly inhibited proliferation (p=0.002). Sulfated alginate increased the RhoA activity of chondrocytes compared with unmodified alginate, an increase that was blocked by β1 blocking antibodies (p=0.017). Expression and synthesis of type II collagen, type I collagen, and proteoglycan was not significantly affected by the encapsulation material evidenced by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry. Alginate sulfate constructs showed an opaque appearance in culture, whereas the unmodified alginate samples remained translucent. In conclusion, alginate sulfate provides a three dimensional microenvironment that promotes both chondrocyte proliferation and maintenance of the chondrogenic phenotype and represents an important advance for chondrocyte-based cartilage repair therapies providing a material in which cell expansion can be done in situ.