Dextran Aldehyde Research Articles

Tailoring the specificity of ficin versus large hemoglobin and small casein by co-immobilizing inert proteins on the immobilized enzyme layer and further modification with aldehyde dextran

Ficin has been immobilized at full loading on glyoxyl agarose beads. Then, ficin was blocked with 2,2′-dipyridyldisulfide. To be effective, the modification must be performed in the presence of 0.5 M urea, as the enzyme was not inhibited under standard conditions, very likely because the catalytic Cys was not fully exposed to the medium. Activity could be fully recovered by incubation with 1 M mercaptoethanol. This biocatalyst could hydrolyze hemoglobin and casein. The objective of this paper was to increase the enzyme specificity versus small proteins by generating steric hindrances to the access of large proteins. The step by step blocking via ionic exchange of the biocatalyst with aminated bovine serum albumin (BSA), aldehyde dextran and a second layer of aminated BSA produced a biocatalyst that maintained its activity versus small synthetic substrates, increased the biocatalyst stability, while reduced its activity to over 50 % versus casein. Interestingly, this treatment almost fully annulled the activity versus hemoglobin, more effectively at 37 °C than at 55 °C. The biocatalyst could be reused 5 times without changes in activity. The changes could be caused by steric hindrances, but it cannot be discarded some changes in enzyme sequence specificity caused by the modifications.

Support Enzyme Loading Influences the Effect of Aldehyde Dextran Modification on the Specificity of Immobilized Ficin for Large Proteins.

It has been reported that the modification of immobilized glyoxyl-ficin with aldehyde dextran can promote steric hindrances that greatly reduce the activity of the immobilized protease against hemoglobin, while the protease still maintained a reasonable level of activity against casein. In this paper, we studied if this effect may be different depending on the amount of ficin loaded on the support. For this purpose, both the moderately loaded and the overloaded glyoxyl-ficin biocatalysts were prepared and modified with aldehyde dextran. While the moderately loaded biocatalyst had a significantly reduced activity, mainly against hemoglobin, the activity of the overloaded biocatalyst was almost maintained. This suggests that aldehyde dextran was able to modify areas of the moderately loaded enzyme that were not available when the enzyme was overloaded. This modification promoted a significant increase in biocatalyst stability for both biocatalysts, but the stability was higher for the overloaded biocatalyst (perhaps due to a combination of inter- and intramolecular crosslinking).

A Conductive and Adhesive Hydrogel Composed of MXene Nanoflakes as a Paintable Cardiac Patch for Infarcted Heart Repair.

Myocardial infarction (MI) is a major cause of death worldwide. After the occurrence of MI, the heart frequently undergoes serious pathological remodeling, leading to excessive dilation, electrical disconnection between cardiac cells, and fatal functional damage. Hence, extensive efforts have been made to suppress pathological remodeling and promote the repair of the infarcted heart. In this study, we developed a hydrogel cardiac patch that can provide mechanical support, electrical conduction, and tissue adhesiveness to aid in the recovery of an infarcted heart function. Specifically, we developed a conductive and adhesive hydrogel (CAH) by combining the two-dimensional titanium carbide (Ti3C2Tx) MXene with natural biocompatible polymers [i.e., gelatin and dextran aldehyde (dex-ald)]. The CAH was formed within 250 s of mixing the precursor solution and could be painted. The hydrogel containing 3.0 mg/mL MXene, 10% gelatin, and 5% dex-ald exhibited appropriate material characteristics for cardiac patch applications, including a uniform distribution of MXene, a high electrical conductivity (18.3 mS/cm), cardiac tissue-like elasticity (30.4 kPa), strong tissue adhesion (6.8 kPa), and resistance to various mechanical deformations. The CAH was cytocompatible and induced cardiomyocyte (CM) maturation in vitro, as indicated by the upregulation of connexin 43 expression and a faster beating rate. Furthermore, CAH could be painted onto the heart tissue and remained stably adhered to the beating epicardium. In vivo animal studies revealed that CAH cardiac patch treatment significantly improved cardiac function and alleviated the pathological remodeling of an infarcted heart. Thus, we believe that our MXene-based CAH can potentially serve as a promising platform for the effective repair of various electroactive tissues including the heart, muscle, and nerve tissues.

Structural and functional properties of sodium caseinate glycosylated by dextran aldehyde

Glycosylation is an effective method of protein modification which can improve the functional properties of proteins. Traditional protein glycosylation methods are typically limited by slow reaction rates. A method for improving the efficiency of protein glycosylation from different degrees of dextran oxidation with periodate, to obtain dextran aldehydes, is presented. Increased molar ratio between periodate and glucose unit in dextran led to dextran aldehyde with higher aldehyde group content and reduced molecular weight. This is due to an increased oxidation, which increases the degree of glycosylation by 43.22%. Compared with dextran glycosylated products, the emulsifying activity, stability indices and foaming capacity of dextran aldehyde glycosylated products increased by 30.8, 301 and 50%, respectively, with poor foam stability. Dextran aldehyde-modified sodium caseinate presented lower digestibility and could maintain better stability against salt ions and heat treatment. The polysaccharide aldehyde showed great potential for expanding protein modification methods to promote its industrialization.

COMPOSITION AND TECHNOLOGY OF NATURAL AND MODIFIED BROMELAIN GELS

Musculoskeletal disorders (MSDs) are one of the most pressing medical issues we face today, due to the modern, sedentary lifestyle of humankind. Because of the serious side effects of nonsteroidal anti-inflammatory drugs, searching for other remedies and selecting the best medicinal form of the drug still remains one of the major challenges in medicine.The aim of this research was the development of a gel for the treatment of Musculoskeletal pathologies. The proteolytic enzyme bromelain from the stems of the pineapple plant (Ananas comosus) was selected as the main active substance, due to its strong anti-inflammatory and analgesic properties. Its chemical modification with dextran aldehyde was performed to reduce its allergic effect and to increase stability. Statistical characteristics of the method for determining the proteolytic activity of bromelain were processed. A mixture of polyethylene glycol-1500 and polyethylene glycol-4000 was selected as the base of the gel. Stem bromelain and modified bromelain gels were prepared. The proteolytic activities of the developed gels were determined for 6 months every 3 months. The results demonstrated that proteolytic activities were maintained over the studied period of time, indicating that the gels are stable.

Naked-eye sensing and target-guiding treatment of bacterial infection using pH-tunable multicolor luminescent lanthanide-based hydrogel

In this work, a pH-tunable multicolor luminescent lanthanide-based hydrogel (CS/DEX/CP) was prepared based on lanthanide coordination polymer (CP), dextran aldehyde (DEX) and chitosan (CS). The CP was obtained by the self-assembly of guanosine acid (GMP), ciprofloxacin (CIP), Eu3+, and Tb3+. As-prepared CS/DEX/CP hydrogel could emit blue, green, and red luminescence of CIP, Tb3+, and Eu3+, respectively. It was also found that the luminescence of CS/DEX/CP hydrogel exhibited visual color change in the pH range of 5.5 to 8. Such pH-sensitive hydrogel was multicolor-responsive to protons produced by bacterial growth, therefore, it could provide early warning of bacterial infection by naked-eye. In addition, the increased acidity resulted in not only the degradation of acid-labile Schiff base linkages between DEX and CS, but also the fracture of coordination between CIP and lanthanide ions. As a result, the released CIP and CS showed significantly antibacterial activity against both S. aureus and E. coli.

Adhesion barriers in laparoscopic myomectomy: Evidence from randomized clinical trials.

To evaluate the effectiveness of different adhesion barriers in the prevention of de novo adhesion development after laparoscopic myomectomy. A systematic review was performed by searching seven electronic databases for all randomized clinical trials (RCTs) comparing the use of any absorbable adhesion barrier (i.e. intervention group) with either no treatment or placebo (i.e. control group) in the prevention of adhesion development after laparoscopic myomectomy. Eight RCTs with a total of 748 participants (392 in the intervention group and 356 in the control group) were included. The assessed adhesion barrier methods were: oxidized regenerated cellulose (ORC) in two studies, auto-crosslinked hyaluronic acid (HA) gel in two studies, 4% icodextrin solution in one study, modified HA and carboxy-methylcellulose in one study, polyethylene glycol ester trilysine amine solution plus a borate buffer solution in one study, and polyethylene glycol amine plus dextran aldehyde polymers in another study. Adhesion barrier methods showing the most promising results were: ORC, auto-crosslinked HA gel, and polyethylene glycol amine plus dextran aldehyde polymers.

Dextran-modified Quercetin-Cu(II)/hyaluronic acid nanomedicine with natural poly(ADP-ribose) polymerase inhibitor and dual targeting for programmed synthetic lethal therapy in triple-negative breast cancer

Serious side effects from chemotherapies are the main problem with cancer treatments. To solve these issues, precision cancer nanomedicine based on natural therapeutic materials is developed, which enables specifically apoptosis by interacting with genetic mutation in cancer cells, while leaving normal cells unaffected. Here, we report a novel nanomedicine (CuQDA/IO@HA) composed of hyaluronic acid (HA) / copper ion (Cu(II))-chelated dextran-aldehyde (DA)-quercetin (Q) with dual targeting for synthetic lethal therapy. The CuQDA/IO@HA prepared using a ratio of metal/Q at 0.5:1 resulted in a stable particle structure with uniform particle distribution. The CuQDA/IO@HA can specifically target and induce specific cytotoxicity in BRCA-mutant cancer cells in vitro. Combination treatment with CuQDA/IO@HA and magnetic navigation can induce poly (ADP-ribose) polymerase (PARP) inhibition and DNA damage in BRCA-mutant triple-negative breast cancer (TNBC) via CD44 targeting. The dual-targeting CuQDA/IO@HA can extend the median survival of the BRCA-mutant xenograft mice from 34 to 61 days in comparison to Q treatment alone in vivo, which is attributed to the significant increase in γH2AX, leading to significant apoptosis. More importantly, the CuQDA/IO@HA displayed biocompatibility and no obvious side-effect in normal organs. These results demonstrate the promising potential of integrating natural and metal ions into a nanomedicine that can provide precision medicine through synthetic lethality.

Peptide Chitosan/Dextran Core/Shell Vascularized 3D Constructs for Wound Healing.

Three-dimensional (3D) bioprinting has emerged to create novel cell-based therapies for regenerative medicine applications. Vascularized networks within engineered constructs are required, and toward this end, we report a promising strategy using core-shell (c/s) extrusion 3D-bioprinting technology that employs biomimetic biomaterials to construct regenerative, prevascularized scaffolds for wound care. A custom-designed cell-responsive bioink consisting of a 13% (w/v) cell-laden gelatin methacryloyl (GelMA) shell surrounding a peptide-functionalized, succinylated chitosan (C)/dextran aldehyde (D) cell-laden core was successfully bioprinted resulting in organized microdesigns exhibiting excellent cell viability and subsequent vessel formation. Our templating strategy takes advantage of GelMA's intrinsic thermoreversible properties of low degree of acryloyl functionalization used in combination with a lightly, chemically cross-linked peptide-CD core to serve as temporal structural supports that stabilize during extrusion onto a cooled platform. Mechanical integrity was further strengthened layer-by-layer via GelMA UV photo-cross-linking. We report the first example of GelMA used in combination with a peptide-CD bioink to c/s 3D-bioprint regenerative, prevascularized constructs for wound care. Particular cell adhesion and proteolytic peptide-CD functionalized pair combinations, P15/MMP-2 and P15/cRGD, were found to significantly increase growth of human bone-marrow-derived mesenchymal stems cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs). The constructs delivered two cell types: hBMSCs in the shell bioink and HUVECs within the core bioink. Cord-like, natural microvascularization was shown with endothelial cell marker expression as confirmed by immunofluorescence (IF) staining exhibiting tubelike structures. In addition, in vitro skin wound healing activity of the construct showed a ∼twofold rate of wound closure. Overall, c/s 3D-bioprinted, peptide-CD/GelMA constructs provided the appropriate microenvironment for in vitro stem and endothelial cell viability, delivery, and differentiation. We foresee these custom constructs as representing a fundamental step toward engineering larger scale regenerative, prevascularized tissues.

Immobilization of Naringinase from Aspergillus Niger on a Magnetic Polysaccharide Carrier.

Naringinase is an enzymatic complex used in the deglycosylation of compounds with a high application potential in the food and pharmaceutical industries. The aim of the study was to immobilize naringinase from Aspergillus niger KMS on a magnetic carrier obtained on the basis of carob gum activated by polyethyleneimine. Response surface methodology was used to optimize naringinase immobilization taking into account the following factors: pH, immobilization time, initial concentration of naringinase and immobilization temperature. The adsorption of the enzyme on a magnetic carrier was a reversible process. The binding force of naringinase was increased by crosslinking the enzyme with the carrier using dextran aldehyde. The crosslinked enzyme had better stability in an acidic environment and at a higher temperature compared to the free form. The immobilization and stabilization of naringinase by dextran aldehyde on the magnetic polysaccharide carrier lowered the activation energy, thus increasing the catalytic capacity of the investigated enzyme and increasing the activation energy of the thermal deactivation process, which confirms higher stability of the immobilized enzyme in comparison with free naringinase. The preparation of crosslinked naringinase retained over 80% of its initial activity after 10 runs of naringin hydrolysis from fresh and model grapefruit juice.

Efficient antibacterial dextran-montmorillonite composite sponge for rapid hemostasis with wound healing

Montmorillonite (MMT) powder, as the most effective hemostats in natural silicates, is restricted for commercial application due to its embolic effect. Until now, it's still a challenge to control the leakage of MMT and avoid its side-effects. Herein, poly aldehyde dextran (PDA)/MMT composite sponge (PM) with commendable tissue adhesion, antibacterial, and wound healing performances is developed for massive hemorrhage control. Based on the high degree of perfect synergism of PDA and MMT, the PM sponge can rapidly seal the wound, and promote cells aggregation and adhesion, whole coagulation system activation, resulting in shortened clotting time from 480 s to <10 s in vitro. Therefore, PM sponge with low exothermic effects achieves hemostasis in limited time, decreasing nearly 95% blood loss in the femoral artery and vein incision in rat models. Furthermore, with the intensive tissue adhesion (~47 kPa), PM sponge not only exhibits antibacterial activity to Escherichia coli, but also succeeds in accelerating wound healing. Importantly, the low cytotoxic sponge verifies to be a little hemolytic and skin irritant hemostat. Thus, the biocompatible PM sponge may provide a new strategy for reintroduction of MMT in hemostatic fields, and a safe-effective avenue for clays to control bleeding.

Preparation of Dextran Aldehyde and BSA Conjugates from Ligno-cellulosic Biowaste for Antioxidant and Anti-cancer Efficacy

The present study attempted to demonstrate the potential application of Kraft lignin (KL) from sugarcane baggasse biomass in the bio-therapeutic areas. Novel conjugate materials (Dex-ald–KL and BSA–KL) were synthesized incorporating KL into dextran aldehyde (Dex-ald) and bovine serum albumin (BSA) via a free radical reaction involving reactive oxygen species induced by ascorbic acid/H2O2 redox pair and studied using various physico-chemical techniques. UV–Visible spectral analysis of the resulting conjugates proved the enhanced conjugation (matrix formation) between constituent biopolymers due to formation of intermolecular linkages. Visual changes were observed in the X-ray diffractogram (XRD) peaks of the conjugates in comparison to free components. Cell viability of the novel conjugate materials was found to decrease by ~ 55–61% against colon cancerous cells (SW480) proving its efficacy as anti-cancer agent while the quantity of reactive oxygen species (ROS) level markedly increased on treatment with conjugate material in comparison to Dex-ald, KL and BSA alone. The above evidences indicated that the conjugates with even low amounts of lignin incorporation exhibited remarkable cytotoxicity suggesting their practical use in the treatment of certain type of cancers.

High stabilization of immobilized Rhizomucor miehei lipase by additional coating with hydrophilic crosslinked polymers: Poly-allylamine/Aldehyde–dextran

Immobilized enzymes have a very large surface region which is not in contact with the support surface and, thus, have potential as a target for novel stabilization strategies. In this paper, coating the surfaces of such enzymes with a highly hydrophilic and compact cross-linked poly-aminated polymer as a strategy to increase the thermal stability of the immobilized enzymes is proposed. In particular, Rhizomucor miehei lipase (RML) was immobilized by interfacial adsorption onto octyl-agarose and further coated with poly-allylamine (PAA), a polymer that is very rich in primary amino groups. Cross-linking of the PAA layer to coat the immobilized enzyme was carried out, in situ, by reaction with freshly oxidized dextran (aldehyde–dextran). The PAA layer only exerted moderate stabilizing effects (around 4-fold), but further cross-linking with aldehyde–dextran highly increased the stabilizing effects; the new derivative was 440-fold more stable than uncoated derivative at 55 °C and pH 7 and exhibited 6-fold more catalytic activity compared to the soluble enzyme used for immobilization. We hypothesize that the hydrophilicity of PAA reduces the exposure of internal hydrophobic pockets to the enzyme surface at high temperatures. Besides, the compactness of the polymer may reduce distortion of the enzyme surface during inactivation.

Novel organic/inorganic hybrid nanoparticles as enzyme-triggered drug delivery systems: Dextran and Dextran aldehyde coated silica aerogels

Today, different therapeutic approaches are being developed because of the increased risk of colorectal cancer. In this context, we synthesized organic/inorganic hybrid nanoparticles using dextran (Dex) and dextran aldehyde (Dex-CHO) as organic polymers for the coating of inorganic silica aerogels. These Dex and Dex-CHO coated silica aerogels served as enzyme-triggered and colon targeted 5- Fluorouracil (5-FU) delivery systems. To improve the efficiency of drug loading and Dex/Dex-CHO coating, the surface of the silica aerogel was functionalized with 3-(aminopropyl)triethoxysilane (APTES). Enzyme-responsive drug release studies were performed with dextranase enzyme in simulated colonic fluid and cytotoxicity of aerogels on the colorectal adenocarcinoma cell line (Caco-2) were investigated by MTT assay. It was demonstrated that the release of 5-FU from Dex and Dex-CHO coated silica aerogels in simulated gastric and intestinal fluids was 1.7% and 3.4%, respectively, while the amount of 5-FU released from uncoated silica aerogels in these media was 86.4%. On the other hand, in the dextranase containing colonic medium 5-FU release in 12 h, straight after degradation of dextran by dextranase, was 24% and 13.4% from Dex and Dex-CHO coated silica aerogels, respectively. MTT assay results of unmodified, amine-modified, Dex and Dex-CHO coated silica aerogels did not show any significant cytotoxic effect on Caco-2 cells. However, MTT assay results of 5-FU loaded silica aerogels (unmodified, amine-modified, Dex and Dex-CHO coated) showed a decrease in the viability of Caco-2 cells. These results demonstrate that Dex and Dex-CHO coated silica aerogels are biocompatible nanoparticles that are not affected by the upper gastrointestinal regions and are powerful enzyme-triggered drug delivery systems for drug targeting to the colon area.

PH-responsive linkages-enabled layer-by-layer assembled antibacterial and antiadhesive multilayer films with polyelectrolyte nanocapsules as biocide delivery vehicles

Application of the polymer capsules as vehicles for antibacterial surface against bacterial infections is restricted by spontaneous leakage and specifically responsive release of antibacterial agents. Herein, we present the integration of pH-responsive nanocapsules as delivery tools for hydrophobic biocide within layer-by-layer (LbL) films utilizing alternating imine linkages as the driving force for assembly, thus enabling the introduction of drug and controlled release. The novel capsules are fabricated by means of electrostatic LbL assembly, namely, tannin acid/chitosan nanocapsules embedded with triclosan@cetyltrimethylammonium bromide micelles (TCS@CTAB/TA/CH). The nanocapsules achieve an excellent pH-responsive activity that the release efficiency of antibacterial agent triclosan (TCS) increases by nearly 61.8% from pH 8 to 4. Subsequently, the smart nanocapsules are alternatively incorporated via imine linkage into the dextran aldehyde (DA) polyelectrolyte multilayers in LbL deposition (denoted as (DA-TCS@CTAB/TA/CH)n films). The as-prepared samples are characterized by FTIR, FESEM, TEM, DLS and AFM. Noticeably, the (DA-TCS @CTAB/TA/CH)20.5 film exhibites optimal pH-responsive activity with release concentration of TCS up to 4.01 mg/L at pH 6. The bacteriostatic percentages of (DA-TCS@CTAB/TA/CH)20.5 against E. coli and P. aeruginosa are respectively 99.62% and 97.35% after 24-h incubation at pH 6. Besides, the multilayers are capable of supplying a long-term (30 days) antibacterial property. The self-polishing mechanism of (DA-TCS@CTAB/TA/CH)n films is proposed to illuminate the enhanced antibacterial and antiadhesive performances. It seems that the films present a promising way to incorporate biocide to resist bacterial infections and prolong the antimicrobial activity of antibacterial surface.

Dextran Aldehyde in Biocatalysis: More Than a Mere Immobilization System

Dextran aldehyde (dexOx), resulting from the periodate oxidative cleavage of 1,2-diol moiety inside dextran, is a polymer that is very useful in many areas, including as a macromolecular carrier for drug delivery and other biomedical applications. In particular, it has been widely used for chemical engineering of enzymes, with the aim of designing better biocatalysts that possess improved catalytic properties, making them more stable and/or active for different catalytic reactions. This polymer possesses a very flexible hydrophilic structure, which becomes inert after chemical reduction; therefore, dexOx comes to be highly versatile in a biocatalyst design. This paper presents an overview of the multiple applications of dexOx in applied biocatalysis, e.g., to modulate the adsorption of biomolecules on carrier surfaces in affinity chromatography and biosensors design, to serve as a spacer arm between a ligand and the support in biomacromolecule immobilization procedures or to generate artificial microenvironments around the enzyme molecules or to stabilize multimeric enzymes by intersubunit crosslinking, among many other applications.

A highly efficient, in situ wet-adhesive dextran derivative sponge for rapid hemostasis

Uncontrolled hemorrhage is closely related to the high risk of death. However, local hemostats still have various defects and side effects. Herein, an aldehyde dextran (PDA) sponge with proper absorption and adhesion properties is developed for hemorrhage control. PDA sponge with pore size of ∼30–50 μm fabricated by lyophilization not only absorbs blood quickly (47.7 g/g), but also possesses strong tissue adhesion (∼100 kPa). PDA sponge with low cytotoxicity and hemolysis achieves effective hemostasis and remarkable blood loss reduction in the ear vein, femoral artery and liver injuries of rabbit models. Furthermore, the exploration of hemostatic mechanisms related to tissue, blood, plasma, cells and coagulation system indicates that PDA sponge can significantly accelerate coagulation by rapid wound block, fast cells aggregation and initiation, and high coagulation factors concentration, instead of by the coagulation cascade activation. Importantly, this hemostat exhibits excellent biodegradability and nearly no skin irritation. Overall, the biodegradable and tissue adhesive PDA sponge will be a promising quick-hemostatic dressing for uncontrollable hemorrhage.

A gel system for single instillation of non-muscle-invasive bladder Cancer: A “divide-and-rule” strategy

Single instillation (SI) reduces recurrence of non-muscle-invasive bladder cancer by chemoresecting floating tumor cells and residual tumor lesions (RTLs) after transurethral resection of the bladder, but with limited efficacy. Current studies improved this by prolonging retention time and increasing penetration to bladder wall, ignoring that the two separate factors should be treated in different ways. Here, we introduced a smart gel system-based SI to prevent re-implantation of tumor cells (RTCs) and ablate RTLs in a “divide-and-rule” approach. The gel system was synthesized by PEG-PAMAM and dextran aldehyde and composed of gold nanorods and gemcitabine for photothermal therapy and chemotherapy, respectively. It was developed to provide dextran aldehyde-selective adhesion with tissue amines. Since tumor surface expressed high levels of collagen, the exposed amines could act as adhesion points for the gel system. Thus, the gel presented more affinity to tumor tissues. When being instilled, it could form a protective layer on the inner face of the entire bladder wall immediately, preventing RTCs in early time. And it persisted long at the tumor site, ablating RTLs. Our data proved the gel system improved intravesical treatment efficacy in a “divide-and-rule” approach and might be a promising treatment strategy for SI.

Cross-linked cytochrome P450 BM3 aggregates promoted by Ru(II)-diimine complexes bearing aldehyde groups

Cross-linked enzyme aggregate (CLEA) methodology has been applied to immobilize cytochrome P450 BM3 variants (F87A and 21B3) with peroxygenase activity. Several Ru(II)-diimine complexes were found to be suitable cross-linking agents, surpassing the traditional glutaraldehyde and dextran aldehyde. They offer modular numbers of aldehyde functionalities and a more rigid framework than their organic counterparts. The F87A CLEAs display significant activity loss compared to the protein in solution. Meanwhile, for the 21B3 CLEAs, high activity recovery (up to 95%) is obtained. In order to minimize enzyme leaching from the CLEA, sodium cyanoborohydride was used to reduce the CLEAs imine bonds. The reduced CLEAs were active for several rounds of reactions leading to an overall increase in protein activity of 170% compared to the free protein in solution.

Water Soluble Antioxidant Dextran-Quercetin Conjugate with Potential Anticancer Properties.

Quercetin, a naturally occurring potent antioxidant, is limited in therapeutic use, owing to its poor water solubility and stability. Herein, a method of conjugating quercetin to an aldehyde functionalized dextran via an HCl catalyzed condensation reaction to yield a water soluble quercetin functionalized polymer is reported. The prepared conjugate is characterized by 1 H and 1 H-13 C heteronuclear single quantum correlation (HSQC) NMR, which demonstrate that conjugation occurs via both the A- and B-rings of quercetin. The degree of quercetin functionalization can be tuned by varying the reaction temperature and/or the concentration of the HCl catalyst. However, as temperatures and HCl concentrations are increased above 40 °C and 2 m, respectively, the increase in functionalization is accompanied by an increase in the oxidation of the conjugated quercetin and a decrease in polymer yield. The prepared conjugate is shown to have improved stability compared with native quercetin while maintaining substantial free-radical scavenging activity. Anticancer activity is evaluated in vitro in a neuroblastoma cell line. The dextran-aldehyde-quercetin conjugate prepared at 40 °C and 2 m HCl is shown to be cytotoxic to neuroblastoma cells (SH-SY5Y-IC50 = 123 µg mL-1 and BE(2)-C-IC50 = 380 µg mL-1 ) but shows no activity against nonmalignant MRC-5 cells at concentrations up to 400 µg mL-1 .