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Fulltext Removal of parabens from aqueous solution using β-cyclodextrin cross-linked polymer

Chin YP, Mohamad S, Abas MR

Int J Mol Sci, 2010 Sep 20;11(9):3459-71.
PMID: 20957106 DOI: 10.3390/ijms11092459

The removal of four parabens, methyl-, ethyl-, propyl-, and benzyl-paraben, by β-cyclodextrin (β-CD) polymer from aqueous solution was studied. Different β-CD polymers were prepared by using two cross-linkers, i.e., hexamethylene diisocyanate (HMDI) and toluene-2,6-diisocyanate (TDI), with various molar ratios of cross-linker. β-CD-HMDI polymer with molar ratio of 1:7 and β-CD-TDI polymer with ratio 1:4 gave the highest adsorption of parabens among the β-CD-HMDI and β-CD-TDI series, and were subsequently used for further studies. The adsorption capacity of β-CD-HMDI is 0.0305, 0.0376, 0.1854 and 0.3026 mmol/g for methyl-, ethyl-, propyl-, and benzyl-paraben, respectively. β-CD-TDI have higher adsorption capacities compared with β-CD-HMDI, the adsorption capacity are 0.1019, 0.1286, 0.2551, and 0.3699 mmol/g methyl-, ethyl-, propyl-, and benzyl-paraben respectively. The parameters studied were adsorption capacity, water retention, and reusability. Role of both cross-linker in adsorption, hydrophobicity of polymers, and adsorption capacity of different parabens were compared and discussed. All experiments were conducted in batch adsorption technique. These polymers were applied to real samples and showed positive results.

Matched MeSH terms: Cross-Linking Reagents/chemistry*
Combined cross-linked enzyme aggregates of cyclodextrin glucanotransferase and maltogenic amylase from Bacillus lehensis G1 for maltooligosaccharides synthesis

Yip YS, Manas NHA, Jaafar NR, Rahman RA, Puspaningsih NNT, Illias RM

Int J Biol Macromol, 2023 Jul 01;242(Pt 1):124675.
PMID: 37127056 DOI: 10.1016/j.ijbiomac.2023.124675

Maltooligosaccharides (MOS) are functional oligosaccharides that can be synthesized through enzymatic cascade reaction between cyclodextrin glucanotransferase (CGTase) and maltogenic amylase (Mag1) from Bacillus lehensis G1. To address the problems of low operational stability and non-reusability of free enzymes, both enzymes were co-immobilized as combined cross-linked enzyme aggregates (Combi-CLEAs-CM) with incorporation of bovine serum albumin (BSA) and Tween 80 (Combi-CLEAs-CM-add). Combi-CLEAs-CM and Combi-CLEAs-CM-add showed activity recoveries of 54.12 % and 69.44 %, respectively after optimization. Combi-CLEAs-CM-add showed higher thermal stability at higher temperatures (40 °C) with longer half-life (46.20 min) as compared to those of free enzymes (36.67 min) and Combi-CLEAs-CM (41.51 min). Both combi-CLEAs also exhibited higher pH stability over pH 5 to pH 9, and displayed excellent reusability with >50 % of initial activity retained after four cycles. The reduction in Km value of about 22.80 % and 1.76-fold increase in starch hydrolysis in comparison to Combi-CLEAs-CM attested the improvement of enzyme-substrate interaction by Tween 80 and pores formation by BSA in Combi-CLEAs-CM-add. The improved product specificity of Combi-CLEAs-CM-add also produced the highest yield of MOS (492 mg/g) after 3 h. Therefore, Combi-CLEAs-CM-add with ease of preparation, excellent reusability and high operational stability is believed to be highly efficacious biocatalyst for MOS production.

Matched MeSH terms: Cross-Linking Reagents
A review: potential usage of cellulose nanofibers (CNF) for enzyme immobilization via covalent interactions

Sulaiman S, Mokhtar MN, Naim MN, Baharuddin AS, Sulaiman A

Appl Biochem Biotechnol, 2015 Feb;175(4):1817-42.
PMID: 25427594 DOI: 10.1007/s12010-014-1417-x

Nanobiocatalysis is a new frontier of emerging nanosized material support in enzyme immobilization application. This paper is about a comprehensive review on cellulose nanofibers (CNF), including their structure, surface modification, chemical coupling for enzyme immobilization, and potential applications. The CNF surface consists of mainly -OH functional group that can be directly interacted weakly with enzyme, and its binding can be improved by surface modification and interaction of chemical coupling that forms a strong and stable covalent immobilization of enzyme. The knowledge of covalent interaction for enzyme immobilization is important to provide more efficient interaction between CNF support and enzyme molecule. Enzyme immobilization onto CNF is having potential for improving enzymatic performance and production yield, as well as contributing toward green technology and sustainable sources.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Robust cross-linked cyclodextrin glucanotransferase from Bacillus lehensis G1 aggregates using an improved cross-linker and a new co-aggregant for the production of cyclodextrins

Jailani N, Jaafar NR, Rahman RA, Illias RM

Enzyme Microb Technol, 2023 Sep;169:110283.
PMID: 37433237 DOI: 10.1016/j.enzmictec.2023.110283

One of the potentials of carrier-free cross-linked enzyme aggregates (CLEA) immobilization is the ability to be separated and reuse. Yet, it might be impeded by the poor mechanical stability resulting low recyclability. CLEA of CGTase from Bacillus lehensis G1 (CGTase G1-CLEA) using chitosan (CS) as a cross-linker demonstrated high activity recovery however, displayed poor reusability. Therefore, the relationship between mechanical strength and reusability is studied by enhancing the CS mechanical properties and applying a new co-aggregation approach. Herein, CS was chemically cross-linked with glutaraldehyde (GA) and GA was introduced as a co-aggregant (coGA). CGTase G1-CLEA developed using an improved synthesized chitosan-glutaraldehyde (CSGA) cross-linker and a new coGA technique showed to increase its mechanical stability which retained 63.4% and 52.2%, respectively compared to using CS that remained 33.1% of their initial activity after stirred at 500 rpm. The addition of GA impacted the morphology and interaction consequently stabilizing the CLEAs durability in production of cyclodextrins. As a result, the reusability of CGTase G1-CLEA with CSGA and coGA increased by 56.6% and 42.8%, respectively compared to previous CLEA after 5 cycles for 2 h of reaction. This verifies that the mechanical strength of immobilized enzyme influences the improvement of its operational stability.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Improvement of combined cross-linked enzyme aggregates of cyclodextrin glucanotransferase and maltogenic amylase by functionalization of cross-linker for maltooligosaccharides synthesis

Yip YS, Jaafar NR, Rahman RA, Puspaningsih NNT, Jailani N, Illias RM

Int J Biol Macromol, 2024 Jul;273(Pt 2):133241.
PMID: 38897508 DOI: 10.1016/j.ijbiomac.2024.133241

Combined cross-linked enzyme aggregates of cyclodextrin glucanotransferase (CGTase) and maltogenic amylase (Mag1) from Bacillus lehensis G1 (Combi-CLEAs-CM) were successfully developed to synthesis maltooligosaccharides (MOS). Yet, the poor cross-linking performance between chitosan (cross-linker) and enzymes resulting low activity recovery and catalytic efficiency. In this study, we proposed the functionalization of cross-linkers with the integration of computational analysis to study the influences of different functional group on cross-linkers in combi-CLEAs development. From in-silico analysis, O-carboxymethyl chitosan (OCMCS) with the highest binding affinity toward both enzymes was chosen and showed alignment with the experimental result, in which OCMCS was synthesized as cross-linker to develop improved activity recovery of Combi-CLEAs-CM-ocmcs (74 %). The thermal stability and deactivation energy (205.86 kJ/mol) of Combi-CLEAs-CM-ocmcs were found to be higher than Combi-CLEAs-CM (192.59 kJ/mol). The introduction of longer side chain of carboxymethyl group led to a more flexible structure of Combi-CLEAs-CM-ocmcs. This alteration significantly reduced the Km value of Combi-CLEAs-CM-ocmcs by about 3.64-fold and resulted in a greater Kcat/Km (3.63-fold higher) as compared to Combi-CLEAs-CM. Moreover, Combi-CLEAs-CM-ocmcs improved the reusability with retained >50 % of activity while Combi-CLEAs-CM only 36.18 % after five cycles. Finally, maximum MOS production (777.46 mg/g) was obtained by Combi-CLEAs-CM-ocmcs after optimization using response surface methodology.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Fulltext The Effect of Cross-linking Efficiency of Drug-Loaded Novel Freeze Gelated Chitosan Templates for Periodontal Tissue Regeneration

Qasim SSB, Nogueria LP, Fawzy AS, Daood U

AAPS PharmSciTech, 2020 Jun 16;21(5):173.
PMID: 32548717 DOI: 10.1208/s12249-020-01708-x

Innovative strategies for periodontal regeneration have been the focus of research clusters across the globe for decades. In order to overcome the drawbacks of currently available options, investigators have suggested a novel concept of functionally graded membrane (FGM) templates with different structural and morphological gradients. Chitosan (CH) has been used in the past for similar purpose. However, the composite formulation of composite and tetracycline when cross-linked with glutaraldehyde have received little attention. Therefore, the purpose of the study was to investigate the drug loading and release characteristics of novel freeze gelated chitosan templates at different percentages of glutaraldehyde. These were cross-linked with 0.1 and 1% glutaraldehyde and loaded with doxycycline hyclate. The electron micrographs depicted porous morphology of neat templates. After cross-linking, these templates showed compressed ultrastructures. Computerized tomography analysis showed that the templates had 88 to 92% porosity with average pore diameter decreased from 78 to 44.9 μm with increasing concentration. Fourier transform infrared spectroscopy showed alterations in the glycosidic segment of chitosan fingerprint region which after drug loading showed a dominant doxycycline spectral composite profile. Interestingly, swelling profile was not affected by cross-linking either at 0.1 and 1% glutaraldehyde and template showed a swelling ratio of 80%, which gained equilibrium after 15 min. The drug release pattern also showed a 40 μg/mL of release after 24 h. These doxycycline-loaded templates show their tendency to be used in a functionally graded membrane facing the defect site.

Matched MeSH terms: Cross-Linking Reagents/pharmacokinetics; Cross-Linking Reagents/chemistry*
Adsorption of lipase on hollow fiber membrane chips

Shamel MM, Azaha RB, Al-Zuhair S

Artif Cells Blood Substit Immobil Biotechnol, 2005;33(4):423-33.
PMID: 16317961

The amount of lipase from Mucor miehei adsorption on ultrafiltration polysulfone hollow fiber membrane chips has been determined using different lipase concentrations at three different temperatures, namely 30, 35, and 40 degrees C. It was experimentally shown that adsorption of lipase increases with temperature. The results were used to evaluate the constants found in the Langmuir adsorption isotherm model coupled with the Van't Hoff's relationship. A temperature dependence correlation for the amount of adsorbed lipase activity, alip,ads, and that present in the supernatant solution, alip,free was determined. The effect of varying the concentration on a cross-linking agent, namely, glutaraldehyde, to the membrane chips was also tested. It was found that, under the same operating conditions, the amount of lipase adsorbed on polysulfone membranes was increased dramatically after pre-treating the membrane with 1% Glutaraldehyde. However, increasing the concentration of the cross-linking agent has a low effect on the amount of lipase adsorbed.

Matched MeSH terms: Cross-Linking Reagents
Dentine collagen cross-linking using tiopronin-protected Au/EDC nanoparticles formulations

Daood U, Akram Z, Matinlinna JP, Fawzy AS

Dent Mater, 2019 07;35(7):1017-1030.
PMID: 31064669 DOI: 10.1016/j.dental.2019.04.005

OBJECTIVE: The aim of this study was to investigate EDC-assisted collagen crosslinking effect with different concentrations of tiopronin-protected gold (TPAu) nanoparticles on demineralized dentine.
METHODS: TPAu nanoparticles were fabricated from 0.31-g tetrachloroauric acid and 0.38-g of N-(2-mercaptopropionyl) glycine (2.4-mmol). Then co-dissolved using 35-mL of 6:1 methanol/acetic acid and mixed using NaBH4. EDC (0.3-M) was conjugated to TPAu nanoparticles at TPAU/EDC-0.25:1, and TPAU/EDC-0.5:1 treatment formulations ratios. Dentin specimens treated with 0.3-M EDC solution alone or left untreated were used as control. Nanoparticles formulations were characterized in term of particles morphology and size, Zeta potential, thermogravimetric analysis and small-angle X-ray scattering. Dentin substrates were characterized in term of TEM investigation, dentin proteases characterization, hydroxyproline liberation, elastic modulus measurement, Raman analysis and confocal microscopy viewing.
RESULTS: TEM evaluation of tiopronin protected gold nanoparticles dispersion revealed nano-clusters formations in both groups. However, based on our TEM measurements, the particle-size was ranging from ˜20 to 50 nm with spherical core-shape which were almost similar for both TPAu/EDC ratios (0.5:1 and 0.25:1). Zeta potential measurements indicate negative nanoparticles surface charge. SAXS profiles for both formulations, suggest a typical profile for uni-lamellar nanoparticles. Superior dentin collagen cross-linking effect was found with the TPAu/EDC nanoparticles formulations compared to the control and EDC treated groups.
SIGNIFICANCE: Cross-linking of dentin collagen using TPAu coupled with EDC through TPAu/EDC nanoparticles formulations is of potential significance in improving the biodegradation resistance, proteases inhibition, mechanical and structural stability of demineralized dentin substrates. In addition, the cross-linking effect is dependent on TPAu/EDC ratio, whereas higher cross-linking effect was found at TPAu/EDC ratio of 0.5:1.

Matched MeSH terms: Cross-Linking Reagents
Fulltext QuadraPure-supported palladium nanocatalysts for microwave-promoted Suzuki cross-coupling reaction under aerobic condition

Liew KH, Loh PL, Juan JC, Yarmo MA, Yusop RM

ScientificWorldJournal, 2014;2014:796196.
PMID: 25054185 DOI: 10.1155/2014/796196

Cross-linked resin-captured palladium (XL-QPPd) was readily prepared by simple physical adsorption onto the high loading QuadraPure macroporous resin and a subsequent reduction process. To enhance the mechanical stability, entrapped palladium nanocatalysts were cross-linked with succinyl chloride. Both transmission electron microscopy images and X-ray diffraction analysis revealed that the palladium nanoparticles were well dispersed with diameters ranging in 4-10 nm. The catalyst performed good catalytic activity in microwave-promoted Suzuki cross-coupling reactions in water under aerobic condition with mild condition by using various aryl halides and phenylboronic acid. In addition, the catalyst showed an excellent recyclability without significant loss of catalytic activity.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Preparation of magnetic, macro-reticulated cross-linked chitosan for tetracycline removal from aquatic systems

Oladoja NA, Adelagun RO, Ahmad AL, Unuabonah EI, Bello HA

Colloids Surf B Biointerfaces, 2014 May 1;117:51-9.
PMID: 24632030 DOI: 10.1016/j.colsurfb.2014.02.006

A novel adsorbent, magnetic, macro-reticulated cross-linked chitosan (MRC) was synthesised for the removal of tetracycline (TC) from water using a source of biogenic waste (gastropod shells) as a pore-forming agent. The insertion of crosslinks into the chitosan frame was confirmed by FTIR analysis, while the stability of the MRC was demonstrated via a stability test performed in an acidic solution. The enhanced porosity of the MRC was confirmed by the evaluation of its porosity, a swelling test and the determination of its specific surface area. The time-concentration profile of the sorption of TC onto the MRC demonstrated that equilibrium was attained relatively quickly (120 min), and the data obtained fitted a pseudo second order (r(2)>0.99) kinetic equation better than a pseudo first order or reversible first order kinetic equation. The optimisation of process variables indicated that the sorption of TC onto the MRC was favoured at a low solution pH and that the presence of organics (simulated by the addition of humic acid) negatively impacted the magnitude of TC removal. The area of coverage of TC on the MRC (2.51 m(2)/g) was low compared to the specific surface area of the MRC (47.95 m(2)/g). The value of the calculated energy of adsorption of TC onto the MRC was 100 kJ/mol, which is far above the range of 1-16 kJ/mol stipulated for physical adsorption.

Matched MeSH terms: Cross-Linking Reagents/chemistry*
'Genipin' - the natural water soluble cross-linking agent and its importance in the modified drug delivery systems: an overview

Manickam B, Sreedharan R, Elumalai M

Curr Drug Deliv, 2014;11(1):139-45.
PMID: 24041312

One of the popular approaches in controlling drug delivery from the polymeric carriers is suitably achieved by the inclusion of crosslinking agents into the formulations at different concentrations. Nevertheless, addition of the chemical crosslinkers such as glutaraldehyde, formaldehyde etc, used in the drug delivery systems causes very serious cytotoxic reactions. These chemical crosslinking agents did not offer any significant advantageous effects when compared to the natural crosslinking agents for instance genipin, which is quite less toxic, biocompatible and offers very stable crosslinked products. Based on the earlier reports the safety of this particular natural crosslinker is very well established, since it has been widely used as a Chinese traditional medicine for long-time, isolated from fruits of the plant Gardenia jasminoides Ellis. This concise article largely portrayed the value of this unique natural crosslinker, utilized in controlling the drug delivery from the various formulations.

Matched MeSH terms: Cross-Linking Reagents/chemistry*
The effect of nanoparticles on gastrointestinal release from modified κ-carrageenan nanocomposite hydrogels

Hezaveh H, Muhamad II

Carbohydr Polym, 2012 Jun 5;89(1):138-45.
PMID: 24750615 DOI: 10.1016/j.carbpol.2012.02.062

In this article, silver and magnetite nanofillers were synthesized in modified κ-carrageenan hydrogels using the in situ method. The effect of metallic nanoparticles in gastro-intestinal tract (GIT) release of a model drug (methylene blue) has been investigated. The effect of nanoparticles loading and genipin cross-linking on GIT release of nanocomposite is also studied to finally provide the most suitable drug carrier system. In vitro release studies revealed that using metallic nanocomposites hydrogels in GIT studies can improve the drug release in intestine and minimize it in the stomach. It was found that cross-linking and nanofiller loading can significantly improve the targeted release. Therefore, applying metallic nanoparticles seems to be a promising strategy to develop GIT controlled drug delivery.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Chitosan and chemically modified chitosan beads for acid dyes sorption

Azlan K, Wan Saime WN, Lai Ken L

J Environ Sci (China), 2009;21(3):296-302.
PMID: 19634439

The capabilities of chitosan and chitosan-EGDE (ethylene glycol diglycidyl ether) beads for removing Acid Red 37 (AR 37) and Acid Blue 25 (AB 25) from aqueous solution were examined. Chitosan beads were cross-linked with EGDE to enhance its chemical resistance and mechanical strength. Experiments were performed as a function of pH, agitation period and concentration of AR 37 and AB 25. It was shown that the adsorption capacities of chitosan for both acid dyes were comparatively higher than those of chitosan-EGDE. This is mainly because cross-linking using EGDE reduces the major adsorption sites -NH3+ on chitosan. Langmuir isotherm model showed the best conformity compared to Freundlich and BET. The kinetic experimental data agreed very well to the pseudo second-order kinetic model. The desorption study revealed that after three cycles of adsorption and desorption by NaOH and HCl, both adsorbents retained their promising adsorption abilities. FT-IR analysis proved that the adsorption of acid dyes onto chitosan-based adsorbents was a physical adsorption. Results also showed that chitosan and chitosan-EGDE beads were favourable adsorbers and could be employed as low-cost alternatives for the removal of acid dyes in wastewater treatment.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Using response surface methodology to optimize process parameters and cross-linking agents for production of combined-cross-linked bovine serum albumin gels

Gan CY, Alkarkhi AF, Easa AM

J Biosci Bioeng, 2009 Apr;107(4):366-72.
PMID: 19332294 DOI: 10.1016/j.jbiosc.2008.12.007

D-optimal design was employed to optimize the mixture of cross-linking agents formulation: microbial transglutaminase (MTGase) and ribose, and the processing parameters (i.e. incubation and heating time) in the mixture in order to obtain combined-cross-linked bovine serum albumin gels that have high gel strength, pH close to neutral and yet medium in browning. Analysis of variance (ANOVA) showed that the contribution of quadratic term to the model over the linear was significant for pH and L* value, whereas linear model was significant for gel strength. Optimization study using response surface methodology (RSM) was performed to the mixture components and process variables and the optimum conditions obtained were: MTGase of 1.34-1.43 g/100 mL, ribose of 1.07-1.16 g/100 mL, incubation time of 5 h at 40 degrees C and heating time of 3 h at 90 degrees C.

Matched MeSH terms: Cross-Linking Reagents/chemistry*
Interactions of hepatitis B core antigen and peptide inhibitors

Tang KF, Abdullah MP, Yusoff K, Tan WS

J Med Chem, 2007 Nov 15;50(23):5620-6.
PMID: 17918821

The core protein (HBcAg) of hepatitis B virus (HBV) has been shown to interact with the large surface antigen during HBV morphogenesis, and these interactions can be blocked by small peptides selected from either linear or constrained phage display peptide libraries. The association of HBcAg with peptide inhibitors was quantitatively evaluated by isothermal titration calorimetry. The thermodynamic data show that the interaction between HBcAg and peptide MHRSLLGRMKGA is enthalpy-driven and occurs at a 3:1 stoichiometry and dissociation constant (Kd) value of 79.4 muM. However, peptide WSFFSNI displays a higher binding affinity for HBcAg with a Kd value of 18.5 muM when compared to peptide MHRSLLGRMKGA. A combinatorial approach using chemical cross-linking and surface-enhanced laser desorption/ionization-time-of-flight-mass spectrometry shows that the Lys of peptide MHRSLLGRMKGA interacted either with D64, E77, or D78 of HBcAg.

Matched MeSH terms: Cross-Linking Reagents/chemistry
Adsorption behaviour of Fe(II) and Fe(III) ions in aqueous solution on chitosan and cross-linked chitosan beads

Ngah WS, Ab Ghani S, Kamari A

Bioresour Technol, 2005 Mar;96(4):443-50.
PMID: 15491825

A batch adsorption system was applied to study the adsorption of Fe(II) and Fe(III) ions from aqueous solution by chitosan and cross-linked chitosan beads. The adsorption capacities and rates of Fe(II) and Fe(III) ions onto chitosan and cross-linked chitosan beads were evaluated. Chitosan beads were cross-linked with glutaraldehyde (GLA), epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDE) in order to enhance the chemical resistance and mechanical strength of chitosan beads. Experiments were carried out as function of pH, agitation period, agitation rate and concentration of Fe(II) and Fe(III) ions. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. Equilibrium data agreed very well with the Langmuir model. The kinetic experimental data correlated well with the second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. Results also showed that chitosan and cross-linked chitosan beads were favourable adsorbers.

Matched MeSH terms: Cross-Linking Reagents/chemistry*
Poly(vinyl alcohol) : a potential matrix for glucose oxidase immobilization?

Azila AA, Barbari T, Searson P

Med J Malaysia, 2004 May;59 Suppl B:51-2.
PMID: 15468814

Considerable effort has been focused on the method of immobilizing glucose oxidase (GOD) for amperometric glucose biosensors since the technique employed may influence the available activity of the enzyme and thus affect the performance of the sensor. Narrow measuring range and low current response are still considered problems in this area. In this work, poly(vinyl alcohol)(PVA) was investigated as a potential matrix for GOD immobilization. GOD was entrapped in cross-linked PVA. The use of a PVA-GOD membrane as the enzymatic component of a glucose biosensor was found to be promising in both the magnitude of its signal and its relative stability over time. The optimum PVA-GOD membrane (cross-linking density of 0.06) was obtained through careful selection of the cross-linking density of the PVA matrix.

Matched MeSH terms: Cross-Linking Reagents*
Optimization strategy for laccase immobilization on polyethylene terephthalate grafted with maleic anhydride electrospun nanofiber mat

Mohd Syukri MS, A Rahman R, Mohamad Z, Md Illias R, Nik Mahmood NA, Jaafar NR

Int J Biol Macromol, 2021 Jan 01;166:876-883.
PMID: 33144251 DOI: 10.1016/j.ijbiomac.2020.10.244

Enzyme immobilization has been known to be one of the methods to improve the stability and reusability of enzyme. In this study, a strategy to optimize laccase immobilization on polyethylene terephthalate grafted with maleic anhydride electrospun nanofiber mat (PET-g-MAH ENM) was developed. The development involves the screening and optimization processes of the crucial factors that influence the immobilization yield such as enzyme concentration, pH values, covalent bonding (CV) time, CV temperature, crosslinking (CL) time, CL temperature and glutaraldehyde concentration using two-level factorial design and Box-Behnken design (BBD), respectively. It was found that laccase concentration, pH values and glutaraldehyde concentration play important role in enhancing the immobilization yield of laccase on PET-g-MAH ENM in the screening process. Subsequently, the optimization result showed at 0.28 mg/ml laccase concentration, pH 3 and 0.45% (v/v) glutaraldehyde concentrations gave the highest immobilization yield at 87.64% which was 81.2% increment from the immobilization yield before optimization. Under the optimum condition, the immobilized laccase was able to oxidize 2, 2-azino-bis 3-ethylbenzothiazoline-6- sulfonic acid (ABTS) in a broad range of pH (pH 3-6) and temperature (20- 70 °C). Meanwhile, the kinetic parameters for Km and Vmax were 1.331 mM and 0.041 mM/min, respectively. It was concluded that the optimization of immobilized laccase on PET-g-MAH ENM enhance the performance of this biocatalyst.

Matched MeSH terms: Cross-Linking Reagents/chemistry
A two-step method using air plasma and carbodiimide crosslinking to enhance the biocompatibility of polycaprolactone

Sahapaibounkit P, Prasertsung I, Mongkolnavin R, Wong CS, Damrongsakkul S

J Biomed Mater Res B Appl Biomater, 2017 08;105(6):1658-1666.
PMID: 27177842 DOI: 10.1002/jbm.b.33708

In this study, polycaprolactone (PCL) film, a high potential material used in biomedical applications, was treated by air plasma prior to a conjugation by carbodiimide cross-linking with various types of proteins, including type A gelatin, type B gelatin, and collagen hydrolysate. The properties of modified PCL films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurement, and atomic force microscopy. The XPS results showed that oxygen and nitrogen atoms were successfully introduced on the air plasma-treated PCL surface. Primary amine was found on the air plasma-treated PCL films. All proteins were shown to be successfully cross-linked on air plasma-treated PCL films. The wettability and roughness of protein-conjugated PCL films were significantly increased compared to those of neat PCL film. In vitro biocompatibility test using L929 mouse fibroblast showed that the attachment percentage and spreading area of attached cells on all protein-conjugated PCL films were markedly increased. Comparing among modified PCL films, no significant difference on the attachment of L929 on modified PCL films was noticed. However, the spreading areas of cells after 24 hours of culture on type A gelatin- and type B gelatin-modified PCL surfaces were higher than that on collagen hydrolysate-modified surface, possibly related to the lower percentage of amide bond on collagen hydrolysate-conjugated surface compared to those on both gelatin-conjugated PCL ones. This indicated that the two-step modification of PCL film via air plasma and carbodiimide cross-linking with collagen-derived proteins could enhance the biocompatibility of PCL films. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1658-1666, 2017.

Matched MeSH terms: Cross-Linking Reagents/chemistry*
Optimized preparation and characterization of CLEA-lipase from cocoa pod husk

Khanahmadi S, Yusof F, Amid A, Mahmod SS, Mahat MK

J Biotechnol, 2015 May 20;202:153-61.
PMID: 25481099 DOI: 10.1016/j.jbiotec.2014.11.015

Cross-linked enzyme aggregate (CLEA) is easily prepared from crude enzyme and has many advantages to the environment and it is considered as an economic method in the context of industrial biocatalysis compared to free enzyme. In this work, a highly active and stable CLEA-lipase from cocoa pod husk (CPH) which is a by-product after removal of cocoa beans, were assayed for their hydrolytic activity and characterized under the optimum condition successfully. Face centered central composite design (FCCCD) under response surface methodology (RSM) was used to get the optimal conditions of the three significant factors (concentration of ammonium sulfate, concentration of glutaraldehyde and concentration of additive) to achieve higher enzyme activity of CLEA. From 20 runs, the highest activity recorded was around 9.407U (83% recovered activity) under the condition of using 20% saturated ammonium sulfate, 60mM glutaraldehyde as cross-linker and 0.17mM bovine serum albumin as feeder. Moreover, the optimal reaction temperature and pH value in enzymatic reaction for both crude enzyme and immobilized were found to be 45°C at pH 8 and 60°C at pH 8.2, respectively. A systematic study of the stability of CLEA and crude enzyme was taken with regards to temperature (25-60°C) and pH (5-10) value and in both factors, CLEA-lipase showed more stability than free lipase. The Km value of CLEA was higher compared to free enzyme (0.55mM vs. 0.08mM). The CLEA retained more than 60% of the initial activity after six cycles of reuse compared to free enzyme. The high stability and recyclability of CLEA-lipase from CPH make it efficient for different industrial applications.

Matched MeSH terms: Cross-Linking Reagents/chemistry

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