Lipase CA Research Articles

Amphiphilic random polycarbonate self-assemble into GSH/pH dual responsive micelle-like aggregates in water

Responsive polymers have been playing an increasingly important role in a wide variety of applications, such as biomedical materials and biosensors. Herein, we reported a dual-responsive polycarbonate (poly(MN-co-MSS)) based on the macrocyclic Sulfur/Nitrogen-substituted carbonate monomer (MSS/MN) via an enzyme-catalyzed ring-opening copolymerization and Lipase CA Novozym-435 as catalyst, with the disulfide and tertiary amine groups situated on the backbone. The structure of the random copolymers was confirmed by NMR and FTIR. In addition, size exclusion chromatography (SEC) results indicated that the copolymer had a symmetric peak and a relatively narrow polydispersity. Also, the random copolymers can self-assemble into micelle-like aggregates in water due to the hydrophilicity endowed by the amino groups, and the aggregates exhibited rich pH and GSH responsive behavior, which was verified by zeta masters instrument and dynamic light scattering (DLS). Moreover, transmission electron microscopy (TEM) demonstrated the morphology of the micellar aggregates and the variation subjected to the lower pH and GSH, and the responsive mechanism was elaborated. Therefore, these results highlighted a facile synthesis of the environment-responsive polymers and provided a novel GSH/pH responsive material platform for further application.

Well-Defined Selenium-Containing Aliphatic Polycarbonates via Lipase-Catalyzed Ring-Opening Polymerization of Selenic Macrocyclic Carbonate Monomer.

The synthesis of well-defined, biodegradable selenium-containing polymers remains a formidable challenge in polymer chemistry. Herein, a selenic cyclic carbonate dimer monomer (MSe) was developed to generate well-defined, biodegradable aliphatic polycarbonates with selenide functionality on the backbone. The monomer was synthesized via the intermolecular cyclization of di(1-hydroxyethylene) selenide and diphenyl carbonate with lipase CA as catalysts in a mass of anhydrous toluene with very dilute monomer concentration. Then living ring-opening polymerization (ROP) was executed by solution method using the same lipase CA as catalysts. Similarly, the copolymerizations with commercial trimethylene carbonate (TMC) generated random copolymers demonstrated by 13C NMR, regulating the density of selenium functional groups. The resulting polymers exhibited a living polymerization characteristic, as evidenced by polymerization kinetics, predictable molecular weights, narrow molecular-weight distribution, and controlled copolymer compositions. Using hydrophilic macroinitiators (PEG), amphiphilic di/triblock copolymers could be obtained, suggesting their potential as controlled drug delivery system (DDS) and hydrogel scaffolds for tissue engineering.

Enzymatic formation of 13,26-Dihexyl-1,14-dioxacyclohexacosane-2,15-dione via Oligomerization of 12-Hydroxystearic acid

The enzymatic polymerization of 12-hydroxystearic acid (12-HSA) was carried out with Lipase CA® in benzene to produce poly(12-hydroxystearate) (PHS) with a low molecular weight. When this polymerization was continued for a long reaction time, the PHS once formed was depolymerized into a cyclic diester, 13,16-dihexyl-1, 14-dioxacyclohexacosane-2,15-dione (12-HSAD). Similar polymerization and depolymerization were observed when 12-hydroxyoleic acid (12-HOA) was treated with Lipase CA®, whereas only polymerization occurred when 12-hydroxydodecanoic acid (12-HDA) was treated in a similar manner. The preferential formation of cyclic diesters for 12-HSA was attributed to the structural requirements due to the bulkyn-hexyl side groups stemming from the ring systems.

Direct Enzymatic Synthesis of a Polyester with Free Pendant Mercapto Groups

An aliphatic polyester with free pendant mercapto groups was prepared by direct lipase-catalyzed polycondensation of hexane-1,6-diol and dimethyl 2-mercaptosuccinate. The polycondensation reaction using immobilized lipase from Candida antarctica (lipase CA) was carried out in bulk at 70 degrees C without any formation of disulfide or thioester linkages to produce the corresponding polyester with Mw = 14000 g/mol in high yield. The content of free mercapto groups in the polyester could be controlled by copolymerization with other monomers. The obtained polyester was easily cross-linked to form gels by the air oxidation of the pendant thiols to disulfides in dimethyl sulfoxide.

Synthesis of poly (1,4-dioxan-2-one) catalyzed by immobilized lipase CA

Polymerization of 1,4-dioxan-2-one was carried out more detailed with immobilized lipase CA as the catalyst. The effect of the enzyme amount, reaction temperature and water content on polymerization was investigated, respectively. Both the conversion of monomer and the M v of poly(1,4-dioxan-2-one) increased with the increase of enzyme amount, and maximized at 80 °C. At the beginning of polymerization, water molecules act as initiators. As the reaction time increased, linear condensation had gradually became dominant and water was released into the reaction system. Excess water may act as a chain cleavage agent. To obtain poly(1,4-dioxan-2-one) with an ideal molecular weight, polymerization of 1,4-dioxan-2-one was conducted by adding solvent and MS to reaction system, and product with a higher molecular weight ( M v = 58,000) was gained.

Microblock Copolymers as a Result of Transesterification Catalyzing Behavior of Lipase CA in Sequential ROP

The copolymerization of ε-caprolactone (CL) and 1,5-dioxepan-2-one (DXO) was performed by sequential addition of monomers in lipase CA catalyzed ring-opening polymerization (ROP) at 60 °C in bulk. CL was first polymerized up to a monomer conversion of 95%, and then DXO was added to the reaction mixture. The polymerization was stopped when the DXO conversion reached a level of more than 95%. The molar feed ratio of CL and DXO was varied from 1.5 to 10, and the copolymer composition, as determined by 1H NMR spectroscopy, agreed well with the feed. The block lengths of PCL and PDXO segments in the structure of these high molecular weight copolymers reduced significantly due to the occurrence of extensive transesterification during ROP. The enzyme, lipase CA, in addition to acting as the catalyst for ROP also promoted transesterification reactions. The increase in number-average molecular weight (Mn) after DXO polymerization in the second step illustrated that the terminal hydroxyl group of preformed PCL chains in the first step possibly initiated the DXO polymerization. A single glass transition, in between the glass transition temperatures of corresponding homopolymers of PDXO and PCL, was observed in the DSC thermograms of all the copolymers. A composition of 15−20% DXO gave optimal balance between strength and elasticity of the copolymers.

Porous Scaffolds from High Molecular Weight Polyesters Synthesized via Enzyme-Catalyzed Ring-Opening Polymerization

Several aliphatic polyesters have been synthesized until now using enzyme-catalyzed ring-opening polymerization (ROP) of different lactones, although their molecular weight, hence mechanical strength, was not sufficient enough to fabricate porous scaffolds from them. To achieve this target, 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (CL) were polymerized in bulk with Lipase CA as catalyst at 60 degrees C, and porous scaffolds were prepared from the polymers obtained thereof using a salt leaching technique. The CL/DXO molar feed ratio was varied from 1.5 to 10, and the reactivity ratios of CL and DXO were determined using the Kelen-Tudos method under such conditions of polymerization. NMR results showed a slightly lower CL/DXO molar ratio in the copolymers than in the feed due to high reactivity of DXO toward Lipase CA catalysis. The crystallinity of the PCL segment of the copolymers was affected by the presence of soft and amorphous DXO domains. The copolymers having high CL content were thermally more stable. The porosity of the scaffolds was in the range 82-88%, and the SEM analysis showed interconnected pores in the scaffolds. Of the two parameters which could affect the mechanical properties, viz., the copolymer composition and the scaffold pore size, the pore size showed a significant effect on the mechanical properties of the scaffolds. The porous scaffolds developed in this way for tissue engineering are free from toxic organometallic catalyst residues, and they are highly suitable for biomedical applications.

Enzyme‐Catalyzed Preparation of Aliphatic Polythioester by Direct Polycondensation of Diacid Diester and Dithiol

AbstractSummary: Aliphatic dithiol‐diacid type polythioesters were first enzymatically prepared by the direct polycondensation of hexane‐1,6‐dithiol and diacid diesters using the immobilized lipase from Candida antarctica (lipase CA). As a typical example, diethyl sebacate and hexane‐1,6‐dithiol were polymerized using lipase CA in bulk in the presence of molecular sieves 4A to produce the corresponding polythioester with an $\overline M _{\rm w}$ of 10 200 in 90% yield. Both the melting and crystallization temperatures of the produced polythioesters were higher when compared to those of the corresponding polyoxyesters. A higher molecular weight polythioester was produced using lipase in a two‐step procedure, i.e., cyclization with subsequent ring‐opening polymerization.Preparation of polythioester and melting temperature of various polythioesters and polyoxyesters.magnified imagePreparation of polythioester and melting temperature of various polythioesters and polyoxyesters.

Preparation of Aliphatic Poly(thioester) by the Lipase-Catalyzed Direct Polycondensation of 11-Mercaptoundecanoic Acid

An aliphatic polythioester was enzymatically prepared by the direct polycondensation of mercaptoalkanoic acid using immobilized lipase of Candida antarctica (lipase CA) in bulk. The commercially available 11-mercaptoundecanoic acid was polymerized by lipase CA in bulk in the presence of molecular sieves 4A as a water absorbent at 110 degrees C for 48 h to produce poly(11-mercaptoundecanoate) with an M(w) of 34 000 in high yield. The 104.5 degrees C melting temperature (T(m)) of poly(11-mercaptoundecanoate) was about 20 degrees C higher than that of the corresponding polyoxyester, poly(11-hydroxyundecanoate). The polythioester was readily transformed by lipase into the corresponding cyclic oligomers mainly consisting of the dimer, which were readily repolymerized by the ring-opening polymerization using lipase as a sustainable chemical recycling.

High-molecular-weight poly(1,5-dioxepan-2-one) via enzyme-catalyzed ring-opening polymerization

To avoid organometallic catalysts in the synthesis of poly(1,5-dioxepan-2-one), the enzymatic ring-opening polymerization of 1,5-dioxepan-2-one (DXO) was performed with lipase CA (derived from C ...

Lipase-catalyzed transformation of poly(lactic acid) into cyclic oligomers.

Enzymatic transformations into cyclic oligomers were carried out with the objective of developing chemical recycling of poly(lactic acid)s, such as poly(D,L-lactic acid) (PDLLA), poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA), which are typical biodegradable polymers. They were degraded by lipase in an organic solvent to produce the corresponding cyclic oligomer with a molecular weight of several hundreds. PDLLA (with a Mw of 84,000) was quantitatively transformed into cyclic oligomers by lipase RM (Lipozyme RM IM) in chloroform/hexane at 60 degrees C. PLLA (with a Mw of 120,000) was transformed into cyclic oligomer by lipase CA (Novozym 435) at a higher temperature of 100 degrees C in o-xylene. The oligomer structure was identified by 1H and 13C NMR spectroscopy and MALDI-TOF (matrix assisted laser desorption/ionization-time-of-flight) mass spectrometry.

Lipase-catalyzed transformation of poly(butylene adipate) and poly(butylene succinate) into repolymerizable cyclic oligomers.

The enzymatic degradation and repolymerization were carried out with the objectives of developing the chemical recycling of aliphatic polyester-type plastics, such as the poly(butylene adipate) (PBA), poly(butylene succinate), and poly(butylene adipate-co-succinate) copolymers which are typical biodegradable plastics. They were degraded by lipase in an organic solvent solution containing a small amount of water to produce cyclic oligomers mainly consisting of the cyclic diester. The produced cyclic oligomer was readily repolymerized by lipase to produce a polyester having an equal or higher molecular weight compared to the parent polymer. As an example, PBA having an Mw of 22,000 was almost quantitatively transformed by lipase CA (Novozym 435) in water-containing toluene at 50 degrees C into the corresponding cyclic oligomers mainly consisting of dimers. Thus, the obtained oligomers were readily polymerized by lipase CA to produce the PBA with an Mw of 52,000.

Enzymatic Synthesis and Polymerization of Cyclic Trimethylene Carbonate Monomer with/without Methyl Substituent

AbstractThe direct enzymatic synthesis of a cyclic trimethylene carbonate (1,3‐dioxane‐2‐one) monomer with/without a methyl substituent was carried out using dimethyl or diethyl carbonate and 1,3‐diol with the objective of producing aliphatic poly(trimethylene carbonate), a typical biodegradable synthetic plastic. The lipase‐catalyzed condensation of dimethyl or diethyl carbonate with aliphatic 1,3‐diols using immobilized Candida antarctica lipase (lipase CA) in an organic solvent at 70 °C afforded the corresponding methyl‐substituted and unsubstituted cyclic trimethylene carbonates. The cyclic trimethylene carbonates obtained by the reaction of dimethyl or diethyl carbonates with 1,3‐propanediol and 2‐methyl‐1,3‐propanediol were polymerized by lipase to produce the corresponding polycarbonates.Total TMC yield as a function of the reaction time.magnified imageTotal TMC yield as a function of the reaction time.

Chemoenzymatic synthesis of glycoconjugate polymers: greening the synthesis of biomaterials

Glycoconjugate polymers with biodegradable poly(vinyl alcohol) (PVA) were synthesized via lipase-catalyzed transesterification of sugar alcohols (maltitol and lactitol) with divinyl dicarboxylates and subsequent radical polymerization. The conversion and chemoselectivity in transesterification were dependent on the lipases, the sugar alcohols, and the alkyl chain length of the dicarboxylates. Chemoselective esterification was attained in the presence of lipase from Candida antarctica (lipase CA) to give maltitol 6-vinyl sebacate, lactitol 6-vinyl sebacate, and lactitol 6-vinyl adipate in high yields. Polymerization of these vinyl esters with hydrogen peroxide/ascorbic acid as initiator gave glycoconjugate polymers. These polymers were suggested to take micellar conformations in water and to bind strongly to specific lectins (concanavalin A or RCA120). The biodegradabilities of these polymers were modest but higher than PVA. This simple synthesis will be useful to develop various glycoconjugate polymers with high biological activities due to the multivalent glyco-cluster effect and biodegradability due to their PVA backbone and ester linkage.

Lipase-catalyzed selective transformation of polycaprolactone into cyclic dicaprolactone and its repolymerization in supercritical carbon dioxide

The lipase-catalyzed selective transformation of poly(e-caprolactone) (PCL) into dicaprolactone (DCL: 1,8-dioxacyclotetradecane-2,9-dione) and the repolymerization of DCL in supercritical carbon dioxide (scCO 2 ) were carried out for the establishment of a sustainable green polymer chemistry for PCL. PCL with a number-average molecular weight of M n 110 000 was selectively transformed into repolymerizable cyclic DCL in 90% yield using immobilized Candida antarctica lipase (lipase CA) in scCO 2 fluid by compression to 18 MPa in the presence of a small amount of water at 40°C. The DCL obtained such was readily polymerized by lipase CA in scCO 2 to produce a PCL with an M n of 33 000 after 6 h.

Lipase‐Catalyzed transformation of Poly(trimethylene carbonate) into Cyclic Monomer, Trimethylene Carbonate: A New Strategy for Sustainable Polymer Recycling Using an Enzyme

The enzymatic degradation and polymerization using an enzyme were carried out with respect to the establishment of a sustainable chemical recycling system for poly(trimethylene carbonate) [P(TMC)] which is a potentially biodegradable synthetic plastic. The enzymatic transformation of P(TMC)s having an M n of 3000-48000 using Candida antarctica hpase (lipase CA) in acetonitrile at 70 °C afforded the corresponding cyclic monomet, trimethylene carbonate (TMC: 1,3-dioxan-2-one), in a yield of up to 80%. Thus obtained TMC readily polymerized again using both fresh lipase CA and reco ered lipase CA.

Lipase-catalyzed transformation of poly(epsilon-caprolactone) into cyclic dicaprolactone.

The enzymatic degradation and polymerization using an enzyme were carried out with respect to the establishment of a sustainable chemical recycling system for poly(epsilon-caprolactone) (PCL) which is a typical biodegradable synthetic plastic. The enzymatic transformation of PCL having an Mn of 110,000 using Candida antarctica lipase (lipase CA) in water-containing toluene at 40 degrees C afforded the corresponding cyclic dicaprolactone (DCL, 1,8-dioxacyclotetradecane-2,9-dione) in a yield of up to 97%. Thus the obtained DCL readily polymerized again using both the fresh and recovered lipase CAs.

A new strategy for sustainable polymer recycling using an enzyme: poly(ɛ-caprolactone)

Enzymatic degradation and polymerization using an enzyme were analyzed with respect to the establishment of a sustainable chemical recycling system for poly(e-caprolactone) (PCL) which is a typical biodegradable synthetic plastic. As the typical example, the enzymatic degradation of PCL having an M n of 110 000 using lipase CA in toluene containing water at 70°C for 6 h afforded a unimodal oligomer having an M n of about 1000 quantitatively consisting of linear and cyclic oligomers. This was again polymerized by lipase CA in toluene under restricted water concentration to produce PCL having an M n of greater than 70 000.

Synthesis of metal-free poly(1,4-dioxan-2-one) by enzyme-catalyzed ring-opening polymerization

To avoid the harmful effects of metallic residues in poly(1,4-dioxan-2-one) (PPDO) for medical applications, the enzymatic polymerization of 1,4-dioxan-2-one (PDO) was carried out at 60 °C for 15 h with 5 wt % immobilized lipase CA. The lipase CA, derived from Candida antarctica, exhibited especially high catalytic activity. The highest weight-average molecular weight (M w = 41,000) was obtained. The PDO polymerization by the lipase CA occurred because of effective enzyme catalysis. The water component appeared to act not only as a substrate of the initiation process but also as a chain cleavage agent. A slight amount of water enhanced the polymerization, but excess water depressed the polymerization. PPDO prepared by enzyme-catalyzed polymerization is a metal-free polyester useful for medical applications.

Increased serum CA 19-9 antibodies in Sjögren's syndrome.

A 67-year-old woman with a history of thyroiditis presented with recent intermittent epigastric pain and nausea. Hyperamylasaemia, oedema of the pancreas, and high serum levels of lipase and CA 19-9...