Molar Mass Mn Research Articles

Structure of a Pueraria root polysaccharide and its immunoregulatory activity on T and B lymphocytes, macrophages, and immunosuppressive mice

In this experiment, the polysaccharide was extracted from Pueraria lobata (Willd.) Ohwi, and its structural characteristics and bioactivity were investigated. The results showed that Pueraria lobata polysaccharide (PLP) was composed of fucose, arabinose, galactose, glucose, xylose, mannose in a molar proportion of 0.09:1.25:2.19:95.74:0.43:0.30 with a number molar masses (Mn) weight of 14.463 kDa. Besides, FT-IR, Methylation, and NMR analysis revealed that PLP were mainly composed of the main chain →4)-α-Glcp (1→ and →4,6)-α-Glcp (1→, and the branched chain α-Glcp (1→. In vitro experiment, the results showed that PLP could stimulate the expression of surface molecules on RAW264.7 and (T and B) lymphocytes proliferation, simultaneously to stimulate their cytokines secretion. In vivo experiment, the immune organ index, cytokine content, and T lymphocyte subtype in cyclophosphamide-induced immunosuppressed mice could be improved by PLP. These data proved that PLP could be used as a useful immunomodulator to enhance the immune activity of RAW264.7, T, and B cells and improve the immune function of cyclophosphamide-treated mice.

In situ preparation of compounds using silanized mPEG inspired by talc-like structures.

Composite materials show improved properties compared to pristine materials, in particular when the filler is dispersed homogeneously in the matrix. For polymer-clay composites, different strategies exist to improve clay mineral dispersion in the polymer matrix. In this study, an innovative approach is suggested which consists of forming a talc-like structure directly in a polymer matrix using a silanized polymer as the silicon source. Poly(ethylene glycol) methyl ether of different average molar masses (Mn = 350, 500, 750, 1900 g mol-1) were functionalized with (3-isocyanatopropyl)triethoxysilane and added to the ethanolic solutions of magnesium nitrate. 1H-29Si CPMAS solid state NMR experiments revealed partial condensation of silane compounds, and FTIR analysis confirmed the presence of both Si-O and Mg-O bonds, but an additional proof of the Si-O-Mg bond is needed to prove the formation of such a structure.

The effect of three pectin fractions variation on the browning of different dried apple products

Pectin is an important active polysaccharide in the matrix of dried fruit slices. Its components and structural character not only affect the texture but also impact the color of the dried fruit products. Present work studied the variation of pectin fractions of water-soluble (WSP), trans-cyclohexane-1,2-diaminetetraacetic acid-soluble (CSP), and sodium carbonate-soluble (NSP) from apple slices dried by using freeze-drying (FD), 60 °C hot air drying (HAD60), and 90 °C hot air drying (HAD90), to investigate the correlation of their monosaccharide composition, molecular weight distribution, Fourier transform infrared (FTIR) spectrum and small-angle X-ray scattering (SAXS) intensity plot of pectin fractions with the appearance browning of the apple slices. It was found that thermally process ruptures the cell wall structure and pectin component, leading to 12.57% less yield of WSP, and a maximum of 6.35% more yield of NSP pectin fractions. In FD, HAD60, and HAD90 apple slices, the linearity of WSP decreased but the branching extent of the rhamnogalacturonan I (RG-I) domain of WSP and NSP increased successively. The weight average molecular mass (Mw) and number average molar mass (Mn) of WSP and NSP increased as drying temperature increased, whereas they decreased in CSP. The thermal treatment promoted the dehydration of the pectin and caused higher methyl esterification, inducing the structure of pectin more compact and tighter. Moreover, the pectin structural characteristics of the degree of esterification (DE), the radius of gyration (Rg) value, conformational index ( ν ), and galactose content of three soluble pectin fractions were positively correlated with the a* and b* value of different dried apple slices. • Different drying techniques induce different changes in three pectin fractions. • The change of pectin fractions notably impacts the browning of dried apple slices. • Thermal treatment induced methyl esterification of pectin fractions of dried apple. • Thermal treatment made the structure of pectin much more compact and tighter.

Improving aqueous solubility of paclitaxel with polysarcosine-b-poly(γ-benzyl glutamate) nanoparticles

New stealth amphiphilic copolymers based on polysarcosine (PSar) rather than poly(ethylene glycol) (PEG) have gained more attention for their use as excipients in nanomedicine. In this study, several polysarcosine-b-poly(γ-benzyl glutamate) (PSar-b-PGluOBn) block copolymers were synthesized by ring opening polymerization (ROP) of the respective N-carboxyanhydrides (NCAs) and were characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) and size-exclusion chromatography (SEC). Copolymers had different PGluOBn block configuration (racemic L/D, pure L or pure D), degrees of polymerization of PSar between 28 and 76 and PGluOBn between 9 and 93, molar masses (Mn) between 5.0 and 24.6 kg.mol−1 and dispersities (Đ) lower than 1.4. Nanoparticles of PSar-b-PGluOBn loaded with paclitaxel (PTX), a hydrophobic anti-cancer drug, were obtained by nanoprecipitation. Their hydrodynamic diameter (Dh) ranged from 27 to 118 nm with polydispersity indexes (PDI) between 0.01 and 0.20, as determined by dynamic light scattering (DLS). Their morphology was more spherical for copolymers with a racemic L/D PGluOBn block configuration synthesized at 5 °C. PTX loading efficiency was between 63 and 92 % and loading contents between 7 and 15 %. Using PSar-b-PGluOBn copolymers as excipients, PTX apparent water-solubility was significantly improved by a factor up to 6600 to 660 µg.mL−1.

Biodegradability Assessment of Polyester Copolymers Based on Poly(ethylene adipate) and Poly(ε-caprolactone).

Biodegradable polymers contain chains that are hydrolytically or enzymatically cleaved, resulting in soluble degradation products. Biodegradability is particularly desired in biomedical applications, in which degradation of the polymer ensures clearance from the body and eliminates the need for retrieval or explant. In this study, a homologues series of poly(ε-caprolactone)-b-poly(ethylene adipate)-b-poly(ε-caprolactone) (PCL-b-PEA-b-PCL) block copolymers, with constant PEA molar mass and different PCL sequence lengths was obtained. The starting point of these copolymers was a dihydroxy-PEA precursor with a molar mass (Mn) of 2500 g/mol. Mn values of the PCL varied between 1000 and 10,000 g/mol. Both the precursors and the copolymers were characterized using different physicochemical methods, such as: NMR, SEC, Maldi-TOFF, DSC, and ATG. The molecular characteristics of the copolymers were in a direct correlation with the sequence length of the PCL. Enzymatic degradability studies were also conducted by using cell-free extract containing Pseudomonas aeruginosa PAO1 for 10 and 21 days, and it appeared that the presence of the PEA central sequence has an important influence on the biodegradability of the copolymer samples. In fact, copolymer PCL7000-PEA2500-PCL7000 had a weight loss of around 50% after 10 days whereas the weight loss of the homopolymer PCL, with a similar Mn of 14,000 g/mol, was only 6%. The results obtained in this study indicate that these copolymer samples can be further used for the preparation of drug delivery systems with modulated biodegradability.

Pellet-Based Fused Filament Fabrication (FFF)-Derived Process for the Development of Polylactic Acid/Hydroxyapatite Scaffolds Dedicated to Bone Regeneration.

Scaffolds can be defined as 3D architectures with specific features (surface properties, porosity, rigidity, biodegradability, etc.) that help cells to attach, proliferate, and to differentiate into specific lineage. For bone regeneration, rather high mechanical properties are required. That is why polylactic acid (PLA) and PLA/hydroxyapatite (HA) scaffolds (10 wt.%) were produced by a peculiar fused filament fabrication (FFF)-derived process. The effect of the addition of HA particles in the scaffolds was investigated in terms of morphology, biological properties, and biodegradation behavior. It was found that the scaffolds were biocompatible and that cells managed to attach and proliferate. Biodegradability was assessed over a 5-month period (according to the ISO 13781-Biodegradability norm) through gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and compression tests. The results revealed that the presence of HA in the scaffolds induced a faster and more complete polymer biodegradation, with a gradual decrease in the molar mass (Mn) and compressive mechanical properties over time. In contrast, the Mn of PLA only decreased during the processing steps to obtain scaffolds (extrusion + 3D-printing) but PLA scaffolds did not degrade during conditioning, which was highlighted by a high retention of the mechanical properties of the scaffolds after conditioning.

Upcycling Polytetrahydrofuran to Polyester

Upcycling Polytetrahydrofuran to Polyester

Associative and Thermoresponsive Aqueous Polymer Formulations Based on Imine Chemistry

Controlling the flow properties of aqueous formulations is essential in fields as diverse as biotechnology, cosmetics, paints, or chemically enhanced oil recovery, to cite a few. This work presents a study of the association, in aqueous solutions, of complementary polyacrylamides carrying amino and aryl aldehyde side-groups. Through free radical polymerization, copolymers with tunable molar masses (Mn ranging from 60 to 370 kg·mol–1), functionality (2 to 17 mol %), and permanent charge degrees (0 to 98 mol %) were obtained. Imine formation was studied on model systems consisting of amino polyacrylamides and a benzaldehyde derivative. It was found that the presence of permanent charges on the amino polyacrylamide does not prevent imine formation but influences the association degree. In addition, imines were efficiently formed in the presence of NaCl and the dynamic cross-links proved to be thermoresponsive, with a reversible displacement of the equilibrium toward amine and aldehyde with increasing temperature. The associative formulations were subsequently studied by rheology. It was shown that the functionality, charge degree, and molar mass of the copolymers can be used to rationally manipulate interchain association, which proved to be a powerful tool to control the viscosity and rheological profile of the different formulations. Dynamic light scattering was utilized to further study the microstructural dynamics of one of the formulations, showing good agreement with rheology. Finally, taking advantage of the influence of temperature on the imine cross-links, a thermoresponsive hydrogel was prepared that undergoes reversible sol–gel transition over multiple heating–cooling cycles between 30 and 80 °C.

High thermal resistance amorphous copolyesters synthesized from bio‐based 2,5‐furandicarboxylic acid

AbstractThe polyesters with high Tg (≥100°C) and good clarity are desired in fabricating heat‐resistance containers such as baby bottles, cups, medical apparatus, and kitchen appliances. In this work, a series of poly(butylene bis[4‐(2‐hydroxyethoxy) phenyl] sulfone 1,4‐cyclohexanedimethylene 2,5‐furandicarboxylate) (PBSCFs) that show superior thermal and mechanical properties against current bio‐based polyesters were synthesized via a melt polycondensation method. The accurate chemical structures of PBSCFs were confirmed by 1H‐NMR and 13C‐NMR. The SEC results show that PBSCFs have number averaged molar mass (Mn) in the range of 9700–28,500 g/mol. The Tg of PBSCFs increase from 94°C for PBSF to 108°C for PBSCF‐50 as the increasing of CHDM unit. Meanwhile, the ductility of PBSCFs also improved with the elongation at break of PBSCF‐40 increased to 223%. In addition, the PBSCF‐40 sample reported in this paper shows thermal decomposition temperature of 427°C, transmittance of 84.6%, haze of only 0.17%, tensile strength of 74.1 MPa, and tensile modulus of 2287 MPa.

Membrane-active diacylglycerol-terminated thermoresponsive polymers: RAFT synthesis and biocompatibility evaluation

Well-defined diacylglycerol end-functionalized poly(N-isopropylacrylamide)s (PNIPAAm) and poly(N-vinylcaprolacam)s (PNVCL) with number-average molar masses (Mn) ranging from 1260 to 19 350 g·mol−1 were synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization from xanthate-functionalized diacylglycerols (DAGs) containing palmitic or oleic acid moieties. The formation of polymeric nanoparticles (PNPs) and their thermoresponsive properties was studied. Phase separation temperature dependence on polymer molar mass and hydrophilic/hydrophobic ratio was investigated in phosphate buffer saline (PBS). Biological tests showed that the particles are non-hemolytic and highly compatible with representatives of immune cells - monocyte/macrophage THP-1 cells. The biocompatibility combined with the potential ability to modulate the cell membrane environment make the proposed polymers a promising foundation for drug carriers.

Improvement of the viscoelastic and thermal properties of polyvinyl acetate reinforced with organophilic clay (Algerian MMT)

Polyvinyl acetate (PVAc) has many favorable characteristics: it is non-toxic, harmless, easily producible, inexpensive, practical to apply and environmentally friendly, the same for clay (maghnite) which is a natural nanomineral, source of a large number of raw materials; it is also inexpensive and accessible. The present study shows the synthesis of PVAc with a molar mass Mn = 120,224 g / mol determined by analysis by gel permeation chromatography and the synthesis of organophilic clay (TBA-maghnite) derived from cation exchange of sodium-clay with Tetrabutylammonium hydrogen sulfate which is characterized by short chains, this exchange has been proven with X-ray diffraction (XRD). These clays were also characterized by infrared spectroscopy and scanning electron microscopy (SEM). The nanocomposites polymer clay NCPCs were prepared by intercalation of the PVAc polymer within the sheets of organophilic clay under a process of intercalation in solution, The mixture was carried out with different percentages of TBA-Maghnite 1 wt.%, 3 wt.% and 4 wt.%. The exfoliated nanocomposites (PVAc / TBA-Maghnite) were obtained at a concentration of 1 wt.% and 3 wt.%, the Different PVAcNCs were characterized using elemental analysis FTIR, XRD, SEM and dynamic light scattering. The mechanical dynamic study has been well determined in this work. The thermal properties of the nanocomposite were investigated using differential scanning calorimetry and thermogravimetric analysis. PVAcNCs showed better viscoelastic property and good thermal stability compared to pure PVAc.

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions

AbstractOrganophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO2 and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6‐Tris[tri(1‐pyrrolidinyl)‐iminophosphorane]‐1,3,5‐triazine (C3N3‐Py‐P3) with a relatively low basicity (pKa=26.5 in CD3CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO2 and cyclohexene oxide (CHO), and produced CO2‐based polycarbonates (CO2‐PCs) with high molar masses (Mn up to 275.5 kDa) at 1 MPa of CO2 and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO2/CHO copolymerization with TOF up to 95 h−1 at 1 atm pressure and room temperature.

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions.

Organophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO2 and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine (C3 N3 -Py-P3 ) with a relatively low basicity (pKa =26.5 in CD3 CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO2 and cyclohexene oxide (CHO), and produced CO2 -based polycarbonates (CO2 -PCs) with high molar masses (Mn up to 275.5 kDa) at 1 MPa of CO2 and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO2 /CHO copolymerization with TOF up to 95 h-1 at 1 atm pressure and room temperature.

Conductive polycaprolactone/gelatin/polyaniline nanofibres as functional scaffolds for cardiac tissue regeneration

The endorsement of functional features such as biocompatibility, mechanical integrity, or electrical conductivity to tissue engineering (TE) scaffolds is essential to stimulate cell adhesion and proliferation. In this study, electrospun nanofibers based on polycaprolactone (PCL) and gelatin (Ge) (ratios 60/40, 50/50, and 40/60), and polyaniline (PAni) particles (0.25, 0.50, and 1.00%wt) were prepared. The time of dissolution in an acid solvent mixture before electrospinning allowed for obtaining nanofibers with controlled features. Changes in the molar mass (Mn from 90·103 to 15·103 g·mol−1), in the crystalline microstructure (Xc from 60 to 25%) and the surface morphology (diameter from 250 to 50 nm) due to the controlled hydrolytic action on PCL were found. In vitro degradability and biocompatibility were favoured as the dissolution time and gelatin percentage increased. The presence of PAni was revealed as non-cytotoxic and promoted a controlled increase of the electrical conductivity, that contributed to in vitro cardiomyocyte proliferation. Cellular centres in the vicinities of PAni microparticles could be identified in the scaffold with the 40/60 PCL/Ge scaffold with PAni (1.00%wt), keeping the macrophages profile unaltered, which may determine the satisfactory resolution of cardiac injury and point out these scaffolds as appropriate candidates for cardiac TE.

Lactides and Lactones Yielding Eco-Friendly and Biocompatible Polymers by Metal-Catalyzed Ring-Opening Polymerization

Currently, there is a growing interest in the development of suitable methods for the preparation of eco-friendly and biocompatible materials in order to increase environmental protection and reduce human health risk. Therefore, this mini-review summarizes several studies involving lactides and lactones as monomers for the synthesis of biodegradable and biocompatible polymers via metal-catalyzed Ring-Opening Polymerization (ROP). Hence, synthetic approaches involving mono, bi and trinuclear metallic catalysts, with different catalytic activity, were reviewed. Complexes mostly based on metals such as Na, Mg, Al, Ti, Zn are considered. Generally, from ROP reactions, it has been found that conversion, stereoselectivity, number-average molar mass (Mn) and dispersity of the molar mass (Ð) of polymers are influenced by the type of monomer, the characteristics of the catalyst, the nature of the solvent, temperature and reaction time. Additionally, the polymer properties can also be controlled by varying the molar ratios between the monomer and the initiating system. Thus, this review may be found helpful for the scientific community and students involved in research in different areas of chemistry such as organic chemistry, inorganic chemistry, polymers chemistry, and materials science. The survey covers selected data published between 2017 and 2020; however, previous relevant reports were also studied.

Poly(HPMA-co-NIPAM) copolymer as an alternative to polyethylene glycol-based pharmacokinetic modulation of therapeutic proteins

PEGylation is the standard approach for prolonging the plasma exposure of protein therapeutics but has limitations. We explored whether polymers prepared by Reversible Addition-Fragmentation chain-Transfer (RAFT) may provide better alternatives to polyethylene glycol (PEG). Four RAFT polymers were synthesised with varying compositions, molar mass (Mn), and structures, including a homopolymer of N-(2-hydroxypropyl)methacrylamide, (pHPMA) and statistical copolymers of HPMA with poly(ethylene glycol methyl ether acrylate) p(HPMA-co-PEGA); HPMA and N-acryloylmorpholine, p(HPMA-co-NAM); and HPMA and N-isopropylacrylamide, p(HPMA-co-NIPAM). The intravenous pharmacokinetics of the polymers were then evaluated in rats. The in vitro activity and in vivo pharmacokinetics of p(HPMA-co-NIPAM)-conjugated trastuzumab Fab' and full length mAb were then evaluated. p(HPMA-co-NIPAM) prolonged plasma exposure more avidly compared to the other p(HPMA) polymers or PEG, irrespective of molecular weight. When conjugated to trastuzumab-Fab', p(HPMA-co-NIPAM) prolonged plasma exposure of the Fab' similar to PEG-Fab'. The generation of anti-PEG IgM in rats 7 days after intravenous and subcutaneous dosing of p(HPMA-co-NIPAM) conjugated trastuzumab mAb was also examined and was shown to exhibit lower immunogenicity than the PEGylated construct. These data suggest that p(HPMA-co-NIPAM) has potential as a promising copolymer for use as an alternative conjugation strategy to PEG, to prolong the plasma exposure of therapeutic proteins.

Precise synthesis of α,ω-chain-end functionalized poly(dimethylsiloxane) with azide groups based on metal-free ring-opening polymerization and a quantitative azidation reaction

We have so far developed a method for the controlled ring-opening polymerization of cyclotrisiloxane catalyzed by strong organobasic compounds to produce various chain-end functionalized polysiloxanes with controlled number-average molar mass (Mn) and narrow molar-mass dispersity (ÐM) values. In this study, well-defined α,ω-chain-end functionalized poly(dimethylsiloxane) with azide groups (N3-PDMS-N3) possessing a narrow ÐM range (ÐM = 1.04) and a relatively high Mn of up to 28.2 kg mol−1 was precisely synthesized in a mixed solvent of tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) in the presence of quaternary ammonium salts as catalysts; N3-PDMS-N3 was obtained by converting α,ω-chain-end functionalized PDMS with bromomethyl groups (Br-PDMS-Br), which was prepared by polymerizing hexamethylcyclotrisiloxane (D3), water, and 1,3-trimethylene-2-n-propylguanidine (TMnPG) as the monomer, the initiator, and the catalyst, respectively. It was necessary to choose proper solvents depending on the Mn of Br-PDMS-Br to achieve the complete conversion of the bromomethyl groups by the azidation reaction. Moreover, we demonstrate the model reaction of copper-catalyzed 1,3-dipolar cycloaddition between N3-PDMS-N3 and phenylacetylene. As a result, the cycloadducted compound was exclusively obtained while maintaining a low ÐM value of 1.06 by employing copper(I) bromide and triethylamine as the catalyst and the ligand, respectively. This system was also effective for a polymer-polymer coupling reaction. Indeed, we successfully synthesized an ABA-type triblock copolymer where A and B are polystyrene (PS) and PDMS segments by reacting N3-PDMS-N3 with ω-chain-end functionalized PS with an alkynyl group.

A Comparison of Adhesion Behavior of Urea-Formaldehyde Resins with Melamine-Urea-Formaldehyde Resins in Bonding Wood

This paper reports a comparison of adhesion behavior of urea-formaldehyde (UF) with those of melamine-urea-formaldehyde (MU) resins in bonding wood by analyzing the results published in literatures. For this purpose, the adhesion behavior of UF resins prepared by blending low-viscosity resin (LVR) with high-viscosity resin (HVR) at five different blending and two formaldehyde/urea (F/U) molar ratios (1.0 and 1.2) was compared with those of two MUF resins synthesized by either simultaneous reaction (MUF-A resins) or multi-step reaction (MUF-B resins) with three melamine contents (5, 10, and 20 wt%). As the blending (LVR:HVR) ratio increased from 100:0 to 0:100, the viscosity and molar mass (Mw and Mn) of the blended UF resins increased while the gelation time decreased. The interphase features such as maximum storage modulus (E′max), resin penetration depth, and bond-line thickness of the UF resins increased to a maximum and then decreased as the blending ratio increased. In addition, both MUF-A and MUF-B resins also showed an increase in the Mw and Mn as the melamine content increased from 5% to 20%. However, the E′max, resin penetration depth, and bond-line thickness of the MUF resins decreased as the molar mass or melamine content increased. These results indicated that the adhesion of UF resins heavily depends on the interphase features while that of the MUF resins highly depends on the cohesion of the resins.

Functionalizable coaxial PLLA/PDLA nanofibers with stereocomplexes at the internal interface

Multifunctionality of electrospun polylactic acid (PLA) nonwovens was generated by the morphological design of nanofibers. Coaxial fibers with a lower number average molar mass Mn PLLA core and a higher Mn PDLA shell form PDLA–PLLA stereocrystals at the interface, induced by annealing. In tensile tests under physiological conditions, the core–shell fibers with higher crystallinity (22% compared to 11–14%) had lower Young’s moduli E (9 ± 1 MPa) and lower elongation at break εb (26 ± 3%) than PDLA alone (E = 31 ± 9 MPa, εb = 80 ± 5%), which can be attributed to simultaneous crystallization and relaxation effects. Gelatin incorporated in the PDLA phase was presented on the outer surface providing a biointerface putatively favorable for cell adherence. Gelatin incorporation did not influence the crystallization behavior but slightly lowered Tg (60 → 54 °C). Employing exclusively polymers established in the clinic, multifunctionality was generated by design.Graphic abstract

Green Stereoregular Polymerization of Poly(methyl methacrylate)s Through Vesicular Catalysis

Green Stereoregular Polymerization of Poly(methyl methacrylate)s Through Vesicular Catalysis