Polycondensation Of Acid Research Articles

New marine-derived indolymethyl pyrazinoquinazoline alkaloids with promising antimicrobial profiles

Due to the emergence of multidrug-resistant pathogenic microorganisms, the search for novel antimicrobials is urgent. Inspired by marine alkaloids, a series of indolomethyl pyrazino [1,2-b]quinazoline-3,6-diones was prepared using a one-pot microwave-assisted multicomponent polycondensation of amino acids. The compounds were evaluated for their antimicrobial activity against a panel of nine bacterial strains and five fungal strains. Compounds 26 and 27 were the most effective against Staphylococcus aureus ATCC 29213 reference strain with MIC values of 4 μg mL−1, and a methicillin-resistant Staphylococcus aureus (MRSA) isolate with MIC values of 8 μg mL−1. It was possible to infer that enantiomer (−)-26 was responsible for the antibacterial activity (MIC 4 μg mL−1) while (+)-26 had no activity. Furthermore, compound (−)-26 was able to impair S. aureus biofilm production and no significant cytotoxicity towards differentiated and non-differentiated SH-SY5Y cells was observed. Compounds 26, 28, and 29 showed a weak antifungal activity against Trichophyton rubrum clinical isolate with MIC 128 μg mL−1 and presented a synergistic effect with fluconazole.

Nanodrug Carrier Based on Poly(Ursolic Acid) with Self‐Anticancer Activity against Colorectal Cancer

AbstractAs the second most common cause of cancer‐related death worldwide, colorectal cancer (CRC) requires novel therapy strategies. Biodegradable polymers are used as drug carriers for treating CRC and other cancers. However, one of the limitations for the polymeric drug carriers is that they do not directly involve the treating procedure. Herein, to develop a polymeric drug delivery system with additional therapeutic effect from that of the polymer itself, poly(ursolic acid) (PUA) is, for the first time, simply synthesized via polycondensation of ursolic acid (UA), a bioactive ingredient widely distributed in herbal medicine. PUA can self‐assemble into nanoparticles (PUA‐NPs) with a diameter of ≈122 nm and an effective load of ≈10.1%, and deliver drugs, such as paclitaxel (PUA‐NPs@PTX). In vitro studies show that PUA‐NPs@PTX have strong cytotoxicity against colorectal cancer CT26 cells, while in vivo results indicate that these NPs have a prolonged blood circulation time, enhanced tumor accumulation, and significantly improved antitumor efficacy in CT26 tumor‐bearing mice. Furthermore, both in vitro and in vivo results confirm that the PUA‐NPs themselves have therapeutic effects on CT26 cells, without causing obvious toxicity to main organs, such as bledding or necrosis. In summary, such a therapeutic polymer platform provides a new therapeutic strategy for treating cancer.

A biobased aliphatic polyester derived from 10-hydroxydecanoic acid: Molecular weight dependence of physical properties

Poly(10-hydroxydecanoate) (PHDA) is of interest as a new-type aliphatic polyester due to its bioresource and flexible mechanical property. A series of PHDAs with varied molecular weights (Mn from 27 kg/mol to 74 kg/mol) were prepared by optimized melt polycondensation of 10-hydroxydecanoic acid (HDA). Through DSC, WAXD, POM and tensile tests, the effects of molecular weight on the physical properties, including thermal properties, crystallization behavior, crystal morphology, rheological behavior and mechanical properties of PHDA were studied in detail. The results demonstrated that the physical properties of PHDA largely rely on the molecular weight. In particular, the brittle-ductile transition of PHDA occurred when the molecular weight increased up to 55 kg/mol. With the increase of molecular weight, the elongation at break was largely improved and finally exceeded 1400%. The ultimate tensile strength kept about 20 MPa. Hence, PHDA has a PE-like mechanical property. Our work highlights that PHDA is a polymer with excellent performance, which provides an alternative to durable petroleum resourced packaging materials.

Polymerization products of lactic acid as synthetic thickening agents for textile printing

Novel biodegradable synthetic thickener was prepared to afford high-quality printed fabrics with decreased wastewater pollution. Biodegradable poly(lactic acid-methacrylic acid) P(LA-MAA) crosslinked polymer hydrogel was formulated in-situ via one-pot reaction employing polycondensation of lactic acid and methacrylic acid followed by free radical polymerization with N,N-methylene diacrylamide crosslinker. The molecular structure of the crosslinked polymer was characterized by 1H NMR and FT-IR. The rheological properties and biodegradation of the prepared composite hydrogels were investigated. The biodegradability was described by studying both of biological oxygen demand (BOD) and chemical oxygen demand (COD). Technical evaluation of P(LA-MAA) as an environmentally friendly thickener in textile printing using a variety of fabrics, including polyester, wool, acrylic, cotton, silk, cotton/polyester, wool/nylon and wool/polyester fabrics was presented. The use of composite thickener to print pigment and different classes of dyestuffs, including acid, disperse, reactive and metal complex dyestuffs was explored. Printed textile substrates, using different composites of different lactic acid ratios, displayed soft handle, and their color strength and colorfastness properties were efficiently similar to prints from commercial thickeners.

A Physicochemical Study of the Process of Modification of Carbon Sorbents with Lactic Acid

With the aim of creating new adsorbing materials with biospecific properties for applications in medicine (obstetrics and gynecology), a technique for the chemical modification of a molded carbon sorbent with lactic acid by polycondensation of the latter on the surface of the former without catalysts is proposed. The completeness of the process of polycondensation of lactic acid on a molded carbon sorbent was controlled by physicochemical methods (low-temperature nitrogen absorption and thermal analysis). The amount of the deposited modifier (lactic acid oligomer) is a determining factor of the completeness of the modification process, which is determined from the results of thermogravimetric analysis of samples. The optimal conditions of the impregnation and thermal processing of a molded carbon sorbent, under which the amount of the deposited modifier reaches the maximum value and equals 7.2–10.5 wt %, have been chosen on the basis of the results of studies. The elemental composition and the content of surface functional groups of the two most promising samples of modified molded carbon sorbents are analyzed. These modified samples are of interest for further analyses and a study of their adsorption properties.

Full biodegradable elastomeric nanocomposites fabricated by chitin nanocrystal and poly(caprolactone-diol citrate) elastomer

Chitin nanocrystal is a biocompatible and biodegradable nanofiller, with great potential in enhancing the mechanical and biological properties of polymers. Poly(caprolactone-diol citrate) is a kind of citrate-based biodegradable elastomer prepared by an additive-free melt polycondensation of polycaprolactone-diol and citric acid coupled with subsequent thermocuring. Here, a facile casting/evaporation method was utilized to prepare full biodegradable poly(caprolactone-diol citrate)/chitin nanocrystal nanocomposites, and their structure and properties were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, uniaxial tensile test, dynamic mechanical analysis, surface wettability and swelling analysis, thermogravimetric analysis, in vitro degradation, and cytocompatibility test. The results showed the chitin nanocrystals were uniformly distributed in the poly(caprolactone-diol citrate) matrix; with increasing chitin nanocrystal loading, the tensile modulus and strength significantly increased; furthermore, the incorporation of chitin nanocrystals endowed the poly(caprolactone-diol citrate) with more hydrophilicity, lower swelling in phosphate buffered saline solution, slow degradation rate, and greatly improved cytocompatibility. Thus, the chitin nanocrystal was a good bio-based nanofiller that could be used to tune the properties of poly(caprolactone-diol citrate) degradable bioelastomer.

One-pot amphiphilic engineering of bioresorbable polymers for constructing colloidal vesicles and prolonging protein delivery

In this study, we sought to develop methods for amphiphilic engineering of bioresorbable polymers, sorbitan–poly(lactic acid) (sorbitan–PLA) and poly(ethylene glycol)–polylactic acid (PEG–PLA), by melt polycondensation of lactic acid in the presence of the binary initiators sorbitan and methoxy PEG in a single reactor. Briefly, oligo(lactic acid) (OLA) was first prepared by distilling water out of lactic acid under vacuum; then, sorbitan and methoxy PEG were introduced in the reactor, followed by the simultaneous polycondensation of OLA onto sorbitan and methoxy PEG, resulting in a mixture containing sorbitan–PLA/PEG–PLA copolymers. Without further purification, the recovered products were dissolved in saline buffer, mixed with squalane oil, and then homogenized to construct a stable colloidal vesicle. Then, we conducted a mechanistic study to progressively elucidate the relationship between the dispersion structure and the sustained release of a model protein bovine serum albumin. This one-pot approach has potential for applications and commercial use in the field of biodegradable controlled-release delivery systems. This study describes the production of the amphiphilic bioresorbable polymers sorbitan–PLA and PEG–PLA in a single reactor. This method aims to simplify the separation process and reduce purification costs while increasing the chemical yield. The obtained mixtures could stabilize squalene/water interfaces, resulting in a double-dispersion structure that is favorable for encapsulation in sustained delivery applications.

Modification of Oligo- and Polylactides With Macrocyclic Fragments: Synthesis and Properties.

Products of lactic acid polycondensation (poly- and oligolactic acids) are widely used as packaging materials, drug delivery agents, implants etc. Variety of their applications is caused by a number of practically important properties, e.g., biocompatibility and biodegradability, non-toxicity, and mechanical durability. Modification of these polymers with different additives allows improving their properties and extending future applications. In this manner, stability toward degradation, recognition of some substrates, extended thermal stability etc. can be improved. Macrocyclic compounds are promising candidates as modifiers. They are able to provide polymer materials with additional binding sites, impart certain orientation to spatial arrangement of polymer chains, change hydrophilic-lipophilic balance, and redox properties. The latter one can be used for assembling various electrochemical sensors and biosensors that combine steric discrimination of the analytes caused by oligolactides and highly sensitive response to their quantities caused by redox labels introduced. Different composite materials based on oligolactides as matrices for such redox labels were described in the assemblies of biosensors for drugs, pesticides, and antioxidants detection. In this mini-review, methods for the synthesis of the lactic acid oligomers and those modified with the macrocyclic fragments (porphyrin, cyclodextrin, and cyclophane) have been described. The effects of modifiers on complexation, thermal, and aggregation properties of materials are described. Analytical performance of oligolactide based sensors and biosensors has been considered with particular emphasis to the mechanism of signal generation.

PREPARATION OF LACTIC ACIDOLIGOMER

The process of obtaining of lactic acid oligomer as by-product for synthesis of biodegradable polylactide was investigated. Synthesis of oligomer was carried out by azeotropic distillation of water. Aromatic hydrocarbons such as toluene, chlorobenzene, bromobenzene and o-dichlorobenzene were used. They form heteroazeotropes. This allowed to control the volume of distilled water. The time of obtaining of oligomer of lactic acid in presence aromatic hydrocarbons and without them was compare in the article. The reaction of obtaining of oligomer was carried out in a rotary vacuum evaporator and in laboratory distillation installation in presence of catalyst (ZnO in the amount of 1.5% by weight) for reaction assessment. It was shown that the using of azeotropic distillation of water from reaction mass allow to reduce the time of oligomer synthesis compared to standard distillation of water from the lactic acid solution. It implements by reducing of viscosity of reaction mass that improves heat and mass transfer in the reactor. These factors contribute to increase rate of distillation of solution water and water which release in the process of polycondensation of lactic acid. The oligomer yield also increases. The actual control of concentrating of the aqueous solution of lactic acid and the oligomer obtaining reaction carried out according to the rate of distillation of the water from the reactor. Also the control was carried out by changing the molecular weight of the oligomer. The molecular weight of the oligomers obtained was determined by gel permeation chromatography. It reached 1600 g/mol. Lactic acid oligomer of a linear structure was obtained under these conditions. IR spectra of the oligomer of lactic acid indicate the simultaneous process of concentration of the lactic acid solution and polycondensation of lactic acid.

Numerical simulation of orthosilicic acid polycondensation and silica particles formation inhydrothermal solutions

Numerical simulation of the process of polycondensation of orthosilicic acid and colloid silica particles growth under different physical and chemical conditions was done: temperature, pH, ionic strength and other. Calculated dependences of orthosilicic acid concentration and mean radius of silica particles versus time, graphs of particles dimensions distributions were received. Results of calculations were compared with experimental data. Research is important for to make clear role of colloid silica on hydrothermal mineral formation and for industrial extraction and utilization of silica, and also for mineral synthesis.

Numerical Simulation of the Polycondensation of Orthosilicic Acid and of the Formation of Silica Particles in Hydrothermal Solutions

This paper reports numerical modeling work for the polycondensation of orthosilicic acid (OSA) and the growth of the number of silica particles (SiO2) in hydrothermal solutions under a variety of physical and chemical conditions: temperature, pH, ionic strength, etc. We have derived relationships to calculate the concentration of orthosilicic acid and the mean radii of silica particles in relation to time and made plots showing the distribution of particles over size. The results were compared with experimental data. This study is important for investigating the role of colloidal silica in hydrothermal mineralization and for practical extraction and applications of silica, as well as for synthesis of minerals.

Synthesis of nanodispersed titanium dioxide via pH-controlled polymerization of titanium acid

The possibility of synthesis of highly photoactive nanosized titania employing ion exchange to exert control over polycondensation of titanium acid in aqueous medium has been demonstrated. The resultant spherical TiO2 nanoparticles exhibits extra high light-induced oxidation activity remaining for some time even after termination of UV illumination. The nanodispersed titania readily penetrate into the surface pores and can be used for deposition of photocatalytic coatings by impregnation technique.

Direct Metal‐Free Preparation of Functionalizable Polylactic Acid‐Ethisterone Conjugates in a One‐Pot Approach

AbstractA series of polylactic acid (PLA) conjugates (PLA‐ES) are synthesized via direct melt polycondensation (DMP) of lactic acid (LA) with ethisterone (ES) in the presence of 0.3 wt% toluenesulfonic acid at 160 °C for 6 h. The drug content of PLA conjugates can be simply adjustable. Further functionalization via Click chemistry is also achieved to extend the biomedicine application of biopolymer based drug delivery.

A mild method to prepare high molecular weight poly(butylene furandicarboxylate-co-glycolate) copolyesters: effects of the glycolate content on thermal, mechanical, and barrier properties and biodegradability

The melt polycondensation of glycolic acid based copolymers with high molecular weights remains a big challenge.

Self-encapsulation and controlled release of recombinant proteins using novel silica-forming peptides as fusion linkers

Recently, the potential use of biomimetic silica as smart matrices for the auto-encapsulation and controlled release of functional proteins has gained increased interest because of the mild synthesis conditions. Inspired by biological silicification, in this study, we studied novel silica-forming peptides (SFPs), Volp1 and Salp1, to mediate the generation of silica hybrids in vitro. The fusion of SFPs to model fluorescent proteins directed their auto-encapsulation in wet sol-gel silica materials. Furthermore, the SFPs served as affinity linkers for the immobilization of recombinant proteins in silica. Interestingly, the SFP fusion proteins modulated silicic acid polycondensation and allowed for the self-immobilization of SFP fusion proteins in two distinct silica formulations depending on the ionic strength—precipitated silica particles or wet silica gel. The controlled release of Salp1/Volp1 fusion proteins from silica matrices was significantly greater than that of the silaffin R5 fusion proteins. Subsequently, we showed that multiple SFP-tagged proteins homogenously entrapped within a silica matrix could be separately released following pre-incubation with different concentrations of l-arginine solution. These new findings provide a simple and reproducible route for silica hybrid formation for in situ stable auto-encapsulation and the sustained release of recombinant proteins with potential applications in biotechnology.

New degradable composite elastomers of POC/PCL fabricated via in-situ copolymerization blending strategy

Poly(1, 8-octanediol citrate) (POC) degradable elastomer have attracted much attention due to its good biological properties. However, there is a compromise, i.e. to improve its extendibility inevitably leads to a sticky feature that causes inconvenient handling. Poly(ε-caprolactone) (PCL) is a commonly used biodegradable, flexible polyester applied in a variety of FDA-approved products. Here, an in-situ copolymerization blending strategy, i.e. melt polycondensation of citric acid and 1, 8-octanediol in the presence of PCL was adopted to produce a POC/PCL composite elastomer, in which partial PCL took part in polycondensation reaction and chemically bonded into the POC network, and the rest physically traversed within the network structure, leading to a transparent, flexible composite elastomer. The wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) analyses confirmed a full-amorphous structure and no crystallization of PCL occurring. Moreover, the introduction of PCL not only improved extendibility but avoided stickiness. Compared to the POC, the time for curing POC/PCL prepolymers was highly reduced; and the degradation of composite elastomers in PBS solution was accelerated despite the slow degradation of PCL incorporated; additionally, surface erosion degradation presumably happened for POC/PCL elastomers, which would allow the implant to retain inner strength for a longer time.

Optimization of Poly(glycerol sebacate) Synthesis for Biomedical Purposes with the Design of Experiments

Efficient, original synthesis of poly(glycerol sebacate) (PGS) via polycondensation of glycerine and sebacic acid was achieved. The process was successfully optimized by using the Box–Behnken design. PGS was obtained with a high conversion of the carboxylic group (89%) and a very high degree of esterification (∼82%), containing no catalysts residues. A method was developed for purification of prepolymer PGS. Because biocompatible substrates are used, this method for obtaining the polymer can be used in medical and pharmaceutical applications.

Biobased flexible aromatic polyester poly(1,5-pentylene terephthalate) (PPeT): Revisiting melt crystallization behaviors and thermo-mechanical properties

Poly(1,5-pentylene terephthalate) (PPeT) is a less studied member of the family of terephthalic polyesters. The presence of flexible pentylene moiety and foreseeable commercialization of bio-based 1,5-pentanediol (PeDO) could make PPeT an attractive polymer. However, as a semi-crystalline flexible polyester, previous studies indicated that PPeT was hardly to crystallize nonisothermally from melt and showed clear brittleness. In this study, high molecular weight biobased PPeT (0.75 dL/g) was synthesized via melt polycondensation of terephthalic acid and biobased PeDO. It was characterized with 1H NMR and FTIR, and its crystallization/melting behaviors and thermo-mechanical properties were assessed with DSC, WAXD, TGA and tensile test. Different from previous reports, it is found that this high molecular weight PPeT product can crystallize slowly from melt, showing half crystallization time of 3.4 min when isothermally crystallized at 70 °C and melt crystallization enthalpy of 5.0 J/g at 61 °C when nonisothermally crystallized at cooling rate of 10 °C/min. It behaves as a typical flexible thermoplastic with excellent ductility rather than a brittle polymer, showing tensile modulus of 650 MPa, tensile stress at break of 21 MPa and elongation at break of 450%. It also exhibits excellent thermal stability.

Synthesis and Characterization of Poly(ester amide)s Consisting of Poly(L-lactic acid) and Poly(butylene succinate) Segments with 2,2′-Bis(2-oxazoline) Chain Extending

An aliphatic polyester based poly(ester amide)s (PEA) consisting of poly (L-lactic acid) and poly(butylene succinate) was successfully prepared via chain extension reaction of poly(L-lactic acid)-dicarboxylic acid (PLLA-COOH) and poly(butylene succinate)-dicarboxylic acid (PBS-COOH) using 2,2′-bis(2-oxazoline) as a chain extender. PLLA-COOH was obtained by direct polycondensation of L-lactic acid in the presence of 1, 4-succinic acid. PBS-COOH was synthesized by condensation polymerization of 1,4-butylene glycol with excessive succinic acid. The structures of PLLA-COOH, PBS-COOH, and PEAs were characterized by fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR). The molar masses were determined by gel permeation chromatography (GPC). The thermal properties of PLLA-COOH, PBS-COOH, and PEAs were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The lattice parameters of PLLA-COOH, PBS-COOH, and PEAs were investigated by X-ray diffraction (XRD). Furthermore, The mechanical properties were characterized by tensile testing and notch Izod impact testing. The FTIR and 1H NMR results demonstrated the formation of PLLA-COOH, PBS-COOH, and PEAs. The GPC measurements showed that the molar masses of copolymer PEAs decreased with increasing PBS-COOH content. The TGA analysis confirmed that the introduction of PBS improved the thermal properties. DSC data indicated that the melting temperatures of the PEAs were lower than that of the prepolymers. The results of XRD suggested that the PLLA crystal structures was destroyed by the PBS units, and the crystallization of the PEAs mainly attributed to the PBS chain segments.The introduction of PBS units into the polymer structure improved the toughness of PLLA, which was detected in mechanical properties.

Degradable Bioelastomers Prepared by a Facile Melt Polycondensation of Citric Acid and Polycaprolactone-diol

Citrate-based bioelastomers have great potentials in various biomedical fields. An appropriate selection of diol monomers could tune their properties to fulfill different application requirements. Herein, polycaprolacone diol (PCL-diol) was selected as the diol monomer to fabricate poly(caprolactone-diol citrate) (PCC) degradable bioelastomers by a one pot melt polycondensation coupled with subsequent thermosetting or post-polymerization. The catalyst-free polycondensation reaction was confirmed by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1HNMR) spectroscopy. The properties of the PCC elastomers were explored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), uniaxial tension tests, dynamics mechanical analysis (DMA), water-contact angle and in-vitro degradation measurements. The results showed that the molar ratio of monomers and thermosetting conditions had significant effects on the ultimate properties of the PCC elastomer. By regulating monomer ratio and thermosetting temperature the crosslink density ranged from 32 ± 6 mol/m3 to 292 ± 18 mol/m3, the tensile strength ranged from 171 ± 28 KPa to 977 ± 112 KPa, Young’s modulus ranged from 252 ± 36 KPa to 1737 ± 212 KPa, ultimate elongation ranged from 70 ± 9% to 260 ± 32%, the static-water-contact-angle was in the range of 65.4 ± 1.8 ∼ 91.0 ± 0.9° and the weight loss of the PCC elastomer in phosphate buffered saline (PBS) (pH =7.4) was in the range of 30 ∼ 100 wt% after 8 weeks degradation. An elastic and compressible, porous scaffold was fabricated via a salt leaching method, which has potential use in soft tissue grafts.