DL-lactic Acid Research Articles

New insight into thermo-solvent tolerant lipase produced by Streptomyces sp. A3301 for re-polymerization of poly (dl-lactic acid)

Poly (lactic acid) (PLA) is a biodegradable plastic that has received considerable attention since it plays an important role in replacing commercial plastics and resolving the global warming problem. Recently, biological degradation and polymerization studies of PLA have been an active topic. Microbial solvent-tolerant and thermostable lipases are interesting since they have the potential to induce PLA polymerization. The aims of this study are to isolate solvent-tolerant and thermostable lipase-producing actinomycetes and to apply the crude enzyme produced by an isolated strain for PLA polymerization. According to the results, the best solvent-tolerant and thermostable lipase-producing actinomycete was strain A3301, with a lipase activity of 108 U/ml in the production medium. The crude enzyme produced by strain A3301 demonstrated the optimum temperature and thermostability at 60 °C and 45–55 °C, respectively. Moreover, the enzyme showed the ability to tolerate 10–20% (v/v) hexane and toluene. Strain A3301 was identified as Streptomyces sp. by using the 16S rDNA sequence. A thermo-solvent-tolerant lipase from this strain was used in PLA polymerization experiments. The optimal conditions for PLA synthesis were 60 °C for 8 h, using dried lipase at a concentration of 10% (w/v) and a fixed lactic acid concentration of 450 g/L under a nitrogen atmosphere. The highest molecular weight of the PLA product was 525 Da, and the degree of polymerization was approximately 7. Subsequently, the repolymerization process of PLA using this enzyme was investigated. The maximum molecular weight of the PLA product was 577 Da, and the degree of polymerization was approximately 8.

Technological properties of autochthonous Lactobacillus plantarum strains isolated from sucuk (Turkish dry-fermented sausage).

Five Lactobacillus strains isolated from sucuk (Turkish dry-fermented sausage) were studied for their genetic and technological properties. For genotypic identification, strains 16S rRNA gene sequences were used. To determine the antimicrobial activity of strains, seven foodborne pathogens were tested. Strains technological properties were characterized. These strains were identified as Lactobacillus plantarum by 16S rRNA gene sequence analysis and the phylogenetic tree obtained by neighbor-joining method allowed grouping of these strains into three subgroups. L. plantarum strains showed antagonistic activities against Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Micrococcus luteus strains. PCR assay, using specific primers, showed the presence of bacteriocin (plantaricin) encoding genes in all L. plantarum strains tested. Antimicrobial metabolite production of these strains started at log phase and reached the maximum level at the end of the stationary phase. Regarding their technological properties, better growth was observed at 25 °C compared with 15 °C and 45 °C. The isolates which grown well within the pH scale pH 4.5-6.5 range additionally showed a decent growth at 6.5% salt concentration. It has been found that strains do not exhibit lipolytic and proteolytic activities nor have lysine, ornithine, and arginine decarboxylase activity. On the other hand, one strain showed weak nitrate reductase activity, and four strains produced acetoin from glucose. In addition, all strains were DL-lactic acid producers. Consequently, L. plantarum strains isolated exhibited some biochemical properties required for a starter culture in sucuk and similar products. All identified strains may be a protective culture in the production of fermented meat products. In particular, L. plantarum S51 was distinguished from other isolates due to the inability to form acetoin from glucose. Further work will be needed to characterize L. plantarum strains as starter culture.

Star-shaped polylactic acid-based triazine dendrimers: the catalyst type and time factors influence on polylactic acid molecular weight

Nowadays, extensive environmental problems due to the use of synthetic polymers have provoked efforts for their replacement with biopolymers as the most important research priorities. Polylactic acid (PLA) is one of the well-known biodegradable biopolymers. In this work, for the first time, PLA was modified with hydrophilic triazine-based dendrimers to obtain PLA with improved hydrophilic properties. In this regard, at first, dl-lactic acid (DLLA) was polymerized through the melt polycondensation to obtain poly-dl-lactic acid (PDLLA). The effects of reaction time and catalyst types on the molecular weight of the PDLLA were investigated. Also, the thermal behavior of PDLLAs with different molecular weights was evaluated using differential scanning calorimetry (DSC) technique. The obtained results from the DSC analysis showed that the PDLLA with higher molecular weight has a higher glass transition temperature (Tg) and melting point (Tm). In the following, various generations (G) of the triazine-based dendrimers were synthesized. To increase the hydrophilicity of the prepared PDLLA, chemical modification of PDLLA with the different generations of triazine-based dendrimer (G1, G1.5 and G2) was performed. Due to the modification of PDLLA with dendrimers, the number of functional groups and hydrophilicity of PDLLA increased. Based on the obtained results, it is expected that the prepared systems could be a good and promising candidate for the production of biocompatible plastics with more hydrolytic degradation ability.

Cell-mimic polymersome-shielded islets for long-term immune protection of neonatal porcine islet-like cell clusters.

Although islet cell transplantation has emerged as a promising treatment for type 1 diabetes, it remains an unmet clinical application due to the need for immunosuppression to prevent islet elimination and autoimmunity. To solve these problems, we developed novel nanoencapsulation of neonatal porcine islet-like cell clusters (NPCCs) with cell-mimic polymersomes (PSomes) based on PEG-b-PLA (poly(ethylene glycol)-b-poly(dl-lactic acid)). To accomplish this, we first formulated NHS-, NH2-, COOH-, and m(methoxy)-PSomes. This coating utilizes interactions involving NPCC surfaces and PSomes that have covalent bonds, electrostatic interactions, and hydrogen bonds. We extended the range of applicability by comparing the binding affinity of electrostatic attraction and hydrogen bonding, as well as covalent bonds. Our protocol can be used as an efficient hydrogen bonding method because it reduces cell membrane damage as well as the use of covalent bonding methods. We verified the selective permeability of NHS-, NH2-, COOH-, and m-PSome-shielded NPCCs. Furthermore, we showed that a novel nanoencapsulation did not affect insulin secretion from NPCCs. This study offers engineering advances in islet encapsulation technologies to be used for cell-based transplantation therapies.

221 Isolation of turkey spermatogonia

Across different types of spermatogenic epithelium, researchers have focused on the study and production of spermatogonial stem cells and their use as genetic material for creating gene pool cryobanks of valuable breeds and lines of poultry. The aim of our research was to identify optimal conditions for obtaining and culturing turkey spermatogonia. A series of experiments were carried out to determine the optimal age of males for isolating spermatogonia and optimize conditions for their isolation and cultivation. Age-related features of turkey spermatogenesis were assessed by testis histological studies. Statistical analysis was performed using SPSS v15.0 (t-test; SPSS Inc./IBM Corp.). Turkey testis tissue was mechanically crushed and treated with enzymes: 0.1% collagenase and 0.25% trypsin. Purification of spermatogonia from other types of cells was performed by adhesion and separation. The conditions and duration of spermatogenic cell cultures were selected experimentally. Primary Sertoli cells of turkeys, Sertoli cells of roosters, STO cell line, and transplanted Sertoli cells of pigs (PTP) were used as a feeder layer for the cultivation of spermatogonia. Spermatogonia culture medium consisted of Dulbecco's modified Eagle's medium (DMEM)-high glucose supplemented with 5% fetal calf serum, 2mM α-glutamine, 10µLmL−1 MEM, 100x antibiotics, 10µLmL−1 ITS solution, 5×10−5 M mercaptoethanol, 5mgmL−1 albumin, 1µLmL−1 DL-lactic acid, 20ngmL−1 epidermal growth factor, 10ngmL−1 basic fibroblast growth factor, and 2ngmL−1 leukemia inhibitory growth factor (LIF). The SSEA-1 antibody was used for identification of spermatogonia colonies. Histological study of the turkey testes at different ages showed that in animals under 12 weeks, the population of generative cells was represented mainly by spermatogonia (P<0.05). Thus, spermatogonia were isolated from the testes of 4-wk-old males. Isolated cells were cultured for 24h, after which the supernatant containing non-adherent cells (mainly spermatogonia) was transferred to a new dish for continued culture. Maximal homogeneity of the cell population was detected after transferring non-adherent cells 3 times at 24-h intervals. The best cell growth was observed when spermatogonia were cultivated on turkey Sertoli cells. The number of these cells in suspension reached 81% purity. Formation of spermatogonia colonies was observed on Days 7 to 8 of cultivation, the presence of which was confirmed by immunohistochemical staining with SSEA-1. This study was supported by the Russian Science Foundation within project no.16-16-04104.

Heterocephalacria mucosa sp. nov., a new basidiomycetous yeast species isolated from a mangrove forest in Thailand.

Strains of yeast were isolated under a nitrogen-depleted culture condition from decaying tree bark (strain N-12.1) and from mangrove forest water (strain 1-7W.1) sampled at different locations within a mangrove forest site in Ranong province, Thailand. They were found to be genetically and phenotypically different from any currently recognised yeast species. Phylogenetic analysis of nucleotide sequence of three genes, the internal transcribed spacer region 1 and 2 plus 5.8S ribosomal RNA gene (ITS), D1/D2 domain of the large subunit ribosomal RNA gene (LSU D1/D2) and the small subunit of the ribosomal RNA gene (SSU), revealed that these two strains were related to but distinguished from Heterocephalacriaarrabidensis. Several distinct physiological characteristics of these two strains were detected, namely inability to assimilate glycerol, dl-lactic acid, succinic acid, citric acid, d-gluconic acid, and ability to grow well at 25 °C, which were different from those of H. arrabidensis. Accordingly, the name Heterocephalacria mucosa sp. nov., is proposed to accommodate this novel species. The MycoBank number is MB 828624.

Cyclic β-(1, 2)-glucan blended poly DL lactic co glycolic acid (PLGA 10:90) nanoparticles for drug delivery

Our group had previously reported the encapsulation efficiency of cyclic β-(1, 2)-glucan for various drugs. The current study is aimed at evaluating the use of glucan as a drug carrier system by blending with poly lactic-co- glycolic acid (L:G = 10:90). Nanoparticles of glucan (0.5, 5, 10 and 20 wt %) blended with PLGA and gentamicin were synthesized. Encapsulation efficiency was higher for the blends (93% with 20 wt % of glucan) than the PLGA alone (79.8%). The presence of glucan enhanced both the biodegradability, and biocompatibility of PLGA. Degradation of the nanoparticles in vitro, was autocatalytic with an initial burst release of active drug and the release profile was modeled using the Korsmeyer-Peppas scheme. In vivo studies indicated that the drug released from the blends had high volume of distribution, and greater clearance from the system. Pharmacokinetics of the drug was predicted using a double exponential decay model. Blending with PLGA improved the drug release characteristics of the cyclic β-(1, 2)-glucan.

Development of biodegradation process for Poly(DL-lactic acid) degradation by crude enzyme produced by Actinomadura keratinilytica strain T16-1

Plastic waste is a serious problem because it is difficult to degrade, thereby leading to global environment problems. Poly(lactic acid) (PLA) is a biodegradable aliphatic polyester derived from renewable resources, and it can be degraded by various enzymes produced by microorganisms. This study focused on the scale-up and evaluated the bioprocess of PLA degradation by a crude microbial enzyme produced by Actinomadura keratinilytica strain T16-1 in a 5 L stirred tank bioreactor. PLA degradation after 72 h in a 5 L bioreactor by using the enzyme of the strain T16-1 under controlled pH conditions resulted in lactic acid titers (mg/L) of 16,651 mg/L and a conversion efficiency of 89% at a controlled pH of 8.0. However, the PLA degradation process inadvertently produced lactic acid as a potential inhibitor, as shown in our experiments at various concentrations of lactic acid. Therefore, the dialysis method was performed to reduce the concentration of lactic acid. The experiment with a dialysis bag achieved PLA degradation by weight loss of 99.93%, whereas the one without dialysis achieved a degradation of less than approximately 14.75%. Therefore, the dialysis method was applied to degrade a commercial PLA material (tray) with a conversion efficiency of 32%, which was 6-fold more than that without dialysis. This is the first report demonstrating the scale-up of PLA degradation in a 5 L bioreactor and evaluating a potential method for enhancing PLA degradation efficiency. How to cite: Panyachanakul T, Sorachart B, Lumyong S, et al. Development of biodegradation process for Poly(DL-lactic acid) degradation by crude enzyme produced by Actinomadura keratinilytica strain T16-1. Electron J Biotechnol 2019;40. https://doi.org/10.1016/j.ejbt.2019.04.005

The effect of polyvinylpyrrolidone nanowires on the metabolic activity of Lactobacillus acidophilus

The effectiveness of the use of polyvinylpyrrolidone (PVP) nanowires for increasing the metabolic activity of probiotic cultures of Lactobacillus acidophilus has been shown. PVP nanowires are obtained by electrospinning in two versions: PVPI based on a solution of high molecular weight polyvinylpyrrolidone and distilled water; PVPII based on a solution of two water zinc acetate in distilled water and a solution of high molecular weight PVP in ethanol. In the presence of PVP, there was an increase in viable lactobacillus cells up to 7.4 108 CFU/ml and accumulation of DL-lactic acid during acidification of the test solution to 3.10 and an increase in Eh to + 360.5 mV. PVPI is a more preferred carrier for lactobacilli than PVPII with ZnO. The zinc ions contained in the PVP matrix are capable of causing oxidative stress, followed by the formation of free radicals that damage membrane lipids, proteins and DNA of the prokaryotic cell. The results are aimed at developing new forms of immobilized drugs that can be used as alternative probiotic agents.

Effect of assembly pH and ionic strength of chitosan/casein multilayers on benzydamine hydrochloride release

Multilayer biopolyelectrolyte films are built from chitosan and casein by layer-by-layer deposition onto corona precharged poly(DL-lactic acid) substrate. Such structure allows optimization with respect to the morphology and ability of drug immobilization and release by changing the assembly conditions. Variation of chitosan and casein solutions ionic strength and chitosan solution pH at constant casein solution pH, effects significantly the polyelectrolyte multilayer structure and drug release. pH and ionic strength increase change the morphology from dense to loose, and the ionic strength increase let to screening effect and complexation of the drug, resulting in slow drug release.

Physical properties of seven deep eutectic solvents based on l-proline or betaine

Density, ρ, refractive index, nD, speed of sound, u, and viscosity, η, of the betaine + dl-lactic acid (1:2), betaine + dl-lactic acid (1:5), betaine + dl-lactic acid-water (1:1:1), betaine-levulinic acid (1:2), betaine-citric acid-water (2:1:6), l-proline + levulinic acid (1:2) and l-proline + dl-lactic acid (1:1) deep eutectic solvents were measured at several temperatures from 293.15 K to 343.15 K and at atmospheric pressure. From the experimental data, coefficients of thermal expansion, α, isentropic compressibility, ks, and molar refraction, Rm, were calculated. Moreover the thermal behavior of these DESs, from glass transition to degradation temperature, was studied by differential scanning calorimetry and thermogravimetric analysis.

The mechanism behind the biphasic pulsatile drug release from physically mixed poly(dl-lactic(-co-glycolic) acid)-based compacts

Successful immunization often requires a primer, and after a certain lag time, a booster administration of the antigen. To improve the vaccinees’ comfort and compliance, a single-injection vaccine formulation with a biphasic pulsatile release would be preferable. Previous work has shown that such a release profile can be obtained with compacts prepared from physical mixtures of various poly(dl-lactic(-co-glycolic) acid) types (Murakami et al., 2000). However, the mechanism behind this release profile is not fully understood. In the present study, the mechanism that leads to this biphasic pulsatile release was investigated by studying the effect of the glass transition temperature (Tg) of the polymer, the temperature of compaction, the compression force, the temperature of the release medium, and the molecular weight of the incorporated drug on the release behavior. Compaction resulted in a porous compact. Once immersed into release medium with a temperature above the Tg of the polymer, the drug was released by diffusion through the pores. Simultaneously, the polymer underwent a transition from the glassy state into the rubbery state. The pores were gradually closed by viscous flow of the polymer and further release was inhibited. After a certain period of time, the polymer matrix ruptured, possibly due to a build-up in osmotic pressure, resulting in a pulsatile release of the remaining amount of drug. The compression force and the molecular weight of the incorporated drug did not influence the release profile. Understanding this mechanism could contribute to further develop single-injection vaccines.

In situ prepared poly(DL-lactic acid)/silica nanocomposites: Study of molecular composition, thermal stability, glass transition and molecular dynamics

The objective of the present study was to prepare a series of poly(DL-lactic acid) (PDLLA) nanocomposites with four different amounts of silica (SiO2) nanoparticles (2.5, 5, 10 and 20 wt%), following a new two-step synthesis route: ring opening polymerization of DL-lactide and polycondensation. Effects of different percentage of SiO2 on various properties such as molecular weight, crystallinity, thermal stability, glass transition temperature (Tg) and molecular dynamics, are discussed and compared with the theoretical models available in literature. Thermal stability of PDLLA was substantially enhanced from the addition of SiO2, while calorimetry and dielectric spectroscopy showed increased Tg in the nanocomposites, as well as indications for formation of interfacial rigid amorphous polymer fraction.

Risk assessment of diabetes mellitus using dried saliva spot followed by ultra-performance liquid chromatography with fluorescence and mass spectrometry

The dried saliva spot (DSS) seems to be a convenient sampling technique for bioanalysis. In our previous research, the DSS sampling was used for the determination of dl-lactic acid (DL-LA) and the D/L ratio of diabetic, pre-diabetic and healthy persons. However, the method required an expensive tandem MS/MS apparatus to obtain a highly sensitive detection. To avoid the use of such instrument, this paper proposes cheaper determination systems by ultra-performance liquid chromatography (UPLC) with fluorescence (FLR) and/or single mass spectrometry (MS). The carboxylic acids including DL-LA in the DSS were labeled with a chiral fluorescence reagent, (S)(+)-4-nitro-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (NBD-(S)(+)-APy), and determined by UPLC-FLR-MS. The limits of detection of LA by FLR and MS were approximately 1.0 μM (0.1 pmol) and 0.20 μM (0.02 pmol), respectively, whereas the limits of quantification were 5.0 μM (0.5 pmol) by FLR and 1.0 μM (0.1 pmol) by MS. The proposed DSS method was used for the determination of the enantiomers of LA of diabetic, pre-diabetic and healthy persons. The D/L-LA ratios obtained from the FLR were correlated with those of MS, although the ratios of the FLR were slightly lower than those of MS. Furthermore, the D/L-LA ratios of the present FLR or single MS were well correlated with those of the tandem MS/MS obtained from our previous study. The results indicated that the UPLC-FLR-MS was alterable to the previous UPLC-MS/MS method. Consequently, the proposed UPLC-FLR and/or UPLC-MS seem to be applicable as a cheaper screening method for diabetes mellitus using the DSS sampling.

Targeted Delivery of Amantadine-loaded Methacrylate Nanosphere-ligands for the Potential Treatment of Amyotrophic Lateral Sclerosis.

This study aimed to develop and analyse poly(DL-lactic acid)-methacrylic acid nanospheres bound to the chelating ligand diethylenetriaminepentaacetic acid (DTPA) for the targeted delivery of amantadine in Amyotrophic Lateral Sclerosis (ALS). The nanospheres were prepared by a double emulsion solvent evaporation technique statistically optimized employing a 3-Factor Box-Behnken experimental design. Analysis of the particle size, zeta potential, polydispersity (Pdl), morphology, drug entrapment and drug release kinetics were carried out. The prepared nanospheres were determined to have particle sizes ranging from 68.31 to 113.6 nm (Pdl ≤ 0.5). An initial burst release (50% of amantadine released in 24 hr) was also obtained, followed by a prolonged release phase of amantadine over 72 hr. Successful conjugation of the chelating ligand onto the surface of the optimised nanospheres was thereafter achieved and confirmed by TEM. The synthesized modified nanospheres were spherical in shape, 105.6 nm in size, with a PdI of 0.24 and zeta potential of -28.0 mV. Conjugation efficiency was determined to be 74%. In vitro and ex vivo cell study results confirmed the intracellular uptake of the modified nanospheres by the NSC-34 cell line and the non-cytotoxicity of the synthesized nanospheres. Biocompatible amantadine-loaded nanospheres were successfully designed, characterized and optimized employing the randomized Box-Behnken statistical design. Delivery of amantadine over 72 hrs was achieved, with the nanospheres being of a size capable of internalization by the NSC- 34 cells.This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Drug Compatibility and Distribution Assessments of a Bupivacaine-Polymer Formulation Measured Following Site-Directed Injection in Mice

Background: A long-acting local anaesthetic agent would enable superior post-operative analgesia. Our slow-release bupivacaine-polymer formulation comprising 15% bupivacaine loaded into a poly (DL-lactic acid co castor oil 3:7), DL-LA:CO was effective for up to 96 hours. In this study we determined in vivo drug levels of the formulation from plasma and tissue assay and we tested the feasibility of drug level assessments from an exudate sample collected in a novel device near the injection-site. Methods: Prior to formulation injection, a titanium cylinder dual-open-ended chamber was implanted in the dorso-lumber region of female ICR mice, to be used as a biological compartment. Following a healing period, the bupivacaine-polymer formulation was injected close to the sciatic nerve. Formulation assay samples were collected over one-week post-injection; exudate was drawn from the chamber in the anaesthetised animal; and blood and tissue samples from the sacrificed animal. Bupivacaine distribution in the exudate and plasma samples was determined by liquid chromatography–mass spectrometry developed for these experiments, and in tissue samples by high -performance liquid chromatography. Results: Bupivacaine was detected during the first 24h following formulation injection in all three samples (exudate, plasma and tissue), and decreased to almost undetectable levels by day 7 post-injection. Conclusion: Bupivacaine drug assay measured from an exudate sample may be applicable in addition or as a replacement for standard plasma and tissue assay in studies of drug pharmacokinetic distribution. The high sensitivity and simplicity of the metallic chamber implant to detect drug concentration and exudate analysis was confirmed in sever hepatic impairment.

Polymer-based nanoparticles loaded with a TLR7 ligand to target the lymph node for immunostimulation

Small-molecule agonists for the Toll-like receptors (TLR) 7 and 8 are effective for the immunotherapy of skin cancer when used as topical agents. Their systemic use has however been largely unsuccessful due to dose-limiting toxicity. We propose a polymer-based nanodelivery system to target resiquimod, a TLR7 ligand, to the lymph node in order to focus the immunostimulatory activity and to prevent a generalized inflammatory response. We demonstrate successful encapsulation of resiquimod in methoxypoly(ethylene glycol)-b-poly(DL-lactic acid) (mPEG-PLA) and mixed poly(DL-lactic-co-glycolic acid) (PLGA)/mPEG-PLA nanoparticles. We show that these particles are taken up mainly by dendritic cells and macrophages, which are the prime initiators of anticancer immune responses. Nanoparticles loaded with resiquimod activate these cells, demonstrating the availability of the immune-stimulating cargo. The unloaded particles are non-inflammatory and do not have cytotoxic activity on immune cells. Following subcutaneous injection in mice, mPEG-PLA and PLGA/mPEG-PLA nanoparticles are detected in dendritic cells and macrophages in the draining lymph nodes, demonstrating the targeting potential of these particles. Thus, polymer-based nanoparticles represent a promising delivery system that allows lymph node targeting for small-molecule TLR7 agonists in the context of systemic cancer immunotherapy.

Facile Production of Biodegradable Bipolymer Patchy and Patchy Janus Particles with Controlled Morphology by Microfluidic Routes.

Patchy and patchy Janus particles composed of poly(dl-lactic acid) (PLA) and polycaprolactone (PCL) regions were produced with a controlled size, patchiness, composition, and shape anisotropy by microfluidic emulsification and solvent evaporation. Isotropic particles composed of PCL patches embedded in the PLA matrix were produced from relatively small drops with a diameter of 14-25 μm because of the fast solvent extraction as a result of high interfacial area of the particles. Anisotropic patchy Janus particles were formed from large drops, 100-250 μm in diameter. A higher degree of polymer separation was achieved using a higher ratio of dichloromethane to ethyl acetate in the organic phase because of the more pronounced patch coarsening via Ostwald ripening. Janus particles with two fully separated polymer compartments were produced by in situ microfluidic mixing of two separate polymer streams within the formed droplets. The advantage of in situ micromixing is that the particle morphology can be changed continuously in a facile manner during drop generation by manipulating the organic stream flow rates. PCL and PLA domains within the particles were visualized by confocal laser scanning microscopy because of the preferential adsorption of rhodamine 6G dye onto PLA domains and higher binding affinity of Nile red toward PCL.

Development of new biodegradable packaging

The aim of this work was the development and the characterisation of biocomposite films obtained from a mixture of corn starch and microcrystalline cellulose and the study of the influence of a plasticisers mixture on the behaviour of these films. These have been characterised in order to use them as new formulations to produce films for food packaging. The films obtained are generally homogeneous, opaque, thin, smooth and having a good coherence with no visual defects. The results of the tests (water sorption isotherm, water vapour permeability, thermogravimetric and mechanical test) have shown improvements on the films’ properties using a plasticisers mixture (glycerol/DL-lactic acid) better than those obtained by plasticisation by glycerol or by DL-Lactic acid taken individually. This is explained by the fact that the plasticisers mixture (glycerol/DL-lactic acid) has a double plasticising effect: internal plasticisation due to the intercalation of polymer-substituted chains between the polymer chains and external plasticisation due to glycerol molecules. In addition, the hydrogen bonds formed in this new plasticisation are more stable than those formed during the use of glycerol or of the DL-lactic acid separately, thereby giving rise to a material with improved properties.

Novel ammonia sensor based on polyaniline/polylactic acid composite films

We propose a new type of ammonia sensor based on composite film between polyaniline (emeraldine base) dissolved in dimethylformamide, and poly(DL-lactic) acid dissolved in chloroform. The two solutions were mixed in weight ratio of the components 1:1 and cast on Al2O3 substrate, on which silver electrodes were deposited previously. The active layer structure and morphology were examined by atomic force microscopy. The sensor resistance at constant humidity and different ammonia concentrations was measured. It was found that an increase in the ammonia concentration leads to resistance increase. This result is explained in the terms of ionic interactions between the polyaniline and the ammonia, which change the permittivity of the sensor active media. A response between 2% and 590% was shown depending on the ammonia concentration. The sensor is reversible and possesses response time of typically 100 s. Based on the changes of the sensor resistance, ammonia concentration from 10 ppm to 1000 ppm could be detected.