Zinc Lactate Research Articles

The effect of a tooth/tongue gel and mouthwash regimen on morning oral malodour: A 3-week single-blind randomized clinical trial.

To compare the effects of a regimen consisting of a tooth/tongue gel, tongue cleaner and mouthwash with the effects of using standard fluoride dentifrice on the organoleptic oral malodour score (ORG) and volatile sulphur compounds (VSCs). A total, 66 non-dental students participated in a 3-week parallel, single-blind, randomized, controlled clinical trial. The test group used a tongue cleaner, a tooth/tongue gel and mouthwash containing amine fluoride/stannous fluoride and zinc lactate as oral malodour counteractive. The control group used a standard fluoride dentifrice. Measurements were taken in the morning at baseline, at days 1, 7 and 21. The primary outcome was the ORG score. The secondary outcome, the VSC measurement, was assessed using OralChroma™ (H2 S, CH3 SH, (CH3 )2 S) and Halimeter® . Tongue coating thickness and tongue discoloration were scored. At baseline and day 21, the participants' self-perceptions were assessed. At day 1 for the ORG, H2 S, CH3 SH and Halimeter® readings, a significant decrease was observed in the test group. At day 21, the decrease in H2 S and the Halimeter® outcomes were maintained for the test group, and a significant increase in tongue surface discoloration was observed. The test group evaluated their "morning breath upon awakening" as significantly better (P=.001) after 21days. A significant overnight effect on morning oral malodour was observed for most of the parameters in favour of the test group. At day 21, the effect of prolonged use was significant for H2 S and the Halimeter® readings, although not for the primary ORG outcome parameter.

Dietary zinc deficiency reduced growth performance, intestinal immune and physical barrier functions related to NF-κB, TOR, Nrf2, JNK and MLCK signaling pathway of young grass carp (Ctenopharyngodon idella)

Our study investigated the effects of dietary zinc (Zn) deficiency on growth performance, intestinal immune and physical barrier functions of young grass carp (Ctenopharyngodon idella). A total of 630 grass carp (244.14 ± 0.40 g) were fed graded levels of zinc lactate (10.71, 30.21, 49.84, 72.31, 92.56, 110.78 mg Zn/kg diet) and one zinc sulfate group (56.9 mg Zn/kg diet) for 60 days. At the end of the feeding trial, fish were challenged with Aeromonas hydrophila for 14 days. These results indicated that compared with optimal dietary Zn level, dietary Zn deficiency (10.71 mg/kg diet) decreased the production of antibacterial compounds, up-regulated pro-inflammatory cytokines related to nuclear factor kappa B (NF-κB) and down-regulated anti-inflammatory cytokines related to target of rapamycin (TOR) in three intestinal segments of young grass carp (P < 0.05), suggesting that dietary Zn deficiency could impair intestinal immune barrier of fish; decreased the activities and mRNA levels of antioxidant enzymes related to NF-E2-related factor 2 (Nrf2), up-regulated the mRNA levels of caspase-3, -7, -8, -9 related to p38 mitogen activated protein (p38 MAPK) and c-Jun N-terminal protein kinase (JNK), down-regulated the mRNA levels of tight junction complexes (TJs) related to myosin light chain kinase (MLCK) in three intestinal segments of young grass carp (P < 0.05), demonstrating that dietary Zn deficiency could injury intestinal physical barrier of fish. Besides, the Zn requirements (zinc lactate as Zn source) based on percent weight gain (PWG), against enteritis morbidity, acid phosphatase (ACP) activity in the proximal intestine (PI) and malondialdehyde (MDA) content in the PI of young grass carp was estimated to be 61.2, 61.4, 69.2 and 69.5 mg/kg diet, respectively. Finally, based on specific growth rate (SGR), feed efficiency (FE) and against enteritis morbidity of young grass carp, the efficacy of zinc lactate relative to zinc sulfate were 132.59%, 135.27% and 154.04%, respectively.

Kinetic modeling on batch-cooling crystallization of zinc lactate: The influence of malic acid

Influence of malic acid, which acts as an impurity, on the crystallization kinetics of zinc lactate has been investigated in this work. Crystallization of zinc lactate with a linear cooling profile was carried out in a batch crystallizer and a population balance model was used to estimate the crystallization kinetics for each studied system by using the nonlinear optimization method. The predicted results related to the concentration profile of zinc lactate are in good agreement with the experimental data. The influence of malic acid on the crystallization of zinc lactate is discussed herein.

Effectiveness of a pre-procedural mouthwash in reducing bacteria in dental aerosols: randomized clinical trial

The aim of this randomized, single blinded clinical trial was to evaluate the effect of a pre-procedural mouthwash containing cetylpyridinium chloride (CPC), zinc lactate (Zn) and sodium fluoride (F) in the reduction of viable bacteria in oral aerosol after a dental prophylaxis with ultrasonic scaler. Sixty systemically healthy volunteers receiving dental prophylaxis were randomly assigned to one of the following experimental groups (15 per group): (i) rinsing with 0.075% CPC, 0.28% Zn and 0.05% F (CPC+Zn+F), (ii) water or (iii) 0.12% chlorhexidine digluconate (CHX), and (iv) no rinsing. Viable bacteria were collected from different locations in the dental office on enriched TSA plates and anaerobically incubated for 72 hours. The colonies were counted and species were then identified by Checkerboard DNA-DNA Hybridization. The total number of colony-forming units (CFUs) detected in the aerosols from volunteers who rinsed with CPC+Zn+F or CHX was statistically significantly (p<0.05) lower than of those subjects who did not rinse or who rinsed with water. When all locations were considered together, the aerosols from the CPC+Zn+F and CHX groups showed, respectively, 70% and 77% fewer CFUs than those from the No Rinsing group and 61% and 70% than those from the Water group. The mean proportions of bacterial species from the orange complex were statistically significantly (p<0.05) lower in aerosols from the CPC+Zn+F and CHX groups compared with the others two groups. In conclusion, the mouthwash containing CPC+Zn+F, is effective in reducing viable bacteria in oral aerosol after a dental prophylaxis with ultrasonic scaler.

Efficacy of two mouthwashes with cetylpyridinium chloride: a controlled randomized clinical trial.

This study aimed to evaluate the anti-plaque and anti-gingivitis effects of two mouthwashes containing cetylpyridinium chloride (CPC), in comparison to negative control mouthwash. One hundred and twenty subjects were randomly assigned to study groups: test (0.075% CPC and 0.28% zinc lactate), positive control (0.07% CPC) and negative control mouthwash without CPC. All volunteers were examined by a calibrated examiner for the Quigley-Hein Plaque Index (Turesky modification) and Löe-Silness Gingival Index (GI). Gingival severity was also measured by the percentage of sites with positive gingival bleeding. During six weeks, oral hygiene consisted of brushing twice daily with a toothbrush and toothpaste and rising with their assigned mouthwash. Plaque and gingival parameters were assessed at baseline, after four and six weeks of product use. Statistical analyses were performed separately for plaque and gingival indices, by ANOVA, paired t-test and ANCOVA (α < 0.05). After 4 and 6 weeks, all mouthwashes groups presented statistically significant reductions in plaque and gingival parameters as compared to baseline. In comparison to the positive control, the test group presented additional reductions in dental plaque of 19.8% and 16.8%, after 4 and 6 weeks, respectively. For GI, the additional reductions in the test group were 9.7% and 14.3%, at 4 and 6 weeks, respectively. The test group showed additional reduction of 35.3% and 54.5% in the gingival severity, at week 4 and 6, respectively. It is concluded that the mouthwash containing CPC and zinc lactate presents significant anti-plaque and anti-gingivitis effects as compared to positive and negative control mouthwashes.

Changes of Some Biochemical Parameters in Rats Supplemented with High Doses of Zinc Lactate

Abstract The experiment was conducted on 18 Wistar rats during a six-week period; 12 animals were given zinc lactate (120 mg/rat and week) in feed mixture and 6 control animals were fed a standard mixture for rats (ST-1). Sixteen biochemical parameters were measured from blood (serum) samples: total protein (TP), albumin (ALB), urea (UREA), glucose (GLU), triacylglycerols (TAG), non-esterified fatty acids (NEFA), cholesterol (CHOL), creatinine (CREAT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), uric acid (UA), magnesium (Mg), calcium (Ca), phosphorus (P), and trace elements such as Fe and Zn. When compared to the control group, we found that rats fed zinc lactate had higher concentrations of GLU, UA, UREA, Fe, Mg, Ca, TAG, TP, ALB, and ALP in the blood serum. Contrarily, the concentrations of AST, NEFA, CHOL, CREAT, P, and Zn were higher in the blood serum of control rats. Statistically significant differences between rats fed Zn and the control were found only in the concentrations of GLU, AST, ALP, UA, and P.

새싹보리 클로로필의 색 안정화

To improve the color stability of chlorophyll in young barley leaf used as functional green biomaterial, the absorption spectrum, color values, and antioxidative activities of young barley leaf (YBL) treated with zinc ion solutions were investigated. The small pieces of fresh YBL in aqueous solution mixtures were autoclaved twice at 110℃ for 30 min (pH 5). Distilled water (BLA), 0.01% zinc chloride (BLAZ), 0.01% zinc citrate (BLAC), and 0.01% zinc lactate (BLAL) solutions were used. Treated YBL powders were extracted with 80% EtOH for 4 h. Chlorophyll a and b contents differed with different treatments. BLA decreased chlorophyll a and b contents, whereas others were maintained. Absorbance spectrums of chlorophyll at 400∼700 nm showed different maximum peak wavelengths. After heating in acidic and neutral solutions (pH 3, 5, and 7), the colors of YBL and BLA changed from green to olive green, whereas BLAZ, BLAC, and BLAL remained green color. The antioxidative activities showed higher values in YBL extract than in treated extracts. From the above results, autoclaved YBL in zinc solution would increase the color stability and maintain green color regardless of acid and heat treatments.

Simultaneous Assessment of Acidogenesis-Mitigation and Specific Bacterial Growth-Inhibition by Dentifrices.

Dentifrices can augment oral hygiene by inactivating bacteria and at sub-lethal concentrations may affect bacterial metabolism, potentially inhibiting acidogenesis, the main cause of caries. Reported herein is the development of a rapid method to simultaneously measure group-specific bactericidal and acidogenesis-mitigation effects of dentifrices on oral bacteria. Saliva was incubated aerobically and anaerobically in Tryptone Soya Broth, Wilkins-Chalgren Broth with mucin, or artificial saliva and was exposed to dentifrices containing triclosan/copolymer (TD); sodium fluoride (FD); stannous fluoride and zinc lactate (SFD1); or stannous fluoride, zinc lactate and stannous chloride (SFD2). Minimum inhibitory concentrations (MIC) were determined turbidometrically whilst group-specific minimum bactericidal concentrations (MBC) were assessed using growth media and conditions selective for total aerobes, total anaerobes, streptococci and Gram-negative anaerobes. Minimum acid neutralization concentration (MNC) was defined as the lowest concentration of dentifrice at which acidification was inhibited. Differences between MIC and MNC were calculated and normalized with respect to MIC to derive the combined inhibitory and neutralizing capacity (CINC), a cumulative measure of acidogenesis-mitigation and growth inhibition. The overall rank order for growth inhibition potency (MIC) under aerobic and anaerobic conditions was: TD> SFD2> SFD1> FD. Acidogenesis-mitigation (MNC) was ordered; TD> FD> SFD2> SFD1. CINC was ordered TD> FD> SFD2> SFD1 aerobically and TD> FD> SFD1> SFD2 anaerobically. With respect to group-specific bactericidal activity, TD generally exhibited the greatest potency, particularly against total aerobes, total anaerobes and streptococci. This approach enables the rapid simultaneous evaluation of acidity mitigation, growth inhibition and specific antimicrobial activity by dentifrices.

Blood serum protein in periparturient goats supplemented with various forms of zinc

The aim of the study was to compare the contents of individual protein fractions determined by electrophoresis in the blood serum of 32 periparturient goats supplemented with various forms of zinc (Zn). Goats were divided into four groups: Group A was a control (without Zn supplementation). The remaining three groups (B, C, D) were supplemented with Zn in various forms. Group B was supplemented with zinc oxide, Group C with zinc lactate, and Group D with zinc chelate. Individual protein fractions (albumins, α1, α2, β1, β2 a γ-globulins) were identified by electrophoretic analysis. All supplemented groups showed the trend of a positive influence of Zn on γG fractions in the serum protein of the goats; this tendency was significant only in Group C. Moreover, Group C had significantly the highest total protein values and albumins. The results indicated that a feed enriched with various forms of Zn had a significant influence on the quantity of individual protein fractions of blood serum. Our results provide new knowledge on the values of individual protein fractions of serum goats and should be taken into consideration when interpreting the serum protein profile with regard to periparturient goats. Furthermore, we showed the possible positive or negative effects on the values of individual fraction on serum proteins with organic and inorganic zinc form supplemented rich in diet.

Efficacy of two mouthwashes on 3-day supragingival plaque regrowth: a randomized crossover clinical trial.

The aim of this study was to evaluate the antiplaque effects of an alcohol-free essential oil (alcohol-free EO) mouthwash and an amine fluoride/stannous fluoride with zinc lactate (SnFl-Zn) mouthwash compared to a positive control of chlorhexidine (CHX) mouthwash, using an in vivo plaque regrowth model of 3 days. The study was designed as a double-masked, randomized, crossover clinical trial, involving 20 volunteers to compare two different mouthwashes, using a 3-day plaque accumulation model. After receiving thorough professional prophylaxis at baseline, over the next 3 days, each volunteer refrained from all oral hygiene measures and performed two daily rinses with 20 ml of the test mouthwashes. A 0.20% CHX rinse served as a positive control. At the end of each experimental period, plaque was assessed, and the panellists completed a questionnaire. Each subject underwent a 14-day washout period, and then, there was another allocation. The SnFl-Zn mouthwash has shown a better inhibitory activity on plaque regrowth compared to the alcohol-free EO mouthwash in the whole mouth (plaque index = 1.93 against 2.45, respectively), but there was less of an effect compared to the CHX group, with an overall plaque index of 1.41. The differences of 0.52 between alcohol-free EO and SnFl-Zn and between SnFl-Zn and CHX and of 0.96 between alcohol-free EO and CHX were all statistically significant (P < 0.001). The alcohol-free EO mouthwash seemed to have less of an inhibiting effect on plaque regrowth than the amine fluoride/SnFl-Zn mouthwash and the CHX control.

Fast Interchange of Coordinated and Guest Dimethylformamide Molecules in the Zinc(II) Lactate Terephthalate Metal–Organic Framework

Mobility of N,N-dimethylformamide (dmf) molecules in a homochiral metal–organic framework [Zn2(bdc)(S-lac)(dmf)]·dmf (bdc = 1,4-benzenedicarboxylate; S-lac = L-(−)-lactate) has been studied using 13C, 1H, and 2H solid-state NMR and DSC experiments. The compound exhibits a phase transition in the vicinity of 240 K, associated with disordering of the dmf molecules. In the high-temperature phase, the dmf molecules undergo intense diffusion accompanied by the exchange between the molecules coordinated with Zn and guest molecules in the framework pores. The activation energy of the molecular migration including exchange between coordinated and guest molecules was estimated to be 37 kJ/mol.

Improvement of thermal properties of poly (L-lactic acid) by blending with zinc lactate

Zinc lactate (RSX) was synthesised from zinc acetate and L-lactic acid, and the structure was characterised using X-ray diffraction (XRD). Thermal decomposition showed that the decomposition temperature of RSX is higher than the processing temperature of composites based on poly (L-lactic acid) (PLLA). Single factor experiments certified that the optimum reaction conditions are a reaction temperature of 80 oC, and a reaction time of 4 hours. Addition of RSX could significantly decrease the half-time of overall PLLA crystallisation. Compared to pure PLLA, the half-time of PLLA with 7 % RSX decreased from 2359.91 seconds to 152.68 seconds at 115 oC. The kinetics of isothermal crystallisation of PLLA/RSX composites can be described using the Avrami equation. J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):247-252

The effect of different mouth rinse products on intra-oral halitosis.

To evaluate the effect of different mouth rinses 12h after rinsing on genuine intra-oral halitosis. Twenty-four adults with halitosis were included in a double-blind, crossover, randomized clinical trial. Halitosis was evaluated 12h after rinsing with placebo and five mouth rinse products containing zinc acetate and chlorhexidine diacetate; zinc lactate, chlorhexidine and cetylpyridinium chloride; zinc acetate and chlorhexidine diacetate with reduced amounts of mint and menthol; zinc chloride and essential oil; and chlorine dioxide using the organoleptic method and a gas chromatograph. Test periods were separated by 1week. Hydrogen sulphide (H2 S), methyl mercaptan (MM) and the organoleptic scores (OLS) were significantly reduced 12h following rinsing with all substances compared to placebo (P<0.05). H2 S was more effectively reduced after rinsing with zinc acetate and chlorhexidine diacetate and zinc acetate and chlorhexidine diacetate with reduced amounts of mint and menthol compared to rinsing with zinc chloride and essential oil (P<0.05), and significantly lower values of MM were obtained after rinsing with zinc acetate and chlorhexidine diacetate compared to zinc lactate, chlorhexidine and cetylpyridinium chloride (P<0.05). The percentage effectively treated individuals (H2 S (<112ppb), MM (<26ppb) and OLS score <2) varied from 58% percentage (zinc acetate and chlorhexidine diacetate) to 26% (zinc chloride and essential oil). All treatments resulted in reduction in halitosis 12h after rinsing compared to placebo. H2 S and MM were most effectively reduced by zinc acetate and chlorhexidine diacetate.

Comparative effect of a new mouthrinse containing chlorhexidine, triclosan and zinc on volatile sulphur compounds: a randomized, crossover, double-blind study.

The aims of this study were to compare the volatile sulphur compounds (VSC)-reducing effect of two commercial mouthrinses using a morning bad breath model and to assess the role of mechanical plaque control (MPC) when performed previously to mouthrinse use. Eleven volunteers with good oral health were enrolled in a double-blind, randomized, six-step crossover design study with a 7-day washout period. Two commercial mouthrinses were tested using a saline solution (NaCl 0.9%) as a negative control: one mouthrinse contained 0.05% chlorhexidine, 0.05% cetylpyridinium chloride and 0.14% zinc lactate (CHX-CPC-Zn), while the other contained 0.05% chlorhexidine, 0.15% triclosan and 0.18% zinc pidolate (CHX-triclosan-Zn). A portable sulphide monitor (Halimeter(®) ) was used for VSC quantification. Measurements were made at baseline, and 1, 3 and 5h after rinsing. Significant differences were detected by analysis of variance. No significant differences between groups were detected at baseline. We were unable to demonstrate a significant influence of mechanical plaque control on the reduction of VSC levels when performed before mouthrinse use (P=0.631). Both mouthrinses effectively lowered VSC levels in all test intervals (P<0.05). No statistically significant differences were found between mouthrinses in any of the test intervals (P=0.629, 0.069 and 0.598 at 1, 3 and 5h). This study demonstrated that CHX-CPC-Zn and CHX-triclosan-Zn have significant and similar effects in reducing VSC levels, which persist for at least 5h. Such effects were independent of previous MPC, which failed to improve on the results of mouthrinse use alone.

Composite film materials based on poly(D,L-Lactide) and acexamic acid

The influence of the hydrophilicity and molecular mass of poly(D,L-lactide) on the solubility of acexamic acid in the polylactide film and on the rate of its release from the polymer was studied. The release of acexamic acid from the polylactide film is described by a two-step model according to which the first step consists in dissolution of acexamic acid occurring in the intrinsic crystalline phase, and the second step, in the release of acexamic acid dissolved in the poly(D,L-lactide) phase. The results of conductometric measurements show that the limiting solubility of acexamic acid in poly(D,L-lactide) is higher in more hydrophilic films prepared using zinc lactate and amounts to 5–8%. The rate of the acexamic acid release increases with a decrease in the molecular mass of poly(D,L-lactide).

Effects of Solvent and Impurities on Crystal Morphology of Zinc Lactate Trihydrate

The crystal morphology of zinc lactate trihydrate in the absence or presence of impurities (viz. succinic acid, L-malic acid and D-malic acid) is investigated by molecular simulation based on surface docking model and COMPASS force field. Combing simulation results with our previous experimental results, it is found that the solvent mainly has an inhibition effect on the (0 0 2) surface, and succinic acid impurity will inhibit the growth of (0 0 2) and (0 1 1) surfaces while two enantiomers of malic acid impurity will inhibit the (0 0 2) and (1 0 0) surfaces, which are in good agreement with the experimental results.

Is bismuth subsalicylate an effective nontoxic catalyst for plga synthesis?

ABSTRACTPoly(d,l‐lactide‐co‐glycolide) (PLGA) copolyesters are commonly used in biomedical applications. Researches were carried out on nontoxic or low‐toxic catalysts that are enough efficient to provide short polymerization times, adequate microstructure chains and similar properties than the commercial PLGA materials. In this study, PLGA were synthesized by ring‐opening copolymerization (ROP) using three different catalysts. Stannous octoate is the first catalyst we used, as it is very efficient, even its toxicity is still on debate. Two others low‐toxic catalysts [zinc lactate and bismuth subsalicylate (BiSS)] were also evaluated. The comparison of these ROP was realized in terms of kinetics and control of the polymerization. Then, the influence of the catalyst on the PLGA microstructure chains is reported. Finally, abiotic hydrolytic degradation rate is studied. Results described in this article show that BiSS is one very attractive catalyst to produce low toxic PLGA for biomedical applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2014,52, 1130–1138

Use of an in vitro flat-bed biofilm model to measure biologically active anti-odour compounds

The objective of this study was to demonstrate the utility of a modified flat-bed perfusion biofilm matrix system for testing toothpaste formulations directly, without dilution, as a layer in direct contact with the biofilm matrix surface. Final biofilm yields and volatile sulphur compounds (VSC) biogenesis were measured to show the relative efficacy of toothpaste formulations. Diffusion characteristics of the flat-bed system to exposure with Meridol® tooth and tongue gel (TTG; 1,400ppmF(-) from amine fluoride/stannous fluoride, 0.5% zinc lactate, oral malodour counteractives) was assessed using a bioluminescent target species Escherichia coli Nissle 1917/pGLITE coupled with a low-light photon camera to visualise the kill kinetics. Tongue-flora derived, mixed culture biofilms (n = 4) received 5, 15 and 30min treatment with TTG, respectively, to determine the optimum time of exposure. VSC biogenesis was measured from headspace samples by gas chromatography prior to and following treatment of two daily applications for 4days of treatment (TTG), positive control (CHX gel) and negative controls (placebo and sham treatment). Viable counts were performed at the end of experiments by destructive sampling of the biofilms and plating onto selective and non-selective agar. Following a single treatment with TTG, the E. coli biofilm with lux target gave >50% reduction of luminescence within 2 to 3h before recovering to a steady state over 10h, suggesting biofilm cidal activity rather biostasis. For mixed culture biofilms, 15- and 30-min treatment exposure with TTG gave almost identical reductions in final biofilm yields. For comparing efficacy of treatments, biofilms treated with TTG gave greatest reductions in both pre-post levels of H2S (P < 0.01) and CH3SH (P < 0.05) and population yields at the end of the experiments (P < 0.001) compared to placebo and positive control. The in vitro flat-bed perfusion model may be used to replicate many of the activities and reactions believed to be occurring by the tongue biofilm microflora within a real mouth, including VSC biogenesis and its inhibition by exposure to active agents as components of toothpastes and gels applied in direct contact with the biofilm.

Efficacy of different mouthrinse formulations in reducing oral malodour: a randomized clinical trial

The aim of this study was to assess the efficacy of mouthrinses formulations in oral malodour. This single-centre, double-blind, randomized, parallel group clinical trial compared the efficacy of Halita™ and meridol(®) with and without zinc lactate versus negative and positive control. Volunteers with confirmed oral malodour (18/group) rinsed with one mouthrinse during 7days (15ml, 2x/day for 1min.). 15min. after a first rinse (masking effect), and after 7days (therapeutic effect) the change in organoleptic scores and level of sulphur compounds was recorded. All rinses showed a masking effect (OLS 1 to 2 values reduced), only the rinses with antimicrobial ingredients showed a therapeutic effect (OLS 1 to 1.5 value less). The addition of zinc resulted in a more pronounced masking effect. Halita™ and meridol(®) with zinc showed the best therapeutic effect. Although the masking effect of the rinses can be attributed partially to a dilution and the effect of aromas, the therapeutic effect should be linked to the anti-microbial action of active ingredients and counter action of zinc ions on VSC. A complete resolution of the unpleasant breath by additional mechanical intervention remains to be proven.

Synthesis of polylactide/poly(ethylene glycol) diblock copolymers with functional endgroups

AbstractAmphiphilic polylactide/poly(ethylene glycol) (PLA–PEG) diblock copolymers with functional groups at the PEG chain ends were synthesized by coupling PLA and PEG homopolymers using different coupling agents. PLA precursors with different endgroups were synthesized by ring‐opening polymerization of l‐lactide in the presence of different initiators such as octanol, acetic acid or benzoic acid, or water, using non‐toxic zinc lactate as catalyst. The mechanism of the ring‐opening polymerization of lactide initiated by carboxyl groups was investigated and discussed in comparison with the literature. N,N'‐carbonyldiimidazole was used to couple the two hydroxyl groups of PLA and PEG, using 4‐dimethylaminopyridine (DMAP) as catalyst. Dicyclohexylcarbodiimide (DCC) and DMAP were adopted to couple the carboxyl group and the hydroxyl group of PLA and PEG, respectively, while DCC and N‐hydroxysuccinimide were used to connect PLA and PEG by coupling their carboxyl and amine groups. Comparison of different coupling routes shows that the DCC/DMAP one exhibits the highest efficiency. A common tumor targeting ligand, folic acid, was attached to PLA–PEG with hydroxyl endgroups using the DCC/DMAP route. The resulting PLA–PEG copolymers bearing folic acid present great interest for targeted delivery of anti‐cancer drugs. © 2012 Society of Chemical Industry