Aliphatic Polyesters with White-Light Clusteroluminescence.

Single-molecule white-light emission (SMWLE) has many advantages in practical applications; however, the fabrication of SMWLE from nonconjugated luminescent polymers, namely, clusteroluminogens (CLgens), is still a big challenge. Herein, the first example of linear nonconjugated polyesters with SMWLE is reported. Twenty-four kinds of nonconjugated aliphatic polyesters with tunable clusteroluminescence (CL) colors and efficiency were synthesized by the copolymerization of six epoxides and four anhydrides. Experimental and calculation results prove that, at the primary structure level, the balance of structural flexibility and rigidity via adjusting the side-chain length significantly enhances the efficiency of CL without wavelength change. However, altering the chemical structures of the monomer from succinic anhydride to trans-maleic anhydride (MA), cis-MA, and citraconic anhydride (CA), secondary structures of these polyesters change from helix to straight and folding sheet accompanied by gradually red-shifted CL from 460 to 570 nm due to the increase in through-space n-π* interactions, as demonstrated by the computational and experimental results. Then, pure SMWLE with CIE coordination (0.30, 0.32) based on overlapped short-wavelength and long-wavelength CL is achieved in CA-based polyesters. This work not only provides further insights into the emission mechanism of CL but also provides a new strategy to manipulate the properties of CL by regulating the hierarchical structures of CLgens.

Spatial-temporal-demographic and virological changes of hand, foot and mouth disease incidence after vaccination in a vulnerable region of China.

BACKGROUND: The enterovirus 71 (EV-A71) vaccine has been used in Hefei for several years, and the epidemiological significance of vaccination in this area is unclear. We aims to explore the spatial-temporal-demographic and virological changes of hand, foot and mouth disease (HFMD) after vaccination in China. METHODS: The data for HFMD from 2012 to 2020 were downloaded with the help of HFMD reporting system of Hefei Center for Disease Control and Prevention and combined with the EV-A71 vaccination status in Hefei. The study defined the period between 2012 to 2016 as the pre-vaccination period and explored the effect of vaccination on the incidence of HFMD by comparing the changes of HFMD before and after vaccination in terms of spatial, temporal, demographic and virological aspects. RESULTS: During the study period, a higher incidence occurred in urban area and the random distribution changed to a slight cluster after vaccination. HFMD incidence had inconsistent seasonality over years, with one or two incidence peaks in varying years. The morbidity decreased from 215.22/105 in 2012-2016 to 179.81/105 in 2017-2020 (p < 0.001). Boys, 0-4 years old children and Scattered children were more susceptible to HFMD compared with the others, the proportions decreased after vaccination except in Scattered children. The main pathogenic enterovirus gradually changed from EV-A71 to Other Enteroviruses, especially coxsackieviruses A6 (CV-A6) after the implementation of EV-A71 vaccination. CONCLUSIONS: The EV-A71 vaccine was effective in reducing the incidence of HFMD and changing the spatial, temporal, demographic, and virological characteristic. These changes should be considered during the vaccination implementation to further reduce the disease burden of HFMD.

Enabling Oxygen-Sulfur Exchange Reaction to Produce Semicrystalline Copolymers from Carbon Disulfide and Ethylene Oxide.

This work describes the first example of semicrystalline poly(thiocarbonate)s from carbon disulfide (CS2 ) and ethylene oxide (EO), two mass producible low-cost monomers. Lewis acid/base pairs (LPs) exhibit high activity (EO conversion up to >99%, 8 h) in catalyzing the copolymerization under low Lewis pair/monomer ratio of 1:1500. Oxygen-sulfur exchange reaction (O-S ER) during the copolymerization of CS2 and EO, the generation and mutual copolymerization with COS, CO2 , and episulfide, is harnessed to introduce crystallizable segments [SC(O)O and SC(S)S] in the copolymer. The type of Lewis base is found to have a great impact on the chain microstructure and the crystalline properties. The formed copolymers with melting point from 117.7 to 245.3 °C are obtained. The maximum crystallinity is estimated to be 78% based on the powder wide-angle X-ray diffraction pattern. This work provides a general method to prepare semicrystalline sulfur-containing polymers.

Photo-Degradable Micelles Capable of Releasing of Carbon Monoxide under Visible Light Irradiation.

Carbon monoxide (CO) has emerged as a potential therapeutic agent for the treatment of many diseases. However, the therapeutic outcome is highly dependent on the dosages and administration sites. Hence, there is mounting interest in the development of CO-releasing materials to accomplish site-specific and dose-controlled delivery of CO. Herein, a micellar nanoparticle platform for the photo-mediated release of CO by using amphiphilic triblock copolymers bearing CO-releasing moieties of 3-hydroxylflavone (3-HF) derivatives within the middle blocks is developed. These micelles are relatively stable without CO leakage but undergo visible light-mediated CO release and simultaneous main chain scission. Moreover, these micellar nanoparticles are cytocompatible regardless of light irradiation, which shows unique anti-inflammatory performance only after light irradiation as a result of photo-triggered CO release. This work may represent the first example of main-chain degradable micellar nanocarriers with controlled CO-releasing performance for potential anti-inflammatory applications.

Sphingobacterium athyrii sp. nov., a cellulose- and xylan-degrading bacterium isolated from a decaying fern (Athyrium wallichianum Ching).

Assessment of the bacterial diversity associated with a decaying fern, Athyrium wallichianum Ching, revealed the presence of a novel bacterial strain named M46T. It was Gram-stain-negative, rod-shaped, non-motile and aerobic with cellulose and xylan degradation abilities. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain M46T was affiliated to the genus Sphingobacterium, exhibiting the highest sequence similarity of 97.9 % to Sphingobacterium ginsenosidimutans THG 07T, Sphingobacterium canadense CR11T and Sphingobacterium detergens6.2 ST. Multilocus sequence analysis (MLSA) based on concatenated sequences of the rpoB, cpn60 and 16S rRNA genes showed that strain M46T clustered together with S. canadense CR11T. The genome of strain M46T had a G+C content of 40.6 mol% and chromosome of 6 853 865 bp. Average nucleotide identity (ANI) between strain M46T and S. detergens 6.2 ST and S. siyangense SY1T was 85.1 and 78.1 %, respectively. DNA-DNA relatedness values among strain M46T and other closely related Sphingobacterium species were <70 %. ANI and DNA-DNA relatedness findings strongly supported M46T as a putative novel strain of Sphingobacterium. The predominant fatty acids of strain M46T were iso-C15 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and iso-C17 : 0 3-OH, and MK-7 was the dominant isoprenoid quinone. The polar lipid profile of strain M46T contained phosphatidylethanolamine as the dominant component, while minor amounts of phosphoglycolipid, one unidentified aminophospholipid, two unidentified phospholipids and four unidentified lipids were also detected. Based on 16S rRNA gene sequence similarities, MLSA results, genomic characteristics, and phenotypic and biochemotaxonomic analyses, strain M46T is considered to represent a novel species in the genus Sphingobacterium, for which the name Sphingobacterium athyrii sp. nov. is proposed. The type strain is M46T (=CGMCC 1.13466T=JCM 32543T).

Highly Efficient One-Pot Synthesis of COS-Based Block Copolymers by Using Organic Lewis Pairs.

A one-pot synthesis of block copolymer with regioregular poly(monothiocarbonate) block is described via metal-free catalysis. Lewis bases such as guanidine, quaternary onium salts, and Lewis acid triethyl borane (TEB) were equivalently combined and used as the catalysts. By using polyethylene glycol (PEG) as the macromolecular chain transfer agent (CTA), narrow polydispersity block copolymers were obtained from the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO). The block copolymers had a poly(monothiocarbonate) block with perfect alternating degree and regioregularity. Unexpectedly, the addition of CTA to COS/PO copolymerization system could dramatically improve the turnover frequency (TOF) of PO (up to 240 h-1), higher than that of the copolymerization without CTA. In addition, the conversion of CTA could be up to 100% in most cases, as revealed by ¹H NMR spectra. Of consequence, the number-average molecular weights (Mns) of the resultant block copolymers could be regulated by varying the feed ratio of CTA to PO. Oxygen-sulfur exchange reaction (O/S ER), which can generate randomly distributed thiocarbonate and carbonate units, was effectively suppressed in all of the cases in the presence of CTA, even at 80 °C. This work presents a versatile method for synthesizing sulfur-containing block copolymers through a metal-free route, providing an array of new block copolymers.

Impact of weather factors on hand, foot and mouth disease, and its role in short-term incidence trend forecast in Huainan City, Anhui Province.

Hand, foot, and mouth disease (HFMD) is one of the most common communicable diseases in China, and current climate change had been recognized as a significant contributor. Nevertheless, no reliable models have been put forward to predict the dynamics of HFMD cases based on short-term weather variations. The present study aimed to examine the association between weather factors and HFMD, and to explore the accuracy of seasonal auto-regressive integrated moving average (SARIMA) model with local weather conditions in forecasting HFMD. Weather and HFMD data from 2009 to 2014 in Huainan, China, were used. Poisson regression model combined with a distributed lag non-linear model (DLNM) was applied to examine the relationship between weather factors and HFMD. The forecasting model for HFMD was performed by using the SARIMA model. The results showed that temperature rise was significantly associated with an elevated risk of HFMD. Yet, no correlations between relative humidity, barometric pressure and rainfall, and HFMD were observed. SARIMA models with temperature variable fitted HFMD data better than the model without it (sR 2 increased, while the BIC decreased), and the SARIMA (0, 1, 1)(0, 1, 0)52 offered the best fit for HFMD data. In addition, compared with females and nursery children, males and scattered children may be more suitable for using SARIMA model to predict the number of HFMD cases and it has high precision. In conclusion, high temperature could increase the risk of contracting HFMD. SARIMA model with temperature variable can effectively improve its forecast accuracy, which can provide valuable information for the policy makers and public health to construct a best-fitting model and optimize HFMD prevention.

Efficient immobilization of AGE and NAL enzymes onto functional amino resin as recyclable and high-performance biocatalyst.

N-Acetylglucosamine-2-epimerase (AGE) and N-acetylneuraminic acid lyase (NAL) were immobilized for synthesis of N-acetylneuraminic acid (Neu5Ac) on three resins: Amberzyme oxirane resin (AOR), poly (styrene-co-DVB)-Br resin (PBR) and amino resin (AR). The loading capacity and immobilized enzyme activity showed that AR was the best carrier. Three methods of glutaraldehyde cross-linking were tested and simultaneous cross-linking and immobilization was demonstrated to be the best method. The functional properties of immobilized AGE and NAL were studied and compared to those of the free enzyme. The highest enzyme activities of free and immobilized AGE were obtained in 0.1 M potassium phosphate buffer at pH 7.5 and a temperature of 37 °C. Comparatively, the highest NAL activities were at pH 8.5. Meanwhile, an increase in K m (from 1.14 to 1.31 mg·mL-1 for AGE and from 1.05 to 1.25 mg·mL-1 for NAL) and a decrease in V max (from 177.53 to 106.37 µg·min-1 mL-1 for AGE and from 126.41 to 95.96 µg·min-1 mL-1 for NAL) were recorded after immobilization. The AR-glutaraldehyde-enzyme system exhibited better thermal stability than the free enzyme, and retained 72% of its initial activity even after eight repeated runs. The apparent activation energy (E a) of the free and immobilized AGE (NAL) was 117.14 kJ·mol-1 (124.21 kJ·mol-1) and 78.45 kJ·mol-1 (66.64 kJ·mol-1), respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limit. Subsequently, Neu5Ac production from GlcNAc using immobilized enzymes in one reactor was carried out resulting 101.45 g·L-1 of Neu5Ac and the highest conversion ratio of 82%. This method of enzyme immobilization may have a promising future for Neu5Ac production in industry.

[Optimize excipients for Yinsang hypoglycemic granules by using multiple indexes].

Optimal excipients were screened by studying the effect of different excipients on the hygroscopicity of the extract, testing polysaccharide in the preparation and blood glucose value. Single factor tests were performed with hygroscopicity, formability and fluidity as the indexes, and the moisture content, granule yield and angle of repose were combined with physical characters of the materials to screen the proportioning and dosage of excipients. Then the critical relative humidity of preferred Yinsang granules were measured. The optimum excipients for Yinsang hypoglycemic granules were mulberry leaf paste-microcrystalline cellulose-mactra veneriformis crude polysaccharides (10∶9∶1.67). The obtained granules had good formability and fluidity, which were not easy to absorb moisture for liquefaction, with a critical relative humidity of 73%. This formation process was reasonable and feasible, suitable for industrial production, which can significantly improve hygroscopicity and liquefaction properties of extracts, improve stability of Yinsang granules, and provide reference for screening of excipients for other preparations.

Impact of temperature variation between adjacent days on childhood hand, foot and mouth disease during April and July in urban and rural Hefei, China.

Previous studies have found that both high temperature and low temperature increase the risk of childhood hand, foot and mouth disease (HFMD). However, little is known about whether temperature variation between neighboring days has any effects on childhood HFMD. A Poisson generalized linear regression model, combined with a distributed lag non-linear model, was applied to examine the relationship between temperature change and childhood HFMD in Hefei, China, from 1st January 2010 to 31st December 2012. Temperature change was defined as the difference of current day's mean temperature and previous day's mean temperature. Late spring and early summer (April-July) were chosen as the main study period due to it having the highest childhood HFMD incidence. There was a statistical association between temperature change between neighboring days and childhood HFMD. The effects of temperature change on childhood HFMD increased below a temperature change of 0 °C (temperature drop). The temperature change has the greatest adverse effect on childhood HFMD at 7 days lag, with 4 % (95 % confidence interval 2-7 %) increase per 3 °C drop of temperature. Male children and urban children appeared to be more vulnerable to the effects of temperature change. Temperature change between adjacent days might be an alternative temperature indictor for exploring the temperature-HFMD relationship.

A green and efficient protocol for large-scale production of glycyrrhizic acid from licorice roots by combination of polyamide and macroporous resin adsorbent chromatography.

A green and efficient method for large-scale preparation of glycyrrhizic acid from licorice roots was developed by combination of polyamide and macroporous resin. The entire preparation procedure consisted of two simple separation steps. The first step is to use polyamide resin to remove licorice flavoniods from the licorice crude extract. Subsequently, various macroporous resins were tried to purify glycyrrhizic acid, and HPD-400 showed the most suitable adsorption and desorption properties. Under the optimized conditions, a large-scale preparation of glycyrrhizic acid from licorice roots was carried out. A 20 kg raw material produced 0.43 kg of glycyrrhizic acid using green aqueous ethanol as the solvent. The purity of glycyrrhizic acid was increased from 11.40 to 88.95% with a recovery of 76.53%. The proposed method may be also extended to produce large-scale other triterpenoid saponins from herbal materials.

Characterization of airborne microplastics at different workplaces of the poly(ethylene:propylene:diene) (EPDM) rubber industry.

Microplastics (MPs) as an emerging air pollutant have received widespread attention, but research on airborne MPs at occupational sites is still limited, especially in the rubber industry. Hence, indoor air samples were collected from three production workshops and an office of a rubber factory producing automotive parts to analyze the characteristics of airborne MPs in different workplaces of this industry. We found MP contamination in all air samples from the rubber industry, and the airborne MPs at all sites mainly showed small-sized (< 100 µm) and fragmented characteristics. The abundance and source of MPs at various locations is primarily related to the manufacturing process and raw materials of the workshop. The abundance of MPs in the air was higher in workplaces where production activities are involved than in office (360 ± 61 n/m3), of which the highest abundance of airborne MPs was in the post-processing workshop (559 ± 184 n/m3). In terms of types, a total of 40 polymer types were identified. The post-processing workshop has the largest proportion of injection-molded plastic ABS, the extrusion workshop has a greater proportion of EPDM rubber than the other locations, and the refining workshop has more MPs used as adhesives, such as aromatic hydrocarbon resin (AHCR).

Zanthoxylum-specific whole genome duplication and recent activity of transposable elements in the highly repetitive paleotetraploid Z. bungeanum genome.

Zanthoxylum bungeanum is an important spice and medicinal plant that is unique for its accumulation of abundant secondary metabolites, which create a characteristic aroma and tingling sensation in the mouth. Owing to the high proportion of repetitive sequences, high heterozygosity, and increased chromosome number of Z. bungeanum, the assembly of its chromosomal pseudomolecules is extremely challenging. Here, we present a genome sequence for Z. bungeanum, with a dramatically expanded size of 4.23 Gb, assembled into 68 chromosomes. This genome is approximately tenfold larger than that of its close relative Citrus sinensis. After the divergence of Zanthoxylum and Citrus, the lineage-specific whole-genome duplication event η-WGD approximately 26.8 million years ago (MYA) and the recent transposable element (TE) burst ~6.41 MYA account for the substantial genome expansion in Z. bungeanum. The independent Zanthoxylum-specific WGD event was followed by numerous fusion/fission events that shaped the genomic architecture. Integrative genomic and transcriptomic analyses suggested that prominent species-specific gene family expansions and changes in gene expression have shaped the biosynthesis of sanshools, terpenoids, and anthocyanins, which contribute to the special flavor and appearance of Z. bungeanum. In summary, the reference genome provides a valuable model for studying the impact of WGDs with recent TE activity on gene gain and loss and genome reconstruction and provides resources to accelerate Zanthoxylum improvement.

An assessment of the genomics, comparative genomics and cellulose degradation potential of Mucilaginibacter polytrichastri strain RG4-7.

In this study, whole genome sequencing and comparative genomic analyses were performed for Mucilaginibacter polytrichastri RG4-7 and its carboxymethyl cellulose degradation potential was assessed. The results showed that the genome of strain RG4-7 was 5.84 Mb and contained 5019 predicted genes, in which a high proportion of strain-specific genes were related to carbohydrate metabolism. The carboxymethyl cellulose (CMC) degradation and cellulase activity tests revealed the strong cellulose degradation ability, CMCase and ß-glucosidase activity in strain RG4-7. Real-time RT-PCR testing of most cellulose degradation related glycoside hydrolase (GH) families showed that GH9 (OKS85969), GH1 (OKS85832), GH3 (OKS89331 and OKS85615) were significantly up-regulated when strain RG4-7 was inoculated with CMC-Na, which suggested that GH9, GH1 and GH3 might determine its cellulose degradation ability. Certainly, further research need to be done to elucidate cellulose degradation mechanisms in strain RG4-7 in order to develop its industrial application value in lignocellulosic biomass degradation and waste management.

Ag(I)-mediated in situ dehydrogenative coupling of 3-amino-1,2,4-triazole into 3,3'-azobis(1,2,4-triazole) in Cd(II) coordination polymers.

Ag(I)-mediated in situ generation of 3,3'-azobis(1,2,4-triazole) (AzTAZ) from 3-amino-1,2,4-triazole (AmTAZ) through dehydrogenative coupling has been realized during the crystallization process of two Cd(II) coordination polymers with novel topological architectures: a (3, 4, 5)-connected (4 x 6(2))(2)(4 x 6(7) x 8(2))(2)(6(5) x 10) net for [Cd(2)(AmTAZ)(2)(AzTAZ)](n) (1) and a 4-connected (6(2) x 8(4))(6(4) x 8(2))(6(5) x 8)(2) net for [Cd(AzTAZ)(2)(H(2)O)](n) (2), whereas AmTAZ retains its original form in a heterometallic complex, [Ag(2)Cd(AmTAZ)(4)](n) (3).

Development of Normal Tissue Complication Probability Model for Trismus in Head and Neck Cancer Patients Treated With Radiotherapy: The Role of Dosimetric and Clinical Factors.

BACKGROUND/AIM: The aim of this study was to develop a normal tissue complication probability (NTCP) model for trismus in head and neck cancer (HNC) patients treated with radiotherapy (RT). PATIENTS AND METHODS: Prospective measurements of maximum inter-incisal opening (MIO) were performed at baseline and 6 months after definitive RT in 132 HNC patients. The primary endpoint of this study was defined when a patient fulfilled both of the following criteria: 1) MIO at 6 months after RT ≤35 mm and 2) MIO at 6 months after RT ≤80% of baseline MIO. Eleven clinical factors and a wide range of dosimetric factors (mean dose, maximum dose, V5, V10, V20, and V40) in twelve organs at risk (OARs) were chosen as candidate prognostic variables. RESULTS: Thirty out of 132 patients (23%) developed the primary endpoint. Multivariate logistic regression analysis revealed that the mean dose to the contralateral mandible joint (p=0.001) and baseline MIO (p=0.027) were independent prognostic factors. CONCLUSION: A multivariable NTCP model for trismus in HNC patients treated with RT was established including the mean dose to contralateral mandible joint and baseline MIO.

A hierarchical assembly strategy to engineer dextran-enveloped polyurethane nanopolyplexes for robust ovarian cancer gene therapy.

A hierarchical assembly strategy is herein investigated to generate bio-responsive, dextran-enveloped, bioreducible polyurethane nanopolyplexes for nonviral gene therapy against ovarian tumor. Initially, a group of poly(urethane amine)s were designed and characterized for in vitro gene transfection. The polyurethane containing 1,4-bis(3-aminopropyl)piperazine residue (PUBAP) could induce the best in vitro transfection efficacy against SKOV-3 or A2780 ovarian cancer cells. Next, dextran-enveloped PUBAP polyplexes (e-polyplexes) were constructed by a hierarchical assembly procedure involving gene neutralization with PUBAP and subsequent gene condensation with a cationic dextran (SSDP800). Such dextran comprised dextran (15 kDa) as the main chain and multiple disulfide-linked branched polyethylenimine (BPEI) oligomers as the side grafts. Additionally, folate-dextran-enveloped PUBAP polyplexes (FA-e-polyplexes) were fabricated by folate-modified SSDP800. These nanoscale-enveloped polyplexes elicited an improved colloidal stability against salt ions and negatively charged heparin, efficient endosomal escaping, and bioreduction-triggered intracellular gene release. In vitro transfection against SKOV-3 cells illustrated that FA-e-polyplexes exerted higher transfection efficiency in the serum than e-polyplexes and 25 kDa BPEI-polyplexes. In vivo, FA-e-polyplexes yielded higher transgene expression level than e-polyplexes in an SKOV-3 tumor-bearing nude mouse model. In the tumor gene therapy with a small hairpin RNA silencing vascular endothelial growth factor, FA-e-polyplexes afforded higher tumor growth inhibition than polyplexes of folate-PEGylated PUBAP and 25 kDa linear polyethylenimine as positive controls. Importantly, such gene therapy had minor toxic effects on the health of the mouse. This work highlights a practical hierarchical assembly method to construct innovative enveloped polyurethane nanopolyplexes enabling robust ovarian cancer gene therapy. STATEMENT OF SIGNIFICANCE: It is indispensable to rationally update binary cationic polyplexes into ternary polyplexes for vigorous tumor gene therapy. In this work, we have confirmed that a hierarchical assembly strategy, by using initial gene neutralization and subsequent gene condensation, is facile and effective to promote cationic polyurethane polyplexes into ternary folate-dextran-enveloped polyurethane polyplexes with a relatively high gene-loading capacity. The enveloped polyplex system enables more efficient gene transfection than the PEGylated polyplex counterpart in ovarian cancer in vitro and in vivo, thereby affording robust ovarian cancer gene therapy. The development of innovative enveloped polyplexes may be a new direction for a non-viral gene delivery system.

Nitrobenzene reduction using nanoscale zero-valent iron supported by polystyrene microspheres with different surface functional groups.

Three polystyrene (PS) resin microspheres supported nanoscale zero-valent iron (nZVI), i.e., nZVI@PS, nZVI@PS-Cl, and nZVI@PS-N, were prepared and characterized by FT-IR, XPS, SEM, EDS, and weighing method. The functional groups on the carriers showed obvious influence on the loading quantity, the micro morphology, and the reduction efficiency of these supported nZVI. The best hybrid reducer was nZVI@PS-N. The load quantity of nZVI was 0.2476 g/g, and some of them were dispersed and the others remained as particles (≤ 50 nm). At optimal reaction conditions, i.e., initial solution pH = 3, 25 °C, 100 r/min stirring, 99% nitrobenzene (NB) in 250 mL 123.1 mg/L NB solution could be totally reduced into AN by 1.31 g fresh nZVI@PS-N within 20 min. The excellent reduction efficiency and fast degradation rate of nZVI@PS-N were mainly attributed to the synergistic effects between the good adsorption property of its carrier and the high reduction activity of nZVI particles. NZVI@PS-N was reproducible and recycled, and 90.6% degradation ratio of NB was till obtained at its seventh recycle. The results showed that nZVI@PS-N had high potential practical application value in the reductive degradation and emergency rescue of nitrobenzene pollutant.

Efficacy of Poly(D,L-Lactic Acid-co-Glycolic acid)-Poly(Ethylene Glycol)-Poly(D,L-Lactic Acid-co-Glycolic Acid) Thermogel As a Barrier to Prevent Spinal Epidural Fibrosis in a Postlaminectomy Rat Model.

STUDY DESIGN: Experimental animal study. OBJECTIVE: The authors conducted a study to determine the efficacy and safety of the poly(D,L-lactic acid-co-glycolic acid)-poly(ethylene glycol)-poly(D,L-lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) thermogel to prevent peridural fibrosis in an adult rat laminectomy model. SUMMARY OF BACKGROUND DATA: Peridural fibrosis often occurs after spinal laminectomy. It might cause persistent back and/or leg pain postoperatively and make a reoperation more difficult and dangerous. Various materials have been used to prevent epidural fibrosis, but only limited success has been achieved. MATERIALS AND METHODS: The PLGA-PEG-PLGA thermogel was synthesized by us. Total L3 laminectomies were performed on 24 rats. The PLGA-PEG-PLGA thermogel or chitosan (CHS) gel (a positive control group) was applied to the operative sites in a blinded manner. In the control group, the L3 laminectomy was performed and the defect was irrigated with the NS solution 3 times. All the rats were killed 4 weeks after the surgery. RESULTS: The cytotoxicity of this thermogel was evaluated in vitro and the result demonstrated that no evidence of cytotoxicity was observed. The extent of epidural fibrosis, the area of epidural fibrosis, and the density of the fibroblasts and blood vessel were evaluated histologically. There were statistical differences among the PLGA-PEG-PLGA thermogel or CHS gel group compared with the control group. Although there was no difference between the PLGA-PEG-PLGA thermogel and CHS gel, the efficiency of the PLGA-PEG-PLGA thermogel was shown to be slightly improved compared with the CHS gel. CONCLUSIONS: The biocompatibility of the PLGA-PEG-PLGA thermogel was proven well. The application of this thermogel effectively reduced epidural scarring and prevented the subsequent adhesion to the dura mater. No side effects were noted in the rats.