CLAY CATALYZED SYNTHESIS OF BIO-DEGRADABLE POLY(GLYCOLIC ACID)

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay.The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (Ⅳ)values.The relative intensity of C=O/CH is increased while increasing the amount of clay.DSC showed the appearance of multiple endotherms of poly(glycolic acid).TGA showed the percentage weight residue remain above 750℃for polymer-nano composite system was 21% and hence proved the fl...

Clinical outcomes and 5-year follow-up results of keratosis pilaris treated by a high concentration of glycolic acid

BACKGROUND Keratosis pilaris is a hereditary abnormal keratosis of the hair follicle orifice.Gray-brown keratotic plugs in the pores and dark red keratotic papules at the openings of hair follicles can be seen,which contain coiled hair and are often accompanied by perifollicular erythema and pigmentation.Glycolic acid can correct the abnormalities of hair follicular duct keratosis and eliminate excessive accumulation of keratinocytes.It also promotes skin metabolism and accelerates the melanin metabolism.The therapeutic effect is related to the glycolic acid concentration.AIM To evaluate the efficacy and safety of a high concentration of glycolic acid in the treatment of keratosis pilaris,and to observe the outcomes at 5-year of follow-up.METHODS Twenty-five participants were recruited and areas with typical keratosis pilaris were selected as testing sites.High concentrations of glycolic acid(50%or 70%)were applied to a circular area(d=8 cm,S=50 cm2)and repeated four times,on days 0,20,40 and 60.Before each treatment and 20 d after the last treatment,on days 0,20,40,60,and 80 and at a 5-year follow-up,The number of follicular keratotic papules were counted and the extent of perifollicular erythema and pigmentation was determined.At the same time,the participants provided subjective evaluations of treatment efficacy and safety.RESULTS Treatment effectiveness was indicated by the percentage of keratotic papules in the test site,on days 20,40,60 and 80,which were 8%,12%,36%,and 60%,respectively.Compared with day 0,each difference was significant(P<0.05).Compared with day 0,differences in melanin content(M)in the skin and skin lightness(L)on days 40,60 and 80,the were statistically significant(P<0.05);skin hemoglobin content(E)on days 60 and 80 was statistically different as compared with before treatment(P<0.05).There were no significant differences in the number of keratotic papules,M,L,and E in 9 participants at the 5-year follow-up compared with before treatment(P>0.05%).CONCLUSION A high concentration of glycolic acid significantly improved skin roughness as well as follicular hyperpigmentation of patients with keratosis pilaris.The treatment was relatively safe,but there was no significant difference at the 5-year follow-up compared to before treatment.

Effect of Chitosan Coating on the Properties of Poly(glycolic acid-lactic acid)Thread-Embedding Material

Poly( glycolic acid-lactic acid)( PGLA) threadembedding material was modified by chitosan coating which could improve the rigidity,hydrophilicity and moisture absorption of the material,and produced better stimulation effect. Thus,this kind of thread-embedding materials which can be buried into acupuncture points to produce a long-time stimulation is popular in the acupuncture and moxibustion therapies. The variation tendencies of diameter,weight, hydrophilicity, and flexibility of the samples under the change of chitosan coating concentration,coating time and coating times were studied respectively. The results showed that the hydrophilicity,weight,and rigidity after coating rose in a certain range with the increase of coating time,coating times and coating concentration. The coating time had little influence on the diameter of fiber.

Electrocatalytic production of glycolic acid via oxalic acid reduction on titania debris supported on a TiO_(2)nanotube array

Electrodes prepared by anodic oxidation of Ti foils are robust and not toxic materials for the electrocatalytic reduction of oxalic acid to glycolic acid, allowing the development of a renewable energy-driven process for producing an alcoholic compound from an organic acid at low potential and room temperature. Coupled with the electrochemical synthesis of the oxalic acid from CO_(2),this process represents a new green and low-carbon path to produce added value chemicals from CO_(2). Various electrodes prepared by anodic oxidation of Ti foils were investigated. They were characterized by the presence of a TiO_(2) nanotube array together with the presence of small patches, debris, or TiO_(2) nanoparticles. The concentration of oxygen vacancies, the amount of Ti^(3+) measured by X-ray photoelectron spectroscopy(XPS) and the intensity of the anodic peak measured by cyclic voltammetry, were positively correlated with the achieved oxalic acid conversion and glycolic acid yield. The analysis of the results indicates the presence of small amorphous TiO_(2) nanoparticles(or surface patches or debris) interacting with TiO_(2) nanotubes, the sites responsible for the conversion of oxalic acid and glycolic acid yield. By varying this structural characteristic of the electrodes, it is possible to tune the glycolic acid to glyoxylic acid relative ratio. A best cumulative Faradaic efficiency(FE) of about 84% with FE to glycolic acid around 60% and oxalic conversion about 30% was observed.

An Approach for Using of Poly Glycolic Acid (PGA) in Reference Standard Dosimetry: PGA/ESR Dosimetry System Response Curve and Post Irradiation Stability

Reference Standard Dosimeters are used to calibrate radiation environments and routine dosimeters. It can also be used in routine dosimetry applications for radiation processing where higher quality dosimetry measurements are required. Electron Spin Resonance (ESR) is a well-established Reference Standard Dosimetry system in industrial applications of ionising radiation, and its use is also proposed in radiation therapy and accident dosimetry. In the present experimental work, PGA solid state dosimeter (SSD) has been investigated using ESR spectroscopy to study the gamma radiation response of this material and to evaluate its dosimetric characteristics: dose response, room temperature fading, heat treatment effect during post-irradiation storage. Results obtained up to now confirm that PGA seems to be suitable material for ESR dosimetry applications.

Biodegradable Poly(butylene adipate-co-terephthalate)/Poly(glycolic acid) Films: Effect of Poly(glycolic acid) Crystal on Mechanical and Barrier Properties

Binary biodegradable polymers films, poly(butylene adipate-co-terephthalate)(PBAT) and poly(glycolic acid)(PGA), were prepared through batch melt mixing to obtain Film Ⅰ and Film Ⅱ under two different processing conditions. PGA crystals played a major role in enhancing the mechanical and barrier properties of the films. For Film Ⅰ, there were initial PGA crystals before the film blowing process, the PGA molecular chain further crystallized, forming the oriented crystallization of PGA. Moreover, the Xcand crystalline size in Film Ⅰ were higher than those in Film Ⅱ. Compared with the different processing methods, Film Ⅰ has excellent mechanical and oxygen barrier properties due to the crystallization and orientation. The tensile strength reached 45.0 MPa, and tear strength exceeded 138.2 kN/m, while the elongation at break was as high as 750% for PBAT/PGA 85/15 in Film Ⅰ. The WVTR, WVP coefficients, and OP coefficients of PBAT/PGA films were decreased obviously with increasing the PGA content both in Film Ⅰ and Film Ⅱ. Moreover, the barrier properties of oxygen in Film Ⅰ were better than that in Film Ⅱ. This work reveals a feasible processing technique by introducing of initial crystallization of PGA to blow PBAT/PGA films with excellent mechanical and barrier properties.

Improvement on the Mechanical Performance and Resistance Towards Hydrolysis of Poly(glycolic acid)via Solid-state Drawing

Poly(glycolic acid)is a biocompatible as well as biocomposable polymer with superior mechanical and barrier properties and,consequently,has found important applications in both medical and packaging fields.However,the high hydrolysis rate in a high humidity environment restricts its application.In this work,a solid-state drawing process after melt extrusion is applied in order to produce fibrous PGA with enhanced mechanical properties and a much better resistance towards hydrolysis.The crystal structure of PGA gradually transformed from spherulites into oriented fibrous crystals in the stretching direction upon solid-state drawing.Meanwhile,both the length of microfibril and the size of lamellae increased initially with the drawing ratio(DR),while the chain-folded lamellae transformed into extended-chain fibrils at high(er)DR.The oriented structures lead to an overall improvement of the mechanical properties of PGA,e.g.,the tensile strength increased from 62.0±1.4 MPa to 910±54 MPa and the elongation at break increased from around 7%to 50%.Meanwhile,the heat capacity of totally mobile amorphous PGA(∆C_(p)^(0)=0.64 J·g^(−1)·℃^(−1))was reported for the first time,which was used to analyze the content of mobile amorphous fraction(XMAF)and rigid amorphous fraction(XRAF).Both the oriented chain-folded lamellae crystals and the tightly arranged RAF are beneficial to prevent water molecules from penetrating the matrix,thus improving the resistance towards hydrolysis.As a consequence,the fibrous PGA with a DR of 5 showed a tensile strength retention rate of 17.3%higher in comparison with the undrawn sample after 7-days accelerated hydrolysis.Therefore,this work provides a feasible method to improve the mechanical and resistance towards hydrolysis performance of PGA,which may broaden its application and prolong the shelf-life of PGA products.

Robust Poly(glycolic acid) Films with Crystal Orientation and Reinforcement of Chain Entanglement Network

The inherent brittleness of biodegradable poly(glycolic acid) (PGA) restricts its utilization in the packaging field. Traditional toughening methods usually require additional components accompanied by a sacrifice of strength. In the present work, PGA films with simultaneously enhanced strength and ductility are achieved via “casting-stretching-annealing” technology. The reinforced chain entanglement network of PGA induced by the intense extensional stress and the highly oriented crystals grown and refined during the stretching and annealing process endowed the improved ductility and strength of the PGA films, respectively. The relationships among the stretching process, microstructure and mechanical properties of the PGA films have been systematically investigated. As a result, the PGA film (SA-2) with low stretch ratios exhibits excellent ductility with an increase in elongation at break from 22% to 220% and tensile strength from 56 MPa to 130 MPa. Meanwhile, the PGA film (SA-4) with large stretch ratios features much higher tensile strength (335 MPa) while maintaining good ductility (elongation at break of 66%). In addition, highly oriented crystals result in obvious enhancement of heat resistance and dimensional stability of the PGA films. Therefore, this work provides an effective route to fabricate PGA films with both high strength and ductility which may promote the application of PGA materials.

Generation of Tough Poly(glycolic acid)(PGA)/Poly(butylene succinate-co-butylene adipate)(PBSA)Films with High Gas Barrier Performance through In situ Nanofibrillation of PBSA under an Elongational Flow Field

Poly(glycolic acid)(PGA)is derived from glycolide obtained by fermenting pineapples or sugarcane,which has excellent gas barrier properties and a small carbon footprint.PGA is a potential substitute for the current aluminum-plastic composite films used in high barrier packaging applications.However,its poor ductility and narrow processing window limit its application in food packaging.Herein,poly(butylene succinate-co-butylene adipate)(PBSA)was used to fabricate PGA/PBSA blend films through an in situ fibrillation technique and blown film extrusion.Under the elongational flow field used during the extrusion process,a unique hierarchical structure based on the PBSA nanofibrils and interfacially oriented PGA crystals was obtained.This structure enhances the strength,ductility and gas barrier properties of the PGA/PBSA blend film.In addition,an epoxy chain extender(ADR4468)was used as a compatibilizer to further enhance the interfacial adhesion between PGA and PBSA.70PGA/0.7ADR exhibited a very low oxygen permeability(2.34×10^(-4)Barrer)with significantly high elongating at break(604.4%),tensile strength(47.4 MPa),and transparency,which were superior to those of petroleum-based polymers.Thus,the 70PGA/0.7ADR blown films could satisfy the requirements for most instant foods such as coffee,peanuts,and fresh meat.

Tailoring the Crystallization Behavior and Mechanical Property of Poly(glycolic acid) by Self-nucleation

Biocompostable poly(glycolic acid)(PGA)crystallizes slowly under fast cooling condition,leading to poor mechanical performance of the final products.In this work,a self-nucleation(SN)route was carried out to promote the crystallization of PGA by regulating only the thermal procedure without any extra nucleating agents.When self-nucleation temperature(Ts)decreased from 250℃ to 227℃,the nuclei density was increased,and the non-isothermal crystallization temperature(Tc)of PGA was increased from 156℃ to 197℃ and the half-life time(t0.5)of isothermal crystallization at 207℃ was decreased by 89%.Consequently,the tensile strength and the elongation at break of the PGA were increased by 12%and 189%,respectively.According to the change of Tc as a function of Ts,a three-stage temperature domain map(Domain I,II and III)was protracted and the viscoelastic behavior of the self-nucleation melt and the homogeneous melt was studied.The results indicated that interaction among PGA chains was remained in Domain IIb,which can act as pre-ordered structure to accelerate the overall crystallization rate.This work utilizes a simple and effective SN method to regulate the crystallization behavior and the mechanical properties of PGA,which may broaden the application range of resulting materials.

Reaction pathways and selectivity in the chemo-catalytic conversion of cellulose and its derivatives to ethylene glycol:A review

Biomass-to-ethylene glycol is an effective means to achieve high-value utilisation of cellulose but is hindered by low conversion efficiency and poor catalyst activity and stability.Glucose and cellobiose are derivatives of cellulose conversion to ethylene glycol,and it is found that studying the reaction process of both can help to understand the reaction mechanism of cellulose.It is desirable to develop a reusable,highly active catalyst to convert cellulose into ethylene glycol.This ideal catalyst might have one or more active sites described the conversion steps above.Here,we discuss the catalyst development of celluloseto-ethylene glycol,including tungsten,tin,lanthanide,and other transition metal catalysts,and special attention is given to the reaction mechanism and kinetics for preparing ethylene glycol from cellulose,and the economic advantages of biomass-to-ethylene glycol are briefly introduced.The insights given in this review will facilitate further development of efficient catalysts,for addressing the global energy crisis and climate change related to the use of fossil fuels.

Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Catalytic Effect of Transition Metal Complexes of Triaminoguanidine on the Thermolysis of Energetic NC/DEGDN Composite

The transition metal complexes of triaminoguanidine(TAG-M,where M=Cobalt(Co)or Iron(Fe))have been prepared.The catalytic effect of these complexes on the thermolysis of energetic composite based on nitrocellulose and diethylene glycol dinitrate,has been investigated.Extensive characterization of the resulting energetic composites was carried out using scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and differential scanning calorimetry(DSC).Isoconversional kinetic analysis was performed to determine the Arrhenius parameters associated with the thermolysis of the elaborated energetic formulations.It is found that TAG-M complexes have strong catalytic effect on the thermo-kinetic decomposition of NC/DEGDN by decreasing the apparent activation energy and significantly increased the total heat release.The models that govern the decomposition processes are also studied,and it is revealed that different reaction processes are accomplished by introduction metal complexes of triaminoguanidine.Overall,this study serves as a valuable reference for future research focused on the investigation of catalytic combustion features of solid propellants.

Vomiting-induced pharyngeal perforation during bowel preparation for colonoscopy:A case report

BACKGROUND Effective bowel cleansing is essential for a successful colonoscopy.Laxatives,such as polyethylene glycol,are commonly used for bowel preparation.Vomiting is a frequent complication during bowel preparation,and forceful vomiting can potentially lead to esophageal perforation,as reported in several previous cases.However,pharyngeal perforation during bowel preparation has not been previously documented.Here,we present a case of pharyngeal perforation induced by forceful vomiting during bowel preparation.CASE SUMMARY A 38-year-old man with a history of hypertension,dyslipidemia,diabetes mellitus,and end-stage renal disease on hemodialysis was admitted for evaluation of recurrent abdominal pain.The patient complained of sudden pain in the neck,throat,and anterior chest following forceful vomiting during bowel preparation.Physical examination revealed crepitus under the skin of the neck and anterior chest on palpation,and upper gastrointestinal endoscopy revealed pharyngeal perforation.The perforation site was located above the upper esophageal sphincter,which distinguished it from Boerhaave’s syndrome.Conservative medical management was chosen after consultation with a thoracic surgeon and an otolaryngologist,considering the patient's mild symptoms,stable vital signs,and the small size of the lesion;the perforation resolved without endoscopic or surgical intervention.The patient was discharged from hospital two weeks after the perforation.CONCLUSION Despite its rarity,pharyngeal perforation should be considered a potential complication of bowel preparation for colonoscopy.

Hepatitis B cure:Current situation and prospects

Achievement of a‘clinical cure’in chronic hepatitis B(CHB)implies sustained virological suppression and immunological control over the infection,which is the ideal treatment goal according to domestic and international CHB management guidelines.Clinical practice has shown encouraging results for specific patient cohorts using tailored treatment regimens.These regimens incorporate either nucleos(t)ide analogs,immunomodulatory agents such as pegylated interferonα,or a strategic combination of both,sequentially or concurrently administered.Despite these advancements in the clinical handling of hepatitis B,achieving a clinical cure remains elusive for a considerable subset of patients due to the number of challenges that preclude the realization of optimal treatment outcomes.These include,but are not limited to,the emergence of antiviral resistance,incomplete immune recovery,and the persistence of covalently closed circular DNA.Moreover,the variance in response to interferon therapy and the lack of definitive biomarkers for treatment cessation also contribute to the complexity of achieving a clinical cure.This article briefly overviews the current research progress and existing issues in pursuing a clinical cure for hepatitis B.

Constipation and colonoscopy

Constipation is a significant sociomedical problem,which can be caused by various reasons.In the diagnostic approach to patients with constipation,the following data are usually sufficient:History,complete physical examination(including rectal examination),and additional diagnostic tests.A colonoscopy is not a necessary diagnostic method for all patients with constipation.However,if patients have alarm symptoms/signs,that suggest an organic reason for constipation,a colonoscopy is necessary.The most important alarm symptoms/signs are age>50 years,gastrointestinal bleeding,new-onset constipation,a palpable mass in the abdomen and rectum,weight loss,anemia,inflammatory bowel disease,and family history positive for colorectal cancer.Most endoscopists do not like to deal with patients with constipation.There are two reasons for this,namely the difficulty of endoscopy and the adequacy of preparation.Both are adversely affected by constipation.To improve the quality of colonoscopy in these patients,good examination techniques and often more extensive preparation are necessary.Good colonoscopy technique implies adequate psychological preparation of the patient,careful insertion of the endoscope with minimal insufflation,and early detection and resolution of loops.Bowel preparation for colonoscopy often requires prolonged preparation and sometimes the addition of other laxatives.

Implementation of a New Solution for the Preservation of Anatomical Specimens Made of Non-Toxic Substances

The preservation of anatomical pieces in Veterinary Anatomy is essential since it is not possible to dissect all domestic species. Most techniques use reagents with high levels of toxicity such as formaldehyde. The objective of this work was to develop a new preservation technique that uses reagents with zero toxicity and that allows obtaining preserved pieces suitable for anatomical studies. The alcohol propylene glycol technique was developed, the method of which uses a fixation step with alcohol, sodium chloride, commercial vinegar and subsequently the impregnation of the preservation solution made from propylene glycol and commercial vinegar, which are non-toxic. As a result of this work, adequately preserved sheep hearts were obtained that preserved their morphology with slight changes in size and weight, which did not affect their external and internal anatomical structure. Its coloration was not substantially affected, remaining a little lighter. The pieces obtained showed flexibility which allowed dissections to be carried out. The time to develop the technique was 20 days. A comparative study was carried out with the phenolated glycerin technique that uses toxic reagents (formaldehyde and phenol) and the pieces obtained with the alcohol propylene glycol technique were of better quality, observing that the pieces with phenolated glycerin tend to darken and are more rigid. And the time to develop the technique is 24 days. In conclusion, a preservation technique for anatomical pieces was developed that allowed the preservation of the organs under study, which allow their use for anatomical studies, and which have been preserved without changes until the time of this publication (8 months) and there are pieces preserved with this technique for 2 years.

Research Progress of Bowel Preparation for Colonoscopy

Colorectal cancer ranks third in the global cancer data in 2020. Colorectal scope is the most effective method to diagnose colorectal diseases such as benign and malignant colorectal tumors. The poor quality of intestinal preparation causes an increased rate of missed diagnosis of colorectal tumors, reduces the rate of cecal intubation for colorectal examination, increases the discomfort, and reduces the compliance of re-examination. Therefore, we should try our best to improve the quality of intestinal preparation. This study reviewed the latest advances related to the preoperative preparation for colonoscopy. Recent research shows that smartphone apps can provide more detailed education and guidance on bowel preparation;Pre-packaged foods are more suitable as a way to eat before colonoscopy. The use of smaller doses, better taste of cathartic agents, and some auxiliary measures, combined with the patient’s situation to provide personalized intestinal preparation measures to improve the quality of intestinal preparation. Starting from the quality of colonoscopy bowel preparation, continuous improvement of patients’ tolerance to bowel preparation, continuous improvement of bowel preparation plan based on individual factors’ needs, and better communication with examined subjects by using existing scientific information technology, may be the hot spot of colonoscopy bowel preparation research in the next few years.

Bacterial cellulose/glycolic acid/glycerol composite membrane as a system to deliver glycolic acid for anti-aging treatment

Glycolic acid(GA),as an anti-aging skincare ingredient,plays a pivotal role in anti-aging treatment.However,its benefits could be overshadowed due to its side effects including skin burning and irritation when overused.Bacterial cellulose(BC)is a highly pure form of cellulose,biosynthesized in the form of a swollen membrane by several kinds of bacteria that was demonstrated to modulate the release of model drugs owing to its porous and 3D fibrous network structure,and glycerol(GL),as a plasticizer,could enhance the controlled drug delivery.Herein,we report a topical controlled drug delivery system based on BC membrane,GA and GL for controlling sustainable release of GA to reduce its side effects on the skin,while maintaining its prolonged and maximum therapeutic effect.The results showed that the incorporation of GL increased the malleability and flexibility of BC/GA/GL membrane,as compared with BC/GA membrane.In addition,the GL enhanced the control of the GA delivery,as evidenced by a higher swelling capacity and thereby a slower release of the GA from BC/GA/GL membrane.More importantly,in vitro study indicated that both BC/GA and BC/GA/GL membranes could effectively stimulate endogenous collagen synthesis in NIH3T3 cells owing to the release of GA,and that BC/GA/GL membrane is more conducive to a long-term cell adhesion,spreading,and proliferation of NIH3T3 and HaCaT cells due to its lower and sustainable release of GA than BC/GA membrane.This study suggests the BC/GL/GA composite membrane holds great promise as an appealing platform to control the release of GA to greatly promote renewal of skin cells for effective anti-aging treatment.

Effect of 5%glycolic acid complex and 20%glycolic acid on mild-to-moderate facial acne vulgaris

To the Editor:Acne vulgaris is a chronic,inflammatory,and disfiguring skin disease with lesions,post-inflammatory hyperpigmentation,and scarring.Chemical peeling is a simple and well-tolerated procedure for mild-to-moderate acne.Glycolic acid(GA)is water-soluble and has the smallest molecular weight among all the alpha-hydroxy acids.High-concentration GA(20%–70%),applied at 2 to 4-week intervals in the hospital or cosmetology clinic,have proved effective for acne.[1]Low-concentration GA(10%)is safe and convenient,and can be used at home.[2]Up to now,differences in efficiency between low and high concentrations of GA for acne vulgaris have not been reported.This study compared the efficacy and safety of 5%GA complex and 20%GA for acne patients,to guide GA selection at different concentrations.