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1.
Zhonghua Wai Ke Za Zhi ; 60(10): 948-954, 2022 Oct 01.
Article in Chinese | MEDLINE | ID: mdl-36207984

ABSTRACT

Objective: To compare the short-term and long-term prognosis of irreversible electroporation(IRE) and conversional resection for locally advanced pancreatic cancer(LAPC). Methods: The clinical and pathological data of 98 LAPC patients who underwent IRE or conversional resection at the Department of Pancreatobiliary Surgery,Sun Yat-sen University Cancer Center from August 2015 to December 2020 were retrospectively collected and analyzed.The study comprised of 53 males and 45 females, with age(M(IQR)) of 57.5(13.5)years old(range:20 to 87 years old). Fifty-three patients received IRE treatment(IRE group) and 45 patients received surgical resection(resection group). The differences of clinical and pathological data between both groups were not significant(all P<0.05). The Mann-Whitney U test was used for quantitative data and the χ2 test was used for categorical data.Survival was analyzed using Kaplan-Meier method and compared using Log-rank test. Results: The operation time and intraoperative blood loss were 5.0(2.4)hours and 50(100) ml in the IRE group,respectively,which were significantly less than those of resection group(7.0(3.3)hours and 400(200)ml,both P<0.05).The hospital stay and hospitalization cost were 9.0(3.0)days and 79 154 (83 738) yuan in the IRE group,respectively,which were also significantly less than those in the resection group(16.0(8.5)days and 109 557(37 795)yuan,both P<0.05).The complication rate of IRE group was significantly lower than that of the resection group(18.8% vs. 55.6%,χ2=14.270,P<0.01).The median overall survival(OS) time of IRE group was 28.9 months(95%CI:23.2 to 34.6 months),with the 1-,2-,and 3-year OS rates of 91.6%,61.7%,and 24.6%,respectively.The median survival of OS of resection group was 27.1 months(95%CI:20.9 to 33.3 months),with the 1-,2-,and 3-year OS rates of 81.8%,53.9%,and 30.3%,respectively.There was no significant difference in OS between the two groups(χ2=0.900,P=0.760).The median progression free survival(PFS) time of IRE group was 18.0 months(95%CI:14.7 to 21.3 months),with the 1-,2-,and 3-year PFS rates of 68.3%,29.7%,and 9.9%,respectively.The median survival of PFS of resection group was 11.1 months(95%CI:6.1 to 16.2 months),with the 1-,2-,and 3-year PFS rates of 45.2%,21.9%,and 14.6%,respectively.There was no significant difference in PFS between the two groups(χ2=1.850,P=0.170). Conclusion: IRE can achieve similar survival for LAPC and may has less complications compared to those with conversion resection.


Subject(s)
Neoplasms, Second Primary , Pancreatic Neoplasms , Adolescent , Adult , Aged , Aged, 80 and over , Electroporation/methods , Female , Humans , Male , Middle Aged , Pancreas/pathology , Pancreatic Neoplasms/pathology , Prognosis , Retrospective Studies , Treatment Outcome , Young Adult
2.
Sci Rep ; 11(1): 23108, 2021 Nov 29.
Article in English | MEDLINE | ID: mdl-34845272

ABSTRACT

Interfacial adhesion between polymer matrix and reinforcing silica nanoparticles plays an important role in strengthening polypropylene (PP) composite. To improve the adhesion strength, the surface of silica nanoparticles can be modified by grafted functional molecules. Using atomistic simulations, we examined the effect of functionalization of silica nanoparticles by hexamethyldisilazane (HMDS) and octyltriethoxysilane (OTES) molecules on the deformation and failure of silica-reinforced PP composite. We found that the ultimate tensile strength (UTS) of PP composite functionalized by OTES (28 MPa) is higher than that of HMDS (25 MPa), which is in turn higher than that passivated only by hydrogen (22 MPa). To understand the underlying mechanistic origin, we calculated the adhesive energy and interfacial strength of the interphase region, and found that both the adhesive energy and interfacial strength are the highest for the silica nanoparticles functionalized by OTES molecules, while both are the lowest by hydrogen. The ultimate failure of the polymer composite is initiated by the cavitation in the interphase region with the lowest mass density, and this cavitation failure mode is common for all the examined PP composites, but the cavitation position is dependent on the tail length of the functional molecules. The present work provides interesting insights into the deformation and cavitation failure mechanisms of the silica-reinforced PP composites, and the findings can be used as useful guidelines in selecting chemical agents for surface treatment of silica nanoparticles.

3.
Zhonghua Wai Ke Za Zhi ; 58(10): 787-792, 2020 Oct 01.
Article in Chinese | MEDLINE | ID: mdl-32993267

ABSTRACT

Objective: To examine the safety and clinical efficacy of ultrasound-guided irreversible electroporation (IRE) using the open surgery approach, after induction chemotherapy, in the treatment of locally advanced pancreatic cancer (LAPC) . Methods: The data of 64 LAPC patients who underwent ultrasound-guided IRE using the open surgery approach after induction chemotherapy at Department of Pancreatobiliary Surgery, Sun Yat-sen University Cancer Center from August 2015 to March 2019 were retrospectively analyzed. The study comprised of 30 males and 34 females, with median age of 58.5 years old (range: 34 to 87 years old) , were included in this study.The tumor was located in the pancreatic head and body/tail in 30 and 34 patients, respectively.The largest recorded tumor size was 6.1 cm (≤4.0 cm: n=35; >4.0 cm: n=29) .To create an electric field around the tumor, Two to six probes were parallelly inserted into each patient's tumor, based on the size of the tumor, at a distance of 2 cm apart through the transverse mesocolon in a caudal-to-cranial direction.According to the numerical sequence of patients undergoing ultrasound-guided IRE, the first 15 cases and following 49 patients were categorized as the primary and secondary treatment group, respectively.T text or χ(2) test was analyzed to the data between two groups.The study endpoints were overall survival (OS) and progression free survival (PFS) , which were investigated using Kaplan-Meier method, and their differences were compared using log-rank test. Results: The overall length of hospital stay was (8.9±2.7) days (range: 5 to 20 days) . Four patients were lost to follow-up.The study follow-up rate was 93.8%, with a median follow-up time of 29.3 months (range: 13.5 to 55.7 months) .The median OS and PFS of the entire cohort was 24.6 months (95% CI: 22.0 to 27.3 months) and 12.0 months (95%CI: 8.8 to 15.2 months) , respectively.One month after IRE, abdominal pain was significantly relieved in 95.3% of the patients (t=-28.55, P<0.01) .The rate of complications in the entire cohort was 20.3% and all were classified as grade B.Of them, pancreatic fistula, incisional infection, and upper gastrointestinal hemorrhage were observed in 7, 4, and 2 cases, respectively.The rate of complications for patients in the primary and secondary treatment groups were significantly different (10/15 vs. 6.1%) , respectively (χ(2)=26.01, P<0.01) .Further, two deaths were observed after IRE in the primary treatment group, while none was observed in the secondary treatment group. Conclusions: Ultrasound-guided IRE using the open surgery approach after induction chemotherapy is found to be safe and effective in treating patients with LAPC.However, these findings should be validated in prospective randomized trials before wide clinical application.


Subject(s)
Antineoplastic Agents/administration & dosage , Electroporation , Pancreatic Neoplasms , Ultrasonography, Interventional , Adult , Aged , Aged, 80 and over , Antineoplastic Agents/therapeutic use , Combined Modality Therapy , Electroporation/methods , Female , Humans , Male , Middle Aged , Neoadjuvant Therapy , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/pathology , Pancreatic Neoplasms/surgery , Retrospective Studies
4.
Zhonghua Xin Xue Guan Bing Za Zhi ; 48(9): 765-771, 2020 Sep 24.
Article in Chinese | MEDLINE | ID: mdl-32957760

ABSTRACT

Objective: To investigate the effects of clopidogrel resistence and CYP2C19 genotype on the clinical prognosis of acute coronary syndrome(ACS) patients undergoing percutaneous coronary intervention(PCI). Methods: This study was a retrospective cohort study. ACS patients who underwent PCI in Beijing Anzhen Hospital from October 2015 to January 2017 were recruited. The inhibition rate of adenosine diphosphate(ADP) was monitored by thromboelastography. All of these patients were divided into clopidogrel resistance and non-resistance group according to the monitoring results. CYP2C19 genotype was detected by TaqMan probe-based real-time quantitative PCR. Patients were divided into slow, medium and fast metabolic group, according to the CYP2C19 genotype. After 12 months of follow-up, the end points included all-cause death, cardiac death, angina, myocardial infarction, stent thrombosis, ischemic stroke and hemorrhage were collected. Combined thrombotic events were defined as a composite of angina, myocardial infarction, stent thrombosis and ischemic stroke. The differences of the incidence of clinical events between groups were compared. Cox regression was used to analyze the effects of clopidogrel resistance and CYP2C19 genotype on the combined thrombotic events, cardiac death and hemorrhage. Results: A total of 1 696 patients were included, and the age was (59.4±9.6) years, with 1 280(75.5%) males. There were 471 cases(27.8%) in clopidogrel resistance group, and 1 225 cases(72.2%) in clopidogrel non-resistance group. There were 218 patients(12.9%) were in slow metabolic group, 668(39.4%) in medium metabolic group, and 810 (47.8%) in fast metabolic group. The median follow-up time was 13.3 months, and 131 cases were lost to follow-up, with a loss follow-up rate of 7.7%. Compared with the clopidogrel non-resistance group, the clopidogrel resistance group had a higher incidence of myocardial infarction(7.6%(36/471) vs. 5.1%(62/1 225), P=0.041), a lower incidence of hemorrhage (13.2%(62/471) vs. 17.9%(219/1 225), P=0.020) and minor hemorrhage(11.5%(54/471) vs. 15.8% (194/1 225), P=0.022). There were no statistically significant difference in all-cause death, cardiac death, angina, stent thrombosis, ischemic stroke and severe bleeding between clopidogrel resistance and non-resistance group(all P>0.05). There was no statistically significant difference in the incidence of endpoint events among different CYP2C19 genotypes (all P>0.05). Cox regression analysis showed that clopidogrel resistance was an independent factor of combined thrombotic events (OR=2.334, 95%CI 1.215-4.443, P=0.016) and bleeding events (OR=0.481, 95%CI 0.174-0.901, P=0.023). While CYP2C19 genotype was not independent factor for combined thrombotic events, cardiac death and hemorrhage (all P>0.05). Conclusion: For ACS patients after PCI, clopidogrel resistance can increase the risk of combined thrombotic events, but also reduce the risk of bleeding; while CYP2C19 genotype is not an independent factor for clinical prognosis.


Subject(s)
Acute Coronary Syndrome , Clopidogrel , Percutaneous Coronary Intervention , Platelet Aggregation Inhibitors , Acute Coronary Syndrome/drug therapy , Acute Coronary Syndrome/genetics , Clopidogrel/pharmacology , Clopidogrel/therapeutic use , Cytochrome P-450 CYP2C19/genetics , Genotype , Humans , Male , Platelet Aggregation Inhibitors/pharmacology , Platelet Aggregation Inhibitors/therapeutic use , Prognosis , Retrospective Studies , Treatment Outcome
5.
Andrology ; 8(2): 268-276, 2020 03.
Article in English | MEDLINE | ID: mdl-31464074

ABSTRACT

BACKGROUND: Erectile dysfunction (ED) is a tough problem in medicine. This article aims to provide the latest evidence for the efficacy and safety of traditional Chinese medicine (TCM) combined with tadalafil in treatment of erectile dysfunction. METHODS: All randomized controlled trials that Chinese herbal medicine combined with tadalafil for erectile dysfunction were included in databases of China National Knowledge Infrastructure (CNKI), Wanfang, Weip Database, China Biology Medicine disc (CBM), MEDLINE, EMBASE, and Cochrane Library. The quality of the included articles was evaluated using Cochrane Reviewer's Handbook 5.3, and meta-analysis was performed using Stata 13.1. RESULTS: A total of 11 studies including 451 cases in the treatment group and 452 cases in the control group were obtained. Compared with tadalafil alone, meta-analysis suggests there were statistically significant differences in International Index of Erectile Function-5 (IIEF-5), effective rate, Sexual Encounter Profile questions 2 and 3 (SEP-Q2, SEP-Q3) between traditional Chinese medicine combined with tadalafil, and no statistically significant differences in side effects between the two groups. All included studies were tested for publication bias, and the results indicated that there was no significant bias. Two of the articles mentioned the scheme that traditional Chinese medicine combined with low-dose tadalafil for erectile dysfunction by down stairs. CONCLUSION: Traditional Chinese medicine combined with tadalafil has significant efficacy in the treatment of ED with no increase in side effects. The specific implementing regulations and effect of de-escalation therapy still need more long-term, multicenter, randomized, and double-blind clinical trials.


Subject(s)
Drugs, Chinese Herbal/therapeutic use , Erectile Dysfunction/drug therapy , Phosphodiesterase 5 Inhibitors/therapeutic use , Tadalafil/therapeutic use , Humans , Male , Treatment Outcome
6.
Genet Mol Res ; 14(4): 12472-8, 2015 Oct 16.
Article in English | MEDLINE | ID: mdl-26505397

ABSTRACT

Crab grows by periodic molting, which is controlled by molt-inhibiting hormone (MIH) and ecdysteroids. Untranslated regions (UTRs) play crucial roles in the posttranscriptional regulation of gene expression. In this study, using crab collected from Changjiang (Yangtze), Huanghe (Yellow), Liaohe, and Yalujiang rivers, 33 haplotypes of the 3ꞌ-UTR of ecdysteroid-regulated protein (ERP) gene were identified, of which 14 haplotypes were observed in more than one individual. One hundred and forty clones of haplotype h2 (41.5%) were observed in samples from all the 4 rivers. Three haplotypes were observed to be insertions. For the whole crab sample, we found a positive Tajima's D value and a negative Fu's Fs test (Tajima's D value = 0.98726; Fu's Fs test = -27.382), although the P values were not significant (P > 0.10). The network profile of these 33 haplotypes presented a single core pattern with h2 as the core. In this study, we found that the UTR of ERP gene had a considerably high genetic polymorphism among crab from regions south to north of China. Furthermore, we observed a relatively high genetic divergence among different haplotypes, which would suggest a high diversity of the crab gene pool.


Subject(s)
Brachyura/genetics , Genetic Variation/genetics , Molting/genetics , 3' Untranslated Regions/genetics , Animals , Haplotypes/genetics , Polymorphism, Genetic/genetics
7.
Genet Mol Res ; 14(1): 2055-62, 2015 Mar 20.
Article in English | MEDLINE | ID: mdl-25867351

ABSTRACT

The major histocompatibility complex (MHC) is one of the most important genetic systems associated with resistance to infectious diseases in vertebrates. The spotted seal (Phoca largha) is one of the most endangered species in China. In this study, we present the first step in the molecular characterization of a DRB-like locus in the spotted seal by analyzing the nucleotide sequence of the polymorphic exon 2 segments, a 288-nucleotide sequence. By examining the segment from a group of 41 individuals, 28 alleles were identified. No deletion, insertion, or exceptional stop codon was detected, suggesting that these alleles could be functional in vivo. The nucleotide and amino acid sequences of the segment both showed a relatively high level of similarity (nucleotides 97%; amino acids 98%) to those of Meles meles and Zalophus californianus. The high level of spotted seal MHC-DRB polymorphism revealed in the present study has not been reported for the Phocidae and could be a consequence of the small spotted seal population adapting to the Bohai Sea, which probably has a relatively high level of pathogens.


Subject(s)
Major Histocompatibility Complex/genetics , Phoca/genetics , Alleles , Amino Acids/genetics , Amino Acids/metabolism , Animals , China , Exons , Gene Duplication , Genetic Variation , High-Throughput Nucleotide Sequencing , Phoca/classification , Phylogeny , Polymorphism, Genetic
8.
Genet Mol Res ; 14(1): 2253-67, 2015 Mar 27.
Article in English | MEDLINE | ID: mdl-25867372

ABSTRACT

C-type lectins are a superfamily of Ca(2+)-dependent carbohydrate-recognition proteins that are well known for their participation in pathogen recognition and clearance. In this study, a putative C-type lectin fold (MyCLF) gene was identified from the Japanese scallop Mizuhopecten yessoensis. The full-length of MyCLF was 645 bp, encoding a polypeptide of 167 amino acids. MyCLF carried a signal peptide of 20 amino acid residues, and a single carbohydrate recognition domain, having relatively high amino acid sequence conservation with C-type lectins reported for other bivalves. The expression of MyCLF mRNA transcripts in adult tissues, after bacterial challenge and during different developmental stages was determined using real-time quantitative RT-PCR. MyCLF was mainly distributed in the mantle, gill, and kidney. The expression of MyCLF clearly increased 3 h after Vibrio anguillarum challenge, and dropped to a minimum level after 9 h compared to the control group. During embryonic development, the expression level increased in the gastrulae, trochophore and early D-shaped larvae, decreased in D-shaped larvae, and then increased hundreds of times in metamorphosing larvae. The results suggested that MyCLF was involved in an immune response and it may play important roles during the metamorphosis phase of M. yessoensis.


Subject(s)
Immunity/genetics , Lectins, C-Type/genetics , Metamorphosis, Biological/genetics , Pectinidae/genetics , Amino Acid Sequence , Animals , Base Sequence , Cloning, Molecular , DNA, Complementary/chemistry , DNA, Complementary/genetics , Gene Expression Profiling , Gene Expression Regulation, Developmental , Larva/genetics , Larva/growth & development , Lectins, C-Type/chemistry , Lectins, C-Type/classification , Models, Molecular , Molecular Sequence Data , Pectinidae/embryology , Pectinidae/growth & development , Phylogeny , Protein Conformation , Reverse Transcriptase Polymerase Chain Reaction , Sequence Analysis, DNA , Sequence Homology, Amino Acid
9.
Genet Mol Res ; 13(4): 10727-40, 2014 Dec 18.
Article in English | MEDLINE | ID: mdl-25526193

ABSTRACT

Chitinase-like proteins (CLP) are important members of the glycoside hydrolase family 18 (GH18) and are involved in growth control and remodeling processes. In this study, a CLP transcript was isolated and sequenced from the Japanese scallop (Mizuhopecten yessoensis) after screening expressed sequence tags. The full-length complementary DNA of M. yessoensis CLP (My-Clp1) was 1555 bp in length, consisting of a 75-bp 5'-untranslated region (UTR), a 160-bp 3'-UTR, and a 1320-bp open reading frame bearing characteristics of the GH18 family. The My-Clp1 protein was well conserved, with similar domain structures and architecture across species (e.g., from mollusks to mammals). Expression analysis in healthy tissues and across developmental stages revealed a strong preference for expression; My-Clp1 was abundantly expressed in the mantle and throughout metamorphosis, which suggests the involvement of My-Clp1 in the synthesis of extracellular components, and tissue degeneration and remodeling. My-Clp1 expression was induced after infection with a bacterial pathogen, Vibrio anguillarum, suggesting its involvement in immunity against this intracellular pathogen.


Subject(s)
Chitinases/genetics , DNA, Complementary/genetics , Pectinidae/physiology , Transcriptome/physiology , Amino Acid Sequence , Animals , Base Sequence , Chitinases/chemistry , Chitinases/metabolism , DNA, Complementary/metabolism , Molecular Sequence Data , Organ Specificity/genetics , Pectinidae/microbiology , Phylogeny , Vibrio/pathogenicity , Vibrio Infections/metabolism
10.
Genet Mol Res ; 13(3): 4956-66, 2014 Jul 04.
Article in English | MEDLINE | ID: mdl-25062483

ABSTRACT

Pattern recognition molecules play an important role in innate immunity by recognizing conserved molecular patterns that are present on the surface of invading microorganisms. In this study, a lipopolysaccharide and ß-1,3-glucan binding protein (LGBP) gene was cloned from the hard clam Meretrix meretrix (designated as Mm-LGBP) by the expressed sequence tags and rapid amplification of cDNA ends method. The cDNA was 1827 bp in length, consisting of a 71-bp 5'-terminal untranslated region, a 62-bp 3'UTR, and a 1734-bp open reading frame encoding a 577-amino acid polypeptide with an estimated molecular mass of 60.7 kDa and a theoretical isoelectric point of 5.56. Characteristic potential polysaccharide binding, cell adhesion, and glucanase motifs were identified in the Mm-LGBP, indicating that Mm-LGBP should be a new member of the LGBP family. Quantitative real-time polymerase chain reaction was developed to detect the mRNA expression level of Mm-LGBP in 6 different tissues. Higher-level mRNA expression of Mm-LGBP was detected in the gill and digestive gland tissues. The upregulation of Mm-LGBP mRNA after Vibrio anguillarum challenge showed that Mm-LGBP play a pivotal role in antibacterial immunity.


Subject(s)
Bivalvia/genetics , Lectins/genetics , Lipopolysaccharides/metabolism , beta-Glucans/metabolism , 3' Untranslated Regions , 5' Untranslated Regions , Amino Acid Motifs , Animals , Base Sequence , Bivalvia/classification , Bivalvia/immunology , Bivalvia/microbiology , Cloning, Molecular , Gene Expression Regulation , Lectins/chemistry , Lectins/immunology , Lipopolysaccharides/chemistry , Molecular Sequence Data , Molecular Weight , Open Reading Frames , Phylogeny , Protein Binding , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Vibrio/pathogenicity , Vibrio/physiology , beta-Glucans/chemistry
11.
Genet Mol Res ; 13(1): 1989-92, 2014 Mar 24.
Article in English | MEDLINE | ID: mdl-24737424

ABSTRACT

Japanese scallop (Mizuhopecten yessoensis) is a cold-water shellfish, and a species of economic importance in China. In this study, we developed and evaluated simple sequence repeat (SSR) markers from the expressed sequence tags (ESTs) of M. yessoensis. The characteristics of 12 EST-SSR loci were investigated in 30 individual scallops, and the result revealed that the number of alleles per locus ranged from 2-4, with an observed heterozygosity ranging from 0.0333-0.7692, and an expected heterozygosity ranging from 0.0333-0.6312. Only two loci were found to depart significantly from the Hardy-Weinberg equilibrium (P < 0.05). The result of our study suggested that these markers could be considered as potential markers for studying the population structure of M. yessoensis and its intraspecific variation.


Subject(s)
Expressed Sequence Tags , Microsatellite Repeats , Pectinidae/genetics , Animals , Genetic Markers , Polymorphism, Genetic
12.
Langmuir ; 27(17): 10538-47, 2011 Sep 06.
Article in English | MEDLINE | ID: mdl-21761846

ABSTRACT

We report the formation and characterization of stable dispersions of hybrid nanoparticles in solution formed via stereocomplexation of enantiomeric poly(lactide) hybrid star polymers. The hybrid starlike polymers, having polyhedral oligomeric silsesquioxane (POSS) nanocages as the core and either poly(L-lactide) (PLLA) or poly(D-lactide) (PDLA) as the arms, are synthesized via ring-opening polymerization of lactide using octafunctional POSS as the macroinitiator. In the solid state, differential scanning calorimetry and wide-angle X-ray scattering measurements confirmed the formation of the stereocomplex in the mixture of POSS-star-PLLA and POSS-star-PDLA (50:50, wt %). In a solution of the same mixture in tetrahydrofuran (THF), sterocomplexation leads to formation of hybrid nanaoparticles. Detailed accounts of the nanoparticle formation and influence of aging and concentration have been presented. It was observed that at low concentration the stereocomplexed nanaoparticles remain stable over 45 days and are not sensitive to dilution, suggesting the formation of a stable hybrid nanoparticle dispersion in solution. In contrast, the aggregates of the individual POSS-star-PLLA or POSS-star-PDLA in THF, formed via weak solvophobic interactions, tended to disintegrate into smaller aggregates on dilution. Exploiting the PLLA-PDLA stereocomplexation with an appropriate molecular design can be a versatile route to develop stable organic/inorganic hybrid nanoparticle dispersions.


Subject(s)
Nanoparticles/chemistry , Organosilicon Compounds/chemistry , Polyesters/chemistry , Models, Molecular , Molecular Structure , Stereoisomerism
13.
Langmuir ; 26(14): 11763-73, 2010 Jul 20.
Article in English | MEDLINE | ID: mdl-20536258

ABSTRACT

A series of well-defined amphiphilic di- and triblock copolymers have been synthesized, using atom transfer radical polymerization, with poly(ethylene glycol) (PEG) and poly(methacrylisobutyl polyhedral oligomeric silsesquioxane) P(MA-POSS) as the hydrophilic and hydrophobic blocks, respectively. The detailed self-assembly behavior of the amphiphilic macromolecules in aqueous media was studied using both static and dynamic light scattering (SLS and DLS) techniques. The evolution of block copolymer micelle formation in THF/water mixture (20/80 v/v) was monitored as the THF evaporated from the solvent mixture. Initially the block copolymer chains existed as unimers in solution, followed by the formation of smaller aggregates (R(h) < 2 nm) after 30 min, eventually growing in size to reach an equilibrium size when all the THF evaporated within 24 h. The micelles formed by the block copolymers were found to be kinetically unstable (not frozen); i.e., they tended to revert to individual copolymer chains on dilution. The hydrodynamic radii, R(h), of the micelles varied with the degree of polymerization (DP) of the hydrophobic P(MA-POSS); for example, for PEG(5K)-b-P(MA-POSS), an increase from R(h) approximately 13.3 +/- 1.1 nm to R(h) approximately 17.5 +/- 1.4 nm was observed with a nominal change in the DP of P(MA-POSS) from 4 to 6. The micelles formed by the triblock copolymers (P(MA-POSS)-b-PEG(10K)-b-P(MA-POSS)) were comparable in size to the diblock copolymer micelles; e.g., R(h) approximately 14.0 +/- 1.3 nm was found for P(MA-POSS)(4)-b-PEG(10K)-b-P(MA-POSS)(4). The micellar structures created by the triblocks in aqueous media were "flowerlike", where the PEG middle block adopted a loop conformation in the micelle corona. In addition to micelles, larger aggregates formed by P(MA-POSS)-b-PEG(10K)-b-P(MA-POSS) were also detected in solution. The larger aggregates may suggest a contribution from some PEG blocks adopting an extended conformation with one end dangling in solution, causing gelation at higher copolymer concentrations via intermicellar interactions. The P(MA-POSS)(4)-b-PEG(10K)-b- P(MA-POSS)(4) formed a gel in water at approximately 8.8 wt % copolymer concentration. No gel formation by diblock copolymers was observed; however, the addition of a small amount of triblock copolymer to an aqueous solution of diblock copolymer results in gel formation. Finally, rheological behavior of the obtained gels was also investigated.

14.
Langmuir ; 26(4): 2361-8, 2010 Feb 16.
Article in English | MEDLINE | ID: mdl-19785395

ABSTRACT

Well-defined fluorinated brush-like amphiphilic diblock copolymers of poly[poly(ethylene glycol)methyl ether methacrylate] (P(PEGMA)) and poly(pentafluorostyrene) (PPFS) have been successfully synthesized via atom transfer radical polymerization (ATRP). The self-assembly behavior of these polymers in aqueous solutions was studied using (1)H NMR, fluorescence spectrometry, static and dynamic light scattering and transmission electron microscopy techniques. The micellar structure comprised of PPFS as the core and brush-like (hydrophobic main chain and hydrophilic branches) polymers as the coronas. The hydrodynamic radius (R(h)) of the micelles in aqueous solution was in the nanometer range, independent of the polymer concentration, consistent with a closed association model. Diblock copolymers with a longer P(PEGMA) block formed micelles with smaller R(h) and lower aggregation numbers consistent with an improved solubilization of the core. The micelles possessed a thick hydration layer as verified by the ratio of the radius of gyration, R(g) to the hydrodynamic radius, R(h). The aggregation number and ratio of R(g) to R(h) were observed to increase with temperature (20-50 degrees C), while the R(h) of the micelle decreased slightly over the same temperature range. An increase in temperature induced the brush-like PEG segments in the corona to dehydrate and shrink while forming micelles with larger aggregation numbers.


Subject(s)
Methacrylates/chemistry , Polyethylene Glycols/chemistry , Polyethylene Glycols/chemical synthesis , Polystyrenes/chemical synthesis , Polymethacrylic Acids , Polystyrenes/chemistry , Solutions , Water/chemistry
15.
Langmuir ; 25(10): 5557-64, 2009 May 19.
Article in English | MEDLINE | ID: mdl-19371048

ABSTRACT

The micelle formation by the amphiphilic polystyrene-block-poly(N-vinylpyrrolidone) (PS48-b-PNVP99) copolymer is investigated in methanol and water-methanol binary mixtures of various compositions using 1H NMR, fluorescence spectroscopy, static/dynamic light scattering (SLS/DLS), and transmission electron microscopy (TEM). Critical micelle concentrations (cmc) are determined by employing fluorescence spectroscopy and DLS measurements. The cmc of the PS48-b-PNVP99 block copolymer increases with increasing methanol content in the water-methanol binary mixtures, suggesting that methanol is a better solvent for the PS48-b-PNVP99 block copolymer than water-methanol mixtures or pure water. The amphiphilic PS48-b-PNVP99 diblock copolymer forms spherical micelles of Rh approximately 16 nm in pure methanol solution as revealed by DLS measurements. In contrast, significantly larger micelles having higher aggregation numbers are formed in water-methanol binary mixtures. Temperature dependent data reveal an increase in aggregation number and radius of gyration (Rg) concomitantly with temperature (10-40 degrees C). In contrast, the overall size (Rh) of the micelles remains almost constant over the same temperature range. An explanation is tendered that PNVP coronas dehydrate/desolvate at higher temperatures counteracting the increase in micelle size (Rh) caused by increased aggregation numbers (Nagg).

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