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1.
Eur J Surg Oncol ; 50(9): 108525, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38991288

RESUMO

This review explores the impact of exercise on post-surgical recovery in breast cancer patients. Breast cancer, the most prevalent cancer globally, necessitates treatments beyond conventional modalities such as surgery, chemotherapy, radiotherapy, and immunotherapy. While exercise as an adjuvant therapeutic tool is not novel, it is generally accepted for improving cancer outcomes. Yet, it is not included in current treatment guidelines. This study reviews literature using the FACT-B (Functional Assessment of Cancer Therapy - Breast) tool to evaluate quality of life in breast cancer patients undergoing exercise interventions post-surgery. Despite mixed results, with some studies showing significant improvements and others indicating no notable benefits, the general consensus suggests potential advantages of integrating structured exercise programs into recovery protocols. Standardizing the use of quality of life measures like FACT-B could enhance future research and clinical practices, leading to more effective patient care strategies.


Assuntos
Neoplasias da Mama , Terapia por Exercício , Qualidade de Vida , Humanos , Neoplasias da Mama/cirurgia , Neoplasias da Mama/terapia , Feminino , Terapia por Exercício/métodos , Mastectomia , Exercício Físico
2.
Orthop Surg ; 16(7): 1530-1537, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38798039

RESUMO

Total knee arthroplasty (TKA) is a common surgery for osteoarthritis, with increasing prevalence expected in the near future. This systematic review and meta-analysis compared the effectiveness of computerized TKA versus traditional TKA, focusing on postoperative outcomes measured by the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and the Knee Society score (KSS). A search on PubMed and Cochrane databases on November 14, 2023 for retrospective randomized controlled trials (RCTs) yielded data on WOMAC and KSS. The search strategy was predefined, and methodological quality of studies was critically appraised. Two researchers extracted data. Unpaired t-testing assessed the mean monthly changes in KSS and WOMAC for computer-aided versus traditional TKA. Review Manager 5.3 was used for data synthesis and analysis. Out of 729 records, five RCTs enrolling 339 patients were eligible and analyzed using a random effects meta-analysis. The mean monthly ΔKSS score differed significantly between the traditional and computerized groups (11.47 ± 8.76 vs. 9.26 ± 6.05, respectively; p < 0.01). However, the pooled mean difference estimate showed no significant differences (D = 0.20, 95% CI = -0.53 to 0.93, p = 0.59), with high heterogeneity (I2 = 85%, p < 0.001). The mean monthly ΔWOMAC score also differed significantly (-14.18 ± 21.54 vs. -18.43 ± 20.65, respectively; p < 0.05), but again, no significant differences were found in the pooled estimate (D = 0.17, 95% CI = -0.46 to 0.79, p = 0.60), with moderate heterogeneity (I2 = 28%, p = 0.24).There is no significant difference in KSS or WOMAC outcomes between traditional and computerized TKA. The study suggests the need for further research with longer follow-up periods, more timepoints, and a broader range of patient outcome measures to fully evaluate the advantages and disadvantages of each method.


Assuntos
Artroplastia do Joelho , Osteoartrite do Joelho , Humanos , Artroplastia do Joelho/métodos , Osteoartrite do Joelho/cirurgia , Cirurgia Assistida por Computador/métodos
3.
Technol Cancer Res Treat ; 20: 15330338211041453, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34542333

RESUMO

Delivery of small-interfering RNA (siRNA) has been of great interest in the past decade for effective gene silencing. To overcome synthetic and regulatory challenges posed by nanoparticle-mediated siRNA delivery, antibody-siRNA conjugate (ARC) platform is emerging as a potential siRNA delivery system suitable for clinical translation. Herein, we have developed a delivery technology based on the ARC platform for stable delivery of siRNA called as Gelatin-Antibody Delivery System (GADS). In GADS, positively charged gelatin acts as a linker between antibody-siRNA and enables the endosomal escape of siRNA for gene silencing postcellular internalization. For proof of concept, we synthesized a scalable GADS conjugate comprising of Cetuximab (CTB), cationized gelatin (cGel) and NSCLC KRASG12C-specific siRNA. CTB was chemically conjugated to cGel through an amide link to form the CTB-cGel complex. Thereafter, siRNA was chemically conjugated to the cGel moiety of the complex through the thioether link to form CTB-cGel-siRNA conjugate. RP-HPLC analysis was used to monitor the reaction while gel retardation assay was used to determine siRNA loading capacity. SPR analysis showed the preservation of ligand binding affinity of antibody conjugates with KD of ∼0.3 nM. Furthermore, cellular internalization study using florescent microscopy revealed receptor-mediated endocytosis. The conjugate targeted EGFR receptor of KRAS mutant NSCLC to specifically knockdown G12C mutation. The oncogene knockdown sensitized the cells toward small molecule inhibitor-Gefitinib causing ∼70% loss in cell viability. Western blot analysis revealed significant downregulation for various RAS downstream proteins postoncogene knockdown. Comparison of the efficiency of GADS vis-à-vis positive siRNA control and CRISPR-Cas9-based knockout of KRAS Exon 2 in the NCI-H23 NSCLC cell line suggests GADS as a potential technology for clinical translation of gene therapy.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Resistencia a Medicamentos Antineoplásicos/genética , Inativação Gênica , Neoplasias Pulmonares/tratamento farmacológico , Proteínas Proto-Oncogênicas p21(ras)/genética , RNA Interferente Pequeno/administração & dosagem , Antineoplásicos/farmacologia , Antineoplásicos Imunológicos/química , Carcinoma Pulmonar de Células não Pequenas/genética , Cátions/química , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Cetuximab/química , Endocitose , Gefitinibe/farmacologia , Gelatina/química , Técnicas de Silenciamento de Genes , Terapia Genética , Humanos , Imunoconjugados/química , Neoplasias Pulmonares/genética , Mutação , Estudo de Prova de Conceito , RNA Interferente Pequeno/química
4.
Cancer Gene Ther ; 28(6): 566-580, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33191402

RESUMO

Continued advancements in CRISPR-Cas systems have accelerated genome research. Use of CRISPR-Cas in cancer research has been of great interest that is resulting in development of orthogonal methods for drug target validations and discovery of new therapeutic targets through genome-wide screens of cancer cells. CRISPR-based screens have also revealed several new cancer drivers through alterations in tumor suppressor genes (TSGs) and oncogenes inducing resistance to targeted therapies via activation of alternate signaling pathways. Given such dynamic status of cancer, we review the application of CRISPR-Cas in non-small cell lung cancer (NSCLC) for development of mutant models, drug screening, target validation, novel target discoveries, and other emerging potential applications. In addition, CRISPR-based approach for development of novel anticancer combination therapies is also discussed in this review.


Assuntos
Sistemas CRISPR-Cas/genética , Carcinoma Pulmonar de Células não Pequenas/genética , Edição de Genes , Terapia de Alvo Molecular , Carcinoma Pulmonar de Células não Pequenas/patologia , Carcinoma Pulmonar de Células não Pequenas/terapia , Detecção Precoce de Câncer , Genoma Humano/genética , Humanos
5.
Mol Microbiol ; 112(4): 1100-1115, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31286580

RESUMO

The cell wall is a crucial structural feature in the vast majority of bacteria and comprises a covalently closed network of peptidoglycan (PG) strands. While PG synthesis is important for survival under many conditions, the cell wall is also a dynamic structure, undergoing degradation and remodeling by 'autolysins', enzymes that break down PG. Cell division, for example, requires extensive PG remodeling, especially during separation of daughter cells, which depends heavily upon the activity of amidases. However, in Vibrio cholerae, we demonstrate that amidase activity alone is insufficient for daughter cell separation and that lytic transglycosylases RlpA and MltC both contribute to this process. MltC and RlpA both localize to the septum and are functionally redundant under normal laboratory conditions; however, only RlpA can support normal cell separation in low-salt media. The division-specific activity of lytic transglycosylases has implications for the local structure of septal PG, suggesting that there may be glycan bridges between daughter cells that cannot be resolved by amidases. We propose that lytic transglycosylases at the septum cleave PG strands that are crosslinked beyond the reach of the highly regulated activity of the amidase and clear PG debris that may block the completion of outer membrane invagination.


Assuntos
Parede Celular/metabolismo , Peptidoglicano Glicosiltransferase/metabolismo , Peptidoglicano/metabolismo , Amidoidrolases/metabolismo , Proteínas de Bactérias/metabolismo , Divisão Celular/fisiologia , Citocinese , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Glicosiltransferases/metabolismo , Lipoproteínas/metabolismo , N-Acetil-Muramil-L-Alanina Amidase/metabolismo , Peptidoglicano Glicosiltransferase/fisiologia , Vibrio cholerae/metabolismo
6.
J Acquir Immune Defic Syndr ; 79(2): 141-148, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-29985803

RESUMO

BACKGROUND: Protease inhibitors (PIs) may inhibit Kaposi sarcoma (KS) carcinogenesis. However, PI-based antiretroviral therapy (ART) is rarely a first-line choice in people living with HIV (PLWH) because of cost and toxicities. This is the first systematic review to assess KS incidence stratified by ART type. METHODS: We searched PubMed to identify original, full research reports of KS incidence in ART-treated adult PLWH, stratified by ART class, published between 1996 and 2017. For overlapping cohorts, we included only the most recent study and supplemented data with earlier relevant analyses. We described study design, sociodemographic characteristics, statistical adjustment factors, and KS incidence. RESULTS: We identified 3 unique retrospective cohort studies, and supplemented one of the studies with results from 6 previous subgroup reports, which included 242,309 PLWH and 3570 incident KS cases. Overall, KS crude incidence decreased by a factor of 10 between untreated and ART-treated PLWH; CD4-adjusted KS incidence decreased by ∼50%, with either non-nucleoside reverse transcriptase inhibitor- or PI-based ART. A single study measured a cumulative dose-/time-dependent effect of ART, which reported a relative risk reduction in only the cohort receiving boosted PI-based ART. Other studies defined ART categories by first-line therapy only. CONCLUSIONS: The risk of incident KS was significantly reduced, regardless of ART class even after adjusting for CD4 count. The quality of evidence (ie, most studies categorizing users by first-line ART) does not permit KS risk reduction comparisons across ART types. Given the limited number and retrospective nature of these studies, prospective data are indicated.


Assuntos
Infecções por HIV/tratamento farmacológico , Inibidores da Protease de HIV/uso terapêutico , Sarcoma de Kaposi/complicações , Contagem de Linfócito CD4 , Infecções por HIV/complicações , Humanos , Incidência , Sarcoma de Kaposi/epidemiologia
7.
Sci Rep ; 6: 30245, 2016 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-27530552

RESUMO

A tri-block nanoparticle (TBN) comprising of an enzymatically cleavable porous gelatin nanocore encapsulated with gefitinib (tyrosine kinase inhibitor (TKI)) and surface functionalized with cetuximab-siRNA conjugate has been synthesized. Targeted delivery of siRNA to undruggable KRAS mutated non-small cell lung cancer cells would sensitize the cells to TKI drugs and offers an efficient therapy for treating cancer; however, efficient delivery of siRNA and releasing it in cytoplasm remains a major challenge. We have shown TBN can efficiently deliver siRNA to cytoplasm of KRAS mutant H23 Non-Small Cell Lung Cancer (NSCLC) cells for oncogene knockdown; subsequently, sensitizing it to TKI. In the absence of TKI, the nanoparticle showed minimal toxicity suggesting that the cells adapt a parallel GAB1 mediated survival pathway. In H23 cells, activated ERK results in phosphorylation of GAB1 on serine and threonine residues to form GAB1-p85 PI3K complex. In the absence of TKI, knocking down the oncogene dephosphorylated ERK, and negated the complex formation. This event led to tyrosine phosphorylation at Tyr627 domain of GAB1 that regulated EGFR signaling by recruiting SHP2. In the presence of TKI, GAB1-SHP2 dissociation occurs, leading to cell death. The outcome of this study provides a promising platform for treating NSCLC patients harboring KRAS mutation.


Assuntos
Antineoplásicos/farmacologia , Cetuximab/farmacologia , Sistemas de Liberação de Medicamentos , Regulação Neoplásica da Expressão Gênica , Proteínas Proto-Oncogênicas p21(ras)/genética , Quinazolinas/farmacologia , RNA Interferente Pequeno/genética , Células A549 , Proteínas Adaptadoras de Transdução de Sinal/antagonistas & inibidores , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Cetuximab/química , Classe Ia de Fosfatidilinositol 3-Quinase/genética , Classe Ia de Fosfatidilinositol 3-Quinase/metabolismo , Gefitinibe , Gelatina/química , Humanos , Nanoconjugados/química , Nanoconjugados/ultraestrutura , Fosforilação , Proteína Tirosina Fosfatase não Receptora Tipo 11/antagonistas & inibidores , Proteína Tirosina Fosfatase não Receptora Tipo 11/genética , Proteína Tirosina Fosfatase não Receptora Tipo 11/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/antagonistas & inibidores , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , RNA Interferente Pequeno/metabolismo , Mucosa Respiratória/efeitos dos fármacos , Mucosa Respiratória/metabolismo , Mucosa Respiratória/patologia , Transdução de Sinais
8.
Langmuir ; 32(19): 4877-85, 2016 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-27088307

RESUMO

Three-dimensional nanocomposites prepared using two different families of nanomaterials holds significant relevance pertaining to biological applications. However, integration of the two distinct nanomaterials with precision to control the overall compositional homogeneity of the resulting 3D nanocomposite is a synthetic challenge. Conventional reactions result in nanocomposites with heterogeneous composition and render useless. To address this challenge, we have developed a fluidics-mediated process for controlling the interaction of nanoparticles to yield a compositional uniform multidimensional nanoparticle; as an example, we demonstrated the integration of gold nanoparticles on gelatin nanoparticles. The composition of the nanocomposite is controlled by reacting predetermined number of gold nanoparticles to a known number of thiolated gelatin nanoparticles at any given time within a defined cross-sectional area. Using the fluidics process, we developed nanocomposites of different composition: [gelatin nanoparticles-(gold nanoparticles)x] where xaverage = 2, 12, or 25. The nanocomposites were further surface conjugated with organic molecules such as fluorescent dye or polyethylene glycol (PEG) molecules. To study the biological behavior of nanocomposite, we investigated the cellular internalization and trafficking characteristics of nanocomposites in two human cancer cell lines. The nanocomposites exhibited a three-stage cellular release mechanism that enables the translocation of gold nanoparticles within various cellular compartments. In summary, the three-dimensional nanocomposite serves as a novel platform for developing well-defined protein-metal nanocomposites for potential drug delivery, sensory, and molecular imaging applications.


Assuntos
Espaço Intracelular/metabolismo , Nanopartículas Metálicas/química , Nanocompostos/química , Proteínas/química , Transporte Biológico , Linhagem Celular , Linhagem Celular Tumoral , Corantes Fluorescentes/química , Gelatina/química , Humanos , Polietilenoglicóis/química
9.
Artigo em Inglês | MEDLINE | ID: mdl-24616442

RESUMO

Conventional imaging technologies (X-ray computed tomography, magnetic resonance, and optical) depend on contrast agents to visualize a target site or organ of interest. The imaging agents currently used in clinics for diagnosis suffer from disadvantages including poor target specificity and in vivo instability. Consequently, delivery of low concentrations of contrast agents to region of interest affects image quality. Therefore, it is important to selectively deliver high payload of contrast agent to obtain clinically useful images. Nanoparticles offer multifunctional capabilities to transport high concentrations of imaging probes selectively to diseased site inside the body. Polymeric nanoparticles, incorporated with contrast agents, have shown significant benefits in molecular imaging applications. These materials possess the ability to encapsulate different contrast agents within a single matrix enabling multimodal imaging possibilities. The materials can be surface conjugated to target-specific biomolecules for controlling the navigation under in vivo conditions. The versatility of this class of nanomaterials makes them an attractive platform for developing highly sensitive molecular imaging agents. The research community's progress in the area of synthesis of polymeric nanomaterials and their in vivo imaging applications has been noteworthy, but it is still in the pioneer stage of development. The challenges ahead should focus on the design and fabrication of these materials including burst release of contrasts agents, solubility, and stability issues of polymeric nanomaterials.


Assuntos
Meios de Contraste/química , Aumento da Imagem/métodos , Imagem Molecular/métodos , Nanocápsulas/química , Nanocápsulas/ultraestrutura , Polímeros/química
10.
Eur J Clin Pharmacol ; 69(3): 439-48, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22777148

RESUMO

AIMS: To determine the extent and time-course of hepatic and intestinal cytochrome P450 3A (CYP3A) inactivation due to the mechanism-based inhibitor clarithromycin. METHODS: Intestinal and hepatic CYP3A inhibition was examined in 12 healthy volunteers following the administration of single and multiple doses of oral clarithromycin (500 mg). Intestinal biopsies were obtained under intravenous midazolam sedation at baseline and after the first dose, on days 2-4, and on days 6-8 of the clarithromycin treatment. The formation of 1'-hydroxymidazolam in biopsy tissue and the serum 1'-hydroxymidazolam:midazolam ratio were indicators of intestinal and hepatic CYP3A activity, respectively. RESULTS: Intestinal CYP3A activity decreased by 64 % (p = 0.0029) following the first dose of clarithromycin, but hepatic CYP3A activity did not significantly decrease. Repeated dosing of clarithromycin caused a significant decrease in hepatic CYP3A activity (p = 0.005), while intestinal activity showed little further decline. The CYP3A5 or CYP3A4*1B genotype were unable to account for inter-individual variability in CYP3A activity. CONCLUSIONS: Following the administration of clarithromycin, the onset of hepatic CYP3A inactivation is delayed compared to that of intestinal CYP3A. The time-course of drug-drug interactions due to clarithromycin will vary with the relative contribution of intestinal and hepatic CYP3A to the clearance and bioavailability of a victim substrate.


Assuntos
Claritromicina/administração & dosagem , Inibidores do Citocromo P-450 CYP3A , Duodeno/efeitos dos fármacos , Inibidores Enzimáticos/administração & dosagem , Fígado/efeitos dos fármacos , Administração Oral , Adulto , Análise de Variância , Biópsia , Biotransformação , Citocromo P-450 CYP3A/genética , Citocromo P-450 CYP3A/metabolismo , Esquema de Medicação , Duodeno/enzimologia , Feminino , Genótipo , Humanos , Hidroxilação , Fígado/enzimologia , Masculino , Midazolam/administração & dosagem , Midazolam/análogos & derivados , Midazolam/farmacocinética , Pessoa de Meia-Idade , Fenótipo , Especificidade por Substrato , Adulto Jovem
11.
Lab Invest ; 91(9): 1396-409, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21606925

RESUMO

The tight junctions of bile duct epithelium form a barrier between the toxic bile and liver parenchyma. Disruption of tight junctions appears to have a crucial role in the pathogenesis of various liver diseases. In this study, we investigated the disruptive effect of hydrogen peroxide and the protective effect of epidermal growth factor (EGF) on the tight junctions and adherens junctions in the bile duct epithelium. Oxidative stress in NRC-1 and Mz-ChA-1 cell monolayers was induced by administration of hydrogen peroxide. Barrier function was evaluated by measuring electrical resistance and inulin permeability. Integrity of tight junctions, adherens junctions and the actin cytoskeleton was determined by imunofluorescence microscopy. Role of signaling molecules was determined by evaluating the effect of specific inhibitors. Hydrogen peroxide caused a rapid disruption of tight junctions and adherens junctions leading to barrier dysfunction without altering the cell viability. Hydrogen peroxide rapidly increased the levels of p-MLC (myosin light chain) and c-Src(pY418). ML-7 and PP2 (MLCK and Src kinase inhibitors) attenuated hydrogen peroxide-induced barrier dysfunction, tight junction disruption and reorganization of actin cytoskeleton. Pretreatment of cell monolayers with EGF ameliorated hydrogen peroxide-induced tight junction disruption and barrier dysfunction. The protective effect of EGF was abrogated by ET-18-OCH(3) and the Ro-32-0432 (PLCγ and PKC inhibitors). Hydrogen peroxide increased tyrosine phosphorylation of ZO-1, claudin-3, E-cadherin and ß-catenin, and pretreatment of cells with EGF attenuated tyrosine phosphorylation of these proteins. These results demonstrate that hydrogen peroxide disrupts tight junctions, adherens junctions and the actin cytoskeleton by an MLCK and Src kinase-dependent mechanism in the bile duct epithelium. EGF prevents hydrogen peroxide-induced tight junction disruption by a PLCγ and PKC-dependent mechanism.


Assuntos
Ductos Biliares/metabolismo , Fator de Crescimento Epidérmico/farmacologia , Peróxido de Hidrogênio/farmacologia , Junções Íntimas/efeitos dos fármacos , Animais , Ductos Biliares/enzimologia , Epitélio/metabolismo , Peróxido de Hidrogênio/metabolismo , Microscopia de Fluorescência , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Ratos
12.
Mol Pharm ; 6(2): 641-7, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19718809

RESUMO

Therapeutic proteins have emerged as a significant class of pharmaceutical agents over the past several decades. The potency, rapid elimination, and systemic side effects have prompted the need of spatiotemporally controlled release for proteins maybe more than any other active therapeutic molecules. This work examines the release of two model protein compounds, bovine serum albumin (BSA) and an anti-integrin antibody (AI), from electrospun polycaprolactone (PCL) nanofiber mats. The anti-integrin antibody was chosen as a model of antibody therapy; in particular, anti-integrin antibodies are a promising class of therapeutic molecules for cancer and angiogenic diseases. The release kinetics were studied experimentally and interpreted in the framework of a recently published theory of desorption-limited drug release from nondegrading--or very slowly degrading--fibers. The results are consistent with a protein release mechanism dominated by desorption from the polymer surface, while the polycaprolactone nanofibers are not degrading at an appreciable rate.


Assuntos
Anticorpos Monoclonais/metabolismo , Endotélio Vascular/metabolismo , Integrina alfaVbeta3/imunologia , Nanoestruturas , Poliésteres/química , Polímeros/química , Soroalbumina Bovina/metabolismo , Animais , Anticorpos Monoclonais/química , Bovinos , Endotélio Vascular/citologia , Humanos , Soroalbumina Bovina/química , Veias Umbilicais/citologia , Veias Umbilicais/metabolismo
13.
Nanotechnology ; 20(27): 275706, 2009 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-19531856

RESUMO

A wide array of technological applications requires localized high-rate delivery of dissolved compounds (in particular, biological ones), which can be achieved by forcing the solutions or suspensions of such compounds through nano or microtubes and their bundled assemblies. Using a water-soluble compound, the fluorescent dye Rhodamine 610 chloride, frequently used as a model drug release compound, it is shown that deposit buildup on the inner walls of the delivery channels and its adverse consequences pose a severe challenge to implementing pressure-driven long-term fluidic delivery through nano and microcapillaries, even in the case of such homogeneous solutions. Pressure-driven delivery (3-6 bar) of homogeneous dye solutions through macroscopically-long (approximately 1 cm) carbon nano and microtubes with inner diameters in the range 100 nm-1 microm and their bundled parallel assemblies is studied experimentally and theoretically. It is shown that the flow delivery gradually shifts from fast convection-dominated (unobstructed) to slow jammed convection, and ultimately to diffusion-limited transport through a porous deposit. The jamming/clogging phenomena appear to be rather generic: they were observed in a wide concentration range for two fluorescent dyes in carbon nano and microtubes, as well as in comparable transparent glass microcapillaries. The aim of the present work is to study the physics of jamming, rather than the chemical reasons for the affinity of dye molecules to the tube walls.


Assuntos
Microfluídica/métodos , Nanotubos de Carbono/química , Fenômenos Químicos , Desenho de Equipamento , Microscopia Eletrônica de Transmissão , Nanotubos de Carbono/ultraestrutura , Polímeros/química , Polimetil Metacrilato/química , Poli-Inos/química , Rodaminas/química , Soluções/química
14.
Langmuir ; 24(3): 965-74, 2008 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-18076196

RESUMO

This work examines the release of a model water-soluble compound from electrospun polymer nanofiber assemblies. Such release attracts attention in relation to biomedical applications, such as controlled drug delivery. It is also important for stem cell attachment and differentiation on biocompatible electrospun nanofiber scaffolds containing growth factors, which have been encapsulated by means of electrospinning. Typically, the release mechanism has been attributed to solid-state diffusion of the encapsulated compound from the fibers into the surrounding aqueous bath. Under this assumption, a 100% release of the encapsulated compound is expected in a certain (long) time. The present work focuses on certain cases where complete release does not happen, which suggests that solid-state diffusion may not be the primary mechanism at play. We show that in such cases the release rate can be explained by desorption of the embedded compound from nanopores in the fibers or from the outer surface of the fibers in contact with the water bath. After release, the water-soluble compound rapidly diffuses in water, whereas the release rate is determined by the limiting desorption stage. A model system of Rhodamine 610 chloride fluorescent dye embedded in electrospun monolithic poly(methylmethacrylate) (PMMA) or poly(caprolactone) (PCL) nanofibers, in nanofibers electrospun from PMMA/PCL blends, or in core-shell PMMA/PCL nanofibers is studied. Both the experimental results and theory point at the above mentioned desorption-related mechanism, and the predicted characteristic time, release rate, and effective diffusion coefficient agree fairly well with the experimental data. A practically important outcome of this surface release mechanism is that only the compound on the fiber and pore surfaces can be released, whereas the material encapsulated in the bulk cannot be freed within the time scales characteristic of the present experiments (days to months). Consequently, in such cases, complete release is impossible. We also demonstrate how the release rate can be manipulated by the polymer content and molecular weight affecting nanoporosity and the desorption enthalpy, as well as by the nanofiber structure (monolithic fibers, fibers from polymer blends, and core-shell fibers). In particular, it is shown that, by manipulating the above parameters, release times from tens of hours to months can be attained.

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