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1.
J Cell Sci ; 137(1)2024 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-38108421

RESUMO

Cellular heterogeneity and extracellular matrix (ECM) stiffening have been shown to be drivers of breast cancer invasiveness. Here, we examine how stiffness-dependent crosstalk between cancer cells and mesenchymal stem cells (MSCs) within an evolving tumor microenvironment regulates cancer invasion. By analyzing previously published single-cell RNA sequencing datasets, we establish the existence of a subpopulation of cells in primary tumors, secondary sites and circulatory tumor cell clusters of highly aggressive triple-negative breast cancer (TNBC) that co-express MSC and cancer-associated fibroblast (CAF) markers. By using hydrogels with stiffnesses of 0.5, 2 and 5 kPa to mimic different stages of ECM stiffening, we show that conditioned medium from MDA-MB-231 TNBC cells cultured on 2 kPa gels, which mimic the pre-metastatic stroma, drives efficient MSC chemotaxis and induces stable differentiation of MSC-derived CAFs in a TGFß (TGFB1)- and contractility-dependent manner. In addition to enhancing cancer cell proliferation, MSC-derived CAFs on 2 kPa gels maximally boost local invasion and confer resistance to flow-induced shear stresses. Collectively, our results suggest that homing of MSCs at the pre-metastatic stage and their differentiation into CAFs actively drives breast cancer invasion and metastasis in TNBC.


Assuntos
Neoplasias da Mama , Fibroblastos Associados a Câncer , Células-Tronco Mesenquimais , Neoplasias de Mama Triplo Negativas , Humanos , Feminino , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Diferenciação Celular , Géis , Microambiente Tumoral/genética , Linhagem Celular Tumoral
2.
J Cell Sci ; 134(23)2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34730180

RESUMO

The mechanisms by which the mechanoresponsive actin crosslinking protein α-actinin-4 (ACTN4) regulates cell motility and invasiveness remain incompletely understood. Here, we show that, in addition to regulating protrusion dynamics and focal adhesion formation, ACTN4 transcriptionally regulates expression of non-muscle myosin IIB (NMM IIB; heavy chain encoded by MYH10), which is essential for mediating nuclear translocation during 3D invasion. We further show that an indirect association between ACTN4 and NMM IIA (heavy chain encoded by MYH9) mediated by a functional F-actin cytoskeleton is essential for retention of NMM IIA at the cell periphery and modulation of focal adhesion dynamics. A protrusion-dependent model of confined migration recapitulating experimental observations predicts a dependence of protrusion forces on the degree of confinement and on the ratio of nucleus to matrix stiffness. Together, our results suggest that ACTN4 is a master regulator of cancer invasion that regulates invasiveness by controlling NMM IIB expression and NMM IIA localization. This article has an associated First Person interview with the first author of the paper.


Assuntos
Miosina não Muscular Tipo IIA , Actinina/genética , Actinas/genética , Movimento Celular/genética , Humanos , Cadeias Pesadas de Miosina , Miosina não Muscular Tipo IIA/genética , Miosina não Muscular Tipo IIB/genética
3.
J Cell Sci ; 134(7)2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-33602741

RESUMO

Phenotypic heterogeneity is increasingly acknowledged to confer several advantages to cancer progression and drug resistance. Here, we probe the collective importance of heterogeneity in cell size and deformability in breast cancer invasion. A computational model of invasion of a heterogeneous cell aggregate predicts that combined heterogeneity in cell size and deformability enhances invasiveness of the whole population, with maximum invasiveness at intermediate cell-cell adhesion. We then show that small cells of varying deformability, a subpopulation predicted to be enriched at the invasive front, exhibit considerable overlap with the biophysical properties of cancer stem cells (CSCs). In MDA-MB-231 cells, these include CD44 hi CD24- mesenchymal CSCs, which are small and soft, and CD44 hi CD24+ hybrid CSCs, which exhibit a wide range of size and deformability. We validate our predictions by tracking the pattern of cell invasion from spheroids implanted in three-dimensional collagen gels, wherein we show temporal enrichment of CD44 hi cells at the invasive front. Collectively, our results illustrate the advantages imparted by biophysical heterogeneity in enhancing cancer invasiveness.This article has an associated First Person interview with the first author of the paper.


Assuntos
Neoplasias da Mama , Antígeno CD24 , Neoplasias da Mama/genética , Adesão Celular , Linhagem Celular Tumoral , Tamanho Celular , Feminino , Humanos , Receptores de Hialuronatos , Invasividade Neoplásica , Células-Tronco Neoplásicas
4.
J Cell Sci ; 131(7)2018 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-29535208

RESUMO

Efficient homing of human mesenchymal stem cells (hMSCs) is likely to be dictated by a combination of physical and chemical factors present in the microenvironment. However, crosstalk between the physical and chemical cues remains incompletely understood. Here, we address this question by probing the efficiency of epidermal growth factor (EGF)-induced hMSC chemotaxis on substrates of varying stiffness (3, 30 and 600 kPa) inside a polydimethylsiloxane (PDMS) microfluidic device. Chemotactic speed was found to be the sum of a stiffness-dependent component and a chemokine concentration-dependent component. While the stiffness-dependent component scaled inversely with stiffness, the chemotactic component was independent of stiffness. Faster chemotaxis on the softest 3 kPa substrates is attributed to a combination of weaker adhesions and higher protrusion rate. While chemotaxis was mildly sensitive to contractility inhibitors, suppression of chemotaxis upon actin depolymerization demonstrates the role of actin-mediated protrusions in driving chemotaxis. In addition to highlighting the collective influence of physical and chemical cues in chemotactic migration, our results suggest that hMSC homing is more efficient on softer substrates.


Assuntos
Actinas/química , Proliferação de Células/genética , Quimiotaxia/genética , Células-Tronco Mesenquimais/química , Actinas/genética , Adesão Celular/genética , Diferenciação Celular/genética , Células Cultivadas , Microambiente Celular/efeitos dos fármacos , Microambiente Celular/genética , Dimetilpolisiloxanos/química , Elasticidade/fisiologia , Fator de Crescimento Epidérmico/química , Fator de Crescimento Epidérmico/genética , Humanos , Células-Tronco Mesenquimais/metabolismo , Multimerização Proteica/genética
5.
Orthod Craniofac Res ; 22 Suppl 1: 76-81, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31074152

RESUMO

OBJECTIVE: Improved methods are needed to remineralize dentin caries in order to promote conservation of dentin tissue and minimize the surgical interventions that are currently required for clinical treatment. Here, we test the hypothesis that bulk substrates can be effectively mineralized via a dual analog system proposed by others, using a tripolyphosphate (TPP) "templating analog" and a poly(acrylic acid) (PAA) or poly(aspartic acid) (pAsp) "sequestration analog," the latter of which generates the polymer-induced liquid-precursor (PILP) mineralization process studied in our laboratory. MATERIAL & METHODS: Demineralized human dentin slices were remineralized with and without pre-treatment with TPP, using either PAA or pAsp as the PILP process-directing agent. A control experiment with no polymer present was used for comparison. RESULTS: No mineralization was observed in any of the PAA groups. In both the pAsp and no polymer groups, TPP inhibited mineralization on the surfaces of the specimens but promoted mineralization within the interiors. Pre-treatment with TPP enhanced overall mineralization of the pAsp group. However, when analysed via TEM, regions with little mineral were still present. CONCLUSION: Poly(acrylic acid) was unable to remineralize demineralized dentin slices under the conditions employed, even when pre-treated with TPP. However, pre-treatment with TPP enhanced overall mineralization of specimens that were PILP-remineralized using pAsp.


Assuntos
Cárie Dentária , Dentina , Humanos , Polímeros
6.
Anal Chem ; 90(20): 11873-11882, 2018 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-30204418

RESUMO

Subcellular fractionation of tissue homogenate provides enriched in vitro models (e.g., microsomes, cytosol, or membranes), which are routinely used in the drug metabolism or transporter activity and protein abundance studies. However, batch-to-batch or interlaboratory variability in the recovery, enrichment, and purity of the subcellular fractions can affect performance of in vitro models leading to inaccurate in vitro to in vivo extrapolation (IVIVE) of drug clearance. To evaluate the quality of subcellular fractions, we developed a simple, targeted, and sensitive LC-MS/MS proteomics-based strategy, which relies on determination of protein markers of various cellular organelles, i.e., plasma membrane, cytosol, nuclei, mitochondria, endoplasmic reticulum (ER), lysosomes, peroxisomes, cytoskeleton, and exosomes. Application of the quantitative proteomics method confirmed a significant effect of processing variables (i.e., homogenization method and centrifugation speed) on the recovery, enrichment, and purity of isolated proteins in microsomes and cytosol. Particularly, markers of endoplasmic reticulum lumen and mitochondrial lumen were enriched in the cytosolic fractions as a result of their release during homogenization. Similarly, the relative recovery and composition of the total membrane fraction isolated from cell vs tissue samples was quantitatively different and should be considered in IVIVE. Further, analysis of exosomes isolated from sandwich-cultured hepatocyte media showed the effect of culture duration on compositions of purified exosomes. Therefore, the quantitative proteomics-based strategy developed here can be applied for efficient and simultaneous determination of multiple protein markers of various cellular organelles when compared to antibody- or activity-based assays and can be used for quality control of subcellular fractionation procedures including in vitro model development for drug metabolism and transport studies.


Assuntos
Sistema Enzimático do Citocromo P-450/análise , Proteínas de Membrana Transportadoras/análise , Preparações Farmacêuticas/metabolismo , Proteômica , Transporte Biológico , Biomarcadores/análise , Biomarcadores/metabolismo , Células Cultivadas , Cromatografia Líquida , Sistema Enzimático do Citocromo P-450/metabolismo , Citosol/química , Citosol/metabolismo , Exossomos/química , Exossomos/metabolismo , Células Hep G2 , Hepatócitos/química , Hepatócitos/metabolismo , Humanos , Proteínas de Membrana Transportadoras/metabolismo , Microssomos/química , Microssomos/metabolismo , Espectrometria de Massas em Tandem
7.
J Food Sci Technol ; 55(6): 2011-2020, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29892101

RESUMO

The study was aimed to isolate antagonistic lactobacilli and the molecules responsible for their antagonistic ability from curd. Preparation of probiotic curd and the ability of the selected lactobacilli to suppress the pathogen therein was also assessed. All the 116 isolates were identified as Lactobacillus spp. based on morphological, biochemical and curdling assays. Five of these lactobacilli (Lb-17, Lb-33, Lb-108, Lb-112, and Lb-N3) were found most promising to inhibit all test pathogens (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Salmonella typhi and Shigella sonnei). The cell-free culture supernatants of these five lactobacilli were recorded as thermo-tolerant when subjected to heat treatment at 100 °C for 20 min. The loss in the activity after protease treatment indicated the proteinaceous nature of the antimicrobial molecule present in the culture supernatants. Active protein (19 kDa) produced by lactobacilli was confirmed by SDS-PAGE followed by agar-overlay method. Antibiotic sensitivity assay revealed that the selected Lactobacillus spp. isolates were resistant to methicillin and vancomycin. Probiotic curd prepared by using Lb-108 and Lb-N3 was found to be superior to rest of the three isolates based on organoleptic tests and shelf-life. Complete inhibition of all the test pathogens in curd was shown by Lb-108 and Lb-N3. Inhibition spectrum, production of thermostable protein and preparation of quality curd suggest Lb-108 and Lb-N3 as promising candidates to prepare probiotic curd.

8.
Rev Biol Trop ; 64(3): 1287-95, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29462544

RESUMO

The Indian hill trout cyprinid, Barilius bendelisis is a member of family Cyprinidae that dwells in shallow, cold, and clear water. In this study, growth parameters and reproductive biology of Indian hill trout, Barilius bendelisis from river Gaula, Central Himalaya region, India, were studied. The length-frequency data were grouped sex wise and were analyzed to determine the growth and mortality parameters using the computer software programme, FAO-ICLARM Stock Assessment Tool (FISAT II). Altogether, 501 individuals were collected from river Gaula (November 2013-October 2014) and were preserved in formalin for further analysis. The results showed that the female outnumbered the male population. The minimum GSI of females was observed in the month of October (4.93 ± 0.26) and for males in the month of June and July (0.093 ± 0.12), whereas, the maximum value was in the month of April for both females (13.47 ± 0.52) and males (1.21 ± 0.12). Fluctuation in GSI values had a bimodal pattern showing two peaks during March-May and August-September in both the sexes, indicating the common spawning period of fish. The slope of regression showed the negative allometric growth for both males and females (b= 2.65 for male and b= 2.5 for female). A significant relationship between length and weight was observed in the present study (p < 0.05). The ELEFAN-I estimated L∞ and K of the von Bertalanffy growth factor for males (17.33 cm and 0.310 per year), females (17.33 cm and 0.3 per year) and pooled sexes (17.33 cm and 0.240 per year). The results indicated that Barilius bendelisis is a small sized fish having negative allometric growth that spawns twice a year. Thus, the present study on biological traits represents the baseline information for effective production, conservation and restoration planning.


Assuntos
Cyprinidae/fisiologia , Reprodução/fisiologia , Animais , Tamanho Corporal , Feminino , Índia , Masculino , Dinâmica Populacional , Valores de Referência , Rios , Estações do Ano , Distribuição por Sexo , Fatores Sexuais , Fatores de Tempo
9.
Rev Biol Trop ; 63(1): 165-73, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26299122

RESUMO

Barilius bendelisis, commonly known as Indian Hill Trout is an upland water fish of South East Asia. It belongs to the family Cyprinidae and dwells in shallow, clear and cold water. In this study, the intraspecific variation of Barilius bendelisis, on the basis of morphometric characters, was investigated. Altogether, 402 specimens were collected from four rivers in the Central Indian Himalaya. A truss network was constructed by interconnecting 12 landmarks to yield 30 distance variables that were extracted from digital images of specimens using tpsDig2 and PAST software. Allometric transformed truss measurements were subjected to univariate analysis of variance, factor analysis and discriminant analysis. All variables exhibited significant differences between the populations. Altogether 88% of the specimens were classified into their original populations (81.98% under a 'leave-one-out' procedure). With factor analysis measurements of the head region, the middle portion and the caudal region had high loadings on the first and second axis. The results indicated that B. bendelisis has significant phenotypic heterogeneity between the geographically isolated regions of Central Indian Himalaya. We hypothesize that the marked interspecific variation in B. bendelisis is the result of local ecological conditions.


Assuntos
Cipriniformes/anatomia & histologia , Animais , Cipriniformes/classificação , Cipriniformes/genética , Análise Discriminante , Feminino , Índia , Masculino , Fenótipo , Análise de Componente Principal , Rios , Especificidade da Espécie
10.
Polymers (Basel) ; 14(4)2022 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-35215688

RESUMO

With the aging population, there is a growing need for mineralized tissue restoration and synthetic bone substitutes. Previous studies have shown that a polymer-induced liquid-precursor (PILP) process can successfully mineralize collagen substrates to achieve compositions found in native bone and dentin. This process also leads to intrafibrillar apatitic crystals with their [001] axes aligned roughly parallel to the long axis of the collagen fibril, emulating the nanostructural organization found in native bone and dentin. When demineralized bovine bone was remineralized via the PILP process using osteopontin (OPN), the samples were able to activate mouse marrow-derived osteoclasts to similar levels to those of native bone, suggesting a means for fabricating bioactive bone substitutes that could trigger remodeling through the native bone multicellular unit (BMU). In order to determine if OPN derived from bovine milk could be a cost-effective process-directing agent, the mineralization of type I collagen scaffolds using this protein was compared to the benchmark polypeptide of polyaspartic acid (sodium salt; pAsp). In this set of experiments, we found that OPN led to much faster and more uniform mineralization when compared with pAsp, making it a cheaper and commercially attractive alternative for mineralized tissue restorations.

11.
Toxicol Appl Pharmacol ; 257(2): 264-71, 2011 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-21964610

RESUMO

WHO has highlighted the need to evaluate dermal toxicity of mycotoxins including Patulin (PAT), detected in several fruits. In this study the skin carcinogenic potential of topically applied PAT was investigated. Single topical application of PAT (400 nmol) showed enhanced cell proliferation (~2 fold), along with increased generation of ROS and activation of ERK, p38 and JNK MAPKs, in mouse skin. PAT exposure also showed activation of downstream target proteins, c-fos, c-Jun and NF-κB transcription factors. Further, single topical application of PAT (400 nmol) followed by twice weekly application of TPA resulted in tumor formation after 14 weeks, indicating the tumor initiating activity of PAT. However no tumors were observed when PAT was used either as a complete carcinogen (80 nmol) or as a tumor promoter (20 nmol and 40 nmol) for 25 weeks. Histopathological findings of tumors found in PAT/TPA treated mice showed that these tumors were of squamous cell carcinoma type and similar to those found in the positive control group (DMBA/TPA) along with significant increase of lipid peroxidation and decrease in free sulfydryls, catalase, superoxide dismutase and glutathione reductase activities. The results suggest the possible role of free radicals in PAT mediated dermal tumorigenicity involving MAPKs.


Assuntos
Proteínas Quinases Ativadas por Mitógeno/fisiologia , Patulina/toxicidade , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/enzimologia , Animais , Testes de Carcinogenicidade/métodos , Feminino , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/fisiologia , Camundongos , Distribuição Aleatória , Espécies Reativas de Oxigênio/metabolismo
12.
STAR Protoc ; 2(1): 100310, 2021 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-33554144

RESUMO

In vivo cell migration is influenced by soluble factors as well as stiffness. Current in vitro strategies mostly account for one of these two factors to study cell migration. To understand the combinatorial effect of stiffness and chemokines on cell behavior, we have developed a microfluidic model to study stiffness-dependent chemotaxis of mesenchymal stem cells (hMSCs). A detailed description of our methodology will help researchers develop microfluidic models that combine these two factors influencing cell behavior. For complete details on the use and execution of this protocol, please refer to Saxena et al. (2018).


Assuntos
Movimento Celular/fisiologia , Técnicas Analíticas Microfluídicas/métodos , Microfluídica/instrumentação , Quimiocinas , Quimiotaxia , Sinais (Psicologia) , Humanos , Dispositivos Lab-On-A-Chip , Células-Tronco Mesenquimais , Técnicas Analíticas Microfluídicas/instrumentação
13.
Toxicol Appl Pharmacol ; 234(2): 192-201, 2009 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-19000704

RESUMO

Patulin (PAT), a mycotoxin found in apples, grapes, oranges, pear and peaches, is a potent genotoxic compound. WHO has highlighted the need for the study of cutaneous toxicity of PAT as manual labour is employed during pre and post harvest stages, thereby causing direct exposure to skin. In the present study cutaneous toxicity of PAT was evaluated following topical application to Swiss Albino mice. Dermal exposure of PAT, to mice for 4 h resulted in a dose (40-160 mug/animal) and time (up to 6 h) dependent enhancement of ornithine decarboxylase (ODC), a marker enzyme of cell proliferation. The ODC activity was found to be normal after 12 and 24 h treatment of patulin. Topical application of PAT (160 mug/100 mul acetone) for 24-72 h caused (a) DNA damage in skin cells showing significant increase (34-63%) in olive tail moment, a parameter of Comet assay (b) significant G 1 and S-phase arrest along with induction of apoptosis (2.8-10 folds) as shown by annexin V and PI staining assay through flow cytometer. Moreover PAT leads to over expression of p(21/WAF1) (3.6-3.9 fold), pro apoptotic protein Bax (1.3-2.6) and tumor suppressor wild type p(53) (2.8-3.9 fold) protein. It was also shown that PAT induced apoptosis was mediated through mitochondrial intrinsic pathway as revealed through the release of cytochrome C protein in cytosol leading to enhancement of caspase-3 activity in skin cells of mice. These results suggest that PAT has a potential to induce DNA damage leading to p(53) mediated cell cycle arrest along with intrinsic pathway mediated apoptosis that may also be correlated with enhanced polyamine production as evident by induction of ODC activity, which may have dermal toxicological implications.


Assuntos
Apoptose/efeitos dos fármacos , Ciclo Celular/efeitos dos fármacos , Inibidor de Quinase Dependente de Ciclina p21/genética , Dano ao DNA/efeitos dos fármacos , Genes p53/efeitos dos fármacos , Mutagênicos/toxicidade , Patulina/toxicidade , Fenômenos Fisiológicos da Pele/genética , Proteína X Associada a bcl-2/genética , Animais , Caspase 3/biossíntese , Caspase 3/genética , Proliferação de Células/efeitos dos fármacos , Ensaio Cometa , Citocromos c/biossíntese , Citocromos c/genética , Immunoblotting , Camundongos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Ornitina Descarboxilase/biossíntese , Ornitina Descarboxilase/genética , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética
14.
Toxicol Lett ; 185(3): 211-8, 2009 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-19382294

RESUMO

At present, more than 20 countries worldwide are manufacturing and marketing different varieties of nanotech-based consumer products of which cosmetics form the largest category. Due to the extremely small size of the nanoparticles (NPs) being used, there is a concern that they may interact directly with macromolecules such as DNA. The present study was aimed to assess the genotoxicity of zinc oxide (ZnO) NPs, one of the widely used ingredients of cosmetics, and other dermatological preparations in human epidermal cell line (A431). A reduction in cell viability as a function of both NP concentration as well as exposure time was observed. ZnO NPs demonstrated a DNA damaging potential as evident from an increased Olive tail moment (OTM) of 2.13 +/- 0.12 (0.8 g/ml) compared to control 1.37 +/- 0.12 in the Comet assay after an exposure of 6 h. ZnO NPs were also found to induce oxidative stress in cells indicated by depletion of glutathione (59% and 51%); catalase (64% and 55%) and superoxide dismutase (72% and 75%) at 0.8 and 0.08 g/ml respectively. Our data demonstrates that ZnO NPs even at low concentrations possess a genotoxic potential in human epidermal cells which may be mediated through lipid peroxidation and oxidative stress. Hence, caution should be taken in their use in dermatological preparations as well as while handling.


Assuntos
Dano ao DNA , Epiderme/efeitos dos fármacos , Células Epiteliais/efeitos dos fármacos , Mutagênicos/toxicidade , Nanopartículas , Óxido de Zinco/toxicidade , Catalase/metabolismo , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Ensaio Cometa , Células Epidérmicas , Epiderme/metabolismo , Células Epiteliais/metabolismo , Células Epiteliais/ultraestrutura , Glutationa/metabolismo , Humanos , Peroxidação de Lipídeos/efeitos dos fármacos , Microscopia Eletrônica de Transmissão , Mutagênicos/química , Estresse Oxidativo/efeitos dos fármacos , Superóxido Dismutase/metabolismo , Propriedades de Superfície , Óxido de Zinco/química
15.
ACS Appl Bio Mater ; 2(5): 1802-1814, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-35030671

RESUMO

Gelatin-based hydrogels have received particular attention for tissue-engineering applications given their biocompatibility, ease of tuning their physical properties through chemical modifications, and incorporation of antibacterial activity. While several studies have focused on the detailed quantification of biomechanical properties of these gels, considerably less attention has been paid to understanding how adhesivity of these gels impacts single as well as collective cell migration, which directly determines the efficacy of wound healing. In this study, we address this question by quantifying fibroblast motility and antibacterial activity of silver nanoparticle (AgNP)-entrapped methacrylated gelatin (GelMA) hydrogels. Using 5 and 15% GelMA soft gels cross-linked with 1 min UV exposure, we first show that cells spread more and migrate faster on 15% GelMA gels. Next, we show that ∼10 nm AgNPs entrapped in 15% GelMA gels get released over a time-scale greater than 72 h and exhibit antibacterial activity against both Gram-positive and Gram-negative bacteria at concentrations nontoxic to cells. Finally, using a polydimethylsiloxane (PDMS) device for simulating wound healing, we show that closure of ∼800 µm gaps on GelMA gels is significantly faster compared with other conditions. Together, our findings illustrate the potential of AgNP-entrapped soft GelMA gels as scaffolds for achieving accelerated wound healing of deep dermal wounds by enabling fast fibroblast migration and minimization of microbial infections.

16.
ACS Biomater Sci Eng ; 5(1): 180-192, 2019 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-33405870

RESUMO

Differentiation of stem cells into neurogenic lineage is of great interest for treatment of neurodegenerative diseases. While the role of chemical cues in regulating stem cell fate is well appreciated, the identification of physical cues has revolutionized the field of tissue engineering leading to development of scaffolds encoding one or more physical cues for inducing stem cell differentiation. In this study, using human mesenchymal stem cells (hMSCs) and mouse embryonic stem cells (mESCs), we have tested if stiffness and topography can be collectively tuned for inducing neuronal differentiation by culturing these cells on polyacrylamide hydrogels of varying stiffness (5, 10, and 20 kPa) containing rectangular grooves (10, 15, and 25 µm in width). While hMSCs maximally elongate and express neuronal markers on soft 5 kPa gels containing 10/15 µm grooves, single mESCs are unable to sense topographical features when cultured directly on grooved gels. However, this inability to sense topography is rescued by priming mESCs initially on soft 1 kPa flat gels and then replating these cells onto the grooved gels. Compared to direct culture on the grooved gels, this sequential adaptation increases both viability as well as neuronal differentiation. However, this two-step process does not enhance neuronal marker expression in hMSCs. In addition to highlighting important differences between hMSCs and mESCs in their responsiveness to physical cues, our study suggests that conditioning on soft substrates is essential for inducing topography-mediated neuronal differentiation in mESCs.

17.
RSC Adv ; 8(43): 24485-24499, 2018 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-35539155

RESUMO

The present study deals with the synthesis, characterization, physical and thermodynamic properties of a novel anionic surfactant derived from Sapindus laurifolius for its potential application against conventional non-biodegradable surfactants. The synthesized surfactant was characterized by FTIR, GC-MS, EDX and FE-SEM analyses. The surfactant showed good thermal stability at different temperatures as obtained from TGA studies. Critical micelle concentration (CMC) values were obtained by surface tensiometry measurements. DLS studies revealed the micelle structures of the CMC aggregates at higher concentrations. Low interfacial tension values were obtained at the oil-aqueous interfaces for surfactant solutions. The effect of temperature on the interfacial behaviour was also investigated. Thermodynamic studies showed that adsorption was more favoured in comparison to micellization for all systems. Foam stability studies were performed as a function of time and concentration by the Bartsch method. The surfactant also formed stable emulsions at concentrations near the CMC value. A comprehensive assessment of the thermal, interfacial, foaming and emulsifying properties of the soap-nut-based surfactant provides grounds for potential application in a wide range of industries.

18.
Dent Mater ; 34(9): 1378-1390, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29935767

RESUMO

OBJECTIVE: The polymer-induced liquid-precursor (PILP) mineralization process has been shown to remineralize artificial dentin lesions to levels consistent with those of native dentin. However, nanoindentation revealed that the moduli of those remineralized lesions were only ∼50% that of native dentin. We hypothesize that this may be due to the PILP process having been previously optimized to obtain high amounts (∼70wt%) of intrafibrillar crystals, but without sufficient interfibrillar mineral, another significant component of dentin. METHODS: Fluoride was added to the PILP-mineralization of collagen from rat tail tendon at varying concentrations to determine if a better balance of intra- versus inter-fibrillar mineralization could be obtained, as determined by electron microscopy. Nanoindentation was used to determine if fluoridated apatite could improve the mechanical properties of the composites. RESULTS: Fluoride was successfully incorporated into the PILP-mineralization of rat tail tendon and resulted in collagen-mineral composite systems with the mineral phase of hydroxyapatite containing various levels of fluoridation. As the fluoride concentration increased, the crystals became larger and more rod-like, with an increasing tendency to form on the fibril surfaces rather than the interior. Nanomechanical testing of the mineralized tendons revealed that fluoride addition did not increase modulus over PILP mineralization alone. This likely resulted from the separated nature of collagen fibrils that comprise tendon, which does not provide lateral reinforcement and therefore may not be suited for the compressive loads of nanoindentation. SIGNIFICANCE: This work contributes to the development of minimally invasive approaches to caries treatment by determining if collagen can be functionally mineralized.


Assuntos
Calcificação Fisiológica , Colágeno/química , Fluoretos/química , Polímeros/química , Remineralização Dentária , Animais , Biomimética , Microscopia Eletrônica , Ratos
19.
Matrix Biol ; 52-54: 384-396, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26898702

RESUMO

The mineralized extracellular matrix (ECM) of bone is essential in vertebrates to provide structure, locomotion, and protect vital organs, while also acting as a calcium and phosphate reservoir to maintain homeostasis. Bone's structure comprises mainly structural collagen fibrils, hydroxyapatite nanocrystals and water, and it is the organization of the densely-packed collagen matrix that directs the organization of the mineral crystallites. Biogenic mineralization occurs when osteoblasts release "mineral bearing globules" which fuse into the preformed collagen matrix, and upon crystallization of this amorphous precursor, the fibrils become embedded with [001] oriented nanocrystals of hydroxyapatite. Our prior work has shown that this nanostructured organization of bone can be reproduced in vitro using the polymer-induced liquid-precursor (PILP) process. In this report, our focus is on using biomimetic processing to recreate both the nano- and micro-structure of lamellar bone. We first applied molecular crowding techniques to acidic, type-I collagen solutions to form dense, liquid crystalline collagen (LCC) scaffolds with cholesteric order. We subsequently mineralized these LCCs via the PILP process to achieve a high degree of intrafibrillar mineral, with compositions and organization similar to that of native bone and with a "lamellar" microstructure generated by the twisting LCC template. In depth characterization of the nano- and micro-structure was performed, including optical and electron microscopy, X-ray and electron diffraction, and thermogravimetric analyses. The results of this work lead us closer to our goal of developing hierarchically structured, collagen-hydroxyapatite composites which can serve as fully synthetic, bioresorbable, load-bearing bone substitutes that are remodeled by the native BRU.


Assuntos
Biomimética/métodos , Matriz Óssea/química , Colágeno/química , Animais , Mimetismo Biológico , Durapatita/química , Microscopia Eletrônica , Microscopia Eletrônica de Transmissão , Nanopartículas/química , Termogravimetria
20.
Genome Announc ; 3(6)2015 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-26564049

RESUMO

The first draft genome of Halostagnicola sp. A56, isolated from the Andaman Islands is reported here. The A56 genome comprises 3,178,490 bp in 26 contigs with a G+C content of 60.8%. The genome annotation revealed that A56 could have potential applications for the production of polyhydroxyalkanoate or bioplastics.

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