• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 34
  • 10
  • 7
  • 4
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 66
  • 66
  • 66
  • 17
  • 12
  • 11
  • 10
  • 9
  • 9
  • 9
  • 9
  • 9
  • 8
  • 8
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

In vitro and in vivo characterization of tendon stem cells and role of stem cells in tendon healing.

January 2014 (has links)
肌腱修復一直是一個難題,因為依靠現在的治療很難將肌腱功能恢復到正常水平,近年來肌腱幹細胞的分離和發現為肌腱修復提供了新的策略。但是在利用肌腱幹細胞修復肌腱之前,我們應該瞭解肌腱幹細胞的哪些方面呢? / 不同來源的成體幹細胞雖然具備相似的幹細胞特性,但是他們仍然具有組織特異性和功能的差異。這就意味選擇合適的細胞來源對於肌腱再生和肌腱組織工程有特殊意義。所以我們認為與骨髓間充質幹細胞相比,肌腱幹細胞具備特殊的幹細胞特性。迄今為止,還沒有研究比較肌腱幹細胞和骨髓間充質幹細胞的幹細胞特性。臨床應用要求幹細胞在體外增殖培養,體外的微環境也會影響幹細胞的幹性和治療潛能,所以我們還並不清楚肌腱幹細胞的幹性在體外培養中維持多久。成功的幹細胞治療需要深入理解組織特異性幹細胞的體內特徵和他們在組織修復中的作用。肌腱幹細胞的体内特徵还有没详细研究过,而且也不知道這些內源性幹細胞是否參與肌腱修復。 / 所以為了更好地利用肌腱幹細胞進行肌腱修復,本研究的總體目標是比較肌腱幹細胞和骨髓間充質幹細胞的幹細胞特性,同時從臨床角度考慮研究肌腱幹細胞體外幹性的維持。進一步研究鑒定肌腱幹細胞的體內特徵,並且探索他們在肌腱癒合中的作用。本研究將會探討我們應該瞭解關於肌腱幹細胞的體內和體外特性。 / 在第一部分研究中, 我們從同一隻GFP大鼠中分離出肌腱幹細胞和骨髓間充質幹細胞。經過比較,我們發現肌腱幹細胞与骨髓間充質幹細胞相比具备更高的克隆形成能力,增殖速度,更強的多向分化能力和更高的肌腱相关的基因表达。所以肌腱幹細胞表現出更好的幹性,可能是比骨髓间充质干细胞更好的用于肌腱再生的细胞来源。 / 在第二部分研究中,我們發現肌腱幹細胞伴隨體外傳代培養細胞衰老β-半乳糖苷酶活性增高,而同時間充質幹細胞標誌物和多向分化能力降低,所以研究人員和臨床醫生在利用肌腱幹細胞進行組織工程時需要考慮在體外傳代培養中他們的幹性的變化。 / 在第三部分研究中,IdU標記滯留細胞方法用於在體內標記幹細胞。我們發現休眠的幹細胞以IdU標記滯留細胞的形式存在於肌腱中,相比肌腱本體更多標記滯留細胞位於和肌腱腱鞘和肌腱骨結合部位。其中我們發現在肌腱腱鞘中的標記滯留細胞位於血管周圍的微環境血管,所以血管周圍的微環境可能是肌腱幹細胞來源之一。肌腱損傷后,位於損傷區域的標記滯留細胞的數量,增殖標誌物,肌腱相關標誌物, 多能性標誌物,和微血管相關標誌物都有明顯增加,意味著標記滯留細胞可能通過遷移,增殖和分化參與肌腱修復。 / 綜上所述,我們的結果為理解肌腱幹細胞的體外幹性特徵和在體外培養中的幹性變化以及体内肌腱幹細胞的鑒定提供了新的解釋,這有利于未來促進肌腱幹細胞的組織工程應用於肌腱修復。 / Tendon repair remains a great challenge due to current therapies cannot restore normal tendon function. Tendon-derived stem cells (TDSCs) have been isolated from tendon tissues and characterized in vitro in recent studies and provide new strategies for tendon repair. But what should we know about tendon stem cells before we use them to repair injured tendon? / Although stem cells that originate from different tissues share some common stem cell characteristics, they might also exhibit some tissue unique properties and hence functional differences. Therefore, we hypothesized that TDSCs have unique stemness properties compared with bone marrow-derived stem cells (BMSCs). There has been no study to compare the stemness properties of TDSCs and BMSCs. Clinical applications often require the in vitro expansion of stem cells. In vitro microenvironment also affects the stemness properties and therapeutic potential of stem cells. It is not clear if the stemness properties of TDSCs can be maintained and how long that they can be preserved during in vitro expansion. Moreover, successful stem cell-based repair therapies will require an understanding of tissue specific stem cells in vivo and their roles in the tissue repair. Tendon stem cells have not been described in details in vivo and it is unknown whether these endogenous stem cells participate in the tendon healing. / Therefore, in order to better make use of TDSCs for tendon repair, the objective of this study is to characterize the stemness properties of TDSCs compared with BMSCs and also to investigate the stemness limitation of TDSCs during culture in vitro for clinical use purpose. Furthermore, this study aims to identify the putative tendon stem cells in vivo and their role in tendon healing. This study would tell how much we should know about tendon stem cells in vitro and in vivo. / In the first part of the study, TDSCs and BMSCs were isolated from the same GFP Sprague-Dawley rat. TDSCs showed higher mensenchymal and pluripotent stem cell makers; clonogenicity; proliferative capacity; and tenogenic, osteogenic, chondrogenic, and adipogenic differentiation markers and multi-lineage differentiation potential than BMSCs. Compared with BMSCs, TDSCs shows great stemness properties and might be an alternative cell source for tendon regeneration. / In the second part of this study, the senescence-associated β-galactosidase activity of TDSCs increased while their stem cell-related marker expression and the multi-lineage differentiation potential decreased during in vitro passaging. It suggests that researchers and clinicians need to consider the changes of stemness properties of TDSCs when multiplying them in vitro for tissue engineering. / In the third part of the study, IdU label-retaining method was used for the labeling of stem cells in vivo. We have identified quiescent stem cells as IdU label retaining cells (LRCs) at the peritenon, tendon mid-substance and tendon-bone junction. More LRCs were found at the peri-tenon and tendon-bone junction compared to the mid-substance. Some LRCs could be identified in the peri-vascular niche in the peri-tenon, suggesting that peri-vascular niche is one source of tendon stem cells. After injury, The LRC number and the expression of proliferative, tendon-related, pluripotency and pericyte-related markers in LRCs in the window wound increased, indicating that LRCs might be involved in tendon repair via cell migration, proliferation and differentiation. / In conclusion, our results have provided new findings about the understanding of tendon-derived stem cells including their stemness properties and their changes during the in vitro culture, as well as in vivo identity of tendon stem cells, which might facilitate the application of TDSCs in tissue engineering for tendon repair in the future. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Tan, Qi. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 130-162). / Abstracts also in Chinese.
32

Nitric oxide and tendon healing

Murrell, George Anthony Calvert, St George Clinical School, UNSW January 2006 (has links)
Nitric oxide is a small free radical generated by family of enzymes, the nitric oxide synthases. In a series of experiments performed over the last 15 years we showed that nitric oxide is induced by all three isoforms of nitric oxide synthase during tendon healing and that it plays a crucial beneficial role in restoring tendon function. In normal tendon we found very little nitric oxide synthase activity while in injured rat and human tendons nitric oxide synthase activity was expressed in healing fibroblasts in a temporal fashion. In healing rat Achilles tendon fibroblasts the first isoform to be expressed was endothelial nitric oxide synthase (eNOS), followed by inducible nitric oxide synthase (iNOS), and then brain or neuronal nitric oxide synthase (bNOS). Systemic inhibition of nitric oxide synthase activity decreased the cross sectional area and mechanical properties of the healing rodent Achilles tendons. Addition of nitric oxide via NO-flurbiprofen or NO-paracetamol enhanced rat Achilles tendon healing. Addition of nitric oxide to cultured human tendon cells via chemical means and via adenoviral transfection enhanced collagen synthesis, suggesting that one mechanism for the beneficial of nitric oxide on tendon healing might be via matrix synthesis. The final part of the work involved three randomized, double-blind clinical trials which evaluated the efficacy of nitric oxide donation via a patch in the management of the tendinopathy. In all three clinical trials there was a significant positive beneficial effect of nitric oxide donation to the clinical symptoms and function of patients with Achilles tendinopathy, tennis elbow and Achilles tendonitis.
33

Post-operative load bearing rehabilitation following autologous chondrocyte implantation

Ebert, Jay Robert January 2008 (has links)
[Truncated abstract] Autologous Chondrocyte Implantation (ACI) has shown early clinical success as a repair procedure to address focal articular cartilage defects in the knee, and involves isolating and culturing a patient's own chondrocytes in vitro and re-implantation of those cells into the cartilage defect. Over time, repair tissue can develop and remodel into hyaline-like cartilage. A progressive partial weight bearing (PWB) program becomes the critical factor in applying protection and progressive stimulation of the implanted cells, to promote best chondrocyte differentiation and development, without overloading the graft. The aim of this thesis was to investigate whether patients could replicate this theoretical load bearing model to possibly render the best quality tissue development. In addition, this proposed external load progression is only a means to loading the articular surface. Several factors, including those that may result from pathology, have the potential to influence gait patterns, and therefore, articular loading. The association between increasing external loads (ground reaction forces - GRF) and knee joint kinetics during partial and full weight bearing gait was, therefore, investigated in the ACI patient group, as was the contribution of other gait variables to these knee joint kinetics which may be modified by the clinician. Finally, current weight bearing (WB) protocols have been based on early ACI surgical techniques. With advancement in the surgical procedure and ongoing clinical experience, we employed a randomised controlled clinical trial to assess the effectiveness of an 'accelerated' load bearing program, compared with the traditionally 'conservative' post-operative protocol. ... Although similar spatio-temporal, knee kinematic and external loading parameters were observed between the traditional and accelerated rehabilitation groups, the accelerated group was 'more comparable' to the controls in their external knee adduction and flexion moments, where the traditional group had lower knee moments. Knee moments greatly affect knee articular loading, and large adduction moments have been related to poor clinical outcomes after surgery. Therefore, the return of normal levels may be ideal for graft stimulation, however, may overload the immature chondrocytes. Acceleration of the intensive rehabilitation program will enable the patient to return to normal activities earlier, whilst reducing time and expenses associated with the rehabilitative process, and may enhance long-term tissue development. However, continued follow-up is required to determine if there are any detrimental effects that may emerge as a result of the accelerated load bearing program, and assess the recovery of normal gait patterns and whether longer term graft outcomes are affected by the recovery time course of normal gait function, and/or abnormal loading mechanics in gait. Furthermore, analysis at all levels of PWB is needed to identify a more complete set of variables attributing to the magnitude of external knee joint kinetics and, therefore, knee articular loading, while the influence muscle activation patterns may have on articular loading needs to be investigated. This becomes critical when you consider loads experienced by the articular surface throughout the early post-operative period following ACI may be important to short- and long-term graft development.
34

Morphological changes of native rat achilles tendons following augmented soft tissue mobilization

Leaman, Jason 03 June 2011 (has links)
Augmented Soft Tissue Mobilization, a massage therapy which uses a solid instrument rather than human fingers to treat musculoskeletal injuries, has been successful in treating tendinitis. Davidson et al. studied the functional and morphological affects of ASTM on collagenase induced Achilles tendinitis in Sprague-Dawley rats. Morphological observations showed a significant increase in the number and activation of fibroblasts in the ASTM treated Groups. The authors suggested that the physical force of ASTM may promote tendon healing via increased fibroblast recruitment. An important, but unexplained, question is how ASTM would affect the fibroblasts of native, noncollagenase injured, tendons. Studies have shown that mechanical forces can alter cellular functions. The purpose of this study was to examine the morphological changes in native Sprague-Dawley rat Achilles tendons after ASTM therapy using different application pressures.Three animal Groups were randomly established: A) control Group with no ASTM; B) light ASTM with 1 Newton of pressure; and C) heavy ASTM with 3 Newtons of pressure. Upon completion of the therapy, the Achilles tendons of each Group were examined with light and electron microscopy techniques to assess fibroblast number, tendon morphology, and the presence of type I and type III collagen. Fibroblast counts from each Group were compared using a two-way ANOVA, multiple regression, and curvilinear regression analysis. Morphological differences were shown between the three Groups, especially between the non force Group and the two force Groups. The ASTM Group treated with one Newton demonstrated the greatest mean fibroblast count (165.1+/-55.8&160.7+/-49.8). Electron microscopy revealed the presence of activated fibroblasts in the tendons of the two force Groups, ASTM Groups. Polarizing microscopy showed a dramatic increase in the amount of Type III collagen in the two force Groups compared to the non force Group.Ball State UniversityMuncie, IN 47306
35

The use of a Chinese medicinal formula (Chuan-Duan-Bu-Gu-San) on experimental fracture healing in a mouse model

朱月華, Chu, Yuet-wah. January 2003 (has links)
published_or_final_version / Orthopaedic Surgery / Master / Master of Philosophy
36

Environmental and pharmacological intervention following cortical brain injury

Hastings, Erica, University of Lethbridge. Faculty of Arts and Science January 2003 (has links)
This thesis focuses on the effects of pharmacological and environmental interventions following perinatal prefrontal cortex lesions. Rats given postnatal day 3 medial prefrontal cortex lesions were provided with one of the following treatments: basic fibroblast growth factor (bFGF), complex-housing, tactile stimulation, or a combined treatment of both bFGF and tactile stimulation or bFGF and complex-housing. Rats given postnatal day 3 orbital prefrontal cortex lesions were housed in a complex environment. The findings of these studies suggest that bFGF, complex-housing or tactile stimulation are beneficial after early brain injury. The combined treatment of bFGF with complex-housing provides a synergistic effect, as the combined condition is more advantageous than bFGF alone. In contrast, the combined treatment of bFGF with tactile stimulation produced adverse effects. These results suggest that pharmacological and environmental manipulations change cortical plasticity and therefore functional recovery after neonatal cortical injury. / xv, 177 leaves : ill. (some col.) ; 29 cm.
37

An epidemiological analysis of traumatic cervical spine fractures at a referral spinal unit : a three-month study

Singh, Natasha January 2008 (has links)
Dissertation submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic Faculty: Health Sciences, Durban University of Technology, 2009 / Aim To determine the profile of traumatic cervical spine fractures with respect to the epidemiology, clinical presentation, types of fractures, conservative and surgical intervention, short-term post-intervention (i.e. post-conservative and post-surgical) complications and short-term post-surgical rehabilitation of patients presenting at the Spinal Unit of King George V Hospital over a 12-week period. Methods Patients who presented to the King George V Hospital Spinal Unit from surrounding hospitals with traumatic cervical spine fractures were evaluated by the medical staff. Data concerning the epidemiology, clinical presentation, types of fractures, conservative and surgical intervention, short-term post-intervention (i.e. post-conservative and postsurgical) complications and short-term post-surgical rehabilitation data were recorded by the researcher. A p-value of <0.05 was considered as statistically significant. Appropriate statistical tests were applied to the hypothesis-testing objectives. These involved the Pearson’s Chi Square Tests for categorical variables or Fisher’s Exact Tests as appropriate where sample sizes were small. Paired t-tests were done to compare preand- post-surgical Frankel grading and Norton Pressure Sore Assessment scores. Results The number of patients who presented to the Spinal Unit over a 12-week period was 20, of this number 17 were males, three were females and all were black. Eleven patients were treated surgically while nine patients were treated conservatively. The most frequent aetiology of cervical spine fractures was motor vehicle accidents (n = 10) followed by falls (n = 9). The most common co-existing medical conditions were smoking (n = 7), HIV (n = 5), alcohol abuse (n = 3) and obesity (n = 3). The most frequent locations of cervical spine fractures were C2 (n = 6), C1 (n = 4) and the posterior column of C6 (n = 3), while dislocations occurred primarily at the C5-C6 levels (n = 5) of the lower cervical spine. Odontoid fractures (n = 6), Jefferson’s fractures (n = 4) and unilateral facet dislocations (n = 6) were the most common fractures and dislocations v observed. Head injuries (n = 4) and lower limb fractures (n = 3) were the most common extra-spinal fractures. All subjects who sustained head injuries also had associated C1 or C2 fractures. Neurological complications most frequently involved the upper limb where loss of motor function (n = 8) and weakness (n = 4) were observed. The majority of the patients (n = 8) reported a Frankel Grading of E. There were no significant associations between types of fracture and gender with the exception of fracture/dislocation observed in two females. There was a statistically significant difference in the NPSA score (p = 0.004). Conservative care utilized included soft collar (n = 6), cones calipers (n = 6), physiotherapy (n = 4), Minerva jacket (n = 4) and SOMI (sterno-occipital mandibular immobilization) brace (n = 1) while surgical intervention included anterior decompression (n = 8), anterior fusion (n = 8), allograft strut (n = 8), discectomy (n = 8), anterior cervical plating (n = 8), anterior screw fixation (n = 2), a transoral approach (n = 1) and a corpectomy (n = 1). The short-term post-conservative care complications observed in this study were an occipital pressure sore (n = 1), severe discomfort (n = 1) as well as severe neck pain (n = 1), while the short-term post-surgical complications were severe neck pain (n = 2), oral thrush (n = 1), pneumonia (n = 1), odynophagia (n = 1) and hoarseness (n = 1). Of the 11 patients who underwent cervical spine surgery, ten were sent for physiotherapy and one for occupational therapy. No significant associations were seen between the type of cervical spine fracture and the age of the subject. There was a significant association between fracture/dislocation and the female gender (p = 0.016). There was significant negative association between odontoid fracture and: anterior decompression, anterior fusion, allograft strut, discectomy and anterior cervical plating (p = 0.006). Conclusion The results of this study reflect the presentation and management of cervical spine fractures at a referral spinal unit of a public hospital in KwaZulu Natal. The impact of HIV and other co-existing medical conditions were not determined due to the small sample size in this study. Further epidemiological studies are required to be conducted in the Spinal Units of all South African public hospitals in order to confirm or refute the observation of this study.
38

Effects of a modified straight leg raise on strength and muscle activity of the vastus medialis oblique in patients with patellofemoral malalignment

Wilson, Timm January 1993 (has links)
The purpose of this study was to determine the effectiveness of a modified sitting position straight leg raise on vastus medialis oblique (VMO) strength and EMG activity as compared to a traditional straight leg raise. A total of twenty-three subjects were recruited for this study. The subjects were randomly assigned to one of the following groups: (group I) modified straight leg raise (MSLR), and (group II) straight leg raise (SLR). The exercise program was three weeks long. University procedures for the protection of human subjects were followed. The subjects began with a 5 minute warm-up on a Cybex stationary bike set at 90 revolutions / minute. The subject then had electrodes placed on the Vastus Lateralis (VL) and Vastus Medialis Oblique (VMO). A Macintosh computer was used to record the EMG data. The subject then performed a standard Cybex test for knee flexion and extension. The Cybex dynamometer was placed at the knee joint line, the chair back tilt was at 85 degrees, the hip, chest, and thigh restraints were all fastened. The subjects in group I (Modified sitting SLR) and II (SLR) then returned the next day for their first rehabilitation lesson. Each subject group then participated in their respected exercise program for a total of three weeks. After three weeks of rehabilitation, the subjects retested using the same procedures followed in the pretest. A two tailed t-test was used to determine significance of the difference between means of the two groups. No significant differences were found between the two groups. / School of Physical Education
39

Chondrocyte : a target for the treatment of osteoarthritis

Lin, Zhen January 2007 (has links)
[Truncated abstract] Osteoarthritis (OA) is the most common form of arthritis, characterized by progressively degeneration of articular cartilage. Chondrocyte is the only cell type in articular cartilage tissue and responsible for cartilage matrix turnover. This thesis focuses on the biological and genetic behaviors of human chondrocyte and potential therapeutic strategies that target on chondrocyte. Chondrocytes have been used for the tissue-engineered cartilage construction, especially in articular cartilage repair. The technique of chondrocyte-base tissue engineering utilizes in vitro propagated chondrocytes combined with several manufactured biomaterials to regenerate cartilage tissue. Although these technologies have been successfully applied in clinic, the biological characteristics of chondrocyte during in vitro propagation and after implantation remain unclear. This thesis reviewed the present studies of chondrocyte biology and its potential uses in tissue engineering. Particularly, chondrocytes have been shown to de-differentiate into fibroblastic-cells when they are exposed to inflammatory conditions or cultured on monolayer in vitro. This thesis investigated the gene expression profile of chondrocytes when they are cultured and serially passaged on monolayer in vitro. Human chondrocytes obtained from OA patients were cultured up to passage 6. Twenty-eight chondrocyte associated genes were measured by Real-time PCR. The results showed that a number of genes were changed in expression levels at various stages of passage as indications of chondrocyte de-differentiation. Chondrocytes derived from OA patients or normal donors exhibited a very similar gene expression pattern. Interestingly, transcription factor Sox-9, which plays a key role in chondrogenesis remained unchanged with increasing passage number, indicating that the de-differentiation process of chondrocyte is reversible. This thesis also focused on the development of novel pharmacological approaches for OA that target on articular chondrocyte. The clinical feature, etiology, pathogenesis, diagnostic approaches, conventional and potential future treatments for OA were briefly reviewed in this thesis. ... The effects of natural compounds on chondrocyte gene expression, proteoglycan degradation and nitric oxide production were measured. The results showed that parthenolide, a NF-kB inhibitor, regulated chondrocyte function by suppressing the up-regulation of gene expression of inflammatory factors and matrix proteinases induced by lipopolysaccharide, and down-regulating COX-2 expression. Parthenolide was able to reduce proteoglycan degradation in human chondrocytes, but had no effect on nitric oxide production. These results suggest that parthenolide mediates inflammatory-activated NF-kB pathway, and subsequently reduces inflammatory response, prevents cartilage destruction and relieves pain, and hence may be useful for OA treatment.
40

Desenvolvimento e análise das propriedades de membranas de quitosana e alginato contendo polihexametileno biguanida para o tratamento de lesões de pele / Development and analysis of the properties of chitosan and alginate membranes containing polyhexamethylene biguanide for the treatment of skin lesions

Bueno, Cecília Zorzi, 1984- 27 August 2018 (has links)
Orientadores: Ângela Maria Moraes, Mara Elga Medeiros Braga / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-27T00:41:42Z (GMT). No. of bitstreams: 1 Bueno_CeciliaZorzi_D.pdf: 3611429 bytes, checksum: 9eeaf42b72e5b1a4778cab231780d7c6 (MD5) Previous issue date: 2015 / Resumo: As lesões de pele representam um grande desafio para os profissionais da saúde, sendo que os curativos mais modernos disponíveis atualmente são, em sua maioria, importados e de alto custo. Existe, assim, a necessidade de criar recursos mais acessíveis à população, os quais utilizem matérias-primas renováveis e sejam produzidos por meio de tecnologias simples e de baixo custo. A quitosana e o alginato são biopolímeros biocompatíveis, apresentam propriedades cicatrizantes e são abundantes na natureza, características estas que os tornam atrativos para a confecção de curativos de lesões de pele. A inclusão de agentes antimicrobianos, como polihexametileno biguanida (PHMB), aos curativos produzidos a partir destes biopolímeros pode levar a um melhor desempenho dos mesmos. Neste trabalho de tese, membranas densas e porosas de quitosana-alginato foram obtidas na presença de diferentes quantidades do tensoativo Pluronic F68. Os resultados obtidos mostraram que a inclusão de até 10% (m/m) de tensoativo provoca o aumento da porosidade (de 0,46 para 0,84), da espessura (de 0,08 para 0,50 mm), da rugosidade (de 1,27 para 21,20 µm), da capacidade de absorção de fluidos (de 14,22 para 21,27 g/g para NaCl a 0,9%) e de vapor d¿água (de 15,5 para 36,5%) e a diminuição da resistência à tração (de 31,1 para 1,1 MPa) e do alongamento na ruptura (de 4,0 para 2,0%) das membranas. Os materiais obtidos não se mostraram citotóxicos a fibroblastos de camundongos. O agente antimicrobiano PHMB foi incorporado às membranas por três diferentes métodos: adição à mistura polimérica, adsorção a partir de solução aquosa e impregnação mediada por CO2 supercrítico. A incorporação de PHMB por adição à mistura polimérica foi considerada como a mais satisfatória, pois não provocou alterações no aspecto e morfologia das membranas e resultou em altas eficiências de incorporação, variando entre 72 e 86 %. Observou-se também adequado controle da cinética de liberação, sendo que grande parte do antimicrobiano incorporado não foi liberada em tampão fosfato-salino (PBS), indicando alta afinidade entre o PHMB e a matriz de quitosana-alginato. As membranas apresentaram atividade antimicrobiana adequada, o que sugere que possam ser empregadas como barreira contra microrganismos comumente presentes em lesões de pele, tais como Staphylococcus aureus e Pseudomonas aeruginosa / Abstract: Skin lesions represent a great challenge for health professionals, since most of the existing modern wound dressings are imported and expensive. Therefore, there is a need to create more accessible products to the public, made from renewable raw materials and processed through simple and low cost technologies. Chitosan and alginate are biocompatible biopolymers that have healing properties and are abundant in nature, which are attractive characteristics to the production of wound dressings. The incorporation of antimicrobial agents, such as polyhexamethylene biguanide (PHMB), to these dressings can lead to a better performance. In this work, dense and porous chitosan-alginate membranes were obtained in the presence of different proportions of the surfactant Pluronic F68. It was noticed that inclusion of up to 10% (w/w) Pluronic F68 caused an increase in porosity (from 0.46 to 0.84), thickness (from 0.08 to 0.50 mm), roughness (from 1.27 to 21.20 µm), fluids absorption capacity (from 14.22 to 21.27 g/g for 0.9% NaCl) and water vapor absorption capacity (from 15.5 to 36.5%) and a decrease in tensile strength (from 31.1 to 1.1 MPa) and elongation at break (from 4.0 to 2.0%) of the membranes. The obtained materials were not toxic to mouse fibroblasts. The antimicrobial agent PHMB was incorporated to the membranes through three different methods: addition to the polymeric mixture, adsorption in aqueous solution and via supercritical fluid. The addition to the polymeric mixture was considered the most promising incorporation method, since it had high yields (between 72 and 86 %) and did not cause changes in the membranes aspect and morphology. Release kinetic studies in PBS showed that most of the PHMB loaded remained in the membranes, indicating high affinity between PHMB and the polymeric matrix. The obtained membranes showed adequate antimicrobial activity, having potential applicability as barriers against microorganims commonly found in skin wounds, such as Staphylococcus aureus and Pseudomonas aeruginosa / Doutorado / Engenharia Química / Doutora em Engenharia Quimica

Page generated in 0.1972 seconds