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Exploitation of natural eumelanin and conductive polymers on the preparation of electroactive systems for skeletal muscle tissue engineering applications
No full textTese de Doutoramento em Engenharia de Tecidos, Medicina Regenerativa e Células EstaminaisSkeletal muscle tissues comprise about 40-45% of the total human body mass. The skeletal muscle
functionality is commonly depreciated as a consequence of congenital abnormalities, traumatic
injuries from accidents or sports activities, and neurological diseases. The defects in muscle structure
can affect the physiological performance of the body as a whole, which further influences the
psychological responses. It has been demonstrated that electrical stimulus can affect cell behavior,
namely, adhesion, proliferation and differentiation and accelerate the healing of damaged tissues like
bone and nerves. Moreover, electrical stimulation is one of the emerging tools being used in clinics
with the purpose of inducing and recovering the physiological functionality in damaged muscle tissues.
However, the clinical outcomes are limited to the specific local area, such as head, legs, arms and
back.
Despite the intrinsic capacity of skeletal muscle tissues to self-repair, in case of severe tissue damage
or loss, such capacity is insufficient to restore the functionality. The conventional clinical treatment
modalities include allocation of autologous muscle by surgical treatment, but clinical outcomes are
not very satisfactory. Thus, by combining the advantages of electrical stimulus, including cell fate
modulation, with electroactive materials and tissue engineering approaches, we expect to overcome
some of the existing limitations. Indeed, skeletal muscle tissue engineering holds great potential to
alleviate the increasing burden of defective muscle tissues by constructing viable substitutes for
replacement therapies. Nevertheless, the reconstruction of tissue engineered skeletal muscle
substitutes should mimic native skeletal muscle-like structural properties including myofibers
uniformity and density throughout the functional muscle cells.
This thesis is focus on the exploitation of novel biomaterials, in particular, natural and synthetic
polymers, with electrical properties, for skeletal muscle tissue engineering applications. Eumelanin
from Sepia ink (Sepia officinalis) was initially purified by a well-established protocol and analyzed by
colorimetric oxidative assay for investigating the redox activity. To explore intrinsic properties of
eumelanin nanoparticles and expand its applications, an innovative approach was developed, which
consisted in the preparation of electrospun PVA nanofibers meshes containing eumelanin
nanoparticles. The physical properties, in particular, electrical conductivity, and biological performance
of the nanofibrous meshes were significantly improved upon eumelanin incorporation, indicating that
EUNp-PVA nanofibrous matrices are excellent candidates to be used in skeletal muscle tissue
engineering applications. In parallel, novel electroactive spongy-like hydrogels were developed by
combining gellan gum (GG) with two different conductive synthetic polymers: polypyrrole (PPy) and polyaniline (PANi). GG is a linear anionic polysaccharide of natural origin that has been extensively
studied for a wide range of biomedical applications and can be transformed in a hydrogel at body
temperature by ionic crosslinking. When processed as spongy-like hydrogels, these materials retain
the structural features of hydrogels relevant for tissue engineering applications and improved
mechanical and cell adhesive properties. Thus, the rationale behind adding synthetic conducting
polymers, PPy and PANi, was to improve the electroconductive properties of the final constructs,
maintaining simultaneously the improved mechanical features and intrinsic cell-adhesive ability of GG
spongy-like hydrogels. The physical, chemical and electrical properties were analyzed, and cytotoxicity,
as well as, biocompatibility was assessed both in vitro and in vivo. Both PPy-GG and PANi-GG
electroactive spongy-like hydrogels have shown high porosity and interconnected pores, showing
enhanced cellular response during in vitro studies. Moreover, negligible inflammatory response was
observed during in vivo analysis. The results demonstrate that the electroactive PPy-GG and PANi-GG
spongy-like hydrogels meet all the functional requirements for mimicking the ECM microenvironment
of muscle tissue, being interesting candidates to be used in skeletal muscle tissue regeneration
strategies.
The results reported in this thesis demonstrate the successful fabrication of eumelanin nanoparticlesincorporated
PVA nanofibrous meshes by electrospinning, as well as, the production of electroactive
PPy-GG and PANi-GG spongy-like hydrogels. Furthermore, physicochemical and biological assessment
of these three different matrices prove that these biomaterials have beneficial properties to be
employed in the development of tissue engineering strategies for the regeneration of skeletal muscle
tissues or other tissues of interest that respond favorably to electrical stimulation.O tecido muscular esquelético constituí cerca de 40-45% da massa total do corpo humano. A
funcionalidade do tecido muscular esquelético é frequentemente comprometida como consequência
de anomalias congénitas, lesões traumáticas decorrentes de acidentes ou atividades desportivas e
doenças neurológicas. Os defeitos no músculo-esquelético podem afetar o desempenho fisiológico do
corpo, influenciando as suas respostas fisiológicas. Foi demonstrado que o estímulo elétrico pode
afetar a comportamento celular, nomeadamente a adesão, proliferação e diferenciação, e acelerar a
cura dos tecidos danificados como os ossos e os nervos. Apesar da estimulação elétrica ser uma
ferramenta emergente usada na prática clínica com o objetivo de induzir e recuperar a funcionalidade
fisiológica dos tecidos danificados, os resultados clínicos são limitados a uma área específica como
cabeça, perna, braço e costas.
Apesar da capacidade intrínseca do músculo-esquelético para auto-reparação, em casos de danos
severos ou perda do tecido, essa capacidade é insuficiente para restaurar a funcionalidade do
músculo. As modalidades de tratamento clínico convencionais incluem alocação de músculo autólogo
por tratamento cirúrgico, no entanto, os resultados clínicos não são muito satisfatórios. Assim, através
da combinação das vantagens do estímulo elétrico com materiais electrocondutores e engenharia de
tecidos, pretendemos ultrapassar algumas das limitações existentes na regeneração do músculoesquelético.
De facto, a engenharia de tecidos do músculo-esquelético apresenta grande potencial
para reduzir a elevada percentagem de tecidos musculares defeituosos através da construção de
substitutos viáveis para terapias de reposição. No entanto, a reconstrução do tecido fabricado pela
engenharia de tecidos deve simular o tecido muscular nativo nas suas propriedades estruturais,
incluindo a uniformidade e densidade das células musculares.
Esta tese foca-se na exploração de novos biomateriais, em particular, polímeros materiais e sintéticos,
com propriedades elétricas, para a engenharia de tecido muscular esquelético. A eumelaninn da Sepia
ink (Sepia officinalis) foi inicialmente purificada por um protocolo estabelecido e analisada por um
ensaio colorimétrico oxidativo para investigar as suas propriedades oxidativas/redutoras.
Para explorar as propriedades intrínsecas das nanopartículas de eumelanina e alargar as suas
aplicações, uma nova abordagem foi desenvolvida, que consistiu na preparação de nanofibras de PVA
por “electrospun” contendo na malha das fibras nanopartículas de eumelanina. As propriedades
físicas, em particular a condutividade e o desempenho biológico das malhas de nanofibras foram
melhoradas significativamente após a incorporação de eumelanina, indicando que as matrizes de
nanofibras de eumelanina nanopartícula-álcool polivinílico (EUNp-PVA) são excelentes para serem
usadas em engenharia de tecidos do tecido muscular esquelético. Em paralelo, novos hidrogéis “spongy-like” foram desenvolvidos com gellan gum (GG) com dois
polímeros condutores diferentes: polypyrrole (PPy) e polianilina (PANi). Gellan gum é um
polissacarídeo aniónico linear cuja origem natural tem sido intensamente estudada para vasto número
de aplicações biomédicas, que pode ser transformado num hidrogel à temperatura do corpo por
reticulação iónica. Quando processado como um “spongy-like” hidrogel, retém as estruturas
estruturais dos hidrogéis relevantes para engenharia de tecidos e melhoram as propriedades
mecânicas e de adesão das células. Assim, o objetivo de adicionar polímeros condutores sintéticos,
PPy and PANi, foi o de melhorar as propriedades electrocondutoras dos construtos finais, mantendo
simultaneamente as características mecânicas e de adesão celular dos “spongy-like” GG hidrogéis.
As propriedades físicas, químicas e elétricas foram analisadas, e a citoxicidade, assim como a
biocompatibilidade foi avaliada in vitro e in vivo. Ambos “spongy-like” hidrogéis PPy-GG e PANi-GG
apresentam grande porosidade e poros interconectados. Demonstrando assim melhor resposta
celular durante os estudos in vitro. No entanto, inflamação celular não significativa foi detetada
durante os estudos in vivo. Os resultados demonstram que os hidrogéis eletroactivos “spongy-like”
PPy-GG e PANi-GG preenchem todos os requisitos funcionais para substituir a matriz extracelular
(ECM) do tecido muscular, sendo candidatos interessantes para serem utilizados nas estratégias de
regeneração do tecido muscular esquelético.
Os resultados desta tese demostram a fabricação de nanopartículas de eumelanin e a sua
incorparação em malhas de nanofibras à base de PVA produzidas por electrospinning, assim como a
produção de hidrogéis “spongy-like” condutores. A avaliação físico-química e biológica destas 3
matrizes diferentes prova que estes biomateriais têm propriedades beneficiais para serem utilizados
no desenvolvimento de estratégias de engenharia de tecidos para a regeneração do músculo
esquelético ou outros tecidos de interesse que respondem favoravelmente à estimulação elétrica
การใช้แป้งข้าวเหนียวดัดแปรด้วยเทคนิคไมโครเวฟเป็นสารยึดเกาะในยาเม็ด Microwave-treated Glutinous Rice Starch as A Tablet Binder
Get PDFบทคัดย่อ วัตถุประสงค์: เพื่อศึกษาการใช้แป้งข้าวเหนียวที่ดัดแปรด้วยไมโครเวฟ (GRMi) เป็นสารยึดเกาะในการผลิตยาเม็ดที่เตรียมด้วยวิธีแกรนูลเปียก วิธีการศึกษา: เตรียมยาเม็ดด้วยวิธีแกรนูลเปียกที่ประกอบด้วยไมโครคริสทัลไลน์เซลลูโลส (MCC) หรือแลคโตสโมโนไฮเดรต (Lac) โดยใช้สารยึดเกาะในปริมาณร้อยละโดยน้ำหนักดังนี้ 1) ร้อยละ 0, 2) GRMi ร้อยละ 2.5 และ 3) แป้งข้าวเหนียวที่ให้ความร้อนโดยตรง (GRB) ร้อยละ 2.5 และใช้แมกนีเซียมสเตียเรตร้อยละ 1 โดยน้ำหนัก โดยตอกอัดยาเม็ดด้วยแรงที่ต่างกัน (40, 60 และ 80 kgf/cm2) แล้วประเมินสมบัติของยาเม็ด ผลการศึกษา: ยาเม็ดที่ใช้ MCC มีความต้านแรงอัดแตกในช่วง 9.52 - 17.72 kgf ซึ่งสูงกว่า Lac (1.10 - 5.98 kgf) เวลาในการแตกตัวและสภาพกร่อนของยาเม็ดที่ใช้ MCC อยู่ในช่วง 11.40 - 59.40 วินาที และร้อยละ 0.08 - 0.41 โดยน้ำหนัก ตามลำดับ ซึ่งต่ำกว่ายาเม็ดที่ใช้ Lac ที่อยู่ในช่วง 70.80 - 5,170.20 วินาที และร้อยละ 0.88 - 3.89 โดยน้ำหนัก ตามลำดับ และยังพบว่าการเพิ่มแรงตอกอัดทำให้ยาเม็ดมีค่าความต้านแรงอัดแตกและเวลาในการแตกตัวเพิ่มขึ้น แต่มีสภาพกร่อนลดลง เมื่อเพิ่มแรงอัดให้แก่ยาเม็ดที่ใช้สารยึดเกาะ GRMi และ GRB พบว่าสามารถทำให้ยาเม็ดมีค่าความแข็งแรง (CSFR) และดัชนีชี้วัดคุณภาพยาเม็ด (CSFR/DT index) เพิ่มมากขึ้นได้ แสดงถึงความสามารถในการยึดเกาะที่ดีและสมบัติการเป็นยาเม็ดที่ดีขึ้น สรุป: สามารถใช้แป้งข้าวเหนียวที่ดัดแปรด้วยไมโครเวฟเป็นสารยึดเกาะในการเตรียมยาเม็ดด้วยวิธีแกรนูลเปียกได้ คำสำคัญ: แป้งข้าวเหนียว, แป้งดัดแปรด้วยไมโครเวฟ, การเตรียมด้วยวิธีแกรนูลเปียก, สารยึดเกาะ Abstract Objective: To investigate microwave-treated glutinous rice starch (GRMi) used as a binder in wet granulation tablets. Methods: Being prepared with wet granulation method, each tablet consisted of filler (microcrystalline cellulose (MCC) or lactose monohydrate (Lac)), binder (0% w/w, 2.5% w/w of GRMi, or 2.5% w/w of heated glutinous rice starch (GRB)) and 1% w/w of magnesium stearate. All tablet formulations were compressed by various compression forces (40, 60, and 80 kgf/cm2) and tablet properties were evaluated. Results: The MCC-tablets had a crushing strength (CS) of 9.52-17.72 kgf. which was higher than that of Lac-tablets (1.10 - 5.98 kgf.). The disintegration time (DT) and friability (F) of MCC-tablets (11.40 - 59.40 sec and 0.08 - 0.41%, respectively) were lower than those of Lac-tablets (70.80 - 5,170.20 sec and 0.88 - 3.89%, respectively). The increase of compression force resulted in increased CS and DT and decreased F. When compression force was increased to tablets using GRMi and GRB as a binder, the higher crushing strength-friability ratio (CSFR) and crushing strength-friability/disintegration time ratio (CSFR/DT index) in both tablets were observed. These results indicated better binding capability with improved tablet properties. Conclusions: microwave-treated glutinous rice starch could be used as a binder in wet granulation tablets. Keywords: glutinous rice starch, microwave-treated starch, wet granulation method, binde
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
PREPARATION AND CHARACTERIZATION OF GRAPEFRUIT OIL BASE MICROEMULSIONS OF CAFFEINE
Get PDFObjective: The objective of the present work was to prepare and characterize grapefruit oil base microemulsions loaded with caffeine as a model hydrophilic compound.
Methods: The formulation ingredients were selected based on surfactant efficiency and solubility studies. Ternary phase diagrams of grapefruit oil were constructed using the water titration method. Nine O/W microemulsions were constructed and prepared by mixing surfactant system, grapefruit oil, water and caffeine together. The resulting microemulsions were investigated for viscosity using Brookfield viscometer, for pH value using a digital pH meter, and for average particle size and polydispersity index (PDI) using a Zetasizer Nano. Ex vivo skin permeation through porcine ear skin was conducted using a side-by-side diffusion cell. The amount of caffeine was analyzed using HPLC-UV method.
Results: Tween 20 yielded the highest emulsification ability for grapefruit oil and the highest caffeine solubility. It was selected as a major surfactant. Caffeine was slightly soluble in ethanol and isopropyl alcohol, but sparingly soluble in propylene glycol (PG). These ingredients were used as the cosurfactants. Nine grapefruit oil base microemulsions were prepared and characterized. The pH of microemulsions was within the range of 4.48-5.96. Particle size was in the range of 10.81±0.03 to 62.18±21.04 µm with the PDI of 0.13±0.02 to 0.64±0.11. Viscosity and particle size of microemulsions increased significantly with increasing grapefruit oil or tween 20 content. Addition of PG as cosurfactant resulted in the increases of viscosity, particle size and PDI. Depending on the formulation parameters, the permeation fluxes of caffeine from grapefruit oil base microemulsions were in the range of 28.4±3.4-361.4±15.2 µg/cm2/h.
Conclusion: The grapefruit oil base microemulsions were successfully formulated. The physical properties and caffeine permeation of these microemulsions were found to be dependent on the grapefruit oil content, tween 20 content, cosurfactant type and content, as well as caffeine loading. The optimal formulation of grapefruit oil base microemulsion suggested composition of 5% grapefruit oil, 50% surfactant system (tween 20 and ethanol at the ratio of 9:1), and water
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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