Vascularization is essential for living tissue and remains a major challenge in the field of tissue engineering. A lack of a perfusable channel network within a large and densely populated tissue engineered construct leads to necrotic core formation, preventing fabrication of functional tissues and organs. While many approaches have been reported for forming vascular networks, including materials processing techniques, such those involving lithography, bioprinting, and sacrificial templating; and cell-based approaches, in which cellular self-organization processes form vessels; all are deficient in their ability to form a vessel system of sufficient complexity for supporting a large cellular construct. What is missing from the literature is a method for forming a fully three-dimensional vascular network over the full range of length-scales found in native vessel systems, which can be used alongside cells and perfused with fluids to support their function. A large number of research groups are thus pursuing novel methods for fabricating vascular systems in order that new tissues and organs can be fabricated in the lab. In this project, a 3D printing-based approach was used to form vascular networks which are hierarchical, three-dimensional, and perfusable. This was performed in thick, cellularized hydrogels similar in composition to native tissue; these being collagen (ECM-like) and fibrin (woundlike), both of which are highly capable of supporting cellular activities, such as cell seeding, cell spreading, and capillary morphogenesis. In order to make use of 3D printed network templates in cellularized hydrogel environments, it was necessary to develop a new approach in which standard 3D printed materials were converted into a gelatin template, via an alginate intermediary, which can be removed quickly in physiologic conditions and which does not reduce cell viability. This multi-casting approach enables a hierarchical channel network to be formed in three-dimensions, capable of being perfused with cell medium to maintain the viability of a cell population, thereby addressing the fundamental problem. Using standard cell staining and immuno-histochemistry techniques, we showed good endothelial cell seeding and the presence of tight junctions between the channel endothelial cells. When fibroblasts were seeded into the bulk of the hydrogel, a high degree of cell viability and cell spreading was observed when a threshold flow rate is met. By counting the number of live and dead cells in a sample regions of the gel, we were able to show a dependency of cell viability upon the perfusion flow rate and further determine a regime in which the vast majority of cells are alive and spreading. This data informs future cellular experiments using this platform technology. The limits of existing 3D printing technology meant that the micro-scale vasculature needed to be formed by other means. Cellular co-culture of endothelial and stromal cell types has been shown to be capable of forming capillary-like structures in vitro. For inclusion with the 3D printed channel system, we investigated the use of an angiogenic method for capillary formation, using multi-cellular spheroids, and a vasculogenic approach, using individual cells, in order that the full vascular system could be constructed. Endothelial and mesenchymal stromal cells were encapsulated in small fibrin and collagen gels and maintained under static culture conditions in order to form capillaries by the above approaches. The aim here was to find a particular gel composition and cell concentration which would support capillary morphogenesis while being suitably robust to handle the mechanical stresses associated with perfusion. As future work, the next step will be to incorporate the vasculogenic co-culture technique, used to form capillary-sized vessels, into a perfusable gel containing the large templated channels, formed via the multi-casting approach. The challenge here is to anastomose the capillary-sized vessels to the large templated channels and thereby enable perfusion of the capillary vessels. This step would be a highly significant development in the field as it would mean large constructs could be fabricated with physiological densities of cells, which could lead to a range of potential therapeutic applications.

abstract: Solar energy is leading in renewable energy sources and the aspects surrounding the efforts to harvest light are gaining importance. One such aspect is increasing the light absorption, where heliotropism comes into play. Heliotropism, the ability to track the sun across the sky, can be integrated with solar cells for more efficient photon collection and other optoelectronic systems. Inspired by plants, which optimize incident sunlight in nature, several researchers have made artificial heliotropic and phototropic systems. This project aims to design, synthesize and characterize a material system and evaluate its application in a phototropic system. A gold nanoparticle (Au NP) incorporated poly(N-isopropylacrylamide) (PNIPAAm) hydrogel was synthesized as a photo-thermo-responsive material in our phototropic system. The Au NPs generate heat from the incident via plasmonic resonance to induce a volume phase change of the thermo-responsive hydrogel PNIPAAm. PNIPAAm shrinks or swells at temperature above or below 32°C. Upon irradiation, the Au NP-PNIPAAm micropillar actuates, specifically bending toward the incident light and precisely following the varying incident angle. Swelling ratio tests, bending angle tests with a static incident light and bending tests with varying angles were carried out on hydrogel samples with varying Au NP concentrations. Swelling ratios ranging from 1.45 to 2.9 were recorded for pure hydrogel samples and samples with very low Au NP concentrations. Swelling ratios of 2.41 and 3.37 were calculated for samples with low and high concentrations of Au NPs, respectively. A bending of up to 88° was observed in Au NP-hydrogel pillars with a low Au NP concentration with a 90° incident angle. The light tracking performance was assessed by the slope of the pillar Bending angle (response angle) vs. Incident light angle plot. A slope of 1 indicates ideal tracking with top of the pillar being normal to the incident light, maximizing the photon absorption. Slopes of 0.82 and 0.56 were observed for the low and high Au NP concentration samples. The rapid and precise incident light tracking of our system has shown the promise in phototropic applications. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2016

abstract: Proton beam therapy (PBT) is a state-of-the-art radiotherapy treatment approach that uses focused proton beams for tumor ablation. A key advantage of this approach over conventional photon radiotherapy (XRT) is the unique dose deposition characteristics of protons, resulting in superior healthy tissue sparing. This results in fewer unwanted side effects and improved outcomes for patients. Current available dosimeters are intrinsic, complex and expensive; hence cannot be used to determine the dose delivered to the tumor routinely. Here, we report a hydrogel based plasmonic nanosensor for measurements of clinical doses in ranges between 2-4 GyRBE. In this nanosensor, gold ions, encapsulated in a hydrogel, are reduced to gold nanoparticles following irradiation with proton beams. Formation of gold nanoparticles renders a color change to the originally colorless hydrogel. The intensity of the color can be used to calibrate the hydrogel nanosensor in order to quantify different radiation doses employed during treatment. The potential of this nanosensor for clinical translation was demonstrated using an anthropomorphic phantom mimicking a clinical radiotherapy session. The simplicity of fabrication, detection range in the fractionated radiotherapy regime and ease of detection with translational potential makes this a first-in-kind plasmonic colorimetric nanosensor for applications in clinical proton beam therapy. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2017

Orientadores: Inez Valéria Pagotto Yoshida, Celso Aparecido Bertran / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-17T05:52:59Z (GMT). No. of bitstreams: 1 Pires_Geovanna_D.pdf: 5851198 bytes, checksum: 225cceb31bb1d2c8cf8b8d8adc32fe02 (MD5) Previous issue date: 2010 / Resumo: Neste trabalho, foram preparados diferentes hidrogéis constituídos à base de quitosana (CN) de alta massa molar e hidroxiapatita (HA), esta última obtida por mineralização in situ, todos com razão fase orgânica/inorgânica próxima de 60:40, em massa, similar à média do tecido ósseo. Nas preparações utilizou-se também a razão Ca/P=1,67, semelhante à da hidroxiapatita biológica. Para alguns hidrogéis adicionou-se uma quantidade de Si (como precursor solúvel de SiO2) próxima à encontrada nos ossos. Após a secagem dos hidrogéis, os materiais resultantes foram caracterizados por espectroscopia infravermelho, ressonância magnética nuclear de P, difração de raios X, termogravimetria, microscopias óptica e eletrônica de varredura. Foram efetuadas análises elementares de Ca e Si (por espectroscopia de absorção atômica) e de P (por espectrocolorimetria). A bioatividade dos hidrogéis foi avaliada pela imersão em solução denominada fluído corpóreo simulado (SBF), monitorando-se a formação de hidroxiapatita. Testes in vitro de viabilidade celular utilizando-se os seguintes procedimentos: redução do MTT; adesão e proliferação celular pela incorporação de cristal violeta; avaliação da expressão e dos níveis de fosforilação de proteínas por immunoblotting e diferenciação celular pela dosagem de fosfatase alcalina foram efetuados com os hidrogéis para a avaliação do seu potencial como biomaterial. Os resultados permitiram avaliar citotoxidade, adesão e proliferação de células, expressão das proteínas cdk4/cdk6/ciclinaD1/ciclinaD3 e atividade enzimática. O teste de bioatividade em SBF mostrou que os hidrogéis são bioativos devido à nucleação de HA. Os hidrogéis CNHA (formado por CN e HA) e CNHAO (formado por CN, HA e Q8-) não apresentaram toxicidade celular in vitro, mostrando resultados bastante significativos de adesão e proliferação de células pré-osteoblastos. Estes hidrogéis demonstraram também características favoráveis para o seu emprego como biomaterial, sugerindo potencial para o uso como scaffolds em engenharia de tecido ósseo / Abstract: In this study, different hydrogels based on high molecular mass chitosan (CN) and hydroxyapatite (HA) were prepared, this last component obtained by the in situ mineralization, all with an organic/inorganic ratio of 60:40 (w/w), similar to the average composition of the bone tissue.These hydrogels were prepared with the Ca/P ratio = 1.67, similar to the biological hydroxyapatite. For some hydrogels an amount of Si (as SiO2 soluble precursor), close to that found in the bones, was added. Dry hydrogels were characterized by infrared spectrum, P nuclear magnetic resonance, X-ray diffraction, thermogravimetry, optical and scanning electron microscopies. The amount of Ca and Si incorporated in the materials was determined by atomic absorption spectroscopy, while the P content was determined by spectrocolorimetry. The bioactivity of the hydrogels was evaluated by immersion in a simulated body fluid (SBF), monitoring the hydroxyapatite formation. The assessment of the hydrogel potential as a biomaterial was performed with in vitro tests of cell viability, corried out by the following procedures: MTT reduction; cell adhesion and proliferation, by the incorporation of violet crystal; evaluating the expression and phosphorylation levels of proteins, by immunoblotting; and cell differentiation, by measuring the level of alkaline phosphatase. The results allowed evaluating the cytotoxicity, adhesion and proliferation of cells, expression of cdk4/cdk6/ciclinaD1/ciclinaD3 proteins and the enzymatic activity. The test of bioactivity in SBF showed that the hydrogels are bioactive due to the nucleation of HA, uniformly dispersed on their surface. The CNHA (composed by CN e HA) e CNHAO (composed by CN, HA e Q8-) hydrogels showed no in vitro cellular toxicity, with very significant results of adhesion and proliferation of pre-osteoblast cells. This characteristic was more evident in the rough surface of the hydrogels. These hydrogels also showed favorable characteristics for their use as a biomaterial, due to the easy handling and fractionation/molding, as well as by its nature, topography and morphology, similar to the bone tissue, suggesting potential as scaffolds in the bone tissue engineering / Doutorado / Quimica Inorganica / Doutor em Ciências

O diabetes mellitus é um transtorno metabólico que leva a uma deficiência na secreção de insulina, na sua ação ou em ambos. O mau controle glicêmico pode acarretar em diversas complicações, entre elas, o pé diabético, que é o responsável pela maior parte de amputações não traumáticas dos membros inferiores e gera um custo muito alto para o tratamento de feridas e de cicatrização das amputações. A tecnologia tem proporcionado a criação de novos métodos de tratamento, como as membranas de hidrogel veiculadoras de fármaco. Com isso o nosso objetivo foi testar a eficiência do hidrogel com papaína no tratamento de úlceras em pés diabéticos. A pesquisa foi realizada no município de Porto Nacional (TO) com todos os pacientes portadores de pé diabéticos que deram entrada no HRPPN de 01 de outubro de 2014 a 31 de outubro de 2015, que se encaixavam dentro dos critérios de inclusão do trabalho e assinaram o TCLE. Para a análise socioeconômica aplicou-se um questionário com perguntas objetivas. Para a aplicação da membrana, as feridas foram lavadas com soro fisiológico a 0,9% e os curativos foram realizados de acordo com o protocolo do hospital e trocados a cada 24 horas. Utilizou-se uma planilha de diagnóstico para realizar o acompanhamento diário das feridas. Dezoito pacientes participaram do estudo, sendo que, 16 deles foram internados devido ao pé diabético e ao DM descompensado. 50% dos pacientes eram do sexo feminino e 50% do masculino, todos com idade entre 29 anos e 80 anos. 22% fazem uso de hipoglicemiante oral e insulina e os outros 78% usam apenas hipoglicemiante oral. 82% têm companheiro ou é casado e a maior parte não possui renda ou recebe até um salário mínimo (61%). Quanto à escolaridade, 28% são analfabetos e 34% não concluíram o ensino médio. 50% dos pacientes são naturais de Porto Nacional e 11% de outros estados. Quanto ao conhecimento que os pacientes tinham das complicações que tem como causa o DM, o pé diabético foi a única citada por todos, as demais complicações eram desconhecidas por muitos; somente um paciente tem ciência de todas as complicações. Dos 18 pacientes, 7 puderam ser tratados com a membrana de hidrogel com papaína, mas como não houve melhora significativa, a membrana teve que ser substituída pelo curativo convencional. A membrana não aderiu à pele saudável e nem na ferida, uma vez que apresentou rigidez, fato que pode ter retardado o processo de cicatrização, já que o curativo não envolveu a ferida completamente. A membrana também apresentou baixa taxa de absorção do exsudato, fazendo com que as feridas ficassem maceradas. A cisteína, composto presente na membrana, fez com que ela liberasse um forte odor que causou repulsa nos pacientes e seus familiares, fato que desmotivou o paciente a querer realizar o tratamento. Dados estes resultados, infere-se que a utilização do hidrogel com papaína não trouxe melhora para as feridas do pé diabético, houve um leve desbridamento em algumas feridas, mas sem cicatrização. / Diabetes mellitus is a metabolic disorder that leads to a deficiency in insulin secretion, its action or both. Poor glycemic control can lead to a number of complications, including diabetic foot, which is responsible for most non- traumatic lower limb amputations and generates a very high cost for wound healing and amputation healing. The technology has provided the creation of new treatment methods, such as drug-bearing hydrogel membranes. Our aim is to test the efficiency of papain hydrogel in the treatment of diabetic foot ulcers. The study was carried out in the municipality of Porto Nacional (TO) with all patients with diabetic foot who entered the HRPPN from October 1, 2014 to October 31, 2015, who fit within the inclusion criteria of the work and signed The TCLE. For the socioeconomic analysis a questionnaire with direct questions was applied. For the application of the membrane the wounds were washed with 0.9% saline and the dressings were performed according to the hospital protocol and changed every 24 hours. A diagnostic worksheet was used to perform the daily follow-up of the wounds. Eighteen patients participated in the study, and 16 of them were hospitalized due to diabetic foot and decompensated DM. 50% of the patients were female and 50% were male, all aged between 29 years and 80 years. 22% use oral hypoglycemic and insulin and the other 78% only use oral hypoglycemic. 82% have a partner or are married and most of them have no income or receive up to a minimum wage (61%). As for schooling, 28% are illiterate and 34% did not finish high school. 50% of the patients are from Porto Nacional and 11% from other states. As for the patients\' knowledge of the complications caused by DM, the diabetic foot was the only one mentioned by all, the other complications were unknown by many; only one patient is aware of all the complications. From 18 patients, 7 could be treated with the papain hydrogel membrane, but as there was no significant improvement, the membrane had to be replaced by the conventional dressing. The membrane did not adhere to healthy skin or even to the wound, since it presented rigidity, a fact that may have delayed the healing process since the dressing did not involve the wound completely. The membrane also had a low absorption rate of the exudate, causing the wounds to become macerated. The cysteine, a compound present in the membrane, caused it to release a strong odor that caused disgust in patients and their families, a fact that discouraged the patient from wanting to perform the treatment. Given these results, it was inferred that the use of the papain hydrogel did not improve the wounds of the diabetic foot, there was a slight debridement in some wounds, but without healing.

Orientador: Marcelo Ganzarolli de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T09:59:43Z (GMT). No. of bitstreams: 1 Gonzalez_RegianedaSilva_D.pdf: 9735531 bytes, checksum: 707cf7da6df6ade965d498be44562499 (MD5) Previous issue date: 2008 / Resumo: Hidrogéis compostos de redes poliméricas são de grande interesse como biomateriais. Neste trabalho, foram sintetizados hidrogéis de poli(Nisopropilacrilamida) copolimerizados com ácido acrílico (P(NIPAAm-co-AAc)) e reticulados com metileno-bisacrilamida (MBAAm) em diferentes graus de reticulação, interpenetrados (IPNs) e semi-IPNs com PVA. A presença de AAc permitiu elevar a temperatura crítica inferior de solução (LCST) para 37° C. Observou-se que as propriedades mecânicas dos hidrogéis melhoram significativamente com a presença de PVA na rede polimérica e com o aumento do grau de reticulação. Observou-se que o aumento de 3 para 5% no grau de reticulação leva a uma mudança da morfologia dos poros dos hidrogéis de esféricos a tubulares e que a difusão de azul de metileno a partir dos hidrogéis com poros tubulares é aumentada quando o eixo principal dos poros está orientado paralelamente ao fluxo de soluto. Demonstrou-se que tanto o aumento do grau de reticulação como a redução da temperatura de 37 para 25° C levam a uma redução das velocidades de difusão de S-nitrosoglutationa (GSNO) e S-nitroso-Nacetilcisteína (SNAC) incorporadas nos hidrogéis. Verificou-se que tanto a absorção como a difusão destes solutos dependem das interações entre suas cargas elétricas resultantes e a carga da matriz polimérica em um determinado pH. Hidrogéis contendo GSNO e SNAC foram capazes de causar vasodilatação local na pele em aplicações tópicas, através de suas ações como doadores de óxido nítrico (NO). A ação vasodilatadora mais intensa e de mais curta duração da SNAC comparada à GSNO foi correlacionada com seu maior coeficiente de difusão na matriz de hidrogel. A aplicação do hidrogel aderido com adesivo de fibrina em um modelo animal de gastrosquises promoveu uma proteção efetiva das alças intestinais herniadas, com redução da inflamação. / Abstract: Hydrogels composed of polymeric networks are of great interest as biomaterials. In this work hydrogels of poly(N-isopropilacrilamide) copolimerized with acrylic acid (P(NIPAAm-co-AAc)) and cross-linked with metilene-bisacrilamide (MBAAm) at different cross-linking degrees, interpenetrated (IPNs) and semi-IPNs with PVA. The presence of AAc allowed increasing the lower critical solution temperature (LCST) to 37° C. It was observed that the mechanical properties of the hydrogels are significantly improved with the presence of PVA in the polymeric network and with the increase in the cross-linking degree. It was observed that an increase from 3 to 5% in the crosslinking degree leads to a change in the pore morphology of the hydrogels from spherical to tubular and that the diffusion of methylene blue from the hydrogels with tubular pores is increased when the main axis of the pores are parallel oriented to the flow of the solute. The diffusion of S-nitrosothiols showed that the increase in the cross-linking degree from as well as the reduction in temperature from 37 to 25° C, leads to a reduction in the diffusion rates of S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylcysteine (SNAC) incorporated in the hydrogels and that both the absorption and diffusion of these solutes depend on the interactions between their net electrical charge and that of the polymeric matrix at a given pH. GSNO and SNAC containing hydrogels were able to cause local vasodilation in the skin in topical applications through their actions as nitric oxide (NO) donors. The more intense and less lasting vasodilation action of SNAC, compared to GSNO was correlated to its higher diffusion coefficient in the hydrogel matrix. Application of the hydrogel bound through fibrin adhesive in an animal model of gastroschisis, provided an effective protection of herniated bowel, with reduction of inflammation. / Doutorado / Físico-Química / Doutor em Ciências

Orientador: Marisa Masumi Beppu / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T04:07:39Z (GMT). No. of bitstreams: 1 Genevro_GiovanaMaria_M.pdf: 2115120 bytes, checksum: 180ca0fdf6523bd07a517e41100339f0 (MD5) Previous issue date: 2013 / Resumo: A busca incansável por qualidade de vida e longevidade torna necessário o desenvolvimento de novos materiais e tecnologias para uso médico. A engenharia tecidual é uma área de pesquisa recente que tem a finalidade de desenvolver materiais para substituir ou regenerar tecidos. Esses materiais devem apresentar uma série de características, incluindo biocompatibilidade, biodegradabilidade, resistência mecânica e porosidade. Dentre os materiais que vem sendo estudados para essa finalidade se destacam os polímeros naturais, em especial alguns polissacarídeos. Portanto, nesse estudo utilizou-se o polissacarídeo glucomanana de konjac (KGM), que é um biopolímero promissor, porém ainda pouco estudado para aplicação como scaffold, para a engenharia tecidual. A técnica de criogelificação é uma técnica interessante para modificar a morfologia dos hidrogéis, assim como aumentar a resistência mecânica dos mesmos. Para o preparo do hidrogel foram verificados os efeitos das variáveis, temperatura, concentração do polímero e concentração do agente alcalino. Os hidrogéis foram congelados a diferentes taxas de resfriamento e a temperaturas diferentes, sendo que a taxa é o fator mais relevante. O hidrogel com composição de 2 % de KGM, concentração da solução de Ca(OH)2 de 0,2 mol/L e temperatura de preparo de 65 °C apresentou consistência e propriedades próximas das quais se buscava. O congelamento lento apresentou estrutura com poros maiores, o que é interessante para a aplicação como biomaterial, pois as células precisam de espaço suficientemente grande para se desenvolverem. Os hidrogéis submetidos ao congelamento são cerca de quatro vezes mais resistentes à compressão do que os hidrogéis não congelados. Além disso, notou-se que a gelificação da KGM é lenta, sendo possível reduzir esse tempo com o processo de criogelificação / Abstract: The relentless pursuit of quality of life and longevity makes necessary the development of new materials and technologies for medical use. Tissue engineering is a recent area of research that aims to develop materials to replace or regenerate tissues. These materials should present a range of characteristics, including biocompatibility, biodegradability, mechanical strength and porosity. Among the materials that have been studied for this purpose we highlight the natural polymers, especially some polysaccharides. Therefore, in this study we used the polysaccharide konjac glucomannan (KGM) which is a promising biopolymer, but poorly studied for use as a scaffold for tissue engineering. For the preparation of the hydrogel, the effects of the variables, temperature, polymer concentration and concentration of alkali were observed. The hydrogel composition of 2% KGM, the solution concentration of Ca(OH)2 0,2 mol/L and preparation temperature of 65 °C showed consistency and properties of which are close sought. The cryogelation technique is an interesting technique to modify the morphology of the hydrogels, as well as increase the mechanical strength. The hydrogels were frozen at different cooling rates and different temperatures and the rate is the most relevant factor. The slow freezing showed structure with larger pores, which is interesting for application as biomaterial because the cells need space large enough to develop. The hydrogels subjected to freezing were about four times more resistant to compression. In addition, it was noted that gelation of KGM is slow, then it is possible to reduce this time using the cryogelation process / Mestrado / Engenharia de Processos / Mestra em Engenharia Química

Master of Science / Department of Grain Science and Industry / X. Susan Sun / Human induced pluripotent stem cells (hiPSCs) are generated from human somatic cells using defined transcription factors. These cells possess characteristics very similar to that of human embryonic stem cells including the ability to differentiate into cell types of all three germ layers. HiPSCs show great potential in clinical researches like drug screening and regenerative medicine, that all require large amount of cells cultured under well-defined conditions. The most common culture methods used for hiPSCs are 2D culture methods using Matrigel or vitronectin coated culture plates or flasks. 2D culture methods require large surface area to produce the same amount of cells compared to 3D methods. In addition, cells cultured in 2D culture environment are far from that in vivo. In this study, we developed a robust 3D culture condition based on hiPSC-qualified PGmatrix (PGmatrix-hiPSC) hydrogel. This 3D culture system provide hiPSCs with well-defined, more in vivo-like environment that encapsulate cells in liquid rich hydrogel with appropriate oxygen supply that resembles the hypoxia condition in vivo. Two hiPSC lines grown continuously in PGmatrix-hiPSC showed higher total population expansion and higher viability, with more consistency compared to the same cell lines grown in 2D on Matrigel or Vitronectin-XF. After grown in 3D PGmatrix-hiPSC for over 25 passages, major pluripotency markers, such as Oct4, Sox2, Nanog, and SSEA4 are expressed in most hiPSCs examined by flow cytometry. RT-qPCR also confirmed adequate expression levels of major pluripotency related genes. In addition, karyotype analysis of hiPSC after 37 passages in 3D PGmatrix-hiPSC was found normal. The same hiPSC lines cultured continuously in parallel in 2D and 3D showed differences in gene expression and surface marker TRA-1-81 expression. These results indicated the 3D PGmatrix-hiPSC system is likely superior in maintaining hiPSC growth as well as pluripotency. The findings also suggest that it is very important to study cells in 3D culture environment to better understand the mechanism of pluripotency maintenance.

Two specific drug-delivery applications were sought in this work using polyamidoamine (PAMAM) dendrimers. One drug-delivery system used a novel dendrimer hydrogel (DH) for sustained delivery of anti-glaucoma drugs. In this work, PAMAM G3.0 dendrimers were covalently bonded with poly(ethylene glycol) (PEG­12000) molecules which were subsequently acrylated, resulting in photocurable DH conjugates. For pharmacological studies, DH were loaded with a solution of intraocular pressure lowering drugs, brimonidine and timolol maleate, and were characterized for in vitro release and ex vivo transport and uptake. DH formulations were shown to increase the loading of drug molecules, increase transcorneal drug delivery, and exhibit sustained-delivery of drug molecules. A second drug-delivery system, utilizing cell-surface engineering, intended to increase the targeting ability of highly toxic anti-cancer drugs to curtail systemic effects. In particular, Qdots and 5-(aminoacetamido) fluorescein-labeled polyamidoamine dendrimer G4.5, both of which were coated with amine-derivatized polyethylene glycol, were immobilized to the sodium periodate-treated surface of RAW264.7 macrophages through a transient Schiff base linkage. Further, a reducing agent sodium cyanoborohydride was applied to reduce Schiff bases to stable secondary amine linkages. The distribution of nanoparticles on the cell surface was observed by fluorescence microscopy and was found to be dependent on the stability of the linkages tethering nanoparticles to the cell surface.

Under specific conditions short peptides modified with an N-terminal fluorenyl-9-methoxycarbonyl (Fmoc) group can self-assemble into hydrogel scaffolds similar in properties to the natural extracellular matrix. Fmoc-diphenylalanine (Fmoc-FF) for instance, has been shown to form hydrogels at physiological pH that have the ability to support 2D and 3D cell culture. The aim of this investigation is to provide further understanding of the self-assembly mechanism of such systems in order to progress towards the establishment of design rules for the preparation of scaffolds with tuneable properties.First, Fmoc-dipeptides composed of a combination of hydrophobic aromatic residues phenylalanine (F) and glycine (G) were studied with a particular emphasis on the effect of pH variations. The systems were investigated in order to assess what influence the position of such residues in the peptide sequence had on the physical properties of the molecules, and what impact the chemical structure had on the self-assembly behaviour and the gelation properties of the materials. Subsequently, phenylalanine was replaced by leucine (L), a non-aromatic amino acid that had the same relative hydrophobicity in order to determine whether the self-assembly of such molecules is driven by aromatic interactions or hydrophobic effects.Using potentiometry, the behaviour of the systems in solution has been investigated, revealing that they were all characterised by pKa shifts of up to six units above the theoretical values. Fmoc-FF exhibited two transitions whereas the other Fmoc-dipeptides only displayed one. These transitions were found to coincide with the formation of distinct self-assembled structures with differing molecular conformations and properties that were characterised using transmission electron microscopy, infrared and fluorescence spectroscopy, X-ray scattering and shear rheometry.π-stacking of the aromatic moieties was thought to be the driving force of the self-assembly mechanism, generating dimers that corresponded to the building blocks of the supramolecular structures formed. On the other hand, the peptide components were stabilised via hydrogen bonding and could form antiparallel β-sheets depending on the amino acid sequence and the associated influence on the rigidity of the molecules. Below their (first) apparent pKa transition, Fmoc-FF, Fmoc-LL, Fmoc-FG, Fmoc-LG and Fmoc-GG formed hydrogels, with the mechanical properties and stability varying depending on the amino acid sequence. Fmoc-FF and Fmoc-LL exhibited the lowest storage modulus values (G′ ~ 0.5–5 Pa) of the studied systems while Fmoc-LG displayed the highest (G′ ~ 1000–2100 Pa). Fmoc-FG and Fmoc-LG had the peculiarity of being obtained upon heating and where found to be particularly stable, as opposed to Fmoc-GG gels which showed a tendency to crystallise. On the microscopic scale, these gels were all associated with the presence of entangled fibrillar networks of different size and morphology, which in some cases could self-assemble further through a lamellar organisation. Again, Fmoc-FG and Fmoc-LG distinguished from the other systems as they were the only Fmoc-dipeptides to show a supramolecular chirality in the form of twisted ribbons under specific pH conditions. In contrast, Fmoc-GF and Fmoc-GL did not form hydrogels below their apparent pKa due to the formation of sheet-like and spherical structures respectively.