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Fundação para a Ciência e a Tecnologia

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Publications

Synthesis of FITC-PAMAM conjugates for in vitro cell studies

Publication . Fernandes, João Tiago Moniz; Rodrigues, João Manuel Cunha; Tomás, Helena Maria Pires Gaspar

2014-12-29Master thesis

Open access

Electroactive properties and biological applications of electrospun PVDF polymer

Publication . Xiang, Yao; Pires, Pedro Filipe Duarte Louzeiro; Tomás, Helena Maria Pires Gaspar

PVDF is a piezoelectric polymer, exhibiting direct and inverse piezoelectric effect, with leading electroactive properties. This material is interesting for building energy transmission and harvesting systems, converting mechanical energy into electrical energy, such as electrospun PVDF sensors. However, only a few reports have shown inverse piezoelectric effect of electrospun PVDF. In this project the electrospinning technique was used to prepare PVDF nanofiber mat scaffolds for tissue engineering. The main objective is the preparation of electroactuated devices for mechanical stimulation of cells. Crystal phase ratios and morphology of the PVDF fiber mats were characterized by attenuated total reflectance Fourier transform infrared (FTIR/ATR) spectroscopy and scanning electron micrograph (SEM). For a better understanding of the differences between polar and non-polar PVDF, and of the effect of the electric field on the fibers’ composition, quantum mechanics and molecular dynamics calculations were performed. Several devices were prepared from assemblies of PVDF fiber meshes and conductive ink electrodes, with different geometries. The devices’ electrical impedances were measured as a function of frequency. Finally, the in vitro biocompatibility of the PVDF fiber meshes was tested. The results revealed that electrospinning parameters have significant effects on the crystal phase ratio and structure. As it was expected, the electrical impedance of PVDF decreased with the increase of β crystal phase ratio, as required for the piezoelectric behaviour of the PVDF fibers. The results also illustrated that the impedance of PVDF fibers mesh assemblies changed with varying shape, thickness, the geometric alignment of the fibers and the distance between conductive ink electrodes. The molecular simulations were able to predict the α to β phase change which results on partially poled fibers. In vitro cytocompatibility tests of PVDF scaffolds shown that PVDF fibers were not cytotoxic to the NIH/3T3 cells which meant PVDF fiber scaffolds can be used for cell stimulation.

2016-11-02Master thesis

Open access

Thermo/redox/pH-triple sensitive poly(N-isopropylacrylamide-co-acrylic acid) nanogels for anticancer drug delivery

Publication . Zhan, Yuan; Gonçalves, Mara; Yi, Panpan; Capelo, Débora; Zhang, Yuhong; Rodrigues, João; Liu, Changsheng; Tomás, Helena; Li, Yulin; He, Peixin

The clinical application of doxorubicin (DOX), like other anticancer drugs, is limited by insuﬃcient cellular uptake and the numerous drug resistance mechanisms existing in cells. The development of smart nanomaterials capable of carrying the drugs into the cells and of releasing them under the control of the microenvironment is an interesting approach that may increase the success of the anticancer drugs currently in use. Herein, we report an easy process to prepare biocompatible nanogels (NGs) with thermo/ redox/pH-triple sensitivity, which are highly eﬀective in the intracellular delivery of DOX. Redox-sensitive/ degradable NGs (PNA-BAC) and nondegradable NGs (PNA-MBA) were prepared through in situ polymerization of N-isopropylacrylamide (NIPAM) and acrylic acid (AA) in the presence of sodium dodecyl sulfate (SDS) as a surfactant, using N,N0-bis(acryloyl)cystamine (BAC) as a biodegradable crosslinker or N,N0-methylene bisacrylamide (MBA) as a nondegradable crosslinker, respectively. After that, the cationic DOX drug was loaded into the NGs through electrostatic interactions, by simply mixing them in aqueous solution. Compared to nondegradable PNA-MBA NGs, PNA-BAC NGs not only presented a higher DOX drug loading capacity, but also allowed a more sustainable drug release behavior under physiological conditions. More importantly, PNA-BAC NGs displayed thermo-induced drug release properties and an in vitro accelerated release of DOX under conditions that mimic intracellular reductive conditions and acidic tumor microenvironments. The thermo/redox/pH multi-sensitive NGs can quickly be taken up by CAL-72 cells (an osteosarcoma cell line), resulting in a high DOX intracellular accumulation and an improved cytotoxicity when compared with free DOX and DOX-loaded nondegradable PNA-MBA NGs. The developed NGs can be possibly used as an eﬀective platform for the delivery of cationic therapeutic agents for biomedical applications.

2015Journal article

Restricted access

Compound high-quality criteria: a new vision to guide the development of drugs, current situation

Publication . Mignani, Serge; Huber, Scot; Tomás, Helena; Rodrigues, João; Majoral, Jean-Pierre

For several decades, the pharmaceutical industry has suffered due to major issues such as reductions of the number of FDA approved drugs and biologics. Several analyses have been highlighted that the 'druglikeness' is one of the strategies to improve succeed rates of screening such as, for instance, high-throughput screening (HTS), and then hits (as starting point), leads and clinical candidates. It is clear that the improvement of compound quality accelerates the drug discovery projects. The monitoring of several indices to avoid 'molecular obesity' (ADMET problems) of final drugs from good-quality 'low-fat' starting points represents today a powerful strategy of optimization process. The development of the new guides to find drugs highlighting attempts at improving the attrition rate from hits to final medicines by focusing on how to improve the druggability of hits, leads and drugs during the drug discovery process represents a key approach to design next better generation of medicines.

2016Journal article

Restricted access

A powerful analytical strategy based on QuEChERS-dispersive solid-phase extraction combined with ultrahigh pressure liquid chromatography for evaluating the effect of elicitors on biosynthesis of trans-resveratrol in grapes

Publication . Ruiz-García, Yolanda; Silva, Catarina L.; Gómez-Plaza, Encarna; Câmara, José S.

A powerful methodological approach based on modified quick, easy, cheap effective, rugged, and safe (QuEChERS) extraction technique, followed by cleanup dispersive solid-phase extraction (dSPE) and combined with ultrahigh pressure liquid chromatography (UHPLC), is presented in this paper, for the rapid determination of the health-promoting phytoalexin, trans-resveratrol, in grapes. This is the first time, to our knowledge, that the combination QuEChERS-dSPE/UHPLC-PDA has been used for trans-resveratrol quantification in grapes. The method has been validated according to European Union Decision 2002/657/EC, in terms of selectivity, linearity, sensitivity, instrument LOD and method LOQ, accuracy, precision, extraction efficiency, and interference assessment. Validation experiments revealed sufficient linearity (R 2 = 0.9931) within the established concentration range confirmed by Mandel’s fitting test. The sensitivity was good with method detection limit (LOD) of 0.003 μg/mL and quantification limit (LOQ) of 0.010 μg/mL. Optimum QuEChERS-dSPE/UHPLC-PDA conditions led to recoveries of the target analyte in grape samples ranging between 75.1 and 99.7 % and precisions in the 0.9–4 % range (RSD, n = 18). The method also afforded satisfactory results in terms of extraction efficiency and interference assessment and provides a valuable and promising tool for determination of trans-resveratrol in grapes with a high resolution within 8 min and a total analysis time of 11 min. The validated methodology was applied to evaluate the effect of the use of elicitors, namely benzothiadiazole and methyl jasmonate, in trans-resveratrol biosynthesis on Vitis vinifera Monastrell grapes. The results obtained revealed an increase of trans-resveratrol level of 2-fold for grapes treated with benzothiadiazole and 3.5-fold for grapes treated with methyl jasmonate.

2015Journal article

Restricted access