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Gavinho, Sílvia R., Manuel P. Graça, Pedro Prezas, João Borges Borges, Jorge Carvalho Silva, Eduardo Pires, Henrique Armês, and José Coucelo. "Antibacterial bioglass in dental implants: a canine clinical study." European Journal of Public Health 31 (2021): ckab120.006. AbstractWebsite

Peri-implantitis is considered the most challenging biological complication in implantology, as untreated disease can progress and result in implant loss. Therefore, disease prevention is crucial in daily clinical practice. It has been reported that the use of bioactive glass, as an implant coating, can stimulate tissue integration and accelerate tissue regeneration. Besides these properties, it is possible to promote bacterial activity by inserting silver into the bioglass

Bioglass with composition 45S5 was synthesised by the fusion method, replacing the amount of Na2CO3 by AgNO3 (BG 2% wt). The implants were resealed by the CoBlast® technique. Clinical cases with pathology of the mandible/maxilla were selected and implants dimensioned for the canine bone structure were applied.

Three months after implantation, imaging exams, namely CT scans, showed no signs of early rejection by septic or cytotoxic loss. No decrease or loss of peri-implant bone was observed. In all cases the implants remained without signs of instability, and with sufficient support for the application of the exo-prosthesis or dental crown. The results of histological analysis showed no signs of infection or osteolysis. The zone of peri-implant fibrosis was not observable in the samples, showing a good evolution in implant osteointegration.

The results show promising evidences for the use of this biomaterial as a coating, since aseptic rejection, later on, and that related to the shape and biomaterials used in the implant's design, usually begins during the first 3 months.

Gavinho, Sílvia R., Mariana Castro Soares, João Borges Borges, Jorge Carvalho Silva, Isabel Sá Nogueira, and Manuel P. Graça. "Preparation and Characterization of Zinc and Magnesium Doped Bioglasses." Nanoscience and Nanotechnology in Security and Protection against CBRN Threats (2020): 465-475. AbstractWebsite

Peri-implantitis is an infectious disease that affects about one of five patients who receive a dental implant within 5 years after the surgery. To minimize this reaction the development of new biomaterials with antibacterial action is needed that can be used as a coating material in orthodontic implants. In addition, these biomaterials can be doped with several ions, which add specific properties that may act at the cellular level, such as increasing the angiogenesis efficiency. In this work, 45S5 Bioglass® has been used as the base material because it presents higher bioactivity compared to other biomaterials. To add antibacterial function and increase positive effects on bone metabolism, zinc and magnesium ions were introduced in the glass network. The main objective was the synthesis of the 45S5 glass by melt-quenching and study the biological performance as function of the zinc and magnesium concentrations. The structural and biological properties of the prepared samples are discussed.

Gavinho, Sílvia R., Pedro R. Prezas, Diogo J. Ramos, Isabel Sá-Nogueira, João Borges Borges, Carmo M. Lança, Jorge Carvalho Silva, Célia Henriques, Eduardo Pires, Jakka Suresh Kumar, and Manuel P. Graça. "Nontoxic glasses: Preparation, structural, electrical and biological properties." Applied Ceramics Technology 16 (2019): 1885-1894. AbstractWebsite

Bacterial infections affect about 1 in 5 patients who receive a dental implant within 5 years of surgery. To avoid the implant rejection it is necessary for the development of innovative biomaterials, with addition or substitution of the ions, for implant coatings that promote a strong bond with the new host bone and antibacterial action. The objective of this work was to synthesize a bioactive glass with different silver concentrations to evaluate their antibacterial performance. The glasses were synthesized with up to 2% silver content by melt-quenching. Structural, morphological, biological, and electrical properties of all samples were studied. The biological behavior was evaluated through cytotoxicity tests and antibacterial activity. The structural analysis shows that the introduction of silver do not promote significant changes, not altering the advantageous properties of the bioglass of the bioglass. It was verified that the glasses with a silver content from 0.5% to 2%, completely prevented the growth of both Staphylococcus aureus and Escherichia coli while being nontoxic toward mammalian cells. Therefore, these bioglasses are promising materials to be used in the production of dental implants with antimicrobial activity.

Godinho, Maria Helena, João Paulo Borges, João Carlos Bordado, Maria Teresa Cidade, and Assis Farinha Martins. "Preparation and liquid-crystalline properties of toluene-4-sulphonyl urethane of hydroxypropylcellulose." Liquid Crystals 14 (1993): 653-659. AbstractWebsite

A novel liquid-crystalline polymer, the toluene-4-sulphonyl urethane of hydroxypropylcellulose (TSUHPC), was prepared through chemical modification of hydroxypropylcellulose (HPC) of Mw = 60000 g mol−1. The resulting polymer was characterized by infrared spectroscopy, differential scanning calorimetry (DSC) and polarizing microscopy. It was found that thermotropic liquid crystal phases are formed between about 60°C and 110°C. Concentrated solutions of TSUHPC in acetone and N,N-dimethylacetamide exhibit cholesteric behaviour, at room temperature. When approaching the lyotropic mesophase to solid transition, either by cooling or by solvent evaporation, very interesting arborescent structures of a seemingly fractal nature may be observed, depending on the kinetics of the transition. A banded texture can be observed when the polymer is sheared near the transition to the isotropic phase.

Godinho, Maria Helena, João Paulo Canejo, Luis FV Pinto, João Paulo Borges, and Paulo IC Teixeira. "How to mimic the shapes of plant tendrils on the nano and microscale: spirals and helices of electrospun liquid crystalline cellulose derivatives." Soft Matter 5 (2009): 2772-2776. AbstractWebsite

We show that suspended nano and microfibres electrospun from liquid crystalline cellulosic solutions will curl into spirals if they are supported at just one end, or, if they are supported at both ends, will twist into a helix of one handedness over half of its length and of the opposite handedness over the other half, the two halves being connected by a short straight section. This latter phenomenon, known as perversion, is a consequence of the intrinsic curvature of the fibres and of a topological conservation law. Furthermore, agreement between theory and experiment can only be achieved if account is taken of the intrinsic torsion of the fibres. Precisely the same behaviour is known to be exhibited by the tendrils of climbing plants such as Passiflora edulis, albeit on a lengthscale of millimetres, i.e., three to four orders of magnitude larger than in our fibres. This suggests that the same basic, coarse-grained physical model is applicable across a range of lengthscales.

Gomes, Susana, Diana Querido, José Luís Ferreira, João Borges Borges, Célia Henriques, and Jorge Carvalho Silva. "Using water to control electrospun Polycaprolactone fibre morphology for soft tissue engineering." Journal of Polymer Research 26 (2019): 222. AbstractWebsite

Control of the properties of electrospun polycaprolactone can be achieved by adjusting the acetic acid:water ratio used to dissolve and electrospin the polymer. In this work, we studied the effect of using up to 15 wt% water in the solvent mixture. Solution conductivity and viscosity and fibre morphology vary dramatically with water content and solution age. Two days after initial solution preparation, electrospinning yields regular fibres for a water content of 0 wt% and 5 wt%, irregular fibres for a 10 wt% water content and irregular and fused fibres for a 15 wt% water content. Fibres with the highest crystallinity (60%) were obtained from solutions containing 5 wt% water while the highest elastic modulus (8.6 ± 1.4 MPa) and tensile stress (4.3 ± 0.3 MPa) pertain to fibres obtained from solutions containing 10 wt% water. Enzymatic fibre degradation is faster the higher the water content in the precursor solution. Adhesion ratio of human foetal fibroblasts was highest on scaffolds obtained from precursor solutions containing 0 wt% water. Cell population increases for all scaffolds and populations quickly become equivalent, with no statistically significant differences between them. Cells exhibit a more extended morphology on the 5 wt% scaffold and a more compact morphology on the 0 wt% scaffold. In summary, a small water content in the solvent allows a significant control over fibre diameter, scaffold properties and the production of scaffolds that support cell adhesion and proliferation. This strategy can be used in soft tissue engineering to influence cell behaviour and the degradation rate of the scaffolds.

Gonçalves, Adriana, Filipe V. Almeida, João Paulo Borges, and Paula I. P. Soares. "Incorporation of Dual-Stimuli Responsive Microgels in Nanofibrous Membranes for Cancer Treatment by Magnetic Hyperthermia." Gels 7 (2021): 28. AbstractWebsite

The delivery of multiple anti-cancer agents holds great promise for better treatments. The present work focuses on developing multifunctional materials for simultaneous and local combinatory treatment: Chemotherapy and hyperthermia. We first produced hybrid microgels (MG), synthesized by surfactant-free emulsion polymerization, consisting of Poly (N-isopropyl acrylamide) (PNIPAAm), chitosan (40 wt.%), and iron oxide nanoparticles (NPs) (5 wt.%) as the inorganic component. PNIPAAm MGs with a hydrodynamic diameter of about 1 μm (in their swollen state) were successfully synthesized. With the incorporation of chitosan and NPs in PNIPAAm MG, a decrease in MG diameter and swelling capacity was observed, without affecting their thermosensitivity. We then sought to produce biocompatible and mechanically robust membranes containing these dual-responsive MG. To achieve this, MG were incorporated in poly (vinyl pyrrolidone) (PVP) fibers through colloidal electrospinning. The presence of NPs in MG decreases the membrane swelling ratio from 10 to values between 6 and 7, and increases the material stiffness, raising its Young modulus from 20 to 35 MPa. Furthermore, magnetic hyperthermia assay shows that PVP-MG-NP composites perform better than any other formulation, with a temperature variation of about 1 °C. The present work demonstrates the potential of using multifunctional colloidal membranes for magnetic hyperthermia and may in the future be used as an alternative treatment for cancer.

Graça, Manuel P., Silvia Soreto Teixeira, Sílvia R. Gavinho, Manuel Almeida Valente, Cristiana Salgueiro, José Nunes, Paula I. P. Soares, Maria Carmo Lança, Tânia Vieira, Jorge Carvalho Silva, and João Borges Borges. "Nanomaterials for magnetic hyperthermia." European Journal of Public Health 31 (2021): ckab120.066. AbstractWebsite

Cancer remains as one of the major causes of mortality worldwide. Recent advances in nanoparticles based therapy mark a new era on cancer treatment. Many groups have investigated biological/physical effects of nanoparticles on tumour cells and how these vary with physical parameters such as particle size, shape, concentration and distribution. Magnetic hyperthermia (MHT) can be an alternative or an add-value therapy with demonstrated effectiveness. MHT uses magnetic nanoparticles, which can be directly applied to the tumour, where, by applying an external ac magnetic field, will promote a localized temperature increment that can be controlled.