Enhanced fibroblast adhesion and proliferation on electrospun fibers obtained from poly(isosorbide succinate-b-l-lactide) block copolymers

Combination of Bioactive Polymeric Membranes and Stem Cells for Periodontal Regeneration: In Vitro and In Vivo Analyses

Regeneration of periodontal tissues requires a concerted effort to obtain consistent and predictable results in vivo. The aim of the present study was to test a new family of bioactive polymeric membranes in combination with stem cell therapy for periodontal regeneration. In particular, the novel polyester poly(isosorbide succinate-co-L-lactide) (PisPLLA) was compared with poly(L-lactide) (PLLA). Both polymers were combined with collagen (COL), hydroxyapatite (HA) and the growth factor bone morphogenetic protein-7 (BMP7), and their osteoinductive capacity was evaluated via in vitro and in vivo experiments. Membranes composed of PLLA/COL/HA or PisPLLA/COL/HA were able to promote periodontal regeneration and new bone formation in fenestration defects in rat jaws. According to quantitative real-time polymerase chain reaction (qRT-PCR) and Alizarin Red assays, better osteoconductive capacity and increased extracellular mineralization were observed for PLLA/COL/HA, whereas better osteoinductive properties were associated with PisPLLA/COL/HA. We concluded that membranes composed of either PisPLLA/COL/HA or PLLA/COL/HA present promising results in vitro as well as in vivo and that these materials could be potentially applied in periodontal regeneration.

Synthesis, characterizations and biocompatibility of alternating block polyurethanes based on P3/4HB and PPG-PEG-PPG

Block copolymers with exactly controlled structures, that is, alternating block polyurethanes based on poly(3-hydroxybutyrate-co-4-hydroxybutrate) (P3/4HB-diol) and poly (propylene glycol)-poly(ethylene glycol)-poly(propylene glycol) (PPG-PEG-PPG) were synthesized by solution polymerization via specifically selective coupling reaction between terminal hydroxyl P3/4HB segment and isocyanate group end-capped PPG-PEG-PPG segment, using 1,6-hexamethylene diisocyanate (HDI) as end-capped agent. The chemical structure, molecular weight and distribution were systematically characterized by nuclear magnetic resonance spectrum (¹H NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis. The hydrophilicity was studied by static contact angle of H₂O and CH₂I₂. DSC revealed that the PU3/4HB-alt-PPG-PEG-PPG exhibited a distinct change from amorphous to 30% crystallinity degree, T(g) from -25 to -50 °C, T(m) from 110 to 145 °C. The polyurethanes were more hydrophilic (water contact angle centers around 80 °) than the raw PHA materials. The platelet adhesion assay showed that the obtained polyurethanes had a lower platelet adhesion than the raw materials and the amount of platelet adhesion could be controlled by varying the segmental length of P3/4HB-diol. This could be explained by the inclusion of PPG-PEG-PPG between the P3/4HB segments, improving the hemocompatibility of P3/4HB. The cell culture assay revealed that the obtained polyurethanes were cell inert and unfavorable for the attachment of mouse fibroblast cell line L929 and rabbit blood vessel smooth muscle cells (RaSMCs). This suggests that these polyurethanes would be promising candidates as hemocompatibility and tissue-inert materials.

Binding of dengue virus particles and dengue proteins onto solid surfaces

The interaction between dengue virus particles (DENV), sedimentation hemagglutinin particles (SHA), dengue virus envelope protein (Eprot), and solid surfaces was investigated by means of ellipsometry and atomic force microscopy (AFM). The surfaces chosen are bare Si/SiO2 wafers and Si/SiO2 wafers covered with concanavalin A (ConA), jacalin (Jac), polystyrene (PS), or poly(styrene sulfonate) (PSS) films. Adsorption experiments at pH 7.2 and pH 3 onto all surfaces revealed that (i) adsorption of DENV particles took place only onto ConA under pH 7.2, because of specific recognition between glycans on DENV surface and ConA binding site; (ii) DENV particles did not attach to any of the surfaces at pH 3, suggesting the presence of positive charges on DENV surface at this pH, which repel the positively charged lectin surfaces; (iii) SHA particles are positively charged at pH 7.2 and pH 3 because they adhered to negatively charged surfaces at pH 7.2 and repelled positively charged layers at pH 3; and (iv) SHA particles carry polar groups on the surface because they attached to silanol surfaces at pH 3 and avoided hydrophobic PS films at pH 3 and pH 7.2. The adsorption behavior of Eprot at pH 7.2 revealed affinity for ConA>Jac>PSS>PS≈bare Si/SiO2 layers. These findings indicate that selectivity of the Eprot adsorption is higher when it is part of virus structure than when it is free in solution. The correlation between surface energy values determined by means of contact angle measurements and DENV, SHA, or Eprot adsorption behavior was used to understand the intermolecular forces at the interfaces. A direct correlation was not found because the contributions from surface energy were probably surpassed by specific contributions.