Polarity studies of single polyelectrolyte layers in polyelectrolyte multilayers probed by steady state and life time doxorubicin fluorescence

Hypothesis: Polarity in polyelectrolyte multilayers (PEMs) may vary from the inner to the top layers of the film as the charge compensation of the layers is more effective inside the PEMs than in outer layers. Doxorubicin hydrochloride (DX) is used here to sense polarity at the single polyelectrolyte level inside PEMS. Experimental: DX is complexed electrostatically to a polyanion, either polystyrene sulfonate (PSS) or polyacrylic acid (PAA) and assembled at selected positions in a multilayer of the polyanion and polyally lamine hydrochloride (PAH) as polycation. Local polarity in the layer domain is evaluated through changes in the intensity ratio of the first to second band of spectra of DX (I1/I2 ratio) by steady state flu orescence, and by Lifetime fluorescence. Findings: PAH/PSS multilayers, show a polarity similar to water with DX/PSS as top layer, decreasing to I1/ I2 ratios similar to organic solvents as the number of polyelectrolyte layers assembled on top increases. For PAH/PAA multilayers, polarity values reflect a more polar environment than water when DX/PAA is the top layer, remaining unaltered by the assembly of polyelectrolyte layers on top. Results show that different polar environments may be present in a PEM when considering polarity at the single layer level.Fil: Martinelli, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Centro de Investigación Cooperativa en Biomateriales; EspañaFil: Tasca, Elisamaria. Centro de Investigación Cooperativa en Biomateriales; España. Università degli Studi di Roma "La Sapienza"; ItaliaFil: Andreozzi, Patrizia. Università degli Studi di Firenze; Dipartimento di Chimica “Ugo Schiff”; Italia. Centro de Investigación Cooperativa en Biomateriales; EspañaFil: Libertone, Sara. Centro de Investigación Cooperativa en Biomateriales; EspañaFil: Ritacco, Hernán Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Giustini, Mauro. Università degli Studi di Roma "La Sapienza"; Italia. Università degli Studi di Firenze; Dipartimento di Chimica “Ugo Schiff” ; ItaliaFil: Moya, Sergio Enrique. Centro de Investigación Cooperativa en Biomateriales; España. Università degli Studi di Roma "La Sapienza"; Itali

Antibacterial Layer‐by‐Layer Films of Poly(acrylic acid)–Gentamicin Complexes with a Combined Burst and Sustainable Release of Gentamicin

There is an urgent need for the development of effective antibacterial coatings to cope with more and more resistant bacterial strains in medical environments, and particularly to prevent nosocomial infections following bone implant surgery. Polyelectrolyte multilayers (PEMs) based on poly-llysine (PLL) and complexes of poly(acrylic acid) (PAA) and gentamicin have been fabricated here applying the layer-by-layer (LbL) technique. Complexes are prepared by mixing PAA and gentamicin solutions in 500 × 10−3 m NaCl at pH 4.5. The assembly of PLL and the complexes follows an exponential growth allowing a high loading of gentamicin in a four bilayer PEM. Although PEMs are stable and do not degrade at physiological pH, there is a continuous release of gentamicin at pH 7.4. PEMs show an initial burst release of gentamicin in the first 6 h, which liberates 58% of the total gentamicin released during the experiment, followed by a sustainable release lasting over weeks. This release profile makes the coating appealing for the surface modification of bone implants as a high concentration of antibiotics is necessary during implant surgery while a lower antibiotic concentration is needed until tissue is regenerated. PEMs are effective in preventing the proliferation of the Staphylococcus aureus strain.Fil: Escobar, Ane. Centro de Investigacion Cooperativa En Biomateriales.; EspañaFil: Muzzio, Nicolás Eduardo. Centro de Investigacion Cooperativa En Biomateriales.; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Andreozzi, Patrizia. Centro de Investigacion Cooperativa En Biomateriales.; EspañaFil: Libertone, Sara. Centro de Investigacion Cooperativa En Biomateriales.; EspañaFil: Tasca, Elisamaria. Università degli studi di Roma "La Sapienza"; ItaliaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Grzelczak, Marek. Fundación Vasca para la Ciencia; España. Donostia International Physics Center; EspañaFil: Moya, Sergio Eduardo. Centro de Investigacion Cooperativa En Biomateriales.; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Antibacterial Coatings: Antibacterial Layer‐by‐Layer Films of Poly(acrylic acid)–Gentamicin Complexes with a Combined Burst and Sustainable Release of Gentamicin (Adv. Mater. Interfaces 22/2019)

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Comparative evaluation of subtyping tools for surveillance of newly emerging HIV-1 strains

HIV-1 non-B subtypes/circulating recombinant forms (CRFs) are increasing worldwide. Since subtype identification can be clinically relevant, we assessed the added value in HIV-1 subtyping using updated molecular phylogeny (Mphy) and the performance of routinely used automated tools. Updated Mphy (2015 updated reference sequences), used as a gold standard, was performed to subtype 13,116 HIV-1 protease/reverse transcriptase sequences and then compared with previous Mphy (reference sequences until 2014) and with COMET, REGA, SCUEAL, and Stanford subtyping tools. Updated Mphy classified subtype B as the most prevalent (73.4%), followed by CRF02-AG (7.9%), C (4.6%), F1 (3.4%), A1 (2.2%), G (1.6%), CRF12-BF (1.2%), and other subtypes (5.7%). A 2.3% proportion of sequences were reassigned as different subtypes or CRFs because of misclassification by previous Mphy. Overall, the tool most concordant with updated Mphy was Stanford-v8.1 (95.4%), followed by COMET (93.8%), REGA-v3 (92.5%), Stanford-old (91.1%), and SCUEAL (85.9%). All the tools had a high sensitivity (\ue2\u89\ua598.0%) and specificity (\ue2\u89\ua595.7%) for subtype B. Regarding non-B subtypes, Stanford-v8.1 was the best tool for C, D, and F subtypes and for CRFs 01, 02, 06, 11, and 36 (sensitivity, \ue2\u89\ua592.6%; specificity, \ue2\u89\ua599.1%). A1 and G subtypes were better classified by COMET (92.3%) and REGA-v3 (98.6%), respectively. Our findings confirm Mphy as the gold standard for accurate HIV-1 subtyping, although Stanford-v8.1, occasionally combined with COMET or REGA-v3, represents an effective subtyping approach in clinical settings. Periodic updating of HIV-1 reference sequences is fundamental to improving subtype characterization in the context of an effective epidemiological surveillance of non-B strains