Bio-Catalysis for the Functionalization of Cellulose Nanocrystals.

In this work, the chemical modification of cellulose nanocrystals (NCs) using an enzyme as a catalyst has been performed by a "grafting from" reaction, in order to covalently functionalize the external surface of NCs with both poly(L-lactic acid) (PLLA) and poly(ε-caprolactone) (PCL) by ring-opening polymerization. Firstly, cellulose nanocrystals were prepared from commercial cellulose microcrystals by acid hydrolysis and then functionalized by using Yarrowia lipolytica lipase immobilized on Lewatit resin as a catalyst. To confirm the success of the grafting reactions, 1H-NMR has been performed as well as FT-IR and Raman spectroscopy. Moreover, thermogravimetric analysis has been used to determine the amount of polymeric chains grafted onto the surface of cellulose nanocrystals. Furthermore, the crystalline nature of the polymeric chains grafted onto the cellulose surface has been studied by DSC, X-ray scattering, as well as SAXS analysis. To our knowledge, it is the first time that a biocatalyst approach has been used to obtain biopolymeric functionalized cellulose nanocrystals.

Semi-Continuous Heterophase Polymerization to Synthesize Poly(methacrylic acid)-Based Nanocomposites for Drug Delivery.

The design of nanocomposites with the potential for drug delivery is a topic of great interest. In this work, the synthesis of nanocomposites of poly(methacrylic acid) (PMAA) grafted onto carbon nanotubes (CNTs) functionalized with poly(amidoamine) (PAMAM) dendrimer by semicontinuous heterophase polymerization SHP, at three different methacrylic acid (MAA) dosing rates, is reported. SHP is a polymerization technique poorly used to prepare nanocomposites containing CNTs and has the potential to produce more ordered alkyl methacrylic polymer chains, which could favor the obtaining of a homogenous nanocomposite. For the nanocomposites synthesized, a lowest addition rate monomer-starved condition was reached. Analysis by X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) demonstrate that functionalized CNTs are grafted onto the PMAA matrix. The ability of prepared nanocomposites to deliver hydrocortisone was evaluated by ultraviolet-visible spectroscopy (UV-Vis). The hydrocortisone release profiles of pure PMAA and of their nanocomposites prepared at the lowest monomer fed rate were fitted with Higuchi and Korsmeyer-Peppas models, successfully. Functionalized CNTs have a crucial role to induce an effective release of hydrocortisone from the prepared nanocomposites.

Synthesis of Poly(methacrylic acid-co-butyl acrylate) Grafted onto Functionalized Carbon Nanotube Nanocomposites for Drug Delivery.

Design of a smart drug delivery system is a topic of current interest. Under this perspective, polymer nanocomposites (PNs) of butyl acrylate (BA), methacrylic acid (MAA), and functionalized carbon nanotubes (CNTsf) were synthesized by in situ emulsion polymerization (IEP). Carbon nanotubes were synthesized by chemical vapor deposition (CVD) and purified with steam. Purified CNTs were analyzed by FE-SEM and HR-TEM. CNTsf contain acyl chloride groups attached to their surface. Purified and functionalized CNTs were studied by FT-IR and Raman spectroscopies. The synthesized nanocomposites were studied by XPS, 13C-NMR, and DSC. Anhydride groups link CNTsf to MAA-BA polymeric chains. The potentiality of the prepared nanocomposites, and of their pure polymer matrices to deliver hydrocortisone, was evaluated in vitro by UV-VIS spectroscopy. The relationship between the chemical structure of the synthesized nanocomposites, or their pure polymeric matrices, and their ability to release hydrocortisone was studied by FT-IR spectroscopy. The hydrocortisone release profile of some of the studied nanocomposites is driven by a change in the inter-associated to self-associated hydrogen bonds balance. The CNTsf used to prepare the studied nanocomposites act as hydrocortisone reservoirs.

Yarrowia lipolytica Extracellular Lipase Lip2 as Biocatalyst for the Ring-Opening Polymerization of ε-Caprolactone.

Yarrowia lipolytica (YL) is a "non-conventional" yeast that is capable of producing important metabolites. One of the most important products that is secreted by this microorganism is lipase, a ubiquitous enzyme that has considerable industrial potential and can be used as a biocatalyst in the pharmaceutical, food, and environmental industries. In this work, Yarrowia lipolytica lipase (YLL) was immobilized on Lewatit and Amberlite beads and is used in the enzymatic ring-opening polymerization (ROP) of cyclic esters in the presence of different organic solvents. YLL immobilized on Amberlite XAD7HP had the higher protein adsorption (96%) and a lipolytic activity of 35 U/g. Lewatit VPOC K2629 has the higher lipolytic activity (805 U/g) and 92% of protein adsorption. The highest molecular weight (Mn 10,685 Da) was achieved at 90 °C using YLL that was immobilized on Lewatit 1026 with decane as solvent after 60 h and 100% of monomer conversion.

Synthesis of biodegradable polymers using biocatalysis with Yarrowia lipolytica lipase.

Yarrowia lipolytica lipase (YLL) was used as catalyst in the enzymatic ring-opening polymerization (ROP) of ε-caprolactone. This low-cost solid-state lipase produces low-molecular-weight polyesters with unique multiphase morphology as determined by carbon-13 NMR. YLL attaches sugar head groups to polycaprolactone in a one-pot biocatalytic pathway. Synthesis of α-ω-telechelic (polymer with two reactive hydroxyl end groups) PCL diols is achieved by enzymatic ROP with YLL immobilized on the macroporous resin Lewatit VPOC 1026, and in the presence of diethylene glycol or poly(ethylene glycol). Biodegradable linear polyester urethanes are prepared by polycondensation between synthesized PCL diols and hexamethylene-diisocyanate.

Optofluidic variable focus lenses.

Here we propose optofluidic spherical microlenses that can change their focal distance by varying the refractive index of the liquid that composes them. These lenses are fabricated in the bulk of a polymeric mixture. Results of a characterization study of the profile of the lenses, the image forming capability, and the behavior of the focal distance as a function of the refractive index are presented. Ionic liquids are suggested as a source of liquids useful for fabricating this type of lens.