Mihai Georgescu

SYNTHESIS AND APPLICATIONS OF Fe3O4/SiO2 CORE-SHELL MATERIALS.

Multifunctional nanoparticles based on magnetite/silica core-shell, consisting of iron oxides coated with silica matrix doped with fluorescent components such as organic dyes (fluorescein isothiocyanate - FITC, Rhodamine 6G) or quantum dots, have drawn remarkable attention in the last years. Due to the bi-functionality of these types of nanoparticles (simultaneously having magnetic and fluorescent properties), they are successfully used in highly efficient human stem cell labeling, magnetic carrier for photodynamic therapy, drug delivery, hyperthermia and other biomedical applications. Another application of core-shell-based nanoparticles, in which the silica is functionalized with aminosilanes, is for immobilization and separation of various biological entities such as proteins, antibodies, enzymes etc. as well as in environmental applications, as adsorbents for heavy metal ions. In vitro tests on human cancerous cells, such as A549 (human lung carcinoma), breast, human cervical cancer, THP-1 (human acute monocytic leukaemia) etc. , were conducted to assess the potential cytotoxic effects that may occur upon contact of nanoparticles with cancerous tissue. Results show that core-shell nanoparticles doped with cytostatics (cisplatin, doxorubicin, etc.), are easily adsorbed by affected tissue and in some cases lead to an inhibition of cell proliferation and induce cell death by apoptosis. The goal of this review is to summarize the advances in the field of core-shell materials, particularly those based on magnetite/silica with applicability in medicine and environmental protection. This paper briefly describes synthesis methods of silica-coated magnetite nanoparticles (Stöber method and microemulsion), the method of encapsulating functional groups based on aminosilanes in silica shell, as well as applications in medicine of these types of simple or modified nanoparticles for cancer therapy, MRI, biomarker immobilization, drug delivery, biocatalysis etc., and in environmental applications (removal of heavy metal ions and catalysis).

Mesoporous materials used in medicine and environmental applications.

Mesoporous materials synthesized in the presence of templates, are commonly used for environment and medical applications. Due to the properties it holds, mesoporous silica nanoparticles is an excellent material for use in medical field, biomaterials, active principles delivery systems, enzyme immobilization and imaging. Their structure allows embedding large and small molecules, DNA adsorption and genetic transfer. Using mesoporous silica nanoparticles for delivery of bioactive molecules can protect them against degradation under physiological conditions, allow controlled drugs release and minimize side effects on healthy tissues. Cellular tests performed on mesoporous silica nanoparticles demonstrate that MSNs cytotoxicity is dependent on the size and concentration and suggests the use of larger size nanoparticles is optimal for medical applications. Mesoporous materials possess high biological compatibility, are non-toxic and can be easily modified by functionalizing the surface or inside the pores by grafting or co-condensation method. The structure, composition and pores size of this material can be optimized during synthesis by varying the stoichiometric reactants, reaction conditions, nature of the templates molecules or by functionalization method.

Applications of mesoporous silica in biosensing and controlled release of insulin

Graphical abstract Figure. No Caption available. Abstract The development of new oral insulin delivery systems could bring significant benefits to insulin‐dependent patients due to the simplicity of the method, avoidance of pain caused by parenteral administration and maintenance of optimal therapeutic levels for a longer period. However, administration of such therapeutic proteins orally remains a challenge because insulin (Ins) is a very sensitive molecule and can be easily degraded under the existing pH conditions in the stomach and intestines. Moreover, due to the large size of insulin, intestinal epithelium permeability is very low. This could be improved by immobilizing insulin in the mesoporous silica pores (MSN), acting as a shield to protect the molecule integrity from the proteolytic degradation existing in the stomach and upper part of the small intestine. Due to the high adsorption capacity of insulin, biocompatibility, ease of functionalization with various organic and/or inorganic groups, high mechanical and chemical resistance, adjustable pore size and volume, MSN is considered an ideal candidate for the development of controlled release systems that are sensitive to various stimuli (pH, temperature) as well as to glucose. Modifying MSN surfaces by coating with various mucoadhesive polymers (chitosan, alginate, etc.) will also facilitate interaction with the intestinal mucus and improve intestinal retention time. Moreover, the development of glucose‐responsive systems for achieving MSN‐based self‐regulated insulin delivery, decorated with various components serving as sensors – glucose oxidase (GODx) and phenylboronic acid (PBA) that can control the insulin dosage, avoiding overdose leading to serious hypoglycemia. MSN have also been tested for application as biosensors for glucose monitoring.

Layered Composites Based on Recycled PET/Functionalized Woven Flax Fibres

Sönmez Maria, Alexandrescu Laurentia, Nituica Mihaela, Georgescu Mihai, Gurau Florentina Dana, Ficai Denisa, Ficai Anton, Trusca Roxana, Constantinescu Doina National Research and Development Institute for Textiles and Leather–division Leather and Footwear Research Institute 93 Ion Minulescu St., Bucharest, Romania maria.sonmez@icpi.ro; laurentia.alexandrescu@icpi.ro; mihaela.nituica@icpi.ro; mihai.georgescu@icpi.ro; dana.gurau@icpi.ro Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science 1-7 Polizu St., Bucharest, Romania denisa.ficai@yahoo.ro; anton.ficai@upb.ro; truscaroxana@yahoo.com SC MONOFIL S.R.L 1 Uzinei St., Savinesti, Romania monofil.srl@gmail.com

New Polymeric Compounds with High Temperature and Impact Resistance

This paper focuses on development and characterization of new impact and flame resistant advanced materials based on polyamide / compatibilizer / polycarbonate / glass fibers (GF) functionalized with organo silane. Polyamides (PA) are highly crystalline hard materials, that have high impact resistance, burn slowly or are self-extinguishing. Polycarbonates (PC) are thermoplastic polymers intended for oil and high temperatures resistant materials. To increase impact resistance, polymeric compounds were reinforced with short functionalized glass fibers. The thermoplastic polymeric materials are visionary and materials for the future, with special properties, depending on the type of elastomers, the type of reinforcement material, the ratio of reinforcement, the functionalization of the reinforcing material, the type of functionalization agent, the ratio of elastomer-compatibilizing agent-reinforcing agent, etc. Thus by determining the optimum types and ratios of polycarbonate, polyamide, compatibilizer, functionalized glass fibers and optimal processing conditions and parameters, special properties can be achieved: flame retardant and especially self-extinguishing properties, physical-mechanical, chemical and technological properties, superior to the current standards in the field. Due to their characteristics the new materials can be employed in development of finished goods for the automotive and electrical insulation industry, which must meet European legislation (directives) into force.