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Since 1970s, collagen became one of the preferred biopolymers for biomedical application due to its unique properties—biocompatibility, weak antigenicity, rich chemistry/versatility, and biological interactions/adhesion motifs providing specific recognition sites for cells. The developed collagen-based biomaterials found applications in drug/gene delivery, wound healing, tissue engineering, etc. The increasing society requirements imposed the production of multifunctional, smart devices with tailored performances. Such a challenge resulted in research and collagen-based biomaterials suppliers' adaptation and compelled them to make use of the new tools offered by the technical evolution (i.e., microfluidics, 3D or 4D bioprinting, modeling and simulation, high performance characterization techniques and instruments for the nano- to molecular level). The review encompasses old and current aspects in the domain.

Combining two or more materials for carrier construction is one of the topical approaches to avoid/diminish deficiencies and to increase functionality in delivery systems for bioactive compounds. In this context, here, multilayered nanoparticles comprising both natural (atelocollagen—AteCol; hyaluronic acid derivative—HA) and synthetic [poly(e-caprolactone)—PCL; polyethylenimine—PEI; poly(l-lysine)—PLL] polymers were prepared and characterized. The combination of a modified double-emulsion method with polymer modification reactions allowed improvement of the polymer particle’s functionality. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, transmission/scanning electron microscopy and fluorescence microscopy investigations confirmed the obtention of the envisaged nanomaterials with the expected composition and structure. The double-layered biopolymer/PCL-based nanoparticles formed in a first synthesis step could be successfully coated with PEI and PLL. The gel electrophoresis assay attested the DNA packing ability of the formed nano-vehicles involving surface grafting of the former biopolymer/PCL-based nanoparticles in the case of both cationic polymers, for N/P ratios of 10 (PEI coating) and 3.5 (PLL coating), respectively. According to the FTIR registration, the protein’s native form was preserved. Considering the advantage of biocompatibility and high versatility (controlled size, tuned chemistry and biodegradation rate) some of the resulted nanomaterials may appear as potential candidates for biomedical uses (i.e., drug/gene delivery and tissue engineering).

Collagen is a key component for devices envisaging biomedical applications, however, current increasing requirements impose the use of multicomponent materials. Here, a series of hybrid collagen-based 3D materials, comprising also poly(ε-caprolactone) (PCL) and different concentrations of hyaluronic acid (HA)—in dense, porous or macroporous form—were characterized in comparison with a commercially available collagen sponge, used as control. Properties, such as water uptake ability, water vapour sorption, drug loading and delivery, were investigated in correlation with the material structural characteristics (composition and morphology). Methylene blue (MB) and curcumin (CU) were used as model drugs. For spongeous matrices, it was evidenced that, in contrast to the control sample, the multicomponent materials favor improved sustained release, the kinetics being controlled by composition and cross-linking degree. The other characteristics were within an acceptable range for the intended purpose of use. The obtained results demonstrate that such materials are promising for future biomedical applications (wound dressings and lab models).

Segmented polyurethane/montmorillonite (MMT) nanocomposites have been obtained by solvent casting or in situ polymerization approaches using poly(tetramethyleneglycol), α,ω-dihydroxylated poly(2-alkyl-2-oxazoline), 4,4′-methylenebis-(phenyl isocyanate) and MMT. The influence of the preparation method on the characteristics of the resulted materials was studied by means of spectral and thermal analysis, X-ray diffraction, scanning electronic microscopy, and dynamic-mechanical analysis.

The paper summarizes the history of the drug/gene delivery domain, pointing on polymers as a solution to specific challenges, and outlines the current situation in the field – focusing on the newest strategies intended to improve systems effectiveness and responsiveness (design keys, preparative approaches). Some recent results of the authors are briefly presented.

The dielectric properties of a series of pure atelocollagen samples and of atelocollagen-based hydrogels long-range cross-linked with bifunctional poly(ϵ-caprolactone) derivative, or further short-range cross-linked by UV irradiation, were discussed in relation to the cross-linking method, composition, and hierarchical assembly. Three main factors with significant influence on the electrical behavior, frequency, temperature, and moisture content, are analyzed in detail.

New hybrid cryogels comprising natural polymers (free atelocollagen or atelocollagen mixed with a hyaluronic acid derivative) and a synthetic polyester—poly(e-caprolactone)—were successfully developed by a cryogenic treatment and a subsequent freeze-drying step. Systematic studies on the effect of preparation conditions (reaction mixture composition, total concentration of the feed dispersion, and freezing regime) on cryogelation efficiency were conducted. The degree of cross-linking and the morphology of the obtained materials were analyzed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and (environmental) scanning electron microscopy (ESEM/SEM) techniques. Considering their possible biomedical application, the developed macroporous hydrogels were also investigated in terms of swelling behavior and hemo/biocompatibility. The produced hydrogels had an uniform interconnected open porous structure with a porosity of up to 95% and pores size in the range of 83–260 μm. All obtained cryogels were elastic, mechanically stable, with a superfast swelling kinetics. In vitro hemocompatibility assay gave hemolysis ratios (HRs) lower than 0.5%, which is below the permissible limit of 5%. The in vivo tolerance tests performed by implantation of cryogel specimens into Wistar rats proved their biocompatibility. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 2689–2698, 2013.

In an attempt to obtain appropriate components for complex transfection systems hydroxyapatite nanoparticles (nHAp) were synthesized by means of wet chemical precipitation method, under atmospheric pressure, in the absence or presence of different low-molecular or polymeric cationic dispersants, i.e. arginine, linear or branched polyethylenimine (LPEI, bPEI). The effect of added compounds' type and concentration on nHAp characteristics (surface chemistry, size, morphology, crystallinity, dispersibility) was comparatively studied. The chemical composition and surface modification of the synthesized nano-HAp was investigated using Fourier Transformed Infrared Spectroscopy (FTIR), Energy Dispersive X-Ray (EDX) analysis, Zeta potential measurements (DLS-dynamic light scattering) and UV-vis spectrophotometry. The crystal morphology and particle size were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-Ray Diffraction technique (XRD). The DNA binding ability of the functionalized nHAp was tested by agarose gel electrophoresis assay.

Attempts to obtain collagen-based biomimetic 3D structures with possible use in the biomedical domain (scaffolds in tissue engineering, component of wound dressing) are presented. Different preparation approaches were applied and the resulted materials were comparatively characterized pointing on advantages/drawbacks of the corresponding preparative alternative. Aiming the material characteristics control in order to achieve the targeted performances required by the application domain, computer aided material selection facilities were considered. Development of supervised artificial network for appropriate composition selection was proved to be an important, efficient tool for control and prediction even for complex multicomponent materials such as those here considered.

A series of polyurethane/montmorillonite (PU/MMT) nanocomposites, based on poly(tetramethyleneglycol) (PTMG), α,ω-dihydroxylated poly(2-alkyl-2-oxazoline) (PROZO), [4,4’-methylenebis-(phenyl isocyanate)] (MDI) or [4,4’-methylenebis-(cyclohexyl isocyanate)] (H12MDI) and montmorillonite (MMT), were investigated. The amount of added clay ranged from 3 up to 10% by weight. The influence of the MMT weight fraction in the polymer matrix on the morphology and thermal, dynamic mechanical and tensile properties was characterized by scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectrophotometry, differential scanning callorimetry, thermogravimetric analysis and dynamic—mechanical analysis. The results of the investigations were used to rank the nanocomposites according to their properties in relation to the polyurethane matrix structure and MMT content. It was evidenced that the silicate layers were preferentially, but not exclusively, attracted to the hydrophilic polar PROZO domains, their level of dispersion being controlled through specific intermolecular interactions and the filler loading amount. Introducing clay in the polyurethane matrix resulted in an increase of both tensile strength and thermal stability. Their non-monotonic dependence on clay content was explained by considering that concomitant and contrasting effects develop as the clay amount increases: an improvement of the filler—matrix interactions and a reduction of the matrix labile physical crosslinking degree by hydrogen bonding coupled with a lower dispersion homogeneity. For high inorganic filler amount aggregated clay particles together with regions with mixture of exfoliated and intercalated morphologies were revealed.

New segmented polyurethanes containing soft and hard segments of different polarity and hydrophilicity, based on 4,4′-methylenebis-(cyclohexyl isocyanate, 4,4′-methylenebis-(phenyl isocyanate) and poly(tetramethylene oxide) or poly(ethylene oxide) were prepared including poly[( N-acylimino) ethylene] sequences as a chain extender. They were comparatively characterized by spectral, thermal and mechanical techniques. Some preliminary investigations on their nanocomposites with montmorillonite as an inorganic component are presented.

Poly(trimethylolpropane trimethacrylate) microspheres with a narrow size distribution were obtained by precipitation polymerization. They were subsequently modified by surface grafting with acrylic ...

In this study, MMA/BMA copolymer nanoparticles were synthesized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS) and initiated by potassium persulphate KPS. Malefic acid terminated poly(N-acetylethylenimine) (PNAEI) with two different chain lengths was also included in the recipe, as a cosurfactant and a comonomer. FTIR and H-1-NMR proved incorporation of the macromonomer in the structure. High polymerization yields were achieved upto 98%. The viscosity average molecular weights of the copolymers were in the range of 2.77-5.50 x 10(5). The glass transition temperatures of these copolymers were between 50.0 and 63.9 degreesC. The average diameter of nanoparticles were in range of 40-96 nm. It was possible to produce nanoparticles smaller than 100 nm and with narrower size distributions by using much lower concentrations of SDS by including the macromonomers in the microemulsion polymerization recipe. (C) 2004 Elsevier Ltd. All rights reserved.

Block and graft copolymers with poly(N-isopropylacrylamide) and poly[(N-acetylimino)ethylene] (PNAI) sequences were synthesized via PNAI derivatives (macroinitiators or macromers). The polymerization yields for block copolymers synthesized in ethanol, using the PNAI macroinitiator, were low (

Three different poly(N-acetyliminoethylene) (PNAI) macromonomers containing maleic acid moieties were tested as stabilizers for the preparation of polymer microparticles by dispersion polymerization in a polar media (alcohol/water). A comparative study on the effect of various factors, such as initiator nature and solvency of the reaction medium, on system stability and particle characteristics was performed. Styrene was used as the main monomer and ethanol, isopropanol and 2-butanol as organic solvents. Chemical and photochemical techniques were applied as initiation routes. The photoinitiators allow the synthesis of microparticles with low diameters and narrow size polydispersity in a high yield. The polymerization duration was significantly improved as compared to the methods available in the literature.

Complex hydrogels consisting of natural and synthetic polymers, stabilized by combining different physical and chemical cross-linking methods, were assessed by in vitro degradation tests performed at 37 °C in phosphate buffer solution. Four biopolymer-based hydrogel series were comparatively evaluated as sponge or dense films as regards mass loss, morphology changes and thermal behavior over the fixed incubation period, considering as main factors of influence the composition, the adopted stabilization mode and the microstructure of the 3D construct. To facilitate the selection of the appropriate material for envisaged applications, matching the specific needs, the obtained data were used to generate an artificial neural network (ANN) model, able to establish correlations of the examined formulations and preparation parameters with mass loss. The comparison of experimental and calculated data showed that the developed ANN shows reasonable predictive performance ( r training / validation 2 = 0.99 ) .

A series of functionalized poly(2-oxazoline)s were synthesized by quenching poly(2-methyl-2-oxazoline) living chains (mono- or bifunctional) with maleic acid as nucleophilic agent. By varying the functionality of the initiating system and the ratio of the nucleophile to oxazolinium ends, three different compounds – two macromers and/or an unsaturated polyester – were obtained. The use of a macromolecular proton scavenger was found to be an easy, efficient alternative to the laborious approach performed with triethylamine. The coupling products were copolymerized with styrene by solution or dispersion polymerization.

2-Ethyl-2-oxazoline (EOZO) was polymerized using two different photocationic initiators: a combination of bis {(4-diphenylsulfonium)phenyl} sulfide bis {hexafluoroantimonate} and (4-phenyl sulfide)phenyl diphenylsulfonium hexafluoroantimonate (Cyracure UVI® 6974) and (η 5 -2,4-cyclopentadien-1-yl)-[η 6 -(1-methylethyl)benzene]iron hexafluorophosphate (Irgacure® 261). The experimental data is consistent with the premise that in the presence of Cyracure UVI® 6974 the initiation proceeds via a Bronstedt acid. In the second case the generation of oxazolinium growing species is intermediated by a complex derived from the initial ferrocenium salt.

The paper discusses different synthetic approaches yielding block and graft copolymers containing siloxane and/or N-acetyliminoethylene moieties. Since the corresponding homopolymer sequences are obtained by quite specific mechanisms, combined techniques are required to build different types of copolymers.

A series of polysiloxane/poly(N-acetyliminoethylene) (PSiO/PNAI) block and graft copolymers were synthesized by the initiation of 2-methyl-2-oxazoline (Me-OZO) polymerization with functional polysiloxane prepolymers. The copolymerization products were characterized by IR- and 1H NMR spectroscopy, elemental analysis, DSC and thermogravimetry. The insertion of both hydrophobic and hydrophilic sequences in the macromolecular structure induces a behavior characteristic of amphiphilic compounds. Their solution and solid state behavior evidenced peculiarities which make them able to act as nonionic emulsifiers, surface modifiers, gels, etc. Eine Reihe von Polysiloxan/Poly(N-acetyliminoethylen)-(PSiO/PNAI)-Block- und -Pfropfcopolymeren wurde durch Polymerisation von 2-Methyl-2-oxazolin (MeOZO) mit funktionellen Polysiloxan-Prepolymeren als Initiatoren synthetisiert. Die Copolymeren wurden mit IR- und 1H NMR-Spektroskopie sowie Elementaranalyse, Differentialkalorimetrie und Thermogravimetrie charakterisiert. Der Einbau sowohl von hydrophoben als auch von hydrophilen Sequenzen verleiht den Polymeren amphiphile Eigenschaften. Ihre Eigenschaften in Losung und als Feststoffe lassen die Produkte fur Anwendungen als nichtionische Emulgatoren, Oberflachenmodifikatoren, Gele, usw. geeignet erscheinen.

The photochemical polymerization of methacrylic acid in dilute aqueous solution in the presence of poly(N-acetyliminoethylene) macroazoinitiators was investigated. The reaction development is the result of the superposition of two different template processes. The effect of some factors, such as initiation mode (photolysis or thermolysis), matrix dimension, monomer, and overall concentration on polymerization features was evidenced.

The kinetic study of the photochemical polymerization of methacrylic acid (MAA) in aqueous dilute solution in the presence of poly(N-acetyliminoethylene) (PNAI) oligomers evidenced template features. The process proceeded in two stages, depending on [PNAI]/[MAA]0 ratio and polymerization duration, two different complexes being formed, both by a “zip” chain-growth mechanism. Computing and transmission electron microscopy data revealed that this aspect is due to the replacing of the initial PNAI template by the newly formed poly(methacrylic acid) daughter polymer, as a result of the structural peculiarities of the latter as a component of the primary complex. Its specific mode of packing in a complex aggregate was considered to be the main reason for the reported behavior. © 1996 John Wiley & Sons, Inc.

The soap-free emulsion polymerization of some hydrophobic vinyl monomers (styrene, methyl methacrylate, n-butyl methacrylate) in the presence of water soluble poly(N-acetyl iminoethylene) macroazoinitiators was investigated. The polymerization system features are controlled by the nature and concentration of both monomer and macroinitiator. The resulting block copolymers were proved to act as emulsifiers in inverse emulsion polymerizations.

New hybrid cryogels comprising natural polymers (free atelocollagen or atelocollagen mixed with a hyaluronic acid derivative) and a synthetic polyester--poly(ε-caprolactone)--were successfully developed by a cryogenic treatment and a subsequent freeze-drying step. Systematic studies on the effect of preparation conditions (reaction mixture composition, total concentration of the feed dispersion, and freezing regime) on cryogelation efficiency were conducted. The degree of cross-linking and the morphology of the obtained materials were analyzed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and (environmental) scanning electron microscopy (ESEM/SEM) techniques. Considering their possible biomedical application, the developed macroporous hydrogels were also investigated in terms of swelling behavior and hemo/biocompatibility. The produced hydrogels had an uniform interconnected open porous structure with a porosity of up to 95% and pores size in the range of 83-260 μm. All obtained cryogels were elastic, mechanically stable, with a superfast swelling kinetics. In vitro hemocompatibility assay gave hemolysis ratios (HRs) lower than 0.5%, which is below the permissible limit of 5%. The in vivo tolerance tests performed by implantation of cryogel specimens into Wistar rats proved their biocompatibility.

Different dense and porous biodegradable matrices based on solely atelocollagen, or with different atelocollagen and hyaluronic acid derivative ratios, were obtained by varying feeding formulations, cross-linking reaction parameters, and preparative protocols. The compositions and methods for forming hydrogels through a combination of physical and chemical cross-linking processes are provided. The chemical cross-linking was mainly mediated by a synthetic component, a poly(ε-caprolactone) reactive derivative, aiming the development of new hybrid hydrogels with tailored characteristics by an appropriate use of the advantages offered by the included natural and synthetic components and the selection of the preparative procedure. The structure and morphology of the 3D hybrid materials were comparatively investigated by means of Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and environmental scanning electron microscopy (ESEM). FTIR and XRD analysis showed no signs of collagen denaturation during the formation of 3D structures. The influence of various factors, such as the chemical composition of the resulted hydrogels and their morphology, on water uptake and water vapor sorption, mechanical behavior, as well as on in vitro degradation characteristics, was systematically investigated. The experimental results point on the advantage offered by the high and modular physicochemical stability of the ternary hydrogels cross-linked by combined approaches. All newly developed materials show no hemolytic effect, which recommends them for potential biomedical applications.

New block copolymers with poly(N-acetyliminoethylene) and vinyl sequences were obtained by a two-step synthetic approach. In the first stage macroinitiators of poly(N-acetyliminoethylene) type, with azo groups inserted in the main chain, were prepared. They were latter used in the radical polymerization of some vinyl monomers [styrene, methacrylic acid, methyl methacrylate, butyl methacrylate, β-(N-carbazolyl)ethyl acrylate, β-(methacryloyfoxy)ethyl 3,5-dinitrobenzoate]. The resulting block copolymers were characterized by spectral methods, elemental analysis, gel permeation chromatography, and electron microscopy. The kinetic study of the thermal and photochemical decomposition of the synthesized macroazoinitiators, as well as the polymerization data, suggest a dependence of their initiating efficiency on the length of the poly(N-acetyliminoethylene) segments. © 1994 John Wiley & Sons, Inc.

The composition dependence of the glass temperatures of copolymers containing monomeric units with electron-donor and/or electron-acceptor groups shows serious deviations from additivity. For electron-donor/electron-acceptor copolymers these deviations are more or less symmetric and, depending on the length of the spacer between the interacting groups and the methacrylic polymeric backbone, they vary from positive for the short ethyl spacer to negative for longer spacers. Glass temperatures of copolymers of methyl and n-butyl acrylates (methacrylates) with the respective electron-donor or electron-acceptor monomers always show asymmetric deviations from additivity. These deviations are mostly positive and situated on the donor-poor side for the donor copolymers and negative and situated on the acceptor-rich side for the acceptor copolymers. The deviations are more pronounced for the methacrylates and decrease from the methyl to the n-butyl ester.

Ternary poly( N-isopropylacrylamide)/poly(2-alkyl-2-oxazoline)/poly(2-hydroxyethyl methacrylate) (PNIPAAm/PROZO/PHEMA) hydrogels were prepared by the free-radical copolymerization of N-isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacrylate (HEMA), and poly(2-alkyl-2-oxazoline) (PROZO) multifunctional macromonomers. The resulting polymeric materials were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), as well as by equilibrium swelling experiments. All synthesized hydrogels display temperature sensitivity in the 28-38 degrees C range. A high rate of response was registered as compared to that of materials based only on PNIPAAm. The swelling-deswelling peculiar behavior was related to the chemical composition (hydrophile/hydrophobe balance), the length of the inserted PROZO sequence, and inner morphology, an aspect which points on its possible control by synthesis. It was evidenced that the architecture of the resulting porous materials has a high order degree, emerging from the self-assembling of the microgel particles, which provided numerous, nearly uniform, large water release channels.

Copolymers with intramolecular charge transfer interactions were synthesized by radical copolymerization of ω-(N-carbazolyl)alkyl methacrylates (where alkyl is propyl and butyl) with 2-(methacryloyloxy)ethyl 3,5-dinitrobenzoate. These copolymers are characterized by a dependence of the electronic absorption, the solubility and the density on the composition. The intramolecular degree of complexation depends on spacer length and exerts a maximum for the spacer with three methylene groups.

The investigation of structures with nanometer dimensions and their use in the fabrication of nanoscale devices is of topical, intense scientific and technological interest. In this context, colloidal dispersions of polymer micro- or nanoparticles, with controlled size and surface functionality, have received much attention. Different applications are possible in environmental management (i.e. sorbents), technical areas (microelectronics, biotechnology) and biomedical domains. Especially the last ones, implying commercial advantages, have determined a rapid development of this research subject. Such polymer materials are used for cell label/targeting, as support for controlled drug delivery, for latex diagnostics or heterogeneous immunoassay, for physico-chemical or affinity bioseparation, as magnetic carriers1. More, new techniques are now developing making use of self-organizing block copolymers, block copolymer micelles or polymer micro-/nanoparticles as templates for the preparation of nanostructured patterns with sizes smaller than those produced by electron beam or photolithography. These techniques are the subject of many investigations due to their use in the preparation of high selectivity membranes, of molecule separation devices, of nanowires with special electro-optical and magnetic properties or of biosensors.

Methyl methacrylate and butyl methacrylate were polymerized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS). A poly(N-acetylethylenimine) (PNAEI) macromer was also included in the recipe, as a cosurfactant and a comonomer. Polymerizations were initiated by UV-irradiation. The average diameters of latex particles, obtained by STM, were in the range of 17–200 nm. The experimental data evidenced that the particle size was mainly dependent on the SDS/PNAEI ratio. Polymerization yields were around 75–85%. The synthesized copolymers have viscosity average molecular weights in the range of 2.1–2.4×106 and glass transition temperatures of 38.0–43.5°C, lower than those obtained without using PNAEI. The investigation by means of FTIR and 1 H-NMR techniques revealed that PNAEI was incorporated into the nanoparticles.

Four novel acrylic and methacrylic monomers (8b, c and 9b, c) containing carbazolylalkyl groups, their corresponding polymers and low-molecular-weight model compounds (7b, c) were synthesized. The charge transfer complexes of the synthesized polymers with 2,5-cyclohexadien-1,4-diylidenedimalononitrile were prepared and characterized by UV-vis spectroscopy. The ionisation potentials and complexation constants were determined. It could be shown that increasing spacer length favours the interaction between donor and acceptor. Polymethacrylates with 3 methylene groups in the spacer show the highest complexation constants.

The possibility of opening cyclic iminoethers and forming linear polymers or copolymers under the action of charge transfer complexes has been studied. The polymerization of 2-methyl-2-oxazoline, acting as donor, proceeds in the presence of various organic electron-acceptors such as tetracyanoethylene 7,7,8,8-tetracyanoquinodimethane and 2,4,7-trinitrofluorenone. Initiation takes place by charge transfer complexes formed between the monomer and the acceptor. With acceptors which possess polymerizable bonds, i.e. tetracyanoethylene and tetracyanoquinodimethane, copolymers are obtained.

The synthesis of three novel oxazoline monomers,all of which contain 3-halogen substituted carbazolyl groups [i.e., 2-(β-N-3′ chlorocarbazolylethyl)-2-oxazoline, 2-(β-N-3′ bromocarbazolylethyl)-2-oxazoline and 2-(β-N-3′ iodocarbazolylethyl)-2-oxazoline]and their polymerization is described.

Nano-hydroxyapatite (nHAp), surface functionalized with linear polyethylenimine (LPEI), was used for the preparation of biocomposites in combination with biopolymers and poly(e-caprolactone) (PCL), by cryogelation technique, to yield biomimetic scaffolds with controlled interconnected macroporosity, mechanical stability, and predictable degradation behavior. The structural characteristics, swelling and degradation behavior of hydroxyapatite and hydroxyapatite/β-tricalcium phosphate (β-TCP) filled matrices were investigated as compared to the corresponding naked polymer 3D system. It was found that the homogeneity and cohesivity of the composite are significantly dependent on the size and amount of the included inorganic particles, which are thus determining the structural parameters. Surface modification with LPEI and nanodimensions favored the nHAp integration in the organic matrix, with preferential location along protein fibers, while β-TCP microparticles induced an increased disorder in the hybrid system. The biocomposite including nHAp only was further investigated targeting biomedical uses, and proved to be non-cytotoxic and capable of acting as gene-activated matrix (GAM). It allowed sustained delivery over time (until 22days) of embedded PEI25-pDNA polyplexes at high levels of transgene expression, while insuring a decrease in cytotoxicity as compared to polyplexes alone. Experimental data recommend such biocomposite as an attractive material for regenerative medicine.

The design of new non-viral gene vectors and their integration into a biomaterial scaffold are intensively explored nowadays, aimed at developing more efficient gene delivery systems capable of clinical translation. Herein, a series of squalene/branched polyethylenimine (Sq/BPEI) based conjugates were synthesized and their potential in gene delivery, as such or included in a three-dimensional hybrid scaffold (atelocollagen-glycosaminoglycan-polycaprolactone/nano-hydroxyapatite), was investigated. The developed materials were characterized through spectral (1H-NMR, 13C-NMR, FT-IR) and optical (STEM) techniques. The extent and duration of gene expression for the developed systems were monitored using luciferase assays and fluorescence microscopy. All the investigated systems exhibited a high transfection efficiency without or with moderate cytotoxic side effects (MTS assay data). The best results were obtained with the guanidinylated compound Sq-BPEI-G for both simple and combined polyplex/matrix systems. The polyplex delivery from the hybrid matrix was assessed through kinetic studies using a labeled Sq/BPEI conjugate. For the polyplex (Sq/BPEI – DNA plasmid)/3D matrix system, the expression of the delivered plasmids was observed over a 26 day- period. The reported preliminary data recommend the studied biomaterials as possible candidates for the development of a new gene-activated matrix (GAM) platform.

The morphologies formed in poly[β-(N-carbazolyl)ethylacrylate-co-β-(metacryloyloxy) ethyl-3,5-dinitrobenzoate] [poiy(HECA-co-DNBM)] and in its triblock copolymer with poly(N-acetyliminoethylene) (pMeOZO) were investigated using transmission electron microscopy and differential scanning calorimetry (DSC) techniques. It was found that a lamellar structure was induced in the block copolymer even at a low content (5%) of poly(N-acetyliminoethylene) as a consequence of the specific, dense, layered texture of the poly(HECA-co-DNBM) blocks, having an electron donor-acceptor complex character. The incorporation of poly(N-acetyliminoethylene) resulted in film quality improvement. The addition of small amounts of the block copolymer to the incompatible mixture of poly(HECA-co-DNBM) and pMeOZO having an appropriate composition leads to homogeneous blends able to form continuous films.

Spontaneous copolymerizations of 2-substituted 2-oxazolines having donor or acceptor pendant groups, i.e. 2-(β-N-carbazolylethyl)-2-oxazoline, 2-(9-anthrylethyl)-2-oxazoline and 2-(3,5-dinitrophenyl)-2-oxazoline, with 7,7,8,8-tetracyanoquinodimethane and tetracyanoethylene have been studied. Initiation takes place through a charge transfer complex intermediate formed between n-type donor oxazoline ring and the π acceptor. A charge transfer complex is formed also between donor pendant groups (anthryl or carbazolyl) and acceptor (π-π type complex) which can be preserved in the copolymer. This method allows the direct obtaining of intramolecular and intermolecular charge transfer complexes by spontaneous copolymerization of donor/acceptor monomer pairs.

The spontaneous and initiated copolymerizations of 2-substituted 2-oxazolines carrying donor ( N -carbazolyl and 9-anthryl) and acceptor (3,5-dinitrophenyl) pendant groups, in bulk or in solution have been investigated. The copolymers possess intramolecular charge transfer complexes properties due to both the complexing of pendant electroactive groups (π-π type complex) as well as to internal complexing of the lone pair of electrons of the nitrogen atoms from the polyethylenimine chain with 3,5-dinitrophenyl acceptor groups (π-π type complex).

Amphiphilic block and graft copolymers with polysiloxane and poly[(acetylimino)ethylene] sequences were used as nonionic surfactants in the emulsion polymerization of some vinyl monomers (styrene, methyl methacrylate, butyl methacrylate). The peculiarities of the systems (polymerization kinetics and emulsion characteristics) were related to the structural features of the studied emulsifiers and suggested their ability to participate in initiation and transfer reactions and respectively clouding phenomena in aqueous phase. Block- und Pfropfcopolymere mit Polysiloxan- und Poly(acetyliminoethylen)-Bestandteilen wurden als nichtionische Emulgatoren bei der Emulsionspolymerisation von einigen Vinylmonomeren (Styrol, Methylmethacrylat, Butylmethacrylat) benutzt. Die Polymerisationssysteme (kinetische Aussagen, Teilchengrose, Teilchengrosenverteilungen, usw.) wurden charakterisiert und die Emulgatorstruktur-Polymerisationseigenschaft-Beziehungen wurden untersucht. Die Teilnahme der Copolymeren an der Initiierungs- und Ubertragungsreaktion wurde festgestellt.