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In this work, the feasibility of some poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA)-based pH-sensitive nanogels as drug nanocarriers is evaluated. The anticancer drug doxorubicin (DOXO) is successfully encapsulated into the nanogels, achieving high drug loading and encapsulation efficiency. It has been found that the in vitro delivery of DOXO from the nanogels was pH-dependent: DOXO release rate is accelerated by decreasing pH from 7.4 (healthy cells) to 5.2 (pH condition for endo/lysosomial compartments and unhealthy cells) due to the swelling of the nanogel particles. The uptake of DOXO-loaded nanogels into MDA-MB-231 tumoral cells and the progressive release of the drug from the nanogels to the cell nuclei are demonstrated by fluorescence microscopy measurements. These results suggest a great potential of these DOXO-loaded nanogels for antitumor drug delivery.

Here, novel methods to encapsulate magnetic nanoparticles (MNPs) into dual-stimuli-responsive nanogels via covalent bonding are reported. With the aim of strengthening the attachment of MNPs with the nanogels, primary amine- and epoxide-functionalized stimuli-sensitive poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA)-based nanogels were firstly synthesized. Then, MNPs were incorporated into the nanogels by using different methods, obtaining different families of magnetic nanogels (MNGs). Those MNGs, showing pH-sensitivity and high superparamagnetic response, could be considered to be widely useful as theranostic agents in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

International audience; The present work investigates the potentiality of poly(N-vinyl caprolactam) (PVCL)-based thermoresponsive microgels decorated with cationic polymer brushes as drug delivery carriers. The effect of physico-chemical features of the colloids on cell viability response have to be carefully investigated to establish the range of suitable hydrodynamic diameters, crosslinking densities, lengths and ratios of the cationic polyelectrolyte shell which allow their efficient and effective use for cargo loading, transport and delivery. The colloidal stability of all cationic thermoresponsive microgels is maintained over several days of incubation at 37 °C in biological mimicking medium (Dulbecco's Modified Eagle's Medium supplemented with fetal bovine serum). The thin cationic polymer shell covalently anchored does not hinder the all range of microgels to be biocompatible while the higher cytotoxicity of the doxorubicin-loaded microgels on HeLa cells proves their anti-tumor activity. The core-shell PVCL drug delivery nanocarriers allow a sustained release of doxorubicin with a slightly higher viability of HeLa cells incubated in the presence of DOXO-loaded microgels compared to the free DOXO. The nature of the endocytosis pathway is investigated through a quantification of the extent of the cellular survival rate in the presence of various cellular uptake inhibitors. A clathrin-dependent internalization was observed.

The synthesis, characterization, and potential application as gene delivery systems of biodegradable dual-responsive core–shell nanogels based on poly(2-diethylaminoethyl) methacrylate (PDEAEMA) and poly(N-vinylcaprolactam) (PVCL) are reported. These core–shell nanogels, having a PDEAEMA-based core and a PVCL-based shell, were synthesized by batch seeded emulsion polymerization. An indepth study of their swelling behavior was carried out, which presented a dual-dependent thermo- and pH sensitivity. Core–shell nanogels synthesized formed complexes spontaneously through electrostatic interactions when mixing with small interfering RNA (siRNA) molecules. Moreover, the core–shell nanogel/siRNA complexes showed higher polyanion exchange resistance compared to that of the PDEAEMA-based nanogel/siRNA complexes, indicating that the PVCL-based shell enhanced the stability of the complexes. In vitro siRNA release profiles showed that siRNA release was controlled by the pH of the medium as well as by the crosslinking density of the PVCL-based shell. These results indicate that dual-responsive core–shell nanogels synthesized could be potentially useful as gene delivery systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016.

In this work, the swelling of pH- and temperature-sensitive [poly(2-(diethylamino) ethyl) methacrylate]-based nanogels has been analyzed with the help of coarse-grained simulations employed in the last decade for polyelectrolyte gels. This computational approach, which is based on particle-particle interactions between polymer units, constitutes an alternative to thermodynamic formalisms. Polymer-polymer hydrophobic forces are accounted for in the model through a solvent-mediated interaction potential whose depth increases with temperature. This model qualitatively captures the swelling behavior of such nanogels when their degree of protonation varies from 0 to 1 without requiring changes in the potential parameters. In addition, our study quantitatively reveals that [poly(2-(diethylamino) ethyl) methacrylate]-based particles are more hydrophobic than those based on poly(N-isopropylacrylamide).

International audience; A series of reactive poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) (P(AETAC)) cationic polymers with varying degrees of polymerization were synthesized by RAFT/MADIX polymerization and investigated as stabilizers for the emulsion polymerization of N-vinylcaprolactam (PVCL) in the presence of a cross-linker. It was demonstrated that the xanthate chain end of the cationic P(AETAC-X) polymers played a crucial role to produce stable cationic PVCL-based microgels at higher initial solids content (5–10 wt %) than usually reported for the synthesis of PVCL microgels. The thermoresponsive PVCL microgels with cationic shell undergo a reversible volume shrinkage upon heating in the absence of any hysteresis in accordance with the narrow particle size distribution. The values of the volume phase transition temperature ranged between 28 and 30 °C for the microgels synthesized using 4 and 8 wt % of P(AETAC-X) based on VCL. The presence of a cationic outer shell onto the microgels was evidenced by the positive values of the electrophoretic mobility. The swelling behavior of the thermoresponsive microgel particles can be tuned by playing on two synthesis variables which are the initial solids content and the content of P(AETAC-X) macro-RAFT stabilizer. Furthermore, the inner structure of the synthesized microgels was probed by transverse relaxation nuclear magnetic resonance (T2 NMR) and small-angle neutron scattering (SANS) measurements. The fit of T2 NMR data confirmed a core–shell morphology with different cross-linking density in PVCL microgels. Through the determination of the network mesh size, SANS was suitable to explain the increase of the values of the PVCL microgel swelling ratios by increasing the initial solids content of their synthesis.

We report a study on the light scattered by temperature-sensitive poly( N -vinylcaprolactam) (PVCL)-based nanogel particles, with different amounts of cross-linker and charged groups. The scattered light I ( q ) is measured as a function of the scattering angle at temperatures below and above the volume phase transition temperature (VPTT) of the nanogel particles. I ( q ) is fitted using an analytical expression with two adjustable parameters: α and the radius of gyration ( R g ). The first parameter ( α ) provides information on the structure of the external shell, and R g on the internal mass distribution of the nanogel. Regarding samples with increasing cross-linker amounts, remarkable differences in I ( q ) are found above the VPTT whereas below the VPTT the differences were not significant. Charged and uncharged nanogels also show noticeable discrepancies between the swollen and the collapsed state. The I ( q ) curves of shrunken uncharged nanogel particles are similar to those of uniform spheres. In the case of charged nanogels, the I ( q ) curves reveal that the core–shell structure of the particle persists in both the swollen state and the shrunken state.

A thorough understanding of the morphology of the environmental sensitive nanogels was indispensable to obtain a deeper insight on their stimuli-responsive behavior. Therefore, in this work the colloidal characterization and the study of the inner morphology were related by using light scattering technique and 1H-nuclear magnetic resonance transverse relaxation measurements combined with the Flory–Rehner theory. Different biocompatible and dual-stimuli-sensitive nanogel particles based on poly(2-diethylaminoethyl) methacrylate were synthesized using three different crosslinkers: two bifunctional and one multifunctional. All the nanogels obtained had a core–shell type heterogeneous morphology, but they presented completely different swelling behaviors due to their different crosslinking points’ distribution and polymeric chains’ microstructure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2017–2025

Nanogels (NGs) are currently under extensive investigation due to their unique properties, such as small particle size, high encapsulation efficiency and protection of active agents from degradation, which make them ideal candidates as drug delivery systems (DDS). Stimuli-responsive NGs are cross-linked nanoparticles (NPs), composed of polymers, natural, synthetic, or a combination thereof that can swell by absorption (uptake) of large amounts of solvent, but not dissolve due to the constituent structure of the polymeric network. NGs can undergo change from a polymeric solution (swell form) to a hard particle (collapsed form) in response to (i) physical stimuli such as temperature, ionic strength, magnetic or electric fields; (ii) chemical stimuli such as pH, ions, specific molecules or (iii) biochemical stimuli such as enzymatic substrates or affinity ligands. The interest in NGs comes from their multi-stimuli nature involving reversible phase transitions in response to changes in the external media in a faster way than macroscopic gels or hydrogels due to their nanometric size. NGs have a porous structure able to encapsulate small molecules such as drugs and genes, then releasing them by changing their volume when external stimuli are applied.

Thermo-responsive and biocompatible cross-linked nanocapsules were synthesized through dimethyldioctadecylammonium bromide (DODAB) vesicle templating. For this, firstly two random copolymers, N-vinylcaprolactam (VCL) and acrylic acid (AA), with different chain lengths but using the same monomer ratio, were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. These anionic random copolymers were adsorbed onto cationic DODAB vesicles. Then, biocompatible and thermo-responsive nanocapsules were obtained by semicontinuous emulsion polymerization under monomer-starved conditions for both the main monomer (VCL) and the cross-linker. Although in all the cases the typical thermal behavior of PVCL-based nanocapsules was observed, hysteresis between cooling and heating cycles was observed at low temperature in the case of non-cross-linked nanocapsules. This behavior was reduced using different types and amounts of cross-linkers. In addition, transmission electron microscopy (TEM) characterization demonstrated the successful formation of nanocapsules either with short or long random copolymers. The formation of stable nanocapsules was confirmed below and above the volume phase transition temperature (VPTT) by surfactant lysis experiments through optical density and DLS measurements in all the nanocapsules synthesized. These biocompatible and thermo-responsive nanocapsules could be suitable and potentially useful as nanocarriers for drug delivery.

1 ] Much attention has been directed in recent years to environmentally responsive cross-linked colloidal particles, known as nanogels, considering their unique property to swell rapidly in a thermodynamically good solvent, responding to external stimuli such as temperature, ionic strength, magnetic fi eld, biomolecules, or pH, among others. Furthermore, their small size allows them to overcome various biological barriers and achieve passive and active tar-geting, which reduce adverse reactions in tumor therapy. What is more, due to their porous structure they are able to contain small molecules inside and release them by changing their volume. These properties make them interesting and suitable materials to be used as nanocarriers in drug/gene delivery.

Two new families of thermo-responsive and enzymatically degradable nanogels were synthesized by batch emulsion polymerization of N-vinylcaprolactam (VCL) with dextran methacrylates (Dex-MA) with different degrees of substitution (DS). The first family was prepared using different amounts of Dex-MA with high DS forming highly cross-linked nanogel particles with the typical thermal behavior of PVCL-based nanogels: below the volume phase transition temperature (VPTT) nanogel particles were swollen and above it they were collapsed. After their enzymatic degradation with dextranase, nanogel particles swelled due to the cleavage of some glucopyranosyl bonds of dextran, but preserved their identity. On the other hand, the second family was prepared using different amounts of Dex-MA with low DS forming slightly cross-linked nanogel particles with an anomalous thermal behavior. Surprisingly, above the VPTT of the nanogel particles monodisperse interparticle reversible aggregates were formed. In addition, after their enzymatic degradation, a release of reducing sugars together with an intense de-swelling due to the fragmentation of the nanogel structure was observed. Both nanogel families could be suitable for drug delivery in tissues or organs where dextranase is present.

International audience; The evolution of the polymer structure during nanocomposite formation and annealing of silica-latex nanocomposites is studied using contrast-variation small angle neutron scattering. The experimental system is made of silica nanoparticles (Rsi ≈ 8 nm) and a mixture of purpose-synthesized hydrogenated and deuterated nanolatex (Rlatex ≈ 12.5 nm). The progressive disappearance of the latex beads by chain interdiffusion and release in the nanocomposites is analyzed quantitatively with a model for the scattered intensity of hairy latex beads and an RPA description of the free chains. In silica-free matrices and nanocomposites of low silica content (7%v), the annealing procedure over weeks at up to Tg + 85 K results in a molecular dispersion of chains, the radius of gyration of which is reported. At higher silica content (20%v), chain interdiffusion seems to be slowed down on time-scales of weeks, reaching a molecular dispersion only at the strongest annealing. Chain radii of gyration are found to be unaffected by the presence of the silica filler.

Poly(N-isopropylacrylamide) (PNIPAM) and poly(N-vinylcaprolactam) (PVCL) are temperature-responsive polymers which show a lower critical solution temperature (LCST) around 32 °C in aqueous solutions. Nanogels based on these temperature sensitive polymers swell at low temperatures and collapse at high ones, showing a volume phase transition temperature (VPTT) near physiological temperature. This unique behavior makes these nanogels attractive for biotechnological applications. PNIPAM is the building block of a huge amount of nanogels reported in the literature. However, PVCL is especially interesting due to the fact that it is very stable against hydrolysis and biocompatible. In this mini-review, various synthesis procedures together with the functionalization of different PNIPAM- and PVCL-based nanogels are revised and compared.

Due to the existing interest in new hybrid particles in the colloidal range based on both magnetic and polymeric materials for applications in biotechnological fields, this work is focused on the preparation of magnetic polymer nanoparticles (MPNPs) by a single-step miniemulsion process developed to achieve better control of the morphology of the magnetic nanocomposite particles. MPNPs are prepared by surfactant-free miniemulsion polymerization using styrene (St) as a monomer, hexadecane (HD) as a hydrophobe, and potassium persulfate (KPS) as an initiator in the presence of oleic acid (OA)-modified magnetite nanoparticles. The effect of the type of cross-linker used [divinylbenzene (DVB) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP)] together with the effect of the amount of an aid stabilizer (dextran) on size, particle size distribution (PSD), and morphology of the hybrid nanoparticles synthesized is analyzed in detail. The mixture of different surface modifiers produces hybrid nanocolloids with various morphologies: from a typical core-shell composed by a magnetite core surrounded by a polymer shell to a homogeneously distributed morphology where the magnetite is uniformly distributed throughout the entire nanocomposite.

Three types of poly(N-vinylcaprolactam)-based temperature-sensitive microgel particles were synthesized by emulsion polymerization. The uptake of a model drug (calcein) into the particles was analyzed in terms of the amount of calcein absorbed and equilibrium–swelling degree. By incubating the microgels with primary neuronal cell cultures of embrionary rats, cell viability and biocompatibility tests were carried out. The results show that the driving force for the model drug to penetrate into the microgel particles is H-bonding associations. On the other hand, cell death was microgel concentration and incubation period dependent. Microgels can be stored in a dried state and resuspended in water when necessary without changing their swelling–deswelling ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1173–1181, 2010

Temperature-sensitive N -vinylcaprolactam (VCL)-based microgel particles were synthesized by emulsion polymerization in a batch reactor. To avoid the hydrolysis of VCL, optimized buffered reactions were carried out by using VCL as main monomer, N , N ′-methylenebisacrylamide (BA) as cross-linker and a sugar-based comonomer (3- O -methacryloyl-1,2:5,6-di- O -isopropylidene-α- d -glucofuranose, 3-MDG). The amounts of initiator, cross-linker, surfactant, comonomer, and reaction temperature were the reaction variables. The effects of these variables on the kinetic features of the different polymerizations were analyzed. The colloidal characterization of the microgel particles consists of the analysis of the evolution of the average hydrodynamic diameters as a function of the temperature of the medium. The results showed that in all cases BA reacted faster than VCL. All final microgel particles showed swelling-de-swelling behavior by changing the temperature of the medium in which they are dispersed. Initially formed microgel particles were not temperature-sensitive being necessary up to about 30% of VCL conversion for the onset of the swelling-de-swelling behavior. The final colloidal characteristics of these new microgels can be tuned by modulating the reaction variables.

The noncommercial functional monomer 4-vinylbenzyl hydrazine (VBH) was synthesized and subsequently copolymerized with styrene (St) by means of dif ferent batch and semicontinuous seeded emulsion polymerization processes, so as to obtain hydrazine-functionalized nanoparticles. The effect of pH, surfactant and initiator amounts, ratio VBH/St, reaction temperature, and ratio acetone/water were studied. Due to the amphiphilic character of VBH at acid pH, the hydrazine groups of the functionalized comonomer were masked with acetone to form hydrazone groups. Secondary nucleations were avoided by using the protected VBH comonomer; however, a decreased radical efficiency achieving limited conversion was observed. Controlling the cationic initiator concentration, complete conversions together with the neat growth of the seed particles were obtained in the semicontinuous seeded emulsion polymerization of styrene and VBH protected with acetone. .

Microgel particles have received an increasing interest in the biomedical field. Temperature-sensitive microgels gained particular interest due to their potential use as controlled drug delivery systems. With the objective to produce new thermoresponsive biocompatible microgels, the synthesis and characterization of two families of microgel particles obtained by using N-vinylcaprolactam (VCL) as main monomer and N,N'-methylenbisacrylamide (BA) or poly(ethylene glycol) diacrylate (PEGDA) as crosslinkers are described. Evidence of hydrolysis VCL during polymerization is also presented.

Summary: Magnetic polymeric composite particles (MPCPs) were prepared by mini-emulsion polymerization of styrene in the presence of hydrophobic magneticnanoparticles with hexadecane (HD) as hydrophobe, 2,2 0 -azobisisobutyronitrile(AIBN), and sodium dodecyl sulfate (SDS) as an emulsifier or sodium p-styrenesulfo-nate (NaSS) as an ionic comonomer. The hydrophobic magnetite particles with anaverage of about 10nm were prepared by acidification of the water-based magnetiteferrofluid, previously synthesized by a chemical coprecipitation method. The resultsshow that miniemulsion polymerization is an effective method for encapsulation ofmagnetite into a hydrophobic polymer. Exposed magnetite particles and purepolymer particles can be avoided by selection of appropriate preparation conditions. Keywords: composite polymer particles; encapsulation; magnetic properties; miniemulsionpolymerization Introduction Currently, there is an immense interestin the preparation of magnetic polymericcomposite particles (MPCPs) for theirapplication in biomedical, bioengineering,and biotechnology fields

The hydrolysis process suffered by vinylcaprolactam (VCL) monomer during polymerization and the way of avoiding it is a matter of considerable interest when the final material is used in biomedical applications. In this work, in order to study the hydrolysis process in the synthesis of VCL-based microgels, VCL was polymerized by emulsion polymerization in batch and semi-batch reactors by using N,N′-methylenebisacrylamide (BA) as cross-linker and potassium persulfate (KPS) as initiator. Moreover, the partial conversion evolutions of VCL and BA were analyzed by 1H NMR. The colloidal characterization was carried out by measuring the final average diameters as a function of temperature. The results showed that there were two competitive reactions (hydrolysis and propagation) in the polymerizations carried out in the absence of a buffer. However, VCL did not suffer hydrolysis by adding a buffer in the recipes. A new reliable method for the determination of the partial conversions was developed using the quantitative NMR method. The final cross-linked colloidal particles (microgel particles) obtained in the buffered reaction presented the conventional swelling de-swelling behavior corresponding to temperature sensitive microgels.

Poly(N-vinylcaprolactam) (PVCL) is well known for its thermoresponsive behavior in aqueous solutions. PVCL combines useful and important properties; it is biocompatible polymer with the phase transition in the region of physiological temperature (32–38 °C). This combination of properties allows consideration of PVCL as a material for design biomedical devices and use in drug delivery systems. In this work, PVCL based temperature-sensitive crosslinked particles (microgels) were synthesized in a batch reactor to analyze the effect of the crosslinker, initiator, surfactant, temperature, and VCL concentration on polymerization process and final microgels characteristics. The mean particle diameters at different temperatures and the volume phase-transition temperature of the final product were analyzed. To obtain information about the inner structure of microgel particles, semicontinuous polymerizations were carried out and the evolution of the hydrodynamic average particle diameters at different temperatures of the microgel synthesized was investigated. In the case of microgel particles obtained in a batch reactor the size and the swelling-de-swelling behavior as a function of the temperature of the medium can be tuned by modulating the reaction variables. When the microgel particles were synthesized in a semibatch reactor different swelling-de-swelling behaviors were observed depending on particles inner structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2510–2524, 2008

New microgel particles produced by using N-vinylcaprolactam (VCL) and poly(ethylene glycol) diacrylate (PEGDA) or N,N′-methylenbisacrylamide (BA) were synthesized in a batch reactor. The influence of the concentration and type of crosslinker on polymerization kinetics and colloidal characteristics of such temperature-sensitive particles was studied. The partial and total conversion evolutions of VCL, PEGDA, and BA were determined by quantitative 1H NMR and the average diameters of microgel particles together with the swelling–deswelling behavior were analyzed by means of photon correlation spectroscopy (PCS). Partial and total conversions, final average diameters at collapsed state, and the swelling–deswelling behavior varied as a function of the type of crosslinker. These results were attributed to the higher solubility and stabilizing ability of PEGDA compared with that of BA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2766–2775, 2008

The cationic emulsion polymerization of styrene in a batch reactor using different concentrations of dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethyl-ammonium bromide (HDTAB) as cationic surfactants, and 2,2′-azobisisobutyramidine dihydrochloride (AIBA), and 2,2′-azobis ( N , N ′-dimethyleneisobutyramidine) dihydrochloride (ADIBA) as cationic initiators has been studied. In the preliminary study, the best conditions to obtain stable cationic latexes at high conversions were identified. When the surfactant concentration was above its cmc, latexes with high conversions were achieved for the two cationic surfactants studied (DTAB and HDTAB). Cationic latexes with less coagulum were obtained using ADIBA as cationic initiator due to its superior resistance to hydrolysis. AIBA is hydrolyzed to amide at basic pHs and in this way, the concentration of radicals formed in the aqueous phase decreases. On the other hand, a stronger effect of the particle size on the kinetics of the cationic emulsion polymerization of styrene using HDTAB as cationic surfactant was observed than using DTAB. Furthermore, different kinetic behaviors were observed with the two cationic initiators (ADIBA and AIBA) using HDTAB as cationic surfactant, due to the lower stabilizing effect of the cationic radicals provided by AIBA.

A mathematical model for a semicontinuous seeded cationic emulsion polymerization was developed. The model includes the most distinctive features of the copolymerization of a cationic hydrophilic monomer with a hydrophobic one, including polymerization of the hydrophilic monomer in the outer shell of polymer particles and in the aqueous phase, and the possibility of having radical concentration profiles in the polymer particles. The reactions were carried out by means of a semicontinuous seeded cationic emulsion polymerization under starved conditions for styrene, which was the main monomer employed. The model predicts the evolution of the fractional overall conversions, the thickness of the outer shell, the total surface charge density and the partial conversions for the semicontinuous seeded cationic emulsion polymerization of styrene and aminoethyl methacrylate hydrochloride. Furthermore, the model can distinguish between the surface charge density provided by the cationic monomer than that given by the cationic initiator. Therefore, this model can predict the best conditions to obtain well-defined latexes with specific amounts of surface amino and amidine groups useful for immunoassays.

An in-depth study on the kinetics of the cationic emulsion polymerization of styrene in a batch reactor is presented. This study is focused on the effect of the amount of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), using two different cationic initiators: 2,2′-azobisisobutyramidine dihydrochloride (AIBA), 2,2′-azobis (N,N′-dimethyleneisobutyramidine) dihydrochloride (ADIBA), on kinetics and colloidal features such as conversion, number of particles, number average of radicals per particle, mean particle diameter, and particle size distribution (PSD) of the polystyrene latices obtained by emulsion polymerization in a batch reactor. Furthermore, the results of the cationic emulsion polymerization were compared with its homologous anionic case. Using DTAB as cationic surfactant an expected increase in the total rate of polymerization was observed when the DTAB concentration increased. However, the total number of particles increased much more than in the anionic system. On the other hand, a dependence on the particle size of the rate of polymerization per particle together with the average number of radicals per particle was found. These differences between cationic and anionic emulsion polymerizations were explained taking into account the limited particle coagulation observed with cationic surfactants, and the high rate of radical formation of cationic initiators. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4461–4478, 2006

A water-based magnetite ferrofluid, with an average size of about 10 nm, was prepared in a first step by the chemical coprecipitation of ferrous and ferric salts. Oil-based styrene (St) magnetite ferrofluid was obtained by the acidification of the water-based magnetite ferrofluid and the dispersion of the acidified magnetite in St. Magnetic polymeric composite particles (MPCPs) were prepared by miniemulsion polymerization in the presence of the oil-based St magnetite ferrofluid with hexadecane as a hydrophobe, 2,2′-azobisisobutyronitrile as an initiator, and sodium dodecyl sulfate as an emulsifier. Methacrylic acid was used as a comonomer, and hydroxyethyl cellulose and polyvinylpyrrolidone were used as aid stabilizers subsequently. With the aim of improving the encapsulation degree of magnetite, avoiding pure polymer particles and exposed magnetite particles, and obtaining the narrowest particle size distributions, the encapsulation conditions of magnetite were investigated in detail. The results show that miniemulsion polymerization is an effective method for encapsulating magnetite into a hydrophobic polymer successfully. Exposed magnetite particles and pure polymer particles can be avoided completely by the selection of the appropriate preparation conditions. All the resulting MPCPs exhibited superparamagnetism and possessed some magnetic response. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4187–4203, 2006

The synthesis of new polymer colloids based on renewable resources, such as sugar-derived monomers, is nowadays a matter of interest. These new polymeric particles should be useful in biomedical applications, such as drug delivery, because of their assumed biodegradability. In this work, two new families of polymer latex particles, based on a sugar-derived monomer, 3-O-methacryloyl-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (3-MDG), were produced and characterized. The syntheses of poly(3-MDG) crosslinked particles and those obtained by copolymerization with methacrylic acid (MAA), poly(3-MDG-co-MAA) crosslinked particles, were prepared by surfactant-free emulsion polymerization in a batch reactor. The average particle diameter evolutions, the effect of pH of the dispersion medium on the final average diameters, together with the microscopic and morphological analysis of the particle's surface and inner dominium, were analyzed. Poly(3-MDG-co-EGDMA) stable particles were obtained by adding low amounts of initiator. The surface-charge density of these particles corresponded to the sulfate groups coming from the initiator. In the second family of latices, poly(3-MDG-co-MAA-co-EGDMA) particles, DCP measurements and SEM and TEM observations showed that the sizes and surface characteristics depended on the amounts of MAA and crosslinker used in the reaction mixture. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 443–457, 2006

Monodisperse latex particles with different amounts of surface amino and amidine groups were synthesized by means of a semicontinuous seeded cationic emul- sion polymerization of styrene and a cationic monomer. High partial overall conver- sions for styrene and limited ones for the cationic monomer were achieved. A reliable method for the quantification of surface amidine and amino groups was developed. It was found that the amount of surface amidine groups provided by the cationic initia- tor was higher when the amount of cationic monomer added increased. The value for the partition coefficient of the cationic monomer indicated that this polymerizes with the same probability in the water phase as in the particle. The colloidal stability, in terms of critical coagulation concentration, shows that the latexes would be useful as polymeric supports in immunoassays. V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3878-3886, 2005

The objective of this work was to analyze the effects of the concentration and type of cationic surfactant on the kinetic features (instantaneous and overall conversions) and colloidal characteristics (mean particle diameter, particle size distri- bution (PSD), and surface charge density) in the semicontinuous seeded cationic emul- sion polymerization of styrene. 2,2-Azobis(N,N-dimethyleneisobutyramidine)di- hydrochloride was used as an initiator. The surfactants were dodecyltrimethylammo- nium bromide (DTAB) and hexadecyltrimethylammonium bromide (HDTAB). So that the evolution of some polymeric and colloidal characteristics of the synthesized latices could be followed, the overall and instantaneous conversions were defined and deter- mined gravimetrically. The PSDs and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The surface charge density was determined by conductimetric titration. The evolution of the in- stantaneous conversions, the total number of particles, and the PSDs of the different reactions were related to the nucleation, growth, and coagulation processes taking place in the semicontinuous seeded emulsion polymerizations. The PSDs obtained from the reactions carried out with the emulsifier DTAB, at a concentration equal to its critical micelle concentration (cmc) and at a concentration twice its cmc, presented more and smaller particles than those obtained by the addition of HDTAB to the polymerization recipe. At lower emulsifier concentrations equal to half of the cmc, the system had lower colloidal stability with DTAB. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2322-2334, 2003

New diblock macromonomers were used as reactive emulsifiers in the emulsion polymerization of styrene. The nature of the reactive group, the molecular weight, the length of the poly(ethylene oxide) (PEO) block, and the molecular structure of the macromonomer were systematically investigated during this process by analyzing the evolution of the conversion and particle diameters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2819–2827, 2002

The dispersion polymerization of styrene in an ethanol−water mixture using polystyrene-b-poly(ethylene oxide) macromonomers as stabilizers has been investigated. The influence of parameters such as the nature of the polymerizable group, the hydrophilic/hydrophobic balance, the overall molar mass, and the molecular architecture of the macromonomers on the colloidal dispersion has indeed been studied. Macromonomers of rather low molar mass and exhibiting high critical micellar concentration were best suited to produce stable particles. Latex particles of rather narrow size distribution could be obtained in the range of 300−350 nm with styrenyl or maleate ended PS-b-PEO macromonomers.

The aim of this introductory chapter is to present an overview of the book to potential readers. Its four sections summarize the aim of the Editors when the book was planned: to show that research on soft nanoparticles for biomedical applications is a multidisciplinary field where biology, medicine, pharmacy, chemistry and physics meet. In particular, special attention is paid to future improvements in research on nanoparticles that may come from colloidal science and simulation techniques.

Nanogels are cross-linked colloidal particles, which can swell by absorption (uptake) of large amounts of solvent, but they do not dissolve owing to the structure of the physically or chemically cross-linked polymeric network,. Micro-/nanogels exhibit a behaviour that extend from a polymeric solutions (swollen form) to hard particles (collapsed form). They can respond to physical stimuli (temperature, ionic strength, magnetic or electric fields, etc.), chemical stimuli (pH, ions, specific molecules, etc.) and biochemical stimuli (enzymatic substrates, affinity ligands, etc.). By changing the degree of swelling of the particles, effective nanogel–nanogel and nanogel–drug interactions can be reversibly tuned, giving rise to a wide range of possibilities.

Nanoparticles are attractive for many biomedical applications such as imaging, therapeutics and diagnostics. This new book looks at different soft nanoparticles and their current and potential uses in medicine and health including magnetoliposomes, micro/nanogels, polymeric micelles, DNA particles, dendrimers and bicelles. Each chapter provides a description of the synthesis of the particles and focus on the techniques used to characterize the size, shape, surface charge, internal structure, and surface microstructure of the nanoparticles together with modeling and simulation methods. By giving a strong physical-chemical approach to the topic, readers will gain a good background into the subject and an overview of recent developments. The multidisciplinary point of view makes the book suitable for postgraduate students and researchers in physics, chemistry, and biology interested in soft matter and its uses.