Well-defined Particles Research Articles

Microfluidic fabrication and characterization of Sorafenib-loaded lipid-polymer hybrid nanoparticles for controlled drug delivery.

Lipid polymer hybrid nanoparticles (LPHNPs) have been merged as potential nanocarriers for treatment of cancer. In the present study, LPHNPs loaded with Sorafenib (SFN) were prepared with PLGA, Lecithin and DSPE-PEG 2000 by using the bulk nanoprecipitation and microfluidic (MF) co-flow nanoprecipitation techniques. Herein, a glass capillary microfluidic device was primed to optimize the LPHNPs and compared to the bulk nanoprecipitation method. The morphological analysis of prepared LPHNPs revealed the well-defined spherical nano-sized particles in bulk nanoprecipitation method. Whereas, core shell morphology was observed in the MF method. The formulation prepared by the MF method (MF1-MF3) indicated relatively higher % EE (95.0%, 93.8% and 88.7%) and controlled release of the SFN from the particles as compared to the LPHNPs obtained by the bulk nanoprecipitation method. However, the release of SFN from all LPHNP formulation followed Higuchi model (R2=0.9901-0.9389) with Fickian diffusion mechanism. Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC) and powder X-rays diffraction (pXRD) studies depicted the compatibility of SFN with all the structural components. In addition, the colloidal stability, in vitro cytotoxicity and cell growth inhibition studies of LPHNPs also demonstrated stability in biological media, biocompatibility and safety with enhanced anti-proliferative effects than the free SFN in breast cancer and prostate cancer cells. In conclusion, LPHNPs provided a prospective platform for the cancer chemotherapy and substantially improved the knowledge of fabrication and optimization of the hybrid nanoparticles.

Preparation of low carbon impact lignin nanoparticles with controllable size by using different strategies for particles recovery

Lignin still remains an underutilized plentiful resource whose conversion to high-added value products is a cornerstone towards establishing a viable biomass biorefinery. Bio-materials in the form of nanoparticles represent promising high-value products with numerous downstream applications. The aim of the current work was to develop a method that would allow controlling the size of (birch and spruce) lignin nano- and micro-particles for their subsequent recovery into a solid product. We tested different two-step and one-step isolation processes and demonstrated that particle size could be easily controlled to meet different ranges (<100 nm, <500 nm, and>1 μm). In general, two-step isolation methods, i.e. a step of decrease of solvent concentration followed by isolation of lignin particles, were better for the isolation of well-defined spherical particles. In particular, the rate at which ethanol concentration was decreased played a significant role in determining the size of lignin particles. Moreover, when lignin concentration was increased from 1 % to 5 % and 10 % (w/v), particle size and homogeneity decreased slightly, but productivity augmented. The present study demonstrates that different isolation methods can be applied to obtain renewable, customarily sized, lignin spherical micro- and nano-particles.

Comparison of polymeric particles synthesised using scCO2 as the reaction medium on the millilitre and litre scale

We describe the first steps to scale-up the free radical dispersion polymerization of poly(methyl methacrylate) (PMMA) from the millilitre to the litre scale, utilising supercritical carbon dioxide (scCO2) as the reaction medium. Our key focus is to develop a reproducible and controlled reactor system that produces well-defined polymer particles with narrow size distribution. Two different approaches to monomer addition were investigated, along with variations of surfactant concentration to consistently achieve control of particle size on the large and small scale. Comparison of scanning electron microscopy images from the 60 mL and 1 L vessel demonstrated that very similar particle sizes and morphologies were obtained at high yield (> 90 %) on the small and the large scale. The impact of the differences between the two vessels and their influence on this well understood reaction was investigated.

Polymer Cubosomes: Infinite Cubic Mazes and Possibilities.

Block copolymers (BCPs) have been indispensable building blocks to create a range of soft nanostructures including discrete particulates (micelles and vesicles) and periodic structures via spontaneous assembly in bulk and in solution. The size, shape, and phase of these structures can be controlled by the rational design of the molecular structure of building blocks based on the structural analogy of BCPs to lipids and small molecule surfactants. Inverse bicontinuous cubic mesophases of polymers, or polymer cubosomes when in colloidal forms, are emerging nanostructures composed of triply periodic minimal surfaces (TPMSs) of block copolymer bilayers. Created by spontaneous assembly of BCPs in solution, polymer cubosomes internalize two nonintersecting nanochannel networks arranged in a cubic crystalline order. As well-defined porous particles with highly ordered internal structures and high surface-area-to-volume ratios, polymer cubosomes can be used for chemical reactors or bioreactors, carriers capable of cargo loading and release, and scaffolds for nanotemplating. However, despite their structural similarity to lipid cubosomes and applicability, polymer cubosomes have been only sporadically observed as an outcome of serendipity until recent studies demonstrated that BCPs could form well-defined polymer cubosomes in solution.In this Account, we describe our recent progress in creating polymer cubic mesophases and their colloidal particles (polymer cubosomes) in dilute solution. BCPs with nonlinear architectures (dendritic-linear, branched-linear, and branched-branched BCPs) preferentially self-assembled to inverse mesophases in solution when the block ratio (f), defined as a molecular weight ratio of the hydrophilic block to that of the hydrophobic block, was small (<10%). The resulting lyotropic structures transformed from flat bilayers to cubic phases of primitive cubic and double diamond lattices and finally to inverted hexagonal phases as f decreased. We proposed that the architecture of a BCP plays an important role in the preferential formation of polymer cubosomes in solution. The presence of the bulky hydrophilic block limited chain stretching of the hydrophobic polymer block, which would increase the packing parameter of the BCP to greater than unity, a prerequisite for inverse mesophase formation. The structural characteristics of polymer cubosomes, such as lattice symmetries, pore sizes, and lattice parameters, could also be controlled by fine-tuning the structural parameters of BCPs. We also suggested nonsynthetic methods to precisely control the phase and internal lattice of inverse mesophases of BCPs by the coassembly of two BCPs with different block ratios (mix-and-match approach) and the modulation of the affinity of the common solvent toward the hydrophobic block of the BCP. To investigate the potential applications of polymer cubosomes, we prepared inorganic photonic crystals using a cubosome-templated synthesis. We also discussed the utilization of cubosomes as chemical reactors by functionalization of the surface and the covalent stabilization of transient self-assembled structures via cross-linking of the hydrophobic domain. This Account reflects the efforts of synthetic chemists to understand the self-assembly behavior of BCPs to form complex morphologies in solution. We hope that our Account inspires efforts from chemists and other scientists to further understand these structures with infinite mazes of complexity and possibility.

Size-dependent aggregation of graphene oxide

Graphene oxides (GO) of highly polydisperse size distribution were prepared by the Brodie method and their dispersion stability was characterized. Exfoliation and fractionation led to well-defined particle populations in the Nano, classical Colloidal (submicron) and Micrometer size ranges, as revealed by atomic force microscopy and light scattering measurements. Time-resolved dynamic light scattering experiments revealed that aggregation processes are fully impeded in the intermediate pH regime of 3–13 in the absence of electrolytes. While the resistance against salt-induced aggregation increases with the pH due to the progressive ionization of the surface functional groups of GO sheets, their dispersions are inherently unstable at supramillimolar concentrations of strong acids and submolar concentrations of bases, in line with the DLVO theory. However, the aggregation behavior quantified by the critical coagulation concentrations (CCCs) shows surprisingly substantial platelet size dependence. The CCC of Nano Brodie-GO reaches 360 mm at pH = 12, which is one of the highest values ever reported for GO aqueous dispersions. These results provide useful quantitative information to design processable GO dispersions of pH- and size-tunable stability for future applications.

Structural, Optical, Photoluminescence Studies onto the Incorporation of Copper in Tin Oxide Nanostructure and Evaluation of their Antimicrobial Property

Biosynthesis of undoped and copper doped tin oxide (SnO2) nanoparticles were carried out using Canna indica leaf extracts as reducing agents. The as-synthesized nanoparticles were characterized using the powder X-ray diffraction (PXRD), scanning electron microscope (SEM), Fourier transformed infrared spectroscopy (FTIR), UV-visible spectroscopy and photoluminescence (PL). Antimicrobial behaviour of the synthesized nanoparticles was examined. The XRD studies revealed that the rutile structure for both undoped and copper doped SnO2 nanoparticles, with the absence of secondary phases. The SEM micrographs clearly showed the formation of well-defined spherical particles with no impure phases. The optical absorption studies explained that the variation of band gap with particle size. The photoluminescent spectra showed an emission peaks at 390, 520 and 790 nm, which are ascribed to the structural defects due to the oxygen vacancy. The antibacterial investigation suggested a better antibacterial activity for Staphylococcus aureus against Escherialia coli bacterial strains

Sequence-defined l-glutamamide oligomers with pendant supramolecular motifs via iterative synthesis and orthogonal post-functionalization

One of the great challenges in polymer chemistry is to achieve discrete and sequence-defined synthetic polymers that fold in defined conformations and form well-defined three-dimensional structured particles.

Investigation of UiO-66 as Flame Retardant and Its Application in Improving Fire Safety of Polystyrene

Dense smoke released during the combustion of polystyrene (PS) potentially limits its applications in some fields. In this study, a Zr-based metal-organic framework (UiO-66) was prepared via the solvothermal method and added to PS to suppress its smoke emission. Well-defined UiO-66 particles showed an excellent dispersion state and good compatibility in the PS matrix. The introduction of UiO-66 improved the flame retardancy and smoke suppression of PS. The peak heat-release rate and total heat release were reduced by 26.8% and 14.7%, respectively, for PS/ UiO-66-5 wt%. Moreover, the smoke emissions of PS composites were evidently suppressed, and more than a 35% reduction in total smoke production was obtained with 5-wt% UiO-66. Through the analysis of the residues and pyrolysis products of PS composites, the mechanisms of enhanced flame retardancy and smoke suppression can being speculated as the promoted char-forming and heat barrier of UiO-66. This work offers a significant reference for the further study of UiO-66 and polymer materials.

Investigation of hydrated smectite microstructure through wet environmental transmission electron microscopy

Water is an essential constituent of all biological materials as well as many non-biological materials. Not only the removal of water may result in undesirable morphological and structure change, the inability to sustain the hydrated conditions in the microscope also prevents the study of reactions which take place in aqueous environment. In order to overcome these problems we used wet environmental-cell transmission electron microscopy TEM (WETEM). Conventional TEM of dry smectite showed well-defined particle outlines (but without a specific shape) and typical smectite aggregates. Selected area electron diffraction (SAD) of dry particles showed stacking of smectite particles (i.e., aggregate) in very clear dot and ring patterns. In contrast, WETEM depicted well-dispersed clay particles showing a variety of different particle shapes. Analysis of SAD patterns obtained from dry and hydrated states illustrated a lattice change in different environments. The small lattice expansion in (h k 0) resulted from the expansion of the (0 0 l) plane resulting from the addition of water molecules in the crystal along the c-axis.

Particle shape matters – Using 3D printed particles to investigate fundamental particle and packing properties

Whereas particle size and its importance is often stressed, the shape of particulate materials is often not considered in detail even though there is plenty of evidence that it is crucial for operations like transport, mixing, and fluidisation. In this study, we experimentally determine the influence of particle shape on fundamental bulk characteristics of process-engineering interest. Well-defined particles of seven different shapes but equal volume are used which are manufactured by selective laser sintering and their morphology is characterized by 2D image analysis. It is found that particles differ strongly in their packing and piling properties. These findings are exemplarily compared with performed DEM simulations where, using the same model parameters, no simple plug-and-play prediction to different shapes is possible. Thus, the current study closes the gap between ever more advanced simulation methods, considering also non-spherical particles, and the often oversimplified or undefined particle shapes encountered in experimental studies.

Visible light photocatalytic activity of Mn-doped BiFeO3 nanoparticles

ABSTRACTThe discharges of effluents from the Textile industries contain bleaching and dyeing chemicals which are very harmful to the environment. Thus, managing textile effluents to make zero discharge of the above chemicals using renewable energy is the need of the hour. Here we report photocatalytic degradation of Acid Red-85, textile dye in visible light by energy bandgap optimized magnetic nanoparticles. The BiFe1-xMnxO3 (x = 0, 0.025, 0.05, 0.075 & 0.1) nanoparticles were synthesized by citrate gel auto-ignition method. The synthesized compounds show well-defined crystalline particles with decrease of crystallite size from 57 to 20 nm with increase of Mn2+ concentration. All samples show well-separated particle morphology with decrease of average particle size with increase of manganese concentration. Optical absorption studies reveal that the energy band-gap of sample decreases from 2.2 to 1.97 eV with increase of Mn ions in BiFeO3 lattice. The coercive field (Hc) and remnant magnetization (Mr) enhance up to 5% of manganese content and then reduces with further increase of dopant concentration due to hindrance of magnetic exchange in Mn-O-Fe network. Manganese doping helps in increasing the degradation efficiency of BiFeO3 nanoparticles and the rate constant (K) increases from 2.6 × 10−2 to 6.84 × 10−2 min−1respectively. It is attributed to long charge separation time in doped samples which is confirmed by photoluminescence spectrum. Mn-doped BiFeO3 has an edge over the widely studied TiO2 and ZnO because of its absorbance in visible light spectrum and its ability to be magnetically removed after treatment.

Biosynthesis of silver nanoparticles using leaf extract of Aesculus hippocastanum (horse chestnut): Evaluation of their antibacterial, antioxidant and drug release system activities.

Biosynthesis of metal nanoparticles is expected as a cost efficient and ecofriendly option in the research study. Therefore, the aqueous extracts made from leaf of Aesculus hippocastanum (horse chestnut) were used as the reducing factors to synthesize silver nanoparticles (AgNPs) and their antioxidant, antibacterial and the application of resveratrol combined AgNPs as efficient delivery vehicles have also been evaluated. The biosynthesized AgNPs were characterized by UV-Visible Spectroscopy, Fourier-Transform Infrared Spectroscopy (FTIR), X Ray Diffraction (XRD), Zeta potential, and Scanning Electron Microscopy (SEM). The AgNPs were found to be stable at -29.1 mV through zeta potential study. According to the UV-Vis measurements, AgNP formation was observed at a wavelength range of 420-470 nm. The Ag NPs were spherical with a size of 50 ± 5 nm. AgNPs exhibited strong antibacterial activity against all tested bacterial species but have no effect against fungal strains. AgNPs showed an important inhibitive activity counter the DPPH radical and thereby indicate a source for antioxidants. The free radical scavenging activity of AgNP was calculated as 54.72% at the highest concentration (100 ppm). The superoxide radical scavenging activity of AgNPs was found to be increased with increasing concentrations and the average inhibition was about 62.9% as compared to the activity of plant extract. In vitro investigations on the drug delivery from AgNPs exhibited pH dependency; the release was significant (45.6%) below acidic terms (pH 5.2) when in proportion to physiological terms (pH7.4). It was observed that the resveratrol-combined to AgNPs stays on the nanoparticle surface for a lengthy time in the plasma at physiological pH (7.4), so very reducing the flank influence on the normal tissues. It can be concluded that horse chestnut leaves has reduction potential as well as being a capping agent to produce well-defined nanoscale silver particles. Our biosynthesized Ag NPs can be used antibacterial, antioxidant agent and also for as effective delivery vehicles in the near future.

Role of particle size on the multicycle calcium looping activity of limestone for thermochemical energy storage

The calcium looping process, based on the reversible reaction between CaCO3 and CaO, is recently attracting a great deal of interest as a promising thermochemical energy storage system to be integrated in Concentrated Solar Power plants (CaL-CSP). The main drawbacks of the system are the incomplete conversion of CaO and its sintering-induced deactivation. In this work, the influence of particle size in these deactivation mechanisms has been assessed by performing experimental multicycle tests using standard limestone particles of well-defined and narrow particle size distributions. The results indicate that CaO multicycle conversion benefits from the use of small particles mainly when the calcination is carried out in helium at low temperature. Yet, the enhancement is only significant for particles below 15 μm. On the other hand, the strong sintering induced by calcining in CO2 at high temperatures makes particle size much less relevant for the multicycle performance. Finally, SEM imaging reveals that the mechanism responsible for the loss of activity is mainly pore-plugging when calcination is performed in helium, whereas extensive loss of surface area due to sintering is responsible for the deactivation when calcination is carried out in CO2 at high temperature.

A novel energy-efficient kapok filter paper with high DHC for solid-oil mixed aerosol: Performance and loading behavior evolution mechanism

Although typical high efficiency filter media for gas turbine exhibit short lifespan under harsh conditions with excessive oily aerosol, rare literatures are available concerning fundamental reason or introducing filter media for addressing aforementioned conditions. Herein, we developed a novel kapok filter paper with high energy-efficiency and dust holding capacity (DHC) against solid-oil mixed aerosol. Loading behavior of filter media was characterized in terms of both macroscopic loading behavior (pressure drop and DHC evolution over oil content) and micro-scale particle deposition behavior. Owing to hollow lumen and waxy surface of kapok fiber, the novel filter paper was fluffy and oleophilic, which made it outperform typical commercial filter media (F01 and F02) in energy saving and DHC. Under harshest conditions where F01 and F02 manifested low DHC of 8.0 g/m2, 13.3 g/m2 and 29.1 g/m2, 34.7 g/m2 at the oil content of 50%, 75%, respectively, the kapok filter paper owned notably excellent DHC of 160.5 g/m2, 240.8 g/m2, respectively. Moreover, it was revealed that loading behavior evolution (resulted from the increase of oil content) was subject to deposition behavior. Once oil content was above 25%, pressure drop profiles transitioned from that of solid particles loading to that of liquid particles loading. Depositions structure varied from well-defined particles to particles-in-oil with films covered. Due to formation of a porous structure, a critical maximum DHC occurred for mixed aerosol with 25% oil content. Finally, a particle deposition mechanism was proposed, for the first time, to explain the loading behavior evolution over oil content.

Preparation of NH2-Functionalized Fe2O3 and Its Chitosan Composites for the Removal of Heavy Metal Ions

NH2-Fe2O3 and NH2-Fe2O3/chitosan (NH2-Fe2O3/CS) with excellent physical properties and high adsorption capacities for several heavy metal ions were synthesized using a one-pot hydrothermal method. The materials were characterized by scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Physicochemical properties were determined by the Fourier transform infrared spectra (FTIR) and nitrogen adsorption analysis (Brunauer–Emmett–Teller (BET) method). The results of the characterization studies show that the material is uniformly dispersed and has good crystallinity and well-defined porous particles. The material is mesoporous, and the particles have a specific surface area of 55.41–233.03 m2·g−1, a total pore volume of 0.24–0.54 cm3·g−1, and a diameter of 3.83–17.56 nm. Additional results demonstrate that NH2-Fe2O3 and NH2-Fe2O3/CS are effective adsorbents for the removal of heavy metal ions from solution. In a ternary system, the order of their selective adsorption was determined to be Pb(II) &gt; Cu(II) &gt; Cd(II), and the adsorption rate of Pb(II) was much higher than that of Cu(II) and Cd (II). The metal ion adsorption capacity of NH2-Fe2O3 and NH2-Fe2O3/CS makes them promising adsorbents for wastewater cleanup.

Synthesis of Homogeneous Distributed Nanoparticles Using a Fluidized Bed Reactor

The proton exchange membrane fuel cell (PEMFC) has drawn attention as a promising alternative to fossil fuel-based combustion engines. The requirements for next-level PEMFC electrocatalysts are severe: high mass activity accompanied by high performance stability for low loaded Pt-based electrodes.[1] This results in a challenging target for the catalyst design on the cathode site. Further reduction of the Pt loading is limited due to additional voltage losses originating from O2 mass transport resistances.[2] The objective of future catalyst design thus needs to include well-ordered Pt distribution and improved Pt particle-ionomer interaction. Orfanidi et al. showed that a more homogeneous ionomer coverage over the entire catalysts’ surface could be achieved when its carbon surface is enriched with N-functionalities, which was deduced to the ionic interaction between negatively charged ionomer groups (-SO3H) and positively charged surface groups of the modified carbon (-NHx).[3] In prior work, we showed an enhanced stability for a Pt nanoparticle catalyst based on N-modified carbon with respect to unmodified carbon.[4] However, the furnace-based Pt deposition used in that work can be further improved to yield a better Pt nanoparticle distribution. In the present study, the carbons were functionalized by introducing N-functionalities to pre-oxidized carbons via ammonolysis at elevated temperatures in pure NH3 atmosphere. Afterwards, we performed the Pt deposition in a homemade fluidized bed reactor, where the N-modified carbons were first impregnated with hexachloroplatinic acid and in a second step reduced in hydrogen atmosphere. The fluidized bed reactor enables a homogenous reduction of the metal precursor, which results in a more well-defined and narrow particle size distribution of the Pt nanoparticles. The synthesized catalysts were investigated as cathode material for the application in fuel cell devices in an accelerated stress test mimicking fuel cell operating conditions. Based on rotating disk electrode experiments reasonable mass activities and high electrochemical stabilities were found. The catalyst based on N-modified carbon showed enhanced electrochemical stability compared to a catalyst based on an unmodified carbon. Complementary in situ X-ray measurements revealed the morphologic stability of the Pt nanoparticles. Therefore, the applied chemical tailoring of carbon supports indicates a strategy toward an improved stability for PEMFC applications.

Shape Characterization of Subvisible Particles Using Dynamic Imaging Analysis.

Protein aggregates and subvisible particles (SbvP), inherently present in all marketed protein drug products, have received increasing attention by health authorities. Dynamic imaging analysis was introduced to visualize SbvP and facilitate understanding of their origin. The educational United States Pharmacopeia chapter <1787> emphasizes that dynamic imaging analysis could be used for morphology measurements in the size range of 4-100 μm. However, adequate morphology characterization, as suggested in the United States Pharmacopeia <1787> proposed size range, remains challenging as nonspherical size standards are not commercially available. In this study, a homogenous and well-defined nonspherical particle standard was fabricated and used to investigate the capabilities of 2 dynamic imaging analysis systems (microflow imaging (MFI) and FlowCAM) to characterize SbvP shape in the size range of 2-10 μm. The actual aspect ratio of the SbvP was measured by scanning electron microscopy and compared to the results obtained by dynamic imaging analysis. The test procedure was used to assess the accuracy in determining the shape characteristics of the nonspherical particles. In general, dynamic imaging analysis showed decreasing accuracy in morphology characterization for 5 μm and 2 μm particles. The test procedure was also capable to compare and evaluate differences between the 2 dynamic imaging methods. The present study should help to define ranges of operation for dynamic imaging analysis systems.

Delaying Dementia: Targeted Brain Delivery Using Lipid Cubic Phases

Microvascular endothelial dysfunction precedes, often by decades, the cognitive decline associated with Alzheimer's disease. Hence, preservation of a healthy cerebrovascular endothelium can be an important therapeutic target. By incorporating appropriate drug(s) into biomimetic (lipid cubic phase) nanocarriers, one obtains a multitasking combination therapeutic which targets certain cell-surface scavenger receptors, mainly class B type I (i.e., SR-BI), and crosses the blood-brain barrier. Documented similarities in lipid composition – among high-density lipoproteins (HDL) and the biomimetic (nanoemulsion) nanocarrier particles – can partially simulate or mimic the known heterogeneity (i.e., subpopulations or subspecies) of HDL particles. Such colloidal-nanocarrier targeting allows for various Alzheimer's-related cell types to be simultaneously searched in a holistic integrative approach, in vivo, for localized drug treatment. Using various biobased lipids and their mixtures to form self-assembled non-lamellar nanostructures, it has continually been reported possible to successfully obtain stable colloidal dispersions of (liquid-crystalline) lipid cubic phases with well-defined particle size and morphology. In particular, monoglyceride-based lyotropic liquid-crystalline phases are relatively unique owing to their rich polymorphism in water and potential application as drug nanocarriers. This (colloidal-nanocarrier) in vivo targeting advantage may be particularly important when delivering pleiotropic natural substances (e.g., an isoflavone) or for repurposing an FDA-approved drug.

Structural Difference in Macro-RAFT Agents Redirects Polymerization-Induced Self-Assembly.

Polymerization-induced self-assembly (PISA) has served as a versatile platform for the large-scale preparation of well-defined block copolymer nano-objects. It appears to be "common sense" that block copolymers with narrow molecular weight distributions are inevitable. In this study, we have conducted the direct comparison of reversible addition-fragmentation transfer (RAFT)-mediated PISA of 2-hydroxypropyl methacrylate (HPMA) using polymethacrylate- and polyacrylate-based macro-RAFT agents. Taking advantage of the poor RAFT controllability of polyacrylate-based macro-RAFT agents with respect to HPMA, uniform submicron-sized polymeric microspheres were prepared by photoinitiated RAFT-mediated PISA of HPMA. The diameter of polymeric microspheres can be precisely controlled by further chain-extension of PHPMA. Finally, uniform epoxy-functionalized multicompartment block copolymer particles (MBCPs) were prepared by a two-step photoinitiated RAFT-mediated PISA with poly(glycidyl methacrylate) (PGlyMA) as the third block. The performance of MBCPs as Pickering emulsifiers was evaluated in detail. This study not only expands the scope of RAFT-mediated PISA for preparing well-defined polymer particles but also provides important insights into the mechanism of RAFT-mediated PISA.

Synthesis of chitosan, pectin, and chitosan/pectin microspheres by two water-in-oil emulsion crosslinking methods

Structuration of biopolymers to provide a smart response in biological systems is of great interest considering potential applications in agriculture, pharmaceutics, and food industry. Namely, chitosan, pectin, and chitosan/pectin particles were obtained by one-step water-in-oil emulsion and water-in-oil emulsion-dehydration by crosslinking methodologies using glutaraldehyde and calcium chloride, correspondingly. Through our methodologies it was possible to obtain well-defined spherical particles with average sizes below two micrometers. In general, glutaraldehyde-crosslinked particles were larger than ionic crosslinked ones. The particle size and morphology of the materials were characterized by Dynamic Light Scattering and Scanning Electron Microscopy and the covalent and ionic interactions were determined by Infrared Spectroscopy. In most cases, we improved the size and/or morphology of the particles compared to base methodologies, as well contributed with its surface potential info and the chemical characterization of the systems. Overall, we obtained the structuring of spheres with potential for biological applications, according to its morphology, size, and superficial charge.