Polymer Shell Research Articles

The Influence of the Specifics of the Formation of the Polymer Shell of a Microcapsule with a Nitrogen-Containing Compound Core on the Durability of the Tool During Blade Cutting

The Influence of the Specifics of the Formation of the Polymer Shell of a Microcapsule with a Nitrogen-Containing Compound Core on the Durability of the Tool During Blade Cutting

Formulation and evaluation of dabigatran loaded microballoons for prolonged drug release

The objective of the present investigation was to formulate microballoons loaded with dabigatran in the polymeric core for achieving sustained release and hence improved bioavailability. Microballoons loaded with dabigatran in the polymer shell were prepared by simple solvent evaporation method using either ethyl cellulose alone or a blend of ethyl cellulose with HPMC/PVP-K30/Eudragit S100/Methyl cellulose in a fixed ratio. The percent yield of the microballoons ranged from 38.7 to 62.4% with highest yield obtained in F3. The particle size was measured using optical microscopy and the particles were observed to be spherical in shape. The particle size ranged from 28.50 ± 16.378 µm (F3) to 48.14 ± 16.748 µm (F1). The angle of repose ranged from 26.37° to 28.09° and the Carr’s index and Hausner’s ratio were in between 6.38 to 19.95 and 1.07 to 1.25 respectively. It was found that all the formulations exhibited buoyancy in the range of 61.42 to 71.71% over a period of 8h. This suggests that the formulations were able to float for sufficient time and would be able to control the release of dabigatran for longer duration. The in vitro drug release study depicted that the highest amount of drug was released from F3 (66.79%) while the lowest was released from F1 (50.27%) at the end of 8 hours of study.

Preparation of PAN@PU coaxial electrostatic spun nanofibers for oil/water separation

AbstractCoaxial electrostatic spinning (co‐electrostatic spinning) technology has greatly expanded the versatility of the preparation of core–shell polymer nanofibers and has found a wide range of applications in the environmental and biological fields. Here we present a method for the preparation of coaxial nanofibers using polyacrylonitrile (PAN) and polyurethane (PU) as raw materials. It was found that the tensile strength ranges from 2.14 to 4.07 MPa with the increasing spinning speed of the nucleated PU layer, and the elongation at break was up to 95.09% for M6:4, which was three times higher than that of the original MPAN (30.54%), and the toughness of the nanofiber film was also significantly improved. Finally, the oil/water separation capacity of the coaxial nanofiber membrane was investigated, and the results showed that the separation fluxes for various oil compounds ranged from 2380.18 to 3130.17 L·m−2·h−1, with separation efficiencies above 99%. This study not only investigates the effect of different flow rates of core (PU)/shell (PAN) on the performance of coaxial electrostatic spun nanofiber membranes, but also provides a new insight into the coaxial electrostatic spinning process.

Dual pH- and temperature-responsive poly(dimethylaminoethyl methacrylate)-coated mesoporous silica nanoparticles as a smart drug delivery system

A robust drug delivery system was created by grafting poly(dimethylaminoethyl methacrylate) (PDMAEMA) onto silica nanoparticles with two different lengths using an in situ atom transfer radical polymerization, resulting in the formation of a pH- and temperature-sensitive shell. The high molecular weight PDMAEMA demonstrated effective controlled drug release, and prevented drug release in healthy cells. Drug release occurred through polymer shell protonation at pH 5. The critical temperature of 41 °C facilitated rapid solvation of the shell polymers in the blood, preventing tissue accumulation and reducing toxicity compared to systems with lower critical solution temperatures. Field-emission scanning electron microscopy analysis and nitrogen adsorption/desorption analysis showed that the nanoparticles have a fine network, mesoporous structure, and a mean size of around 17 nm that show their excellent capacity for loading drugs. Fourier-transform infrared spectroscopy showed that all the modification steps and polymerization were successfully implemented. Thermogravimetric analysis showed PDMAEMA chains with two different lengths grafted onto the nanoparticles. Transmission electron microscopy analysis also showed grafted polymer chains on the hybrid nanoparticles. The release profile of model cancer drugs (doxorubicin and methotrexate) varied with pH and temperature, with high molecular weight PDMAEMA shells effectively preventing drug release at neutral pH. In vitro analysis using the HeLa cell line showed minimal toxicity in blank samples and significant release profile in acidic environment.

A novel spherical micro-absorber for dehumidification systems

In this work, a novel design concept for absorbers used in dehumidification systems is proposed to overcome the practical challenges of the conventional packed-column absorbers. In the proposed design, spherical micro-absorbers (microcapsules) that contain a liquid LiBr desiccant inside a semi-permeable polymeric membrane shell are produced by using a custom-built microfluidic technique. The produced microcapsules are capable of containing the salt during crystallization. The X-ray diffraction analysis has confirmed that the observed crystals in the microscopes images were indeed for the encapsulated (LiBr) salt. Due to the indirect contact between the liquid desiccant and the process air, problems such as solution carryover and corrosion associated with packed-column absorbers can be eliminated. The collected sorption data show that the spherical microcapsules offer a high sorption capacity of 1 gw/gdry under 80% relative humidity. The proposed microcapsules offer surface-to-volume ratios between 6,000–12,000 m2/m3, which is up to two orders of magnitude higher than the conventional packed-column absorbers (200–600 m2/m3). The produced micro-absorbers can withstand a compression force up to 2 × 105 their weight, elastically expanded during the absorption process without rupture, and did not show a leakage or a reduction in capacity even after an accelerated test of 200 sorption-desorption cycles.

Fabrication of core–shell beads, hollow capsules, and AuNP-embedded catalytic beads from an ultrasmall peptide hydrogel

Hydrogel beads have emerged as a new class of soft materials that infuse the noble properties of macro-dimensional hydrogels in tiny, easily operable, and robust droplets. Usually, polymeric hydrogels are used in the production of hydrogel beads due to their high structural rigidity and durability, and low molecular weight hydrogel beads are relatively uncommon. Herein, we employed an ultra-short peptide (Pyrene-Lys-Cys, PyKC) based low molecular weight injectable hydrogel, that remains insoluble in bulk solvents, to create stable hydrogel beads using a simple extrusion technique. To enhance durability and applicability, the beads are coated with a polymeric shell, resulting in a core–shell configuration. The shell of the core–shell beads can be modified through a variety of organic conjugation reactions. Also, the core (hydrogel) can be sacrificed using DMSO, resulting in the formation of hollow organic capsules. Furthermore, the core–shell beads enabled the in-situ synthesis and stabilization of gold nanoparticles on the bead surface. The gold-loaded beads demonstrated remarkable catalytic efficiency in the reduction of p-nitrophenol and hazardous azo dyes. In a nutshell, the extremely modular and customizable nature of the PyKC-based core–shell hydrogel bead may allow it to function as a unified platform for multifaceted applications.

ISX9 loaded thermoresponsive nanoparticles for hair follicle regrowth

There is a high demand for an optimal drug delivery system to treat androgenetic alopecia. Topical application of ISX9, which is a neurogenesis inducer, has been found to stimulate hair follicle (HF) regrowth by upregulating the Wnt/β-catenin signaling pathway, an essential pathway involved in initiating HF growth and development. In the present study, a temperature-sensitive, biopolymer-based, biocompatible, and eco-friendly drug-delivery system was synthesized. This system comprised chitosan-grafted poly(glycidyl methacrylate-co-N-isopropyl acrylamide) (Poly(GMA-co-NIPAAm)@CS-PGNCS) as the shell component and PF127 as the core polymer. The hydrophobic nature of the PF127 block copolymer efficiently dissolved the partially water-soluble drug, ISX9, and the thermos-responsive shell polymer effectively released the drug at a definite skin temperature. The optimized spherical nanoparticles demonstrated the lowest critical solution temperature (LCST) at 32 ± 2 °C with a diameter of 100–250 nm, which delivered encapsulated ISX9 with greater precision than topical ISX9. In a series of in vivo experiments, we demonstrated that ISX9-coated TBNPs upregulated the expression of β-catenin, active β-catenin, Wnt target genes, stemness marker genes, proliferating cell nuclear antigen, HF stem cell markers, and HF markers including VEGF, TGF, and IGF-1 more effectively than topical ISX9. These results suggest that TBNPs could be employed as a platform for effective transdermal delivery of various hydrophobic drugs.

The Influence of the Specifics of the Formation of the Polymer Shell of a Microcapsule with a Nitrogen-Containing Compound Core on the Durability of the Tool During Blade Cutting

Microcapsules with gelatin shells are obtained by coacervation. In the process of microcapsulation,the shells of microcapsules are treated with ozone and ozonated water is introduced into their core. Magneticsensitivity was imparted to microcapsules by introducing magnetite in their shell. The influence of the compositionand concentration of microcapsules in an aqueous emulsion on the durability of the tool during bladecutting is studied. It is shown that the lubricating and cooling technological means obtained by introducingozonated water into the core of a gelatin microcapsule is more effective for increasing the tool’s durabilityduring blade cutting.

Polymer Mechanochemistry in Microbubbles.

Polymer mechanochemistry is a promising technology to convert mechanical energy into chemical functionality by breaking covalent and supramolecular bonds site-selectively. Yet, the mechanochemical reaction rates of covalent bonds in typically used ultrasonication setups lead to reasonable conversions only after comparably long sonication times. This can be accelerated by either increasing the reactivity of the mechanoresponsive moiety or by modifying the encompassing polymer topology. Here, a microbubble system with a tailored polymer shell consisting of an N2 gas core and a mechanoresponsive disulfide-containing polymer network is presented. It is found that the mechanochemical activation of the disulfides is greatly accelerated using these microbubbles compared to commensurate solid core particles or capsules filled with liquid. Aided by computational simulations, it is found that low shell thickness, low shell stiffness and crosslink density, and a size-dependent eigenfrequency close to the used ultrasound frequency maximize the mechanochemical yield over the course of the sonication process.

Development of a nature-inspired polymeric fiber (BioFiber) for advanced delivery of self-healing agents into concrete

In this study, we developed nature-inspired multi-functional polymeric fibers (called BioFiber) to deliver bio-self-healing agents into cementitious materials. BioFibers were manufactured using a load-bearing core-fiber, a sheath of endospore-laden hydrogel, and an outer damage-responsive polymeric shell layer. The innovative BioFiber integrates three key functionalities into the quasi-brittle matrix: (i) autonomous bio-self-healing, (ii) crack growth control, and (iii) damage-responsiveness. The hydrogel sheath contained endospores, as bio-agents, to establish microbially-induced calcium carbonate precipitation (MICCP) as a self-healing end-product. The core-fibers provided crack growth control functionality into quasi-brittle engineering materials. Additionally, the outer shell coating integrated a robust damage-responsive self-healing activation strategy in concrete. A comprehensive parametric study was conducted to explore material options and the influential parameters for tailoring the processing-compositions-structure properties of the developed BioFiber. The findings of this study revealed that a concentration of 8 w/v sodium-alginate crosslinked with calcium acetate provided higher solution uptake capacity required for MICCP. As for the shell, the polymer blend of polystyrene and polylactic acid (1:1 wt%), with polymer/solvent ratio of 18 w/v-single layer coating, effectively protected BioFibers during simulated concrete casting process. Lastly, each BioFiber was able to produce 40–80 mg of calcium carbonate within the first 30 h of activation.

Controlling the protein corona of polymeric nanocapsules: effect of polymer shell on protein adsorption.

Understanding the interactions between nanocarriers and plasma proteins is essential for controlling their biological fate. Based on the reported potential of polymeric nanocapsules (NCs) for the targeted delivery of oncological drugs, the main objective of this work has been to investigate how the surface chemical composition influences their protein corona fingerprint. Thus, we developed six NC prototypes with different polymer shells and physicochemical properties and quantified the amount of protein adsorbed upon incubation in human plasma. Using sequential window acquisition of all theoretical mass spectra (SWATH-MS) and following the Minimum Information about Nanomaterial Biocorona Experiments (MINBE) guidelines, we identified different protein corona patterns. As expected, the presence of polyethylene glycol (PEG) in the polymer shell reduced the protein corona, particularly the adsorption of immunoglobulins. However, by comparing the different prototypes, we concluded that the protein adsorption pattern was not exclusively driven by PEG. In fact, a highly PEGylated prototype exhibited intense apolipoprotein IV adsorption. On the other hand, we also observed that polymeric NCs containing 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) exhibited high adsorption of vitronectin, a protein that is known for enhancing the uptake of nanosystems by lung epithelium and several cancer cells. Overall, the gathered information allowed us to identify promising polymeric NCs with an expected prolonged circulation time, enhanced tumor targeting, liver accumulation, and preferential uptake by the immune system. In this sense, the analyses of the protein corona performed along this work will hopefully contribute to advancing a new generation of rationally designed nanometric drug delivery systems.

Fabrication of glucose-immobilizing fluorescent polymer particles with high magnetic responsiveness

Glycan-immobilizing particles are useful for a wide variety of biomedical applications, such as the detection, separation, and purification of proteins, viruses, and bacteria, which can be specifically bound by the glycan moieties. One strategy for the quick and accurate detection of these components is to collect the particles magnetically after binding the components to the particle surface. We fabricated core–shell particles composed of a magnetic core and a thin polymer shell. The shell was incorporated with a fluorescent dye with glucose molecules immobilized on its surface. As the magnetic core, we selected Fe3O4 particles. Taking into consideration its low environmental impact, we adopted soap-free emulsion polymerization to form the polymer shell. Thus, methyl methacrylate was polymerized in the presence of Fe3O4 particles, octyl-β-d-glucopyranoside, and rhodamine B to generate a glucose-capped fluorescent PMMA thin shell on the Fe3O4 particles. The resulting particles exhibited a saturation magnetization of ∼53 emu/g. The novelty of this research is that glucose-immobilized polymer particles with excellent magnetic properties that can be collected in 5 s using a magnet can be synthesized with an environmentally friendly method.

Polyurethane/n-Octadecane Phase-Change Microcapsules via Emulsion Interfacial Polymerization: The Effect of Paraffin Loading on Capsule Shell Formation and Latent Heat Storage Properties.

Organic phase-change materials (PCMs) hold promise in developing advanced thermoregulation and responsive energy systems owing to their high latent heat capacity and thermal reliability. However, organic PCMs are prone to leakages in the liquid state and, thus, are hardly applicable in their pristine form. Herein, we encapsulated organic PCM n-Octadecane into polyurethane capsules via polymerization of commercially available polymethylene polyphenylene isocyanate and polyethylene glycol at the interface oil-in-water emulsion and studied how various n-Octadecane feeding affected the shell formation, capsule structure, and latent heat storage properties. The successful shell polymerization and encapsulation of n-Octadecane dissolved in the oil core was verified by confocal microscopy and Fourier-transform infrared spectroscopy. The mean capsule size varied from 9.4 to 16.7 µm while the shell was found to reduce in thickness from 460 to 220 nm as the n-Octadecane feeding increased. Conversely, the latent heat storage capacity increased from 50 to 132 J/g corresponding to the growth in actual n-Octadecane content from 25% to 67% as revealed by differential scanning calorimetry. The actual n-Octadecane content increased non-linearly along with the n-Octadecane feeding and reached a plateau at 66-67% corresponded to 3.44-3.69 core-to-monomer ratio. Finally, the capsules with the reasonable combination of structural and thermal properties were evaluated as a thermoregulating additive to a commercially available paint.

Nanocomposite colloids prepared by the Ouzo effect

HypothesisThe organization of nanoparticles within nanocomposite colloids can imbue added functionality to these suprastructures. We hypothesize that the arrangement of nanoparticles in nanocomposite colloids can be systematically controlled by inducing co-precipitation of oil and a hydrophilic polymer in the presence of nanoparticles with a range of wetting properties. This process will produce oil core/polymer shell nanocapsules with nanoparticles strategically positioned within the suprastructures. ExperimentsCoprecipitation of oil and polymer in the presence of nanoparticles is performed in glass capillary microfluidics. Silica nanoparticles of varying surface properties and morphology are used to investigate the relationship between nanoparticle wetting properties and nanocolloid morphology. The features of the nanocomposites formed are investigated using electron microscopy, sessile drop, and zeta potential measurements. FindingsWhen spherical nanoparticles with wetting properties ranging from hydrophilic to hydrophobic are used, the nanocomposite morphologies formed range from nanoparticles partially engulfed in the polymer shell to nanoparticles embedded in the oil core of the nanocapsule. The number of nanoparticles introduced in the nanocomposite is adjusted by changing their concentration in the precursor solution. The structure of nanocolloids formed with non-spherical or hollow silica nanoparticles depends on their wetting properties.

Reduction of interfacial polycondensation self-limitation through solvent swelling to dynamically modulate shell thickness and structure of microcapsules

The thickness and structure of microcapsule shell is the most important factor affecting essential performance of microcapsule. The growth of microcapsule shell prepared by interfacial polycondensation is self-limited which produces thin microcapsule shells with low mechanical strength. In this study, solvent dynamic swelling is employed to overcome the self-limitation of microcapsule shell prepared by interfacial polycondensation. It was found that the solvent dynamic swelling can enhance polyurethane shell and epoxy shell growth, and so that different shell structures could be regulated and the thickness of the shell could be increased. Finally, capsaicin microcapsules were prepared using epoxy resin as microcapsule shell, and capsaicin microcapsules with different core-shell structures were obtained by solvent regulation. The embedded microcapsule structure had lower release rate. The general effect of solvent evaporation and swelling on the interfacial polymerized microcapsule shell was explained, which provided a new paradigm for interfacial polymerized microcapsule shell structure regulation, especially the regulation of shell thickness.

Brownian Relaxation Shakes and Breaks Magnetic Iron Oxide-Polymer Nanocomposites to Release Cargo.

Magnetic nanoparticles (NPs) are widely employed for remote controlled molecular release applications using alternating magnetic fields (AMF). Yet, they intrinsically generate heat in the process by Néel relaxation limiting their application scope. In contrast, iron oxide NPs larger than ≈15nm react to AMF by Brownian relaxation resulting in tumbling and shaking. Here, such iron oxide NPs are combined with polymer shells where the shaking motion mechanically agitates and partially detaches the polymer chains, covalently cleaves a fraction of the polymers, and releases the prototypical cargo molecules doxorubicin and curcumin into solution. This heat-free release mechanism broadens the potential application space of polymer-functionalized magnetic NP composites.

Membrane fouling monitoring by 3ω sensing

Membrane fouling significantly reduces membrane permeability, leading to higher operational expenses. In situ monitoring of membrane fouling can potentially be used to reduce operation cost by optimizing operational parameters and cleaning conditions. In this study, a platinum wire with a diameter of 20 µm was attached to the surface of a ceramic ultrafiltration membrane, and by measuring the voltage across the wire while applying an AC current, the amplitude of the third harmonic wave, the so-called 3ω signal, was obtained. Results showed increasing 3ω signals during formation of fouling layers, which correlates directly to the hydraulic resistance of the formed fouling layer in semi-dead end filtration of polymeric core shell particles and crossflow filtration of diluted milk. This is explained by the insulating effect of the fouling layers which reduces heat convection by crossflow and the different thermal conductivity in the fouling layer compared with the feed. After membrane cleaning, the permeability and the magnitude of the 3ω signal were partly restored, showing that the 3ω method can be used to monitor the effect of cleaning. The frequency of the AC current was varied so it was possible to measure the heat conductivity in the fouling layer (high frequency) and heat convection due to cross-flow (low frequency). This may potentially be used to get information of the type of fouling (heat conductivity) and thickness of the fouling layer (AC frequency where heat conductivity becomes dominating).

The Effect Of Polymer Concentration On Coaxial Electrospinning Of Pvp/Pcl Core-Sheath Nanofibers

Core-sheath nanofibers are being developed with coaxial electrospinning for use in drug release studies. In this study, nanofiber structures were developed as hydrophobic PCL in the sheath and hydrophilic PVP in the core. The effect of polymer concentrations on fiber structure and water contact angle was observed by forming two different test groups. In the first group, fiber diameters were observed to decrease depending on viscosity as the polymer concentration decreased from 10% PCL / 10% PVP to 6% PCL / 6% PVP. It was also observed that the contact angle decreased from 104.3° to 57.61° as the concentration decreased. In the second group, the shell polymer ratio was kept constant as 10% wt PCL, while the core polymer ratio was decreased to 10 %, 8% and 6%. It was observed that the core polymer in the structure became hydrophilic as its viscosity decreased. Compared to the first group, the decrease in the contact angles of the surfaces was less since the shell polymer ratio was kept constant. Contact angles decreased from 104.3° to 96.29°.

Strategies for thermal performance improvements of polymeric thermal ground planes (TGP)

This paper presents a study on the thermal performance and enhancement techniques of polymeric thermal ground planes (TGPs). The literature features a range of polymeric TGPs that exhibit an effective thermal conductivity up to twice that of copper. However, the TGP effective thermal conductivity does not provide insight into the performance and potential improvements that could be made to a specific TGP design and configuration. Relying only on this metric can be limiting to compare different TGPs performances, since effective conductivity is affected by the device size, layout of heated and cooled zones, and the fabrication materials. In this paper, we adapted a model by connecting the TGP pumping capacity to its thermal resistance to predict the polymeric TGP thermal performances as a function of their geometry, test configuration and material used. This approach enables the development of strategies to optimize the polymeric TGPs performances and identify their limitations rather than relying on effective thermal conductivity as a benchmark for comparison. The present model considers vapor flow through a mechanical structure for the first time in TGPs. Indeed, the polymeric TGP in contrast to the metallic one requires a denser mechanical structure to support the vapor core thickness during vacuum due to the flexibility of the polymeric shell. The generated vapor pressure drop along the TGP has a dual impact on its performance as it affects both the capillary limit and vapor resistance resulting in a tradeoff between the TGP pumping capacity and thermal resistance, for a given TGP thickness. To back up the proposed model, experimental characterization was carried out on a one-step assembled polymeric TGP, to extract simultaneously the total and vapor thermal resistances. The model highlighted a trade-off in designing the vapor core and wicking structure, balancing the polymeric TGP pumping capacity and thermal resistance, for a target TGP thickness. Hence, the current study provides guidelines for defining improvement strategies for TGPs thermal performances based on the geometry and the type of material used during the fabrication process. The recommended approach also permits the identification of polymeric TGPs capabilities and limits rather than depending on the thermal metrics, which may be misleading while comparing performances.

Development of nanomodified eco-friendly thermal energy storing cementitious composite using PCM microencapsulated in biosourced encapsulation shell

This study presents the development of a thermal energy storing cementitious composite that incorporates phase change material (PCM) microencapsulated in biosourced polymer shell (m-PCM). The biodegradability of the encapsulated PCM was assessed using Nuclear Magnetic Resonance (NMR), which confirmed the high biodegradability of the m-PCM shell under specific environmental conditions. To examine the thermophysical properties of the m-PCM, Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA) were performed. The DSC results revealed exothermic enthalpies of 84.7 J/g and 140.2 J/g, with associated peak temperatures of − 3.2 °C and − 22.9 °C, respectively. Subsequently, the m-PCM was incorporated into cement-based mortar at proportions of 5%, 10%, and 15% by weight of binder. Uniaxial compression tests were conducted to evaluate the effect of the m-PCM on the mechanical properties of the mortar. The results indicated a significant decrease in mechanical strength upon incorporating the m-PCM. However, this reduction in strength was mitigated by the addition of silica fume (SF) and multiwalled carbon nanotubes (MWCNTs) in combination. Furthermore, a thermal cycling test was performed to examine the behavior of the nanomodified m-PCM incorporated mortar under varying ambient conditions. The results showed that the addition of MWCNTs improved both the mechanical performance and thermal performance of the composite.