Preparation of TiO2 nanocapsules for loading and release of antimicrobial triclosan molecules

Well-defined nanosized hollow TiO₂ capsules with the diameter of 80-100 nm were prepared through aging dissolvation technique for the first time to remove the templates of core-shell composite spheres. The as-prepared TiO₂ nanocapsules were characterized by TEM. Furthermore, the antimicrobial triclosan was loaded into these nanocapsules. The loading of triclosan was determined by TGA-DTA, and the loading amount is about 29 wt.%. The release behavior of the entrapped triclosan molecular was investigated by UV-visible absorption (UV-vis). There is a moiety of triclosan that was loaded inside the TiO₂ shell. The results indicated that this drug release system has a sustained-release property. Such antimicrobial-loaded TiO₂ nanocapsules can be used as additive in household and personal care chemical industry.     

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates

A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol-gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N₂ adsorption-desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m²/g, large pore volume with more than 0.8 cm³/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.     

A dual template method for synthesizing hollow silica spheres with mesoporous shells

PS/silica core/shell composites were synthesized by the modified Stöber method using polystyrene spheres and cetyltrimethylammonium bromide as dual templates under room temperature. The silicate species and the templates were self-assembled to form mesoporous silica shell on the surface of the PS spheres. Hollow silica spheres with mesoporous shell were obtained by removing the polymer core and the templates through calcination. The hollow silica spheres showed high specific surface area of 1099.5 m²/g and narrow pore size distribution centered at 2.31 nm.     

A New Process for Drug Loaded Nanocapsules Preparation Using a Membrane Contactor

ABSTRACT

In this paper, we describe a new process for the preparation of drug loaded nanocapsules using a membrane contactor which may be scaled up for industrial applications. Nanocapsules are prepared according to the nanoprecipitation method. The organic phase (solvent, polymer, oil, and drug) is pressed through the pores of an ultrafiltration membrane via the filtrate side. The aqueous phase (water and surfactant) circulates inside the membrane module, and sweeps away the nanocaspules forming at the pore outlets. Two model drugs are selected for the preparation of drug loaded nanocapsules: indomethacin and vitamin E. It is shown that indomethacin loaded nanocapsules with a mean diameter of 240 nm and vitamin E loaded nanocapsules with a mean diameter of 230 nm are obtained with a 150,000 daltons ultrafiltration membrane, a transmembrane pressure of 3 bar, and a crossflow rate of 1.7 m.s^{? 1}. High fluxes are also obtained (around 0.6 m³/h.m²), leading to the preparation of 1.8 10^{? 3} m³ drug loaded nanocapsules in 8 min. The advantage of this membrane contactor compared to other processes for drug loaded nanocapsules preparation is shown to be its scale-up ability.     

Preparation and characterization of bowl-like porous ZnO film by electrodeposition using two-dimensional photonic crystal template

A rapid and low-cost method combining electrodeposition with two-dimensional (2D) photonic crystal template technique to prepare large scale bowl-like porous ZnO films is described. The 2D photonic crystal templates were fabricated by self-assembly of monodispersed polystyrene (PS) microspheres on indium-tin-oxide coated glass substrates using spinning coating method. The interstitial spaces among the spheres of the templates were filled with ZnO via electrodeposition from an aqueous solution containing 0.02 M zinc nitrate as electrolyte under a constant potential of ?1.0 V at 65 °C for 10 min. After removal of the PS photonic crystal template, bowl-like porous ZnO film was obtained. The entire process can be accomplished within 30 min. Scanning electron microscopic images showed good homogeneity in morphology, X-ray diffraction spectra demonstrated the wurtzite structure of the obtained ZnO film, and transmission electron microscopy indicated the single-crystallinity of the ZnO. Ultraviolet–visible (UV–vis) spectrophotometer was used to detect the absorption in UV–vis region of the PS template, opal ZnO-PS composite and inverse opal ZnO respectively. Two strong emission bands at 400 and 550 nm were displayed in photoluminescence spectrum.     

Development,characterization, and photocytotoxicity assessment on human melanoma of chloroaluminum phthalocyanine nanocapsules

In this work we have developed nanocapsules containing chloroaluminum phthalocyanine (ClAlPc) and assessed their phototoxic action on WM1552C, WM278, and WM1617 human melanoma cell lines. The ClAlPc-loaded nanocapsules were prepared by the nanoprecipitation method and optimized by means of a 2³ full factorial design. The ClAlPc nanocapsules were characterized by particle size and distribution, zeta potential, morphology, encapsulation efficiency, singlet oxygen production, stability, and phototoxic action on melanoma cells. Both the development and optimization studies revealed that stable colloidal formulations could be obtained by using 1.75% (w/v) soybean lecithin, 1.25% (w/v) Poloxamer 188, 2.5% (v/v) soybean oil, and 0.75% (w/v) poly(D,L-lactide-co-glycolide). The nanocapsules had a mean diameter of 230 nm, homogeneous size distribution (polydispersity index < 0.3), and negative zeta potential (about ? 30 mV). Their morphology was spherical, with evident polymer membrane coating droplet. The encapsulation efficiency was 70%, as expected for hydrophobic drugs, and the nanoencapsulated ClAlPc was able to produce high singlet oxygen quantum yield. ClAlPc nanocapsules exhibited good physical stability over a 12-month period. WM1552C primary melanoma cells were more sensitive (p < 0.05) to the phototoxic effect elicited by ClAlPc nanocapsules (0.3 μg ml^? 1) under light irradiation at 20 mJ cm^? 2. On the other hand, the cell survival percentage for all the melanoma cell lines treated with the highest light dose (150 mJ cm^? 2) was lower than 10%. In summary, ClAlPc nanoencapsulation could enable application of this hydrophobic photosensitizer in the treatment of malignant melanoma with the use of both low sensitizer drug concentration and light dose.     

Novel temperature-sensitive crosslinked polymeric nanocapsules

Novel temperature-sensitive polymeric nanocapsules crosslinked via amide groups were prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) technique based on the widely used sacrificial SiO₂ nanoparticle templates. In the strategy developed, the silica templates were removed by being etched with HF to obtain the crosslinked polymeric nanocapsules after the poly(methyl acrylate) (PMA) chains grafted on the SiO₂ templates were crosslinked with ethylenediamine (EDA). FTIR spectroscopy showed that the silica templates were completely removed by being etched and the transmission electron microscopy (TEM) analysis demonstrated the hollow structure with inner diameter of about 10 nm. The dynamic light scatting analysis showed that the temperature-responsive crosslinked polymeric nanocapsules had a wider scope of the temperature-response about 10 °C and a higher lower critical solution temperature (LCST) about 35 °C.     

Pb(Zr0.52Ti0.48)O3 nanotubes synthesis and infrared absorption properties

Herein a useful methodology to synthesize the lead zirconate titanate (PZT) nanotubes via a dip-coating deposition process with anodic aluminum oxide (AAO) template is proposed. The nano-porous AAO templates were produced using a controlled two-step electrochemical anodization technique. The PZT/AAO composite was formed using the dip-coating wetting technique. The prepared PZT precursor solution was driven into the nanopore channels of AAO template under the driving force of capillary action, subsequently the sintering process of the as-filled templates was carefully tuned to obtain Pb(Zr_0.52Ti_0.48)O₃ nanotubes of crystalline tetragonal phase with uniform pore size and ordered arrange. Fourier transform infrared spectroscopy (FTIR) results show that in the 1200–1900 cm⁻¹ band, the composite structure of PZT/AAO has obvious absorption peaks at 1471.56 cm⁻¹ and 1556.09 cm⁻¹, the absorption intensity of the composite structure is about six times of pure AAO template. The unusual optical properties found in PZT/AAO composite will stimulate further theoretical and experimental interests in ferroelectric nanostructures.     

Silver nanoparticles modified nanocapsules for ultrasonically activated drug delivery

Novel ultrasound-sensitive nanocapsules were designed via layer-by-layer assembly (LbL) of polyelectrolytes for remote activated release of biomolecules/drug. Nanocapsules embedded with silver nanoparticles in the walls were synthesized by alternate assembly of poly(allylamine hydrochloride) (PAH) and dextran sulfate (DS) on silica template followed by nanoparticle synthesis and subsequent template removal thus yielding nanocapsules. The silver NPs were synthesized in situ within the capsule walls under controlled conditions. The nanocapsules were found to be well dispersed and the silver NPs were evenly distributed within the shell. FITC-dextran permeated easily into the capsules containing silver NP's due to the pores generated during the formation of NP's. When the loaded nanocapsules were sonicated, the presence of the silver NPs in the shell structure led to rupturing of the shell into smaller fragments thus releasing the FITC-dextran. Such nanocapsules have the potential to be used as drug delivery vehicles and offer the scope for further development in the areas of modern medicine, material science, and biochemistry.     

Sol–gel derived CaO–B2O3–SiO2 glass/CaSiO3 ceramic composites: processing and electrical properties

The CaO–B₂O₃–SiO₂ glass/CaSiO₃ ceramic (CBS/CS) composites were fabricated via sol–gel processing routes. Their densification behavior, structures and dielectric properties were investigated. The precursors of CBS glass and CS ceramic filler were firstly obtained via individual soft chemical route and then mixed together in various proportions. The results indicated that the structures of CBS/CS composites are characteristic of CS and CaB₂O₄ (CB) ceramic phases distributed in the matrix of glass phase at 800–950 °C. The CS ceramic phase not only acts as fillers, but nuclei for the crystallization of CBS glass as well such that the CS content exhibits an effect on the densification and dielectric properties of the composites. The CBS/CS composites with 10% CS sintered at 850 °C own dielectric properties of ε_r < 5 and tanδ = 6.4 × 10⁻⁴ at 1 MHz.     

Templated synthesis of single-component polymer capsules and their application in drug delivery

We report a general and facile approach for the fabrication of a new class of monodispersed, single-component and thick-walled polymer nanocapsules via the single-step assembly of macromolecules in solid core/mesoporous shell (SC/MS) silica particle templates, followed by cross-linking of the macromolecules and removal of the SC/MS templates. The general applicability of this approach is demonstrated by the preparation of nanocapsules using various polymers, including synthetic polyelectrolytes, polypeptides, and polypeptide-drug conjugates. The potential of doxorubicin (Dox)-loaded poly(L-glutamic acid) nanocapsules in tumor therapy applications is demonstrated via in vitro degradation experiments, which show a near-linear release of the Dox in the presence of a lysosomal hydrolase, nanocapsule uptake by human colorectal tumor cells, and delivery of the anticancer drug into the tumor cells, leading to tumor cell death.     

Biomimetic mineralisation of apatites on Ca2+ activated cellulose templates

We investigated the activation of regenerated cellulose 2D model thin films and 3D fabric templates with calcium dihydroxide. The Langmuir–Blodgett (LB) film technique was applied for manufacturing of the model thin films using a trimethylsilyl derivative of cellulose (TMS-cellulose). Regenerated cellulose films were obtained by treating the TMS-cellulose LB-films with hydrochloric acid vapours. For 3D templates, regenerated cellulose fabrics (Lyocell®) were used. The regenerated cellulose templates were activated with a Ca(OH)₂-suspension and subsequently exposed to 1.5 × SBF to induce the in situ formation of biomimetic calcium phosphate phases. FTIR and Raman spectroscopy showed that the Ca(OH)₂ and calcite present from reaction with HCO₃⁻ on the template surface were dissolved in the initial stage of exposure to the 1.5 × SBF. After 1 day, the formation of apatitic phases in 1.5 × SBF was observed. According to detailed calculations, high supersaturation levels S in close vicinity to the template surface (S > 16) resulting from the Ca²⁺ diffusion induced the formation of biomimetic calcium phosphate. The biomimetic calcium phosphates were identified by FTIR and Raman spectroscopy as highly carbonated apatites (HCA) lacking hydroxyl ions. 3D fabric templates of regenerated cellulose covered with a biomimetic coating of apatite might be of particular interest for novel scaffold architectures in bone repair and tissue engineering.     

The effect of polymeric wall on the permeability of drug-loaded nanocapsules

The aim of this work was to establish a quantitative correlation between the drug permeability and the polymer concentration in the nanocapsules. Indomethacin ethyl ester-loaded nanoemulsion and nanocapsules containing poly(epsilon-caprolactone) at different concentrations (0, 2, 4, 6, 8 and 10 mg/mL) presented drug loading between 0.981 and 1.005 mg/mL, pH values from 5.0 to 5.4, particle sizes between 232 and 261 nm, polydispersity lower than 0.24 and zeta potentials from − 8.54 mV to − 11.86 mV. An alkaline hydrolysis of indomethacin ethyl ester carried out at the particle/water interface was used to simulate a sink condition of release. The number of particles in each suspension was estimated. The calculated values ranged from 5.84 × 10¹² to 6.60 × 10¹² particles cm^− 3, showing similar concentration of particles in the formulations. The diffusion was proposed as the main mechanism of the indomethacin ester release after fitting the data to the Higuchi model. Applying the Fick's first law, the calculated indomethacin ester fluxes (J) decreased from 2.20 × 10^− 7 to 1.43 × 10^− 7 mg cm^− 2 min^− 1. Then, the drug relative permeability decreased according to the increase in the polymer concentration fitting a power law.     

Fabrication and characteristic of conductive and ferromagnetic hollow composite microcapsules

The fabrication of conductive and ferromagnetic hollow composite microcapsules with polypyrrole (PPy) shell and Fe₃O₄ inner-wall was successfully accomplished via a sequential processes of electrostatic attraction between negatively charged polystyrene (PS) latex and Fe₃O₄ nanoparticles, the polymerization of pyrrole and the dissolution of PS core. The morphology of the hollow composite microcapsules was testified by TEM and XRD. The hollow microcapsules possessed a conductivity of 10^− 2 S/cm, and their ferromagnetic property was attributed to the presence of magnetic Fe₃O₄ nanoparticles on the inner-wall. The improved thermal stability of the hollow microcapsules could be interpreted due to the interaction between Fe₃O₄ nanoparticles and PPy chains.     

Controllable Fabrication of Highly Uniform Sub-10 nm Nanoparticles from Spontaneous Confined Nanoemulsification

Sub-10 nm nanoparticles are known to exhibit extraordinary size-dependent properties for wide applications. Many approaches have been developed for synthesizing sub-10 nm inorganic nanoparticles, but the fabrication of sub-10 nm polymeric nanoparticles is still challenging. Here, a scalable, spontaneous confined nanoemulsification strategy that produces uniform sub-10 nm nanodroplets for template synthesis of sub-10 nm polymeric nanoparticles is proposed. This strategy introduces a high-concentration interfacial reaction to create overpopulated surfactants that are insoluble at the droplet surface. These overpopulated surfactants act as barriers, resulting in highly accumulated surfactants inside the droplet via a confined reaction. These surfactants exhibit significantly changed packing geometry, solubility, and interfacial activity to enhance the molecular-level impact on interfacial instability for creating sub-10 nm nanoemulsions via self-burst nanoemulsification. Using the nanodroplets as templates, the fabrication of uniform sub-10 nm polymeric nanoparticles, as small as 3.5 nm, made from biocompatible polymers and capable of efficient drug encapsulation is demonstrated. This work opens up brand-new opportunities to easily create sub-10 nm nanoemulsions and advanced ultrasmall functional nanoparticles.     

Synthesis of macro/mesoporous silica and carbon monoliths by using a commercial polyurethane foam as sacrificial template

A commercial macrocellular polyurethane foam was used as template to fabricate macro/mesoporous silica and carbon monoliths. These materials have a cellular structure which is a faithful replica of that of the polymeric foam. In addition, they have a high surface area and a large porosity made up of accessible mesopores. The synthesis of silica monoliths was carried out by impregnating the polymeric foam with a mixture of a silica precursor and a surfactant. The carbon monoliths were prepared by using the silica monoliths as sacrificial templates. They retain the foamy vesicular structure and exhibit a high surface area of 1800 m² g^− 1 and a large porosity made up of framework-confined mesopores of around 3.4 nm.     

Effect of membrane hydrophilization on ultrafiltration performance for biomolecules separation

This paper compares the performance of different hydrophilization methods to prepare low fouling ultrafiltration (UF) membranes. The methods include post-modification with hydrophilic polymer and blending of hydrophilic agent during either conventional or reactive phase separation (PS). The post-modification was done by photograft copolymerization of water-soluble monomer, poly(ethylene glycol) methacrylate (PEGMA), onto a commercial polyethersulfone (PES) UF membrane. Hydrophilization via blend polymer membrane with hydrophilic additive was performed using non-solvent induced phase separation (NIPS). In reactive PS method, the cast membrane was UV-irradiated before coagulation. The resulting membrane characteristic, the performance and hydrophilization stability were systematically compared. The investigated membrane characteristics include surface hydrophilicity (by contact angle /CA/), surface chemistry (by FTIR spectroscopy), and surface morphology (by scanning electron microscopy). The membrane performance was examined by investigation of adsorptive fouling and ultrafiltration using solution of protein or polysaccharide or humic acid. The results suggest that all methods could increase the hydrophilicity of the membrane yielding less fouling. Post-modification decreased CA from 44.8 ± 4.2^o to 37.8 ± 4.2^o to 42.5 ± 4.3^o depending on the degree of grafting (DG). The hydrophilization via polymer blend decreased CA from from 65^o to 54^o for PEG concentration of 5%. Nevertheless, decreasing hydraulic permeability was observed after post-modification as well as during polymer blend modification. Stability examination showed that there was leaching out of modifier agent from the membrane matrix prepared via conventional PS after 10 days soaking in both water and NaOH. Reactive PS could increase the stability of the modifier agent in membrane matrix.     

Ultrastable Liquid–Liquid Interface as Viable Route for Controlled Deposition of Biodegradable Polymer Nanocapsules

Liquid–liquid interfaces are highly dynamic and characterized by an elevated interfacial tension as compared to solid–liquid interfaces. Therefore, they are gaining an increasing interest as viable templates for ordered assembly of molecules and nanoparticles. However, liquid–liquid interfaces are more difficult to handle compared to solid–liquid interfaces; their intrinsic instability may affect the assembly process, especially in the case of multiple deposition. Indeed, some attempts have been made in the deposition of polymer multilayers at liquid–liquid interfaces, but with limited control over size and stability. This study reports on the preparation of an ultrastable liquid–liquid interface based on an O/W secondary miniemulsion and its possible use as a template for the self‐assembly of polymeric multilayer nanocapsules. Such polymer nanocapsules are made of entirely biodegradable materials, with highly controlled size—well under 200 nm—and multi‐compartment and multifunctional features enriching their field of application in drug delivery, as well as in other bionanotechnology fields.     

Fabrication of Ag nanoparticles-coated macroporous SiO2 structure by using polystyrene spheres

Ag nanoparticles-coated macroporous SiO₂ structure was fabricated by a novel approach in which at first Ag nanoparticles were coated onto polystyrene (PS) spheres without a surfactant, then these Ag nanoparticles-coated PS beads (Ag/PS) were self-assembled by sedimentation-aggregation with tetraethyl orthosilicate (TEOS), and finally Ag nanoparticles-coated macroporous silica (Ag/SiO₂) was obtained after removal of the PS cores. The heat-treatment temperature and the gelation time were investigated to optimize the microstructural morphology, thermal decomposition of organic materials, matrix wall thickness and densification behavior. The three dimensionally assembled Ag/SiO₂ had 200 nm uniform macropores and a high specific surface area of 142 m² g⁻¹. The XRD, FE-SEM, EDX, BET and optical absorbance analysis indicated that the exactly three-dimensional structure of the template had been imprinted in the final samples and the walls of the macroporous SiO₂ were coated uniformly with Ag nanoparticles.     

Tunable amorphous carbon nanotubes prepared by a simple template

An easy versatile method is reported to synthesize tunable amorphous carbon nanotubes (a-CNTs) with different pore diameter, length and orientation of graphene layers at a low temperature of 450 °C in the absence of metal catalysts by using porous anodic aluminum oxide (AAO) as a template and citric acid as a precursor. Since citric acid was adsorbed by hydrogen bonds with the -OH groups at the walls of the AAO templates, which can be influenced by the concentration of H⁺ ions in the solution, the pH leads to the change of the orientation of graphene layers and the graphitization degree.