Rapid Indomethacin Release from Porous Pectin Particles as a Colon-Targeted Drug Delivery System.

The conventional pectin delivery systems in the colon are often impaired by a slow release rate. Nanostructured particles, especially porous ones, have gained popularity as drug delivery systems owing to their high mass transfer efficiency. In this research, porous pectin particles were synthesized as drug carriers (using indomethacin as a model drug) via template-assisted spray drying. Specific surface areas of the porous pectin particles have been improved by up to 203 m2 g-1 compared with nonporous particles (1 m2 g-1). The porous structure shortened the diffusion path and improved the release rate of drug molecules. Additionally, the predominant drug release mechanism from porous pectin particles is Fickian diffusion, which is different from the combination of erosion and diffusion mechanism observed for nonporous particles. As a result, these porous drug-loaded pectin particles demonstrated rapid drug release rates of up to three times faster than nonporous particles. Control of the release rate could be achieved by changing the porous structure of the particles. This strategy is an efficient means to synthesize porous particles allowing rapid drug release into the colonic target.

Tuning of water resistance and protein adsorption capacity of porous cellulose nanofiber particles prepared by spray drying with cross-linking reaction.

Porous particles composed of 2,2,6,6-tetramethylpiperidinyl-1-oxyl-oxidized cellulose nanofiber (TOCN) as building block, i.e., porous TOCN particles, are attracting attention due to their environmental friendliness, superior properties, such as easy handling, large surface area, and high adsorption capacity. However, the instability of TOCNs in aqueous environments limits their applications. An effective solution to improve water resistance of TOCN particles is to reduce the hydrophilicity of TOCNs by forming chemical bonds with a cross-linker. In this study, Carbodilite, a common, easy-to-use, commercially available cross-linker with carbodiimide groups, was used to investigate a chemical cross-linking strategy for porous TOCN particles prepared by spray drying. The water resistance of cross-linked TOCN particles was evaluated through morphological observation by SEM images. The presence of polycarbodiimide significantly increased water resistance of cross-linked TOCN particles up to 24 h. This study demonstrates the trade-off between water resistance and adsorption efficiency according to cross-linker concentrations. These data are useful for interface science of TOCNs in liquids, assisting in controlling specific properties of porous TOCN particles for particular applications in adsorption and separation.

Enhanced Protein Adsorption Capacity of Macroporous Pectin Particles with High Specific Surface Area and an Interconnected Pore Network.

There has been much interest in developing protein adsorbents using nanostructured particles, which can be engineered porous materials with fine control of the surface and pore structures. A significant challenge in designing porous adsorbents is the high percentage of available binding sites in the pores owing to their large surface areas and interconnected pore networks. In this study, continuing the idea of using porous materials derived from natural polymers toward the goal of sustainable development, porous pectin particles are reported. The template-assisted spray drying method using calcium carbonate (CaCO3) as a template for pore formation was applied to prepare porous pectin particles. The specific surface area was controlled from 177.0 to 222.3 m2 g-1 by adjusting the CaCO3 concentration. In addition, the effects of a macroporous structure, the specific surface area, and an interconnected pore network on the protein (lysozyme) adsorption capacity and adsorption mechanism were investigated. All porous pectin particles performed rapid adsorption (∼65% total capacity within 5 min) and high adsorption capacity, increasing from 1543 to the highest value of 2621 mg g-1. The results are attributed to the high percentage of available binding sites located in the macropores owing to their large surface areas and interconnected pore networks. The macroporous particles obtained in this study showed a higher adsorption capacity (2621 mg g-1) for lysozyme than other adsorbents. Moreover, the rapid uptake and high performance of this material show its potential as an advanced adsorbent for various macromolecules in the food and pharmaceutical fields.

Synthesis of High Specific Surface Area Macroporous Pectin Particles by Template-Assisted Spray Drying.

Many types of porous particles containing inorganic and organic substances, such as carbon, metals, metal oxides, inorganic-organic hybrids, and polymers, have been developed. However, natural polymer-derived particles are relatively rare. To our knowledge, this report describes the first synthetic method for obtaining meso-/macroporous particles made from pectin, which is a natural polymer with a wide range of biological activities suitable for active substance support applications. These porous particles were prepared using a template-assisted spray-drying method, followed by a chemical etching process. An organic template [i.e., poly(methyl methacrylate) (PMMA)] or an inorganic template [i.e., calcium carbonate (CaCO3)] was used to evaluate the resulting formation of macroporous structures in the pectin particles. Furthermore, the concentration of the templates in the precursor solution was varied to better understand the mechanism of porous pectin particle formation. The results showed that the final porous particles maintained the characteristic properties of pectin. The differences between the two templates resulted in two distinct types of porous particles that differed in their particle morphologies (i.e., spherical or wrinkled), particle sizes (ranging from 3 to 8 µm), pore sizes (ranging from 80 to 350 nm), and pore volume (ranging from 0.024 to 1.40 cm3 g-1). Especially, the porous pectin particles using the CaCO3 template have a significantly high specific surface area of 171.2 m2 g-1, which is 114 times higher than that of nonporous pectin particles. These data demonstrated the potential for using PMMA and CaCO3 templates to control and design desired porous materials.

TEMPO-oxidized cellulose nanofiber (TOCN) decorated macroporous silica particles: Synthesis, characterization, and their application in protein adsorption.

Effective protein adsorption has attracted attention for broad application in the biomedical field. In this study, we introduce the synthesis of a TEMPO-oxidized cellulose nanofiber (TOCN) decorated macroporous SiO2 (TOCN@macroporous SiO2) particle and its protein adsorption performance. The TOCN@macroporous SiO2 particles have a unique cellulose nanofiber network structure on the macroporous, highly-negative zeta potential (-62 ±â€¯2 mV) and high surface area (30.8 m2/g) for dried-state cellulose based particles. These characteristics provide sites that are rich in electrostatic interaction to exhibit an outstanding adsorption capacity of lysozyme (1865 mg/g). Furthermore, the TOCN@macroporous SiO2 particles have remarkably high reusability (>90% adsorption capacity) and good release of adsorbate (>80%) after 10 times of use. The material proposed in this paper has the potential for application in drug delivery, protein adsorption, biosensors, and other biomedical fields.