IL-4-loaded alginate/chitosan multilayer films for promoting angiogenesis through both direct and indirect means.

Vascularization remains a major challenge in tissue engineering. In tissue repair with the involvement of biomaterials, both the material properties and material-induced immune response can affect angiogenesis. However, there is a scarcity of research on biomaterials that modulate angiogenesis simultaneously from both perspectives. Meanwhile, the effects and mechanisms of biomaterial-induced macrophages on angiogenesis remain controversial. In this study, a cytokine-controlled release system from our previous work was employed, and the effects thereof on angiogenesis through both direct and indirect means were investigated. Alginate/chitosan multilayer films were fabricated on interleukin (IL)-4-loaded titania nanotubes to achieve a sustained release of IL-4. The released IL-4 and the multilayers synergistically promoted angiogenic behaviors of endothelial cells (ECs), while up-regulating the expression of early vascular markers. Furthermore, polarized macrophages (both M1 and M2) notably elevated the expression of late vascular markers in ECs via the high expression of pro-maturation factor angiogenin-1. After subcutaneous implantation, the IL-4-loaded implants induced increased neovascularization in a short period, with the surrounding tissue returning to normal at the later stage. Therefore, the proposed IL-4-loaded implants exhibited superior pro-angiogenic capability in vitro and in vivo through both direct stimulation of ECs and the indirect induction of a suitable immune microenvironment.

Macrophage phenotype switch by sequential action of immunomodulatory cytokines from hydrogel layers on titania nanotubes.

Inflammatory response occurring between tissues and implants after implantation has attracted increasing attention because it can cause local tissue necrosis and even implant failure. Macrophages play a key role in all stages of inflammation. Pro-inflammatory (M1) and anti-inflammatory (M2) macrophages comprise two main phenotypes and the switch from M1 to M2 at specific time points is important for wound healing and tissue regeneration. Therefore, we hypothesized that biomaterial systems capable of facilitating macrophage phenotype switching should attenuate inflammation and enhance healing. To this end, a system of double hydrogel layers on titania nanotubes (TNT) was prepared as reservoir to modulate the release of interleukin-4 (IL-4) and interferon-γ (IFN-γ). In this system, IL-4, an anti-inflammatory cytokine, was loaded in TNT and IFN-γ, a pro-inflammatory cytokine, was located between two hydrogel layers of chitosan/ß-glycerophosphate disodium and carboxymethyl chitosan/genipin. IFN-γ released rapidly in 3 days, whereas IL-4 exhibited a sustained release profile. In culture with mesenchymal stem cells and macrophages, this system displayed good cytocompatibility and significantly promoted cell proliferation. Macrophage phenotype switch was determined by ELISA, FACS and PCR. The results manifested that IFN-γ released from the system stimulated switching of macrophages to M1 in 3 days, whereas sustained release of IL-4 polarized macrophages to M2 after 4 days. This system can modulate macrophage phenotype switching from M1 to M2 by sequential action of the two cytokines, and might be used to research immune response between tissues and implants. The present study also provided a novel strategy for designing functional biomaterials.

Classification of microcrystalline celluloses via structures of individual particles measured by synchrotron radiation X-ray micro-computed tomography.

Microcrystalline cellulose (MCC) is one of the most important excipients due to its outstanding binding and tableting properties. Owing to the absence of high resolution characterization techniques at the single particle scale, 3D (three dimension) microstructure of MCC and its effects on formulation performance remain unexamined. The aim of this work was to establish a methodology for single particles of MCC type 102 based on synchrotron radiation X-ray micro computed tomography (SR-µCT), principal component analysis (PCA) and partial least square discriminant analysis (PLSDA). Scanning electron microscopy, SR-µCT, powders properties together with tensile strength (TS), disintegration time (DT), Kawakita plots and force/displacement profiles of tablets were measured. PCA-PLSDA was applied to evaluate the structural classification of MCC particles on the basis of 2D and 3D SR-µCT derived images. The studied MCCs were found to differ in the TS, DT, Kawakita plot and force/displacement, while box ratio and Feret ratio had major influence on the principal components, but the angle of repose, bulk and tapped density did not exhibit significantly. These findings verified that different samples of MCCs from alternative suppliers have morphological diversity when assessed at the individual particle level, which could result into variation in powder properties and tableting performance.

Microstructural investigation using synchrotron radiation X-ray microtomography reveals taste-masking mechanism of acetaminophen microspheres.

The structure of solid drug delivery systems has considerable influence on drug release behaviors from particles and granules and also impacts other properties relevant to release characteristics such as taste. In this study, lipid-based microspheres of acetaminophen were prepared to mask the undesirable taste of drug and therefore to identify the optimal formulation for drug release. Synchrotron radiation X-ray computed microtomography (SR-µCT) was used to investigate the fine structural architectures of microspheres non-destructively at different sampling times during drug release test, which were simultaneously determined to quantitatively correlate the structural data with drug release behaviors. The results demonstrated that the polymeric formulation component, namely, cationic polymethacrylate (Eudragit E100), was the key factor to mask the bitter taste of acetaminophen by inhibiting immediate drug release thereby reducing the interaction intensity of the bitter material with the oral cavity taste buds. The structure and morphology of the microspheres were found to be influenced by the shape and particle size of the drug, which was also an important factor for taste-masking performance. The quantitative analysis generated detailed structural information which was correlated well with drug release behaviors. Thus, SR-µCT has been proved as a powerful tool to investigate the fine microstructure of particles and provides a new approach in the design of particles for taste masking.

Hydration induced material transfer in membranes of osmotic pump tablets measured by synchrotron radiation based FTIR.

Osmotic pump tablets are reliable oral controlled drug delivery systems based on their semipermeable membrane coating. This research used synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy and imaging to investigate the hydration induced material transfer in the membranes of osmotic pump tablets. SR-FTIR was applied to record and map the chemical information of a micro-region of the membranes, composed of cellulose acetate (CA, as the water insoluble matrix) and polyethylene glycol (PEG, as the soluble pore forming agent and plasticizing agent). The microstructure and chemical change of membranes hydrated for 0, 5, 10 and 30min were measured using SR-FTIR, combined with scanning electronic microscopy and atom force microscopy. The SR-FTIR microspectroscopy results indicated that there was a major change at the absorption range of 2700-3100cm(-1) in the membranes after different periods of hydration time. The absorption bands at 2870-2880cm(-1) and 2950-2960cm(-1) were assigned to represent CA and PEG, respectively. The chemical group signal distribution illustrated by the ratio of PEG to CA demonstrated that the trigger of drug release in the preliminary stage was due to the rapid transfer of PEG into liquid medium with a sharp decrease of PEG in the membranes. The SR-FTIR mapping results have demonstrated the hydration induced material transfer in the membranes of osmotic pump tablets and enabled reassessment of the drug release mechanism of membrane controlled osmotic pump systems.

Visualization and quantitative profiling of mixing and segregation of granules using synchrotron radiation X-ray microtomography and three dimensional reconstruction.

Tomographic imaging techniques have great potential for improving understanding of the dynamics of granular materials during manufacturing, handling, and storage. In this study, the synchrotron radiation X-ray computed microtomography (SR-µCT) was used non-invasively to monitor blend homogeneity of binary mixtures. Granular samples of microcrystalline cellulose and starch were characterized using the SR-µCT individually. Simultaneously, particle distribution was investigated by calculating the frequency distribution of a statistic for testing sphericity. Then, the microcrystalline cellulose and starch granules were blended in a cylindrical container. Influences of the time of rotations TR and the time of vibration TV on the mixture homogeneity were studied with the SR-µCT and statistical evaluation. The mixing index is also adopted to evaluate the mixture homogeneity of the particle system. The results showed that mixture homogeneity is improved with increasing TR. Furthermore, segregation increased with longer TV when particles are different in size and shape. The larger starch granules of non-spherical shape have a tendency to rise to the top, while the smaller microcrystalline cellulose granules which are spherical tend to migrate to the bottom of the mixture. Therefore, we demonstrate that SR-µCT can investigate the mixing and segregation of granular materials in three-dimensions combined with statistic method.