Tailoring thermoresponsive microbeads in supercritical carbon dioxide for biomedical applications

Pectin from carrot pomace: Optimization of extraction and physicochemical properties

In this study, the central composite design for four variables in five levels was applied to determine the effects of pH (0.5-2.5), temperature (50-90°C), heating time (30-150min) and liquid/solid ratio (10-50v/w) on the yield and degree of esterification (DE) of carrot pomace pectin. The results showed that the pectin yield ranged from 5.0 to 15.2% and also, this pectin is classified as low methoxyl pectin (DE of 22.1-51.8%). The pH of 1.3, temperature of 90°C, time of 79.8min and liquid/solid ratio of 23.3v/w were determined as optimal conditions with a maximum yield of 15.6±0.5%, which was close to the predicted values (16.0%). Under the optimal extraction conditions, the galacturonic acid content and emulsifying activity were 75.5 and 60.3% respectively; moreover, the emulsions had a high stability at two different storage temperatures (4 and 23°C). Furthermore, carrot pectin solutions exhibited viscous and pseudoplastic behavior at 1% w/v.

Temperature-Responsive Smart Nanocarriers for Delivery Of Therapeutic Agents: Applications and Recent Advances

Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external stimulus when heat is applied from the outside, or can be internal when pathological lesions have a naturally elevated termperature. A low critical solution temperature (LCST) is a special feature of some polymeric materials, and most of the temperature-responsive nanocarriers have been designed based on this feature. In this review, we attempt to summarize recent efforts to prepare innovative temperature-responsive nanocarriers and discuss their novel applications.

Starch-based microspheres for sustained-release of curcumin: preparation and cytotoxic effect on tumor cells

Curcumin (CUR) has been proved to be highly cytotoxic against different tumor cell lines. However, its poor solubility in aqueous medium and fast degradation in physiological pH are the common drawbacks preventing its efficient practical use. Herein, we report the development of original microspheres based on the biopolymer starch crosslinked with N,N-methylenebisacrylamide (MBA) to be applied as an efficient delivering system for CUR. The starch-based microspheres showed high loading efficiency even in loading solution with different CUR concentrations. In vitro release assays data showed that the CUR release is governed by anomalous transport (n=0.73) and it is pH-dependent. Cytotoxicity assays showed that starch microspheres could improve the cytotoxicity of CUR toward Caco-2 and HCT-116 tumor cell lines up to 40 times than that found for pure CUR. This behavior was attributed to the slowly and sustained release of CUR from the microspheres.

Tuning smart microgel swelling and responsive behavior through strong and weak polyelectrolyte pair assembly

The layer-by-layer (LbL) assembly of polyelectrolyte pairs on temperature and pH-sensitive cross-linked poly(N-isopropylacrylamide)-co-(methacrylic acid), poly(NIPAAm-co-MAA), microgels enabled a fine-tuning of the gel swelling and responsive behavior according to the mobility of the assembled polyelectrolyte (PE) pair and the composition of the outermost layer. Microbeads with well-defined morphology were initially prepared by synthesis in supercritical carbon dioxide. Upon LbL assembly of polyelectrolytes, interactions between the multilayers and the soft porous microgel led to differences in swelling and thermoresponsive behavior. For the weak PE pairs, namely poly(L-lysine)/poly(L-glutamic acid) and poly(allylamine hydrochloride)/poly(acrylic acid), polycation-terminated microgels were less swollen and more thermoresponsive than native microgel, whereas polyanion-terminated microgels were more swollen and not significantly responsive to temperature, in a quasi-reversible process with consecutive PE assembly. For the strong PE pair, poly(diallyldimethylammonium chloride)/poly(sodium styrene sulfonate), the differences among polycation and polyanion-terminated microgels are not sustained after the first PE bilayer due to extensive ionic cross-linking between the polyelectrolytes. The tendencies across the explored systems became less noteworthy in solutions with larger ionic strength due to overall charge shielding of the polyelectrolytes and microgel. ATR FT-IR studies correlated the swelling and responsive behavior after LbL assembly on the microgels with the extent of H-bonding and alternating charge distribution within the gel. Thus, the proposed LbL strategy may be a simple and flexible way to engineer smart microgels in terms of size, surface chemistry, overall charge and permeability.

A Combined Strategy to Surface-Graft Stimuli-Responsive Hydrogels Using Plasma Activation and Supercritical Carbon Dioxide

Differently shaped polymeric matrices were efficiently coated with stimuli-responsive hydrogels for a wide range of applications using a new methodology. By combining plasma surface activation and polymerization in supercritical media at mild conditions, we report the direct smart coating of microcarriers and membranes in gram-scale quantities with a scalable, green, and low-cost approach.