Internally self-assembled particles entrapped in thermoreversible hydrogels

Characterization of cubosomes immobilized in hydrogels of hyaluronic acid and their use for diclofenac controlled delivery

Cubosomes are dispersions of bicontinuous surfactant phases that constitute an assertive option to carry and release drugs and biomolecules, offering high efficiency of entrapment and specificity towards biological targets. This paper reports, for the first time to the best of our knowledge, the immobilization and characterization of cubosomes in chemically cross-linked oxi-hyaluronic acid and the evaluation of their use for controlled delivery of diclofenac, which is chosen as a model drug. Immobilized cubosomes prepared with phytantriol and bearing either negative or positive charges (in this case due to the addition of a cationic surfactant) were characterized by small angle X-ray scattering (SAXS) analysis and high-resolution confocal microscopy, confirming that their internal structure remains unaltered and that they appear uniformly distributed within the hydrogel matrix. Their release properties were assessed, and a limited leaching of the cubosomes from the hydrogel matrix with sustained release of the entrapped diclofenac was confirmed. These results enable the use of immobilized cubosomes as an attractive platform for biomedical applications, significantly extending the already promising features of cubosomes.

Cubosomes and Hexosomes as Novel Nanocarriers for Bioactive Compounds

Cubosomes and hexosomes are nanostructured liquid crystalline particles, known as biocompatible nanocarriers for drug delivery. In recent years, there has been good interest in using cubosomes and hexosomes for the delivery of bioactive compounds in functional foods. These systems feature thermodynamic stability, encapsulate both hydrophobic and hydrophilic substances, and have a high tolerance to environmental stresses and potential for controlled release. This review outlines the recent advances in cubosomes and hexosomes in the food industry, focusing on their structure, composition, formation mechanisms, and factors influencing phase transformation between cubosomes and hexosomes. The potential applications especially for the bioactive delivery are presented. The integration of cubosomes and hexosomes with other emerging encapsulation technologies such as surface coating, gelation, and incorporation of polymers are also discussed.

Physicochemical data on aqueous polymeric systems of methyl cellulose and lambda- and kappa-carrageenan: SAXS, rheological, densitometry, and sound velocity measurements

General as well as more specific physicochemical data obtained by studying the structure and various dynamical properties of aqueous polymer systems of methyl cellulose, λ−carrageenan, and κ−carrageenan are presented in graphical and numeric tabular form. The data provide basic polymer characterization info as also a specific structural and dynamical info for aqueous solutions of three industrially very important polymers (food additives) that are available commercially. The commercial availability has much bigger impact to applications, research and connected advances, when the basic substances are well characterized – a feature that is still missing for many commercially available polymers unfortunately.

Supramolecular structure of methyl cellulose and lambda- and kappa-carrageenan in water: SAXS study using the string-of-beads model

A detailed data analysis utilizing the string-of-beads model was performed on experimental small-angle X-ray scattering (SAXS) curves in a targeted structural study of three, very important, industrial polysaccharides. The results demonstrate the quality of performance for this model on three polymers with quite different thermal structural behavior. Furthermore, they show the advantages of the model used by way of excellent fits in the ranges where the classic approach to the small-angle scattering data interpretation fails and an additional 3D visualization of the model's molecular conformations and anticipated polysaccharide supramolecular structure. The importance of this study is twofold: firstly, the methodology used and, secondly, the structural details of important biopolymers that are widely applicable in practice.

Lipid-hydrogel films for sustained drug release

We report a hybrid system, fabricated from nanostructured lipid particles and polysaccharide based hydrogel, for sustained release applications. Lipid particles were prepared by kinetically stabilizing self-assembled lipid nanostructures whereas the hydrogel was obtained by dissolving kappa-carrageenan (KC) in water. The drug was incorporated in native as well as lipid particles loaded hydrogels, which upon dehydration formed thin films. The kinetics of drug release from these films was monitored by UV-vis spectroscopy while the films were characterized by Fourier transform infra-red (FTIR) spectroscopy and small angle X-ray scattering techniques. Pre-encapsulation of a drug into lipid particles is demonstrably advantageous in certain ways; for instance, direct interactions between KC and drug molecules are prohibited due to the mediation of hydrophobic forces generated by lipid tails. Rapid diffusion of small drug molecules from porous hydrogel network is interrupted by their encapsulation into rather large sized lipid particles. The drug release from the lipid-hydrogel matrix was sustained by an order of magnitude timescale with respect to the release from native hydrogel films. These studies form a strong platform for the development of combined carrier systems for controlled therapeutic applications.

Lipid transfer between submicrometer sized Pickering ISAsome emulsions and the influence of added hydrogel

Transfer of lipids between droplets in Pickering emulsions has been studied by time-resolved small-angle X-ray scattering (SAXS). The special features of self-assembled liquid-crystalline phases have been applied to examine the kinetics of internal phase reorganization imposed by lipid release and uptake by the droplets. The findings reveal faster transfer kinetics in Pickering emulsions than in emulsions stabilized with Pluronic F127. It is shown that the transfer kinetics can be accelerated by adding free surfactant to the dispersions and that this acceleration becomes more dominant when micelles are formed. The effect of immobilization of the droplets has been studied by incorporating them into the appropriate hydrogel network. The droplets are arrested, and the transfer slows down significantly at high enough concentrations of the hydrogel where nonergodic systems are obtained.

Lipid transfer in oil-in-water isasome emulsions: influence of arrested dynamics of the emulsion droplets entrapped in a hydrogel

The transfer kinetics of lipids between internally self-assembled droplets of O/W emulsions is studied. The droplets (isasomes) consist of various liquid-crystalline phases or W/O microemulsions stabilized by a polymeric stabilizer F127. The various internal phases were identified by the relative peak positions in the small-angle X-ray scattering (SAXS) curves. An arrested system composed of isasomes embedded in a gel matrix actually provides an additional possibility to control these systems in terms of the release of various host molecules. These experiments have been applied to examine the kinetics of the internal phase reorganization imposed by the lipids' release and uptake by the droplets embedded in a κ-carrageenan (KC) hydrogel network. Increasing the concentration of the gelling agent slows down the transfer from one droplet to the other through the aqueous phase. We examined the region where the free diffusion is stopped. i.e., the point where the system changes from the ergodic to the nonergodic state and the kinetics is essentially slowed down. This effect can be balanced by the addition of small amounts of free polymeric stabilizer, which speeds up the kinetics. This is even possible in the case of highly arrested dynamics of the emulsion droplets, as found for the highest KC hydrogel concentrations forming nonergodic systems.

Small-Angle X-ray Scattering Investigations of Biomolecular Confinement, Loading, and Release from Liquid-Crystalline Nanochannel Assemblies

This Perspective explores the recent progress made by means of small-angle scattering methods in structural studies of phase transitions in amphiphilic liquid-crystalline systems with nanochannel architectures and outlines some future directions in the area of hierarchically organized and stimuli-responsive nanochanneled assemblies involving biomolecules. Time-resolved small-angle X-ray scattering investigations using synchrotron radiation enable monitoring of the structural dynamics, the modulation of the nanochannel hydration, as well as the key changes in the soft matter liquid-crystalline organization upon stimuli-induced phase transitions. They permit establishing of the inner nanostructure transformation kinetics and determination of the precise sizes of the hydrophobic membraneous compartments and the aqueous channel diameters in self-assembled network architectures. Time-resolved structural studies accelerate novel biomedical, pharmaceutical, and nanotechnology applications of nanochannel soft materials by providing better control of DNA, peptide and protein nanoconfinement, and release from diverse stimuli-responsive nanocarrier systems.

Immobilization of nanostructured lipid particles in polysaccharide films

Lipid-based equilibrium self-assemblies and their hierarchically ordered forms have been known since the last few decades. Related progress in colloids and interface science led the development of oil-in-water type internally self-assembled lipid particles, known as Isasomes, which have aroused great interest in biotechnological applications. These submicrometer-sized lipid particles are internally nanostructured in a form of various liquid-crystalline or microemulsion phases, which facilitate their loading with hydrophilic, hydrophobic, and amphiphilic molecules. Their internal nanostructure can also be finely tuned. Recently, it has been shown that Isasomes can be entrapped in thermoreversible polysaccharide hydrogels. Herein, we report on the immobilization of Isasomes in solid polysaccharide films prepared by drying particle-loaded κ-carrageenan and methyl cellulose-based hydrogels. These rather simple but elegant media facilitate the storage of these functional particles and their subsequent release by simple resolubilization in water and/or thermal transitions. Systematic rehydration studies of such Isasome-loaded films have shown that the Isasomes can be remobilized and/or recovered after resolubilization of loaded films, even after several months.

Internally self-assembled thermoreversible gelling emulsions: ISAsomes in methylcellulose, kappa-carrageenan, and mixed hydrogels

Self-assembled thermo-gelling emulsions were developed by blending internally self-assembled particles (ISAsomes) with thermoreversible polysaccharide hydrogels of methylcellulose (MC), kappa-carrageenan (KC), and their 1:1 mixture. In this way, the hierarchical structure of ISAsome samples was successfully promoted. The gelified polymer network corresponds to the highest level of the hierarchical structure and as such represents the capturing matrix for the medium structural level, i.e., dispersed emulsion particles, which are further internally structured as the lowest level of structure. Utilizing small-angle X-ray scattering, differential scanning calorimetry, dynamic light scattering, and oscillatory rheological experiments in the temperature regime from 20 to 70 degrees C, we were able to show that the ISAsomes stay practically intact during such embedment into a hydrogel matrix retaining its internal self-assembled structure and its functionality. The characteristic sol-gel and gel-sol transition temperatures of the ISAsome-loaded hydrogel samples showed a slight shift in comparison to the unloaded hydrogel samples. Furthermore, we found that MC is actually able to stabilize the ISAsomes at higher temperatures (tests were conducted up to 90 degrees C). Gels made from MC and KC show quite different features in terms of rheology and differential scanning calorimetry. However, the most interesting results were obtained for the ISAsome-loaded MC-KC (1:1) gelifying system, which behaves as a low- and high-temperature gel with a narrow intermediate temperature window where it is a sol. This specific thermal behavior allows for easy temperature tuning of the system's aggregate state as well as the internal self-assembled structure. As such, this system is suggested to be further tested as the potential media for a temperature-controlled burst/sustained release media of various hydrophilic, hydrophobic, or amphiphilic guest functional molecules.