Formation and characterisation of a modifiable soft macro-porous hyaluronic acid cryogel platform

<div><p>A facile method for the synthesis of cell supportive, highly macro-porous hyaluronic acid (HA) hydrogels via cryogelation is presented. Unmodified HA was chemically cross-linked via EDC/NHS zero-length cross-linking at sub-zero temperatures to yield cryogels with high porosity and high pore interconnectivity. The physical properties of the HA cryogels including porosity, average pore size, elasticity and swelling properties were characterised as a function of cryogelation conditions and composition of the precursor solution. The HA cryogels swell extensively in water, with the average porosities observed being ~90% under all conditions explored. The morphology of the cryogels can be controlled, allowing scaffolds with an average pore size ranging from 18 ± 2 to 87 ± 5 μm to be formed. By varying the cross-linking degree and HA concentration, a wide range of bulk elastic properties can be achieved, ranging from ~1 kPa to above 10 kPa. Preliminary cell culture experiments, with NIH 3T3 and HEK 293 cell lines, performed on biochemically modified and unmodified gels show the cryogels support cell proliferation and cell interactions, illustrating the biomedical potential of the platform.</p></div

Size and Phase Control of Cubic Lyotropic Liquid Crystal Nanoparticles

The effective use of lyotropic liquid crystalline dispersions, such as cubosomes, as drug delivery vehicles requires that they have tailored physical characteristics that suit specific therapeutics and external conditions. Here, we have developed phytantriol-based cubosomes from a dispersion of unilamellar vesicles and show that we can control their size as well as the critical packing parameter (CPP) of the amphiphilic bilayer through regulation of temperature and salt concentration, respectively. Using the anionic biological lipid 1,2-dipalmi-toylphosphatidylserine (DPPS) to prevent the cubic phase from forming, we show that the addition of phosphate buffered saline (PBS) results in a transition from small unilamellar vesicles to the cubic phase due to charge-shielding of the anionic lipid. Using dynamic light scattering, we show that the cubosomes formed following the addition of PBS are as small as 30 nm; however, we can increase the average size of the cubsosomes to create an almost monodisperse dispersion of cubosomes through cooling. We propose that this phenomenon is brought about through the phase separation of the Pluronic F-127 used to stabilize the cubosomes. To complement previous work using the salt-induced method of cubosome production, we show, using synchrotron small-angle X-ray scattering (SAXS), that we can control the CPP of the amphiphile bilayer which grants us phase and lattice parameter control of the cubosomes

Photocontrolled Cargo Release from Dual Cross-Linked Polymer Particles

Burst release of a payload from polymeric particles upon photoirradiation was engineered by altering the cross-linking density. This was achieved via a dual cross-linking concept whereby noncovalent cross-linking was provided by cyclodextrin host–guest interactions, and irreversible covalent cross-linking was mediated by continuous assembly of polymers (CAP). The dual cross-linked particles (DCPs) were efficiently infiltrated (<i>∼</i>80–93%) by the biomacromolecule dextran (molecular weight up to 500 kDa) to provide high loadings (70–75%). Upon short exposure (5 s) to UV light, the noncovalent cross-links were disrupted resulting in increased permeability and burst release of the cargo (50 mol % within 1 s) as visualized by time-lapse fluorescence microscopy. As sunlight contains UV light at low intensities, the particles can potentially be incorporated into systems used in agriculture, environmental control, and food packaging, whereby sunlight could control the release of nutrients and antimicrobial agents

Photocontrolled Cargo Release from Dual Cross-Linked Polymer Particles

Burst release of a payload from polymeric particles upon photoirradiation was engineered by altering the cross-linking density. This was achieved via a dual cross-linking concept whereby noncovalent cross-linking was provided by cyclodextrin host–guest interactions, and irreversible covalent cross-linking was mediated by continuous assembly of polymers (CAP). The dual cross-linked particles (DCPs) were efficiently infiltrated (<i>∼</i>80–93%) by the biomacromolecule dextran (molecular weight up to 500 kDa) to provide high loadings (70–75%). Upon short exposure (5 s) to UV light, the noncovalent cross-links were disrupted resulting in increased permeability and burst release of the cargo (50 mol % within 1 s) as visualized by time-lapse fluorescence microscopy. As sunlight contains UV light at low intensities, the particles can potentially be incorporated into systems used in agriculture, environmental control, and food packaging, whereby sunlight could control the release of nutrients and antimicrobial agents