50-nm diameter halloysite clay nanotubules with 15 nm lumen were used for loading poorly soluble drugs and sustaining their release. Loading was optimized by varying pH and alcohol/water ratio in the solvent with a maximum drug loading of 12 volume%. Near linear release of Dexamethasone, Furosemide, and Nifedipine was demonstrated for 5–10 hours. Its capacity for the time release of drugs, along with its simple loading procedure and the biocompatibility of halloysite nanotubules makes this method a prospective drug delivery system.

Mouse mesenchymal stem cells have been individually encased by polyelectrolyte layers of poly (L-lysine) and hyaluronic acid using the electrostatic layer-by-layer assembly technique, resulting in a shell consisting of nanolayers of thickness around 6-9 nm. Maintenance of cell morphology and viability were demonstrated for up to one week. Further adjustments to shell permeability and flexibility will facilitate the use of these encapsulated cells in tissue engineering and targeted-delivery applications.

The use of tubular halloysite clay as a nanotemplate for layer-by-layer (LbL) shell assembly and its utilization for controlled release of drug macromolecules are studied. The LbL nanoshell allowed additional control for the sustained release of drug loaded halloysite tubes. The number of polymeric layers in the shell and molecular weight of the assembled polymers influences the drug release rate. Three bilayer shells of chitosan and gelatin of 15 nm thicknesses gave the best encapsulation and retardation in the release rate of dexamethasone. An encapsulation of the macromolecules inside the lumen of the biocompatible clay nanotubes coupled with the polyelectrolyte shell formation provides a novel formulation for the controlled release of bioactive agents.

Layer-by-layer assembly uses alternating charged layers of polyionic polymers to coat materials sequentially in a sheath of functionalized nanofilms. Bacterial spores were encapsulated in organized ultrathin shells using layer-by-layer assembly in order to assess the biomaterial as a suitable core and determine the physiological effects of the coating. The shells were constructed on Bacillus subtilis spores using biocompatible polymers polyglutamic acid, polylysine, albumin, lysozyme, gelatin A, protamine sulfate, and chondroitin sulfate. The assembly process was monitored by measuring the electrical surface potential (zeta-potential) of the particles at each stage of assembly. Fluorescent laser confocal microscopy and scanning electron microscopy confirmed the formation of uniform coatings on the spores. The coating surface charge and thickness (20-100 nm) could be selectively tuned by using appropriate polymers and the number of bilayers assembled. The effect of each coating type on germination was assessed and compared to native spores. The coated spores were viable, but the kinetics and extent of germination were changed from control spores in all instances. The results and insight gained from the experiments may be used to design various bioinspired systems. The spores can be made dormant for a desired amount of time using the LbL encapsulation technique and can be made active when appropriate.

Cover: Halloysite clay nanotubes are used for encapsulation and sustained release of bioactive compounds. A layer-by-layer assembly of polyelectrolyte shells of different compositions on these nanotubes allows additional control over drug release rate. Further details can be found in the article by N. G. Veerabadran, D. Mongayt, V. Torchilin, R. R. Price, and Y. M. Lvov* on page 99.