Poly(ϵ-caprolactone) microcapsules and nanocapsules in drug delivery.

INTRODUCTION: Poly(ϵ-caprolactone) (PCL), a biodegradable and biocompatible polymer, is useful to encapsulate a wide range of drugs making it an interesting material for the preparation of carriers with potential applications in therapeutics. AREAS COVERED: The design and development of those carriers to modulate drug release, to improve the drug stability or apparent solubility in aqueous media, as well as to target tissues and organs are discussed. EXPERT OPINION: Microencapsulation is a well-established process in pharmaceutical industry to protect drugs from chemical degradation and to control drug release. In this context, PCL is a useful polymer to prepare microcapsules. Nanoencapsulation, a more recent approach, offers new possibilities in drug delivery. PCL can be used as polymer to prepare different types of nanocapsules presenting diverse flexibility according to the chemical nature of the core. Those nanocapsules are capable of controlling drug release and improving photochemical stability. In addition, they can modulate cutaneous drug penetration/permeation and act as physical sunscreen due to their capability of light scattering. Considering the pharmaceutical point of view, PCL nanocapsules are versatile formulations, once they can be used in the liquid form, as well as incorporated into semi-solid or solid dosage forms.

Hydrogels containing redispersible spray-dried melatonin-loaded nanocapsules: a formulation for transdermal-controlled delivery.

The aim of the present study was to develop a transdermal system for controlled delivery of melatonin combining three strategies: nanoencapsulation of melatonin, drying of melatonin-loaded nanocapsules, and incorporation of nanocapsules in a hydrophilic gel. Nanocapsules were prepared by interfacial deposition of the polymer and were spray-dried using water-soluble excipients. In vitro drug release profiles were evaluated by the dialysis bag method, and skin permeation studies were carried out using Franz cells with porcine skin as the membrane. The use of 10% (w/v) water-soluble excipients (lactose or maltodextrin) as spray-drying adjuvants furnished redispersible powders (redispersibility index approximately 1.0) suitable for incorporation into hydrogels. All formulations showed a better controlled in vitro release of melatonin compared with the melatonin solution. The best controlled release results were achieved with hydrogels prepared with dried nanocapsules (hydrogels > redispersed dried nanocapsules > nanocapsule suspension > melatonin solution). The skin permeation studies demonstrated a significant modulation of the transdermal melatonin permeation for hydrogels prepared with redispersible nanocapsules. In this way, the additive effect of the different approaches used in this study (nanoencapsulation, spray-drying, and preparation of semisolid dosage forms) allows not only the control of melatonin release, but also transdermal permeation.