Processing and Scale-up of Polymeric Nanoparticles - Intracellular Delivery: Fundamentals and Applications - page 449

(Labarre et al. 2005 ; Bertholon et al. 2006 ). (4) Once the drug carrier has reached
the target site, the cargo should be released. The main challenge in this task is that
the drug will be retained by the formulation all along the way from the site of
administration down to the target site. Indeed, burst release from nanoparticles is
often pointed out as a problem which compromises the delivery of enough amount
of drug to the target because of the premature leak of the carrier. New formulation
approaches integrate stimuli responsive materials allowing triggered drug release.
Thus, the drug remains associated with the carrier until it is triggered by local
in vivo variation of either temperature, pH or electrolyte concentrations due to the
physiopathology of the targeted area. The drug release can also be triggered from
the outside of the body using the action of a magnetic field or of the illumination
by light (Bawa et al. 2009 ). Design of nanoparticles with such properties are fea-
sible with the recent development of stimuli-responding polymers (Stuart et al.
2010 ) but lots of efforts are still needed to make these materials acceptable for a
safe use in drug delivery formulations. (5) By integrating both drug delivery proper-
ties and contrast agent properties in a single nanoparticle, this more complex nano-
particulate drug delivery system is ready to enter the era of theragnostic. A couple
of prototypes have been designed and it can be expected that multifunctional
nanoparticles will be the next step in the development of drug delivery systems
(Schärtl 2010 ).

6 Conclusion and Perspectives

Numerous methods can be used to produce nanoparticles from preformed
polymers to improve drug delivery. Several methods are ready for large scale
production. Purification, freeze drying and sterilization still need improvements
to make possible treatment of large batches and to prevent aggregation. Future
developments of nanoparticles for drug delivery are going towards multifunc-
tional nanoparticulate systems eventually integrating stimuli responsive function-
alities. The methods described in this chapter should easily be applicable with
minor modifications with the new materials to produce the next generation of
nanocapsules and nanospheres.

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