Biomedical Engineering Reference
In-Depth Information
microparticulate systems were described, including microspheres or microcapsules as delivery sys-
tems for naproxen, succinyl sulfathiazole, histatins, alendronate, minocycline, chlorhexidine, doxy-
cycline, or tetracycline. Polymers as alginate, chitosan, polyhydroxybutirate-co-hydroxyvalerate and
polyester polymers such as poly( L -lactide), poly( D , L -lactide), poly(glycolide) and copolymers, poly-
caprolactones, and polyphosphazenes were used to obtain the particulate systems. Some of these car-
riers have the advantage that they can be incorporated into typical oral formulations as suspensions
or toothpastes, or in hydrogels or novel bioadhesive drug-delivery systems, or they can even be
directly injected into the periodontal pocket. Local polymeric-based drug-delivery systems, such as
fibers, films, strips, gels, vesicular systems, microparticles, or nanoparticles have been used in den-
tistry for local drug delivery to provide adequate drug concentrations directly at the site of action.
These systems are usually inserted into the periodontal pocket or injected in periodontal tissues to
enhance the therapeutic effect of drugs and reduce the side effects of drugs associated with their sys-
temic use [7,28,53,59,64] . Several specialized local delivery systems have been designed for the con-
trolled release of drugs in periodontal tissues; however, the complexity of accessing periodontal
tissues makes all of these systems only partially successful [25,28,59,60,65] .
Compared to microparticles, nanoparticles offer several advantages, such as the ability to pene-
trate extracellular and intracellular areas that may be inaccessible to other delivery systems due to
their small size, including the periodontal pocket areas below the gum line [7,28,61,66] , as shown
in Figure 23.7 . The confocal laser scanning microscopy studies carried out by Ganem-Quintanar
[67] established that biodegradable nanoparticles, when gently applied to the porcine gingival sul-
cular space, are able to penetrate into the junctional epithelium. Likewise, nanoparticles in the peri-
odontal pocket could be a drug-delivery system that reduces the frequency of administration, in
addition to providing an efficient active agent accumulation in the target sites over an extended
period of time, maintaining an effective drug release rate [2,7,59] . Furthermore, nanoparticles have
better stability in biological fluids. Unfortunately, there are very few studies on the preparation of
antibacterial nanoparticles for periodontal therapy [28] .
Poly( D , L -lactide) acid (PLA), poly(glycolic) acid, and poly( D , L -lactide-co-glycolide) acid (PLGA),
have been the central focus in the development of nano/microparticles encapsulating therapeutic
drugs in controlled release applications [68] . These materials offer several advantages, such as good
biocompatibility and biodegradability, mechanical strength, and ease of administration via injection;
in addition, the use of biodegradable materials allows sustained drug release within the target site
over a period of days or even weeks [55,63,68] .
In 2005, our research group [25] produced and characterized triclosan-loaded nanoparticles of
less than 500 nm in diameter to obtain a novel intrapocket delivery system adequate for the treatment
of periodontal disease. Triclosan (2,4,4 0 -trichloro-hydroxydiphenylether) (TCS) is a noncationic anti-
microbial agent with a recognized efficacy against several plaque-forming bacteria. The nanoparti-
cles are prepared using the previously patented emulsification
diffusion technique [69] . PLGA,
PLA, and cellulose acetate phthalate were used as polymer and nanoparticles were stabilized with
poly(vinyl alcohol). Different TCS/polymer ratios were used in order to analyze the effect of TCS on
nanoparticle properties. Scanning electron microscopy and light scattering analysis indicated that
high concentrations of TCS appear to cause an increase in nanoparticles mean size. Differential scan-
ning calorimetry showed that solid TCS nanoparticles behaved as a homogeneous polymer matrix-
type delivery system where the drug (TCS) is molecularly dispersed, suggesting that TCS could
behave as a plasticizer. Additionally, a preliminary in vivo study was performed on dogs in which
Search WWH ::




Custom Search