**Author details**

Recently, Shamma et al. [102] have investigated injectable *in situ* forming scaffolds loaded with risedronate (bone resorption inhibitor) and with lornoxicam (anti-inflammatory drug) for non-surgical treatment of periapical lesions. They have tested two insoluble copolymers, such as PLGA (ester-terminal) and PLGA-A (acid-terminal). Additionally, sucrose acetate isobutyrate (SAIB) has also been added as a high viscosity water-insoluble carrier as well as porogenic agents like hydrolysed collagen. The scaffolds prepared using 30% (w/v) PLGA or combined PLGA: SAIB (1:1, w/w) with total polymer concentration of 30% (w/v) possessed the most sustained drug-release profile and their application improved the inflammation and enhanced the formation of new bony regions. These results confirm the success of the pre-

Nagarajan et al. [103] have synthesized two star-shaped PLA polymers with dipyridamole molecular core as a coating material for making coronary stents. The authors have used *l*-lactide and *dl*-lactide for their preparation. The difference in the features of both coating biomaterials was explained with the crystallinity of the polymers synthesized as well as with the fact that the *l*-form is normally available in humans. The experimental results showed that the new star-shaped PLA polymers with dipyridamol core were bio- and hemo-compatible, and possessed enhanced angiogenic properties. This is another proof for the great importance of the synthetic-based polymer carriers and their application in the pharmaceutical practice.

The main application of NPs as DDSs and the challenges, regarding to this, lies on the efficient administration of these carriers. Along with all the benefits that these DDSs provide, the choice of route of administration is essential to their performance. The difficulties are related

Unconditionally, the use of NPs as DDSs may solve most of the problems of drug delivery, mainly related with low bioavailability in the target tissues. Mucoadhesive, mucus-penetrating NPs or 'nano-in-micro-particle' DDSs may significantly increase the retention time on the mucous surface by enhancing the drug absorption and thereby improving drug bioavailability. Nanotechnologies are able to overcome the physiological barriers of the different tissues regarding the route of administration. Polymeric carriers have a stabilizing role on the drug included. They protect it from the unfavourable impact of the environment or the biological fluids. The synthetic-based polymer nano-carriers can assure a controlled release in the target tissue and minimize the side effects. The advantages that these could provide unconditionally improve the drug bioavailability, reduce the administration frequency and dose and enhance the patient compliance. Still not well assessed, the problem with the eventual toxicity and adverse effects of these drug carriers must draw our attention. Although polymeric particles may be biodegradable, their degradation rate must be analysed and toxicity profiles must be assessed in various *in vitro*, *ex vivo* and *in vivo* models. The development and application of

strict safety rules are needed to create an effective and safe drug formulation.

In the future, the main emphasis of investigations will be put on the achievement of a noninvasive drug administration, aiming targeted and controlled release of API with a minimal

pared scaffolds as an innovative approach in the treatment of bone defects.

**3. Conclusion and future prospects**

116 Acrylic Polymers in Healthcare

to their absorption at the proper organs, tissues and cells.

Velichka Andonova

Address all correspondence to: andonova\_v@abv.bg

Faculty of Pharmacy, Department of Pharmaceutical Sciences, Medical University of Plovdiv, Plovdiv, Bulgaria
