**9.2. Determination of polymer stability**

may represent a future challenge to achieve promising agents for regional drug delivery in

Nanoparticles can also be solid or soft colloidal matrix‐like polymeric particles or lipids. They can be drug carrier system such as liposomes. Other drug delivery sys‐ tems are based on using nanoparticles composed of biodegradable polymers, this has been explained in the earlier subsection on polymeric drug delivery system [17]. These microparticles may consist of polymeric nanospheres in an oily reservoir or aqueous medium. It was shown in research that a numbers of analgesic drugs such as ibuprofen, flurbiprofen, and acetyl salicylic acid have been successfully delivered by entrapping in

Liposome is a drug delivery system suitable for various routes of drug administration, i.e., oral, rectal, parenteral, and particularly local administration to the skin, eye, and mucous membranes [19]. Liposomes are microscopic phospholipid‐bilayered vesicles and they have the advantage in which they can be used to entrap both hydrophilic and lipophilic drug for delivery. **Figure 15** illustrates the formation of liposome for drug delivery. Liposomes are generally administered by intravenous route but they are also developed for transdermal or

Using the liposomal concept "LipoSpray" is an innovative idea in delivering an analge‐ sic in the form of liposomal suspension. The suspension is sprayed into the mouth and under the tongue. Liposomes penetrate the mucosal tissue of the mouth, and the drug is released from the liposome into the bloodstream, distributing the drug throughout the

This path bypasses the gastrointestinal (GI) track and bypasses the first‐pass effect of the liver.

The analgesic in question would have a fast effect in pain management.

**Figure 15.** Various morphology of the polar and nonpolar arrangements in liposome and its formation.

pain management strategy.

26 Pain Relief - From Analgesics to Alternative Therapies

nanoparticles [18].

subcutaneous implantation.

body in minutes.

**8.1. The concept of LipoSpray**

**8. Multiphase liposomal drug delivery system**

Another important criterion is to determine the *in vitro* degradation of the polymer so as to ensure its stability as required. The *in vitro* degradation study can be carried out through preparing polymeric devices and placing them in phosphate buffer solution for different peri‐ ods of time, and analyzing their wet and dry weight loss [20].

Scanning electron micrographs of sample need to be taken by scanning electron microscope (SEM) to observe the erosion characteristics of the polymer. SEM is a technique for the preparation of high resolution images from surface of different compounds. Electrons are used for imaging in scanning electron microscopes.

The differential scanning calorimetry (DSC) is also a requirement in the determination of the thermal stability of the polymeric system [21].

## **9.3. Cytotoxicity issues**

If the polymer being optimized is a new polymer then it is important to establish the cytotoxicity of the synthesized polymer to evaluate whether the polymer is appropriate for application in drug delivery systems or not. In other words, the synthesized polymer should be nontoxic to normal body cells and tissues, and cause minimum side effects at the site of action. There are different types of tests and assays for the evaluation of cytotoxicity of polymers, as well as drugs. Cell‐based assays are the most widely used methods for assessing cell toxicity effects of different polymers or drugs on a particular cell line.

#### **9.4. Preparation of drug‐loaded polymeric system**

Thin film hydration method can be one of the methods for the preparation of the drug‐loaded polymeric system. An example is by using a solution of 2 mg/ml of polymer in ethanol (10 ml) and mixed with a solution of 5 mg/ml model drug in ethanol (1 ml). After stirring for 15 minutes at room temperature, the solvent needs to be evaporated by rotary evaporator. The precipitant is then mixed with 20 ml distilled water. The mixture is then centrifuged at 6000 rpm for 10 minutes. The supernatant is then taken for further analysis for entrapment characteristics of the drug in the polymer.
