Reagents and Materials
Poly(lactic-co-glycolic acid) (PLGA) with a 50:50 monomer ratio and a defined molecular weight was used as the polymer matrix. [Name of model drug, e.g., curcumin or another appropriate compound] was used as a model hydrophobic active pharmaceutical ingredient (API). Polyvinyl alcohol (PVA, 87–89% hydrolysis degree) was used as an emulsion stabilizer. Organic solvents (dichloromethane, acetone) and buffer components were of analytical grade or higher.
Synthesis of Drug-Loaded Nanoparticles
Model drug-loaded PLGA nanoparticles (NPs) were prepared using the double emulsion water-in-oil-in-water (w/o/w) solvent evaporation method. Briefly, an aqueous solution of the internal phase was emulsified in a solution of PLGA and the hydrophobic drug in an organic solvent (dichloromethane) using an ultrasonic homogenizer to obtain a primary emulsion (w/o). The resulting emulsion was slowly introduced into an external aqueous phase containing a stabilizer (PVA) under continuous stirring to form a secondary emulsion (w/o/w). The organic solvent was removed by evaporation under reduced pressure using a rotary evaporator. The resulting nanoparticles were collected by centrifugation, washed three times with distilled water to remove excess PVA and unencapsulated drug, and then lyophilized for further storage.
Encapsulation Efficiency (EE%)
Encapsulation efficiency ($EE\%$) was determined by an indirect method. For this purpose, the NP suspension was centrifuged, and the supernatant was analyzed for free drug content using high-performance liquid chromatography (HPLC). The $EE\%$ was calculated using the following formula:
$$EE\% = \frac{\text{Total amount of drug} – \text{Amount of free drug}}{\text{Total amount of drug}} \times 100\%$$
In Vivo Pharmacokinetics and Biodistribution Studies
The experiments were conducted on male Wistar rats (weighing 200–250 g). The animals were housed under standard vivarium conditions with free access to food and water. All procedures were performed in accordance with ethical standards for the handling of laboratory animals.
The animals were randomized into two groups (n = 6 per group). The first group (control) received an intravenous injection (via the tail vein) of the free drug solution, while the second group received an equivalent dose of the drug encapsulated in PLGA-NPs.
