## 4 Discussion  
Particle surface chemistry influences the initial interaction of this foreign material with the cells. Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible and biodegradable copolymer that is extremely attractive and effective as a polymeric drug delivery carrier for clinical applications. For instance, when paclitaxel-loaded PLGA nanoparticles (NPs) were introduced in Hela cells to test their antiproliferative effects, the use of the NP system resulted in enhanced cell apoptosis compared to the use of the drug alone, possibly because of the sustained release of drugs inside the cancer cells [31]. Poly(ethylene glycol) (PEG) is a neutrally charged polymeric material that has been used widely to produce stealth nanocarriers. This hydrophilic material prevents the aggregation of NPs by forming hydrogen bonds with the solvent, and it increases the steric distance between NPs [32]. PEG also produces surface barrier layers that reduce the adsorption of opsonin's present in the blood serum onto the NPs, thereby making the NPs \"invisible\" to phagocytic cells [33]. Therefore, coating the surface of PLGA with PEG, or \"PEGylation,\" is a commonly used approach for improving the efficiency of drug and gene delivery to target cells and tissues. [PERSON] and [PERSON] (2008) [34] reported that polymeric NPs have promising potential in cancer therapy. Particle size influences the distribution of carriers in vivo; the bioavailability, transport, and toxicity to the body; and the specificity of the carriers in the delivery systems [35]. In our study, the slightly larger size of the geranin-encapsulated poly(ethylene glycol)-_block_-poly(lactic-co-glycolic acid) (PEG-b-PLGA) NPs could have been due to the encapsulation in the PLGA segment, which formed a larger inner (hydrophobic) layer of the NP. The particle must be small enough to enter vesicles, which range in size from 10 nm to 5 \(\mu\)m diameter. [PERSON] and [PERSON] (2014) [36] suggested that polymeric NPs with sizes \(<\) 200 nm were taken up efficiently by cells. Thus, our data show that both types of synthesized PEG-b-PLGA NPs were at an optimal size for drug delivery and potentially for cellular uptake. The PDI value indicates monodispersity. When the particle size is distributed evenly, we would expect more NPs to be internalized into the cells once they have been exposed to the biological environment. A PDI value of \(\leq\) 0.2 is most commonly deemed acceptable in practice for polymer-based NP materials [37]. Figure 7: CCD 841 CoN cells viability after treatment with blank PEG-b-PLGA NPs and PEG-b-PLGA NPs encapsulated with geranin for 3 h. Data are expressed in mean \(\pm\) standard error of the mean from three independent experiments. \({}^{*}p<\) 0.05 indicates a significant difference from the untreated control group. Although our result did demonstrate a slightly higher PDI value, it is still considered to be in the acceptable range of 0.20 to 0.29. Particle stability is shown by the zeta potential value, which is measured to identify the repulsion between particles; the higher the zeta potential value, the stronger the repulsion and more stable the NPs are. In our study, both groups of NPs were in a stable suspension, with zeta potential values of \(<-25\) mV. The value of the PEG-b-PLGA NPs was due to the presence of an ether bond in the PEG structure. Alkoxide ions in the ether bond are negatively charged. These amphiphilic NPs have hydrophilic and hydrophobic terminals. The outer shell of the hydrophilic layer consists of PEG, and it has a negative charge. When it was encapsulated with geranin, which is very hydrophilic, the zeta potential value decreased slightly. Presumably, the presence of oxygen atoms in the ester bonds of this structure contributed to additional negative charges for this NP. Zeta potential also is pH-dependent. NPs undergo a pH change from the acidic pH 2 in the stomach to pH 7 in the gastrointestinal tract.