## 3 Results
### Analysis Part  
#### 3.2.1 Comparative PDI, Particle Size and Stability Analyses of DFMACs at Different pH Values  
The surface charge, zeta potential and pH of particles are crucial for understanding the state and stability of dispersions [27; 28]. In Zeta-sizer measurements, the polydispersity index, particle size, mobility and zeta potential of drugs and DFMACs were monitored in terms of homogeneity, charge of the particles and stability. The gastrointestinal tract (GI) spans from the stomach (pH 1.5-3.5) through the duodenum (pH 5-6) to the intestine (pH 7-8) [29; 30]. Therefore, the drugs and DFMACs were evaluated across a broad pH scale. Figure 7: FTIR/ATR spectra of PEMA, CEF and PEMA-CEF. The polydispersity index (PDI) defines the distribution of particle sizes in a population. A PDI 0.0 value indicates perfectly uniform particles (monodispersity) whereas a PDI 1.0 value indicates a range of particle sizes, namely, polydispersity [31]. PDI analyses are crucial for assessing the efficiency of the DFMACs. All drugs and DFMACs were evaluated in terms of PDI, particle size and stability analyses, respectively. In Table 2, polydispersity index (PDI) values of AMP, CEF and all DFMACs are shown with changing pH values. The polydispersity index belonging to DFMACs in solution should be as low as possible and the size distribution should be monodispersed [32]. Particles of all DFMACs were monodispersed in this pH range. Although all drugs and DFMACs were monodispersed, PIBMA-conjugated drugs exhibited lower PDI values than the others at different pH values. Hydrophobic group attachment leads to a slight decrease in PDI values [33]; likewise, the same effect was seen in PDI analysis. The distribution of particles was not significantly affected by the pH change. Particle size affects the drug dissolution, absorption [34] and pharmacokinetics [31] in orally given solid drugs like AMP and CEF. In Table 3, at both extremes of the studied pH range, the size of the particles of AMP and DFMACs increased and clustered. pH values between 5 and 8 gave the ideal particle size for AMP and DFMACs, in terms of aggregation. According to Table 3, CEF particles accumulated in the middle of the pH range, whereas particles of CEF conjugated maleic anhydride copolymers were dispersed in solution when their particle size was considered. All particles were of a sub-micro scale less than 1000 nm. Particle sizes between 1 and 1000 nm have special advantages in the oral administration of drugs [35]. According to [PERSON] et.al. 's study [36], polymeric particles of sub-micro scale possess certain properties such as standardized fabrication, higher drug loading capacity, biodegradability and in vivo degradability. The mobility values of AMP, CEF and all DFMACs with changing pH values are given in Table S1. All the particles of drugs and DFMACs were negatively charged across the whole pH range. The absolute mobility values of DFMACs were higher than those of AMP and CEF. The stability of particle dispersion in a solution is assessed by zeta potential analysis. A value of zeta potential of \(\pm 10\) mV indicates incipient stability [37] while a value greater than \(\pm 25\) mV indicates a stable suspension [38]. The stability of dispersion is maintained by the electrostatic repulsion between the charged particles [38]. A higher value of zeta potential whether positive or negative indicates physically stable suspensions [39; 40].