## 8 Degradation of PCL-Based Multiarms  
The degradation of PCL-based products has been mentioned in several studies. PCL completely degrades in the presence of _Pseudomonas lipase_ within 4 days [209], whereas hydrolytic degradation in the absence of enzymes takes several years [210]. This rapid enzymatic degradation of PCL highlights its importance in terms of biodegradation [211]. Only three types of lipases obtained from bacteria or fungi, namely _Rhizopus demer_[212], _Rhizopus arrhizus_[213], and _Pseudomonas_[214], effectively accelerate the degradation of PCL.  
When multi-arm copolymers with poly (caprolactone) (PCL) were subjected to degradation in a pH 7.4 PBS solution at 37 \({}^{\circ}\)C, it was observed that the degradation rate increased with a decrease in the arm length of PCL or an increase in the number of arms. Previous research has indicated that the enzymatic degradation of PCL is caused by random chain scission of the polymer backbone, regardless of the length of the chain [215].  
Figure 21: The effect of arm number on the encapsulation parameters of micelles formed from supramolecular structures based on \(\beta\)-cyclodextrintrin.  
According to reports, the enzymatic degradation of PCL is affected by the degree of crystallinity, with the level of crystallinity increasing during the initial stages of degradation, indicating that the amorphous regions are primarily broken down. Furthermore, it has been suggested that the degradation of PCL occurs mainly at the chain ends, folds, and crystal edges, where chain mobility is higher. This finding suggests that the type of architecture, including variations in the number of branches, can affect the degradation process [216; 217; 218].  
In a work by [PERSON] [219], a comparative study of degradation of different PCL-PEG-based architectures (Figure 22) is proposed. Four-armed PCL were connected to a PEG central unit (PCL)\({}_{2}\)-PEG-(PCL)\({}_{2}\) (with different PEG contents), six-armed star-shaped PCL (PCL)\({}_{3}\)-b-(PCL)\({}_{3}\) were compared with Y-shaped copolymers PEG-(PCL)\({}_{2}\), and linear triblock copolymers PCL-b-PEG-b-PCL were subjected to enzymatic hydrolysis using lipase and cutinase. These studies showed an increased swelling and fragmentation in all copolymers due to the presence of PEG, leading to a faster loss of mass during enzymatic degradation using lipase. In contrast, the enzymatic degradation rate using cutinase generally decreased with an increase in PEG content in the case of PEG (PCL)\({}_{2}\)-b-PEG-b-(PCL)\({}_{2}\), indicating that PEG chains slowed down the degradation effect of PCL in copolymers and that PCL was the only one subjected to enzymatic degradation. As mentioned earlier, this study showed that the %xc increased during the first two days of degradation, during which time mainly the amorphous regions were degraded. The second stage of degradation was followed by a decrease in crystallinity, as the PCL chains in the copolymers were degraded.  
Figure 22: Impact of Architecture of Different PCL-Based Polymers on Degradation Profile.  
Significantly, the Y-shaped copolymer PEG-(PCL)\({}_{2}\) showed the fastest enzymatic degradation rate by both cutinase and lipase enzymes. In fact, the slowest enzymatic degradation rate was observed in the case of the six-armed PCL copolymer (PCL)\({}_{3}\)-PEG-(PCL)\({}_{3}\), which is due to its high hydrophobicity and relatively high molecular weight.