**2. The usage of polyvinylpyrrolidone (PVP) in biomaterials**

PVP was largely employed as a reinforcing material for biocomposites in a variety of applications, including bone tissue engineering, soft implants, biosensors, and artificial cartilage substitutes [2]. PVP can also be used in the fabrication of PVA hydrogels-based composite scaffolds for bone tissue engineering [6].

Cheng et al. have shown that, in the case of bioactive glass ceramics (BG), PVP induced faster apatite deposition and maintained the hybrid structure during electrospinning and pre-oxidation. This led to bioactivity improvement of bioactive glass [5]. For bioactive glass fibers (sol-gel synthesis), Hatcher [7] have demonstrated that PVP facilitated the synthesis process and the control of the rheological properties (more homogeneous fibrous material). PVP acted as a stabilizer by preventing gelation of the sample for 4 months. This was effective for enhancing *in vitro* bioactivity and increased proliferation of such bioactive glass fibers [7].

Moreover, Xia et al., have also shown that the addition of PVP resulted in sufficient chain entanglement and the formation of smooth bioactive glass nanofibers (electrospinning technique combined with sol-gel processing) [8]. Borate-modified bioactive glass [9] (burning-out method) was successfully achieved thanks to PVP, which greatly improved the blend's homogeneity. Ali et al. have obtained ceriumdoped bioactive glass nanoparticles (scaffold fabrication) [10] by optimization of its mechanical properties using PVP. **Table 1** presents a list of published works focusing on bioactive glasses involving PVP.

Otherwise, PVP was used in some biomaterials for articular cartilage replacement because of its high hydrophilicity, which aids in the lubricating conditions of the resulting hydrogel [12]. PVP-based hydrogel was also obtained by radiation crosslinking and was effective for skin regeneration and wound dressing [13]. Multifunctional chitosan/ PVP/45S5 Bioglass® scaffolds were also innovative for bone tissue engineering applications because of their outstanding bioactivity and *in situ* antibiotic-releasing capability [11]. PVP acted as stabilizer by inhibiting the enzymatic degradation of chitosan [11].


#### **Table 1.**

*List of published works on bioactive glasses involving PVP.*
