# Recent Developments in Materials Science for the Conservation and Restoration of Historic Artifacts
## 5 Biopolymers: Sustainable Conservation Solutions
### Case Studies  
Although the studies in this area are in the early stages, several case studies illustrate the successful application of biopolymers in artifact conservation. The study of [PERSON] et al. [92] evaluated the potential of chitosan as a treatment agent for textile artifacts, demonstrated on two Romanian traditional shirts. The results of the study shirts (performed by chitosan application and subsequent investigations by scanning electron microscopy) revealed the removal of foreign materials on the shirt fibers, as well as a limitation of the number of microorganisms observed, thus proposing a simple and sustainable method for textile conservation. [PERSON] et al. [93] explored the use of calcium/chitosan nanoparticles (Ca/CS NPs) as an innovative solution to preserve paper-based historical artifacts from microbial damage, particularly from bacteria and fungi commonly found on paper. The results obtained suggested that the addition of calcium to chitosan nanoparticles notably improved their antimicrobial efficacy against microbial strains such as _E. coli_ and _C. albicans_ compared to chitosan nanoparticles. Antibacterial tests demonstrated that Ca/CS NPs showed a stronger inhibitory effect, especially against Gram-positive bacteria like Bacillus megaterium and Bacillus subtilis. This suggests that Ca/CS NPs can be applied at lower doses while maintaining robust antimicrobial protection, reducing potential stress on fragile artifacts. Moreover, the increase in pH initially observed upon the application of Ca/CS NPs was stabilized over time, a significant aspect, as maintaining a neutral or slightly alkaline pH is essential for the longevity of paper artifacts and acidic conditions accelerate degradation. As a conclusion of the study, the authors support the use of Ca/CS NPs as a conservation material for paper artifacts, offering the dual benefits of effective microbial inhibition and pH stabilization [93]. [PERSON] et al. [94] investigated the use of chitosan (Cs), chitosan nanoparticles (CsNPs), and silica-loaded chitosan nanoparticles (SiO\(\underline{\oplus}\)CsNPs) to enhance the consolidation and protection of mural paintings, specifically focusing on the facade of [PERSON]'s palace gate from ancient Egypt. The findings show that these biopolymer-based materials, especially when modified with nanosilica, offer significant benefits for mural conservation, offering a sustainable alternative to traditional synthetic consolidants. According to the cited study, both CsNPs and SiO\(\underline{\oplus}\)CsNPs proved more effective than traditional chitosan in consolidating and stabilizing painted stone surfaces. The study indicates that the inclusion of silica nanoparticles improves the hydrophilic/hydrophobic balance, providing enhanced adhesion to stone and painted layers, which is crucial for mural preservation. At 1% concentration, the SiO\(\underline{\oplus}\)CsNPs formed a homogeneous layer, as shown by SEM analysis, which connected the pigment and stone layers effectively without altering the surface's visual characteristics. Moreover, SiO\(\underline{\oplus}\)CsNPs exhibited better mechanical scrub resistance, an important property for murals exposed to environmental wear. The nano-silica additive also increased UV resistance, suggesting a longer-lasting preservation effect under exposure to light. The biopolymer formulations displayed robust antimicrobial activity, inhibiting the growth of bacteria and fungi such as Staphylococcus aureus, _E. coli_, Candida albicans, and Aspergillus niger. This antimicrobial effect reduces biodeterioration risks, which are common in exposed cultural heritage artifacts. The colorimetric analysis showed minimal changes in the visual appearance of the treated surfaces, which is critical in conservation to preserve the artifact's original aesthetic. SiO2@CsNPs, in particular, achieved better consolidation without clumping or affecting color, making it suitable for maintaining the artifact's integrity. [PERSON] et al.