Gels and Eco-Materials Used for Heritage Conservation

A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Applications".

Deadline for manuscript submissions: closed (31 May 2024) | Viewed by 10674

Special Issue Editors


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Guest Editor
Department of Musicology and Cultural Heritage, University of Pavia, Cremona, Italy
Interests: non-invasive techniques; FTIR spectroscopy; X-ray fluorescence; artwork cleaning
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Special Issue Information

Dear Colleagues,

The scientific interest in eco-friendly gels and biopolymers is consistently growing in different fields including Cultural Heritage conservation. Gels are highly versatile products with different physicochemical and rheological properties which can be modified according to the purpose of use. Outstanding advancements in Cultural Heritage applications relate to the production of environmentally responsible materials (e.g., hydrogels, organogels, high-density polymer dispersion) with the ability to control the solvent delivery during the cleaning of heritage objects; their use as selective substrates for sampling bio-pollutants or volatile organic compounds in the environment is of great interest as well.

The intent of this Special Issue is to collect the latest advances in biomaterials and green gels and their applications in Cultural Heritage conservation, to progress our knowledge about the physicochemical properties of these products and to promote their eco-sustainable production.

In this respect, this Special Issues welcomes original and review articles on topics including—but not limited to—the following:

  • Hydrogels, organogels, aerogels, bio-polymer gel-like materials and their applications in Cultural Heritage field;
  • Eco-sustainable gels, green gels, green solvents with potential application in Cultural Heritage conservation;
  • Mechanical properties and retention capability measurements;
  • Analytical evaluation of gels’ performances with a specific focus on non-invasive and micro-invasive methods;
  • Applications in artworks cleaning, bio-active coatings, VOC sampling, gel-assisted sampling.

Dr. Francesca Volpi
Dr. Antonio Sansonetti
Guest Editors

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Keywords

  • bio-based hydrogels
  • green gels
  • aerogel
  • Cultural Heritage
  • cleaning
  • consolidation
  • analytical evaluation
  • swelling and retention capability
  • mechanical measurements
  • VOC sampling

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Published Papers (6 papers)

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Research

14 pages, 3391 KiB  
Article
Bacterial Nanocellulose Hydrogel for the Green Cleaning of Copper Stains from Marble
by Erica Sonaglia, Emily Schifano, Mohammad Sharbaf, Daniela Uccelletti, Anna Candida Felici and Maria Laura Santarelli
Gels 2024, 10(2), 150; https://doi.org/10.3390/gels10020150 - 18 Feb 2024
Cited by 6 | Viewed by 2069
Abstract
Cultural heritage stone materials frequently experience significant discoloration induced by copper corrosion products, especially calcareous stones associated with bronze or copper statues and architectural elements. This alteration originates from the corrosion of unprotected copper, resulting in the formation of various Cu minerals and [...] Read more.
Cultural heritage stone materials frequently experience significant discoloration induced by copper corrosion products, especially calcareous stones associated with bronze or copper statues and architectural elements. This alteration originates from the corrosion of unprotected copper, resulting in the formation of various Cu minerals and the migration of soluble ions to adjacent stone materials. Traditional cleaning methods involve mechanical, chemical, and laser techniques, which are generally time-consuming, costly, not ecological, or can possibly damage original materials. The loading of highly effective chelating agents, such as ethylenediaminetetraacetic acid (EDTA), into hydrogels has recently been exploited. However, the preference for synthetic hydrogels has been prominent until now, although they lack renewability and biodegradability and require high costs. This study explores for the first time the potential to clean copper corrosion with bacterial nanocellulose (BC) loaded with EDTA as a biologically based, sustainable, and biodegradable hydrogel. The BC hydrogel was characterised by field emission–scanning electron microscopy (FE–SEM), X-ray diffraction analysis (XRD), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR), simultaneous thermal analysis (TG-DSC), and tensile testing. It revealed a nano-fibrous structure with high crystallinity and purity and mechanical properties suitable for cultural heritage applications. The EDTA-loaded hydrogel effectively removed copper stains from marble after 120 min of application. Micro-Raman and colorimetric analyses assessed the cleaning efficacy. The study introduces bacterial nanocellulose as a green and effective alternative for heritage conservation, aligning with sustainable methodologies in stone conservation. Full article
(This article belongs to the Special Issue Gels and Eco-Materials Used for Heritage Conservation)
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16 pages, 4125 KiB  
Article
In Vitro Viability Tests of New Ecofriendly Nanosystems Incorporating Essential Oils for Long-Lasting Conservation of Stone Artworks
by Flavia Bartoli, Leonora Corradi, Zohreh Hosseini, Antonella Privitera, Martina Zuena, Alma Kumbaric, Valerio Graziani, Luca Tortora, Armida Sodo and Giulia Caneva
Gels 2024, 10(2), 132; https://doi.org/10.3390/gels10020132 - 6 Feb 2024
Cited by 2 | Viewed by 1679
Abstract
The study explores the application of natural biocides (oregano essential oil and eugenol, directly applied in solutions or encapsulated within silica nanocapsules) for safeguarding stone cultural heritage from biodeterioration, using green algae (Chlorococcum sp.) and cyanobacteria (Leptolyngbya sp.) as common pioneer [...] Read more.
The study explores the application of natural biocides (oregano essential oil and eugenol, directly applied in solutions or encapsulated within silica nanocapsules) for safeguarding stone cultural heritage from biodeterioration, using green algae (Chlorococcum sp.) and cyanobacteria (Leptolyngbya sp.) as common pioneer biodeteriogens. Core-shell nanocontainers were built for a controlled release of microbicidal agents, a safe application of chemicals and a prolonged efficacy. The qualitative and quantitative evaluations of biocide efficiency at different doses were periodically performed in vitro, after six scheduled intervals of time (until 100 days). The release kinetics of composite biocide-embedding silica nanocapsules were characterized by the UV-Vis spectroscopy technique. Data showed both promising potential and some limitations. The comparative tests of different biocidal systems shed light on their variable efficacy against microorganisms, highlighting how encapsulation influences the release dynamics and the overall effectiveness. Both the essential oils showed a potential efficacy in protective antifouling coatings for stone artifacts. Ensuring compatibility with materials, understanding their differences in biocidal activity and their release rates becomes essential in tailoring gel, microemulsion or coating products for direct on-site application. Full article
(This article belongs to the Special Issue Gels and Eco-Materials Used for Heritage Conservation)
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25 pages, 19068 KiB  
Article
Agar and Chitosan Hydrogels’ Design for Metal-Uptaking Treatments
by Luana Cuvillier, Arianna Passaretti, Elodie Guilminot and Edith Joseph
Gels 2024, 10(1), 55; https://doi.org/10.3390/gels10010055 - 11 Jan 2024
Cited by 8 | Viewed by 1926
Abstract
In the field of cultural heritage, the use of natural gels is rising for the application of active agents. Here, two natural polymers are assessed: agar, a pioneer hydrogel for conservation treatments, and chitosan, a rather novel and metal-binding gel. For chitosan, a [...] Read more.
In the field of cultural heritage, the use of natural gels is rising for the application of active agents. Here, two natural polymers are assessed: agar, a pioneer hydrogel for conservation treatments, and chitosan, a rather novel and metal-binding gel. For chitosan, a state-of-the-art based formulation (CS–ItA–LCys) is evaluated as it was reported for silver-complexing properties. It is evaluated whether these polymers can withstand the addition of the chelating compound deferoxamine, which is a bacterial siderophore. This allows for the obtainment of completely bio-sourced gel systems. A Fourier-transformed (FT) infrared spectroscopy characterization is performed, completed with rheological measurements and Cryo-Scanning Electron Microscopy (cryo–SEM) to investigate the physico–chemical properties of the gels, as well as their interaction with deferoxamine. Both polymers are also tested for their inherent complexing ability on silver ions using FT–Raman spectroscopy. A multi-analytical comparison shows different microstructures, in particular, the presence of a thick membrane for chitosan and different mechanical behaviors, with agar being more brittle. Neither hydrogel seems affected by the addition of deferoxamine; this is shown by similar rheological behavior and molecular structures in the presence or absence of the chelator. The intrinsic abilities of the chitosan formulation to make silver complex are demonstrated with the observation of two peaks characteristic of Ag–S and Ag–O bonds. Agar and chitosan are both proven to be reliable gels to act as carriers for bio-based active agents. This paper confirms the potential asset of the chitosan formulation CS–ItA–LCys as a promising gel for the complexation of soluble silver. Full article
(This article belongs to the Special Issue Gels and Eco-Materials Used for Heritage Conservation)
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18 pages, 2983 KiB  
Article
Evaluation of Enzyme Agarose Gels for Cleaning Complex Substrates in Cultural Heritage
by Mattia Morlotti, Fabio Forlani, Ilaria Saccani and Antonio Sansonetti
Gels 2024, 10(1), 14; https://doi.org/10.3390/gels10010014 - 22 Dec 2023
Cited by 3 | Viewed by 1388
Abstract
This study starts from the need to remove a mix of proteins, oils and natural resin, called beverone in the Italian literature, from the back of canvas paintings. The aim of this study is to develop and evaluate the effectiveness of two different [...] Read more.
This study starts from the need to remove a mix of proteins, oils and natural resin, called beverone in the Italian literature, from the back of canvas paintings. The aim of this study is to develop and evaluate the effectiveness of two different agarose/enzyme gels containing, respectively, a trypsin derived from porcine pancreas and a lipase from Candida rugosa, both in an aqueous solution of deoxycholic acid-triethanolamine soap. Enzymes were selected because of their action on peptide and ester bonds, effectiveness at maintaining a weak alkaline pH and low cost. Several series of model samples, resulting from a combination of rabbit skin glue, linseed oil and colophony, were prepared to test the enzyme gels with two different values for each of the following variables: agarose concentration, application modes and time of application. Measurements of weight loss after the gel application and Fourier transform infrared analysis were conducted to underline the hydrolysis occurring due to the enzyme gels and their effectiveness. Results confirmed what has been found in the literature and improved our knowledge about the action of agarose enzyme gels on complex substrates (hydrophilic/hydrophobic). The gels applied fluidly, with a longer contact time and a lower agarose concentration, are more effective. Furthermore, trypsin gels provided better results on substrates with oil and glue, while lipase gels turned out to be more effective on substrates made of a mix of oil, glue and colophony. Full article
(This article belongs to the Special Issue Gels and Eco-Materials Used for Heritage Conservation)
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13 pages, 2663 KiB  
Article
Looking for Novel Natural Gels to Improve Cleaning Methods for Bronze Leachates on Marble
by Iñaki Vázquez-de la Fuente, Inés Barbier, Sara Puente-Muñoz, Nagore Prieto-Taboada, Gorka Arana and Juan Manuel Madariaga
Gels 2023, 9(11), 843; https://doi.org/10.3390/gels9110843 - 25 Oct 2023
Cited by 1 | Viewed by 1538
Abstract
Marble is one of the materials most susceptible to copper leaching, resulting in easily identifiable turquoise stains on the marble. This problem is particularly relevant when we are talking about marble structures of heritage value. For this reason, conservators look for cleaning materials [...] Read more.
Marble is one of the materials most susceptible to copper leaching, resulting in easily identifiable turquoise stains on the marble. This problem is particularly relevant when we are talking about marble structures of heritage value. For this reason, conservators look for cleaning materials that are specific to the structure to be treated without damaging the original surface. Materials such as agar have been studied for a long time. Agar creates a controlled water release system that adapts to the needs of conservators who seek the greatest possible cleanliness without damaging the material to be treated. To improve the cleaning, chelating agents such as EDTA are added to the agar composition. However, the microbiological growth and the damage it produces to the original material are disadvantages to take into account. In order to solve these problems, other natural materials with cleaning potential such as kudzu and konjac gels were studied in combination with other chelating agents such as citrate, oxalate, and gluconic acid. For the characterization and evaluation of copper cleaning, various analytical techniques were used, including Raman spectroscopy, colorimetry, X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS). In this study, both konjac and kudzu emerged as promising alternatives to agar, revealing distinctive features such as simplified preparation methods and inherent antimicrobial properties. The EDTA chelator was found to be the most harmful for marble surfaces, as it extracted a greater amount of calcium from the marble during application of the gels doped with it. Citrate and gluconic acid have been identified as a promising substitute to prepare doped gels for the removal of copper stains. These compounds exhibit comparable or potentially superior cleaning capabilities than EDTA, with no negative side effects. Full article
(This article belongs to the Special Issue Gels and Eco-Materials Used for Heritage Conservation)
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15 pages, 3103 KiB  
Article
Ultrasound-Stimulated PVA Microbubbles as a Green and Handy Tool for the Cleaning of Cellulose-Based Materials
by Leonardo Severini, Alessia D’Andrea, Martina Redi, Sultan B. Dabagov, Valeria Guglielmotti, Dariush Hampai, Laura Micheli, Rocco Cancelliere, Fabio Domenici, Claudia Mazzuca, Gaio Paradossi and Antonio Palleschi
Gels 2023, 9(7), 509; https://doi.org/10.3390/gels9070509 - 23 Jun 2023
Viewed by 1219
Abstract
One of the main issues in the cultural heritage field of restoration chemistry is the identification of greener and more effective methods for the wet cleaning of paper artefacts, which serve as witnesses to human history and custodians of cultural values. In this [...] Read more.
One of the main issues in the cultural heritage field of restoration chemistry is the identification of greener and more effective methods for the wet cleaning of paper artefacts, which serve as witnesses to human history and custodians of cultural values. In this context, we propose a biocompatible method to perform wet cleaning on paper based on the use of 1 MHz ultrasound in combination with water-dispersed polyvinyl alcohol microbubbles (PVAMBs), followed by dabbing with PVA-based hydrogel. This method can be applied to both old and new papers. FTIR spectroscopy, X-ray diffraction, HPLC analysis, pH measurements and tensile tests were performed on paper samples, to assess the efficacy of the cleaning system. According to the results, ultrasound-activated PVAMB application allows for an efficient interaction with rough and porous cellulose paper profiles, promoting the removal of cellulose degradation byproducts, while the following hydrogel dabbing treatment guarantees the removal of cleaning materials residues. Moreover, the results also pointed out that after the treatment no thermal or mechanical damages had affected the paper. In conclusion, the readability of these kinds of artifacts can be improved without causing an alteration of their structural properties, while mitigating the risk of ink diffusion. Full article
(This article belongs to the Special Issue Gels and Eco-Materials Used for Heritage Conservation)
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