A reverse degradation vs. temperature relationship for a carbonate-containing gemini surfactant

New horizons on advanced nanoscale materials for Cultural Heritage conservation

Nanomaterials have permeated numerous scientific and technological fields, and have gained growing importance over the past decades also in the preservation of Cultural Heritage. After a critical overview of the main nanomaterials adopted in art preservation, we provide new insights into some highly relevant gels, which constitute valuable tools to selectively remove dirt or other unwanted layers from the surface of works of art. In particular, the recent "twin-chain" gels, obtained by phase separation of two different PVAs and freeze-thawing, were considered as the most performing gel systems for the cleaning of Cultural Heritage. Three factors are crucial in determining the final gel properties, i.e., pore size, pore connectivity, and surface roughness, which belong to the micro/nanodomain. The pore size is affected by the molecular weight of the phase-separating PVA polymer, while pore connectivity and tortuosity likely depend on interconnections formed during gelation. Tortuosity greatly impacts on cleaning capability, as the removal of matter at the gel-target interface increases with the uploaded fluid's residence time at the interface (higher tortuosity produces longer residence). The gels' surface roughness, adaptability and stickiness can also be controlled by modulating the porogen amount or adding different polymers to PVA. Finally, PVA can be partially replaced with different biopolymers yielding gels with enhanced sustainability and effective cleaning capability, where the selection of the biopolymer affects the gel porosity and effectiveness. These results shed new light on the effect of micro/nanoscale features on the cleaning performances of "twin-chain" and composite gels, opening new horizons for advanced and "green"/sustainable gel materials that can impact on fields even beyond art preservation, like drug-delivery, detergency, food industry, cosmetics and tissue engineering.

Development of niosomes for encapsulating captopril-quercetin prodrug to combat hypertension

Novel and effective anti-hypertensive agents are required to manage hypertension; therefore, we synthesised a novel antihypertensive drug from captopril and quercetin (cap-que) and explored its antihypertensive potential in a niosomal formulation via molecular hybridisation. The cap-que hybrid was synthesised, and its structure was characterised via NMR, FTIR, and HRMS. Niosomes were then loaded with cap-que using the thin-film hydration method. The particle size, polydispersity index, surface charge and drug entrapment efficiency (EE%) of the formulation were 418.8 ± 4.21 nm, 0.393 ± 0.063, 16.25 ± 0.21 mV, and 87.74 ± 2.82%, respectively. The drug release profile showed a sustained release of the active compound (43 ± 0.09%) from the niosomal formulation, compared to the parent drug (80.7 ± 4.68%), over 24 h. The cell viability study confirmed the biosafety of the formulation. The in vivo study in a rat model showed enhanced antihypertensive activity of the hybrid molecule and niosomal formulation which reduced systolic and diastolic pressure when compared to the individual, bare drugs. The findings of this study concluded that the antihypertensive potential of captopril can be enhanced by its hybridisation with quercetin, followed by niosomal nano drug delivery.

Self-Assembling Drug Formulations with Tunable Permeability and Biodegradability

This review focuses on key topics in the field of drug delivery related to the design of nanocarriers answering the biomedicine criteria, including biocompatibility, biodegradability, low toxicity, and the ability to overcome biological barriers. For these reasons, much attention is paid to the amphiphile-based carriers composed of natural building blocks, lipids, and their structural analogues and synthetic surfactants that are capable of self-assembly with the formation of a variety of supramolecular aggregates. The latter are dynamic structures that can be used as nanocontainers for hydrophobic drugs to increase their solubility and bioavailability. In this section, biodegradable cationic surfactants bearing cleavable fragments are discussed, with ester- and carbamate-containing analogs, as well as amino acid derivatives received special attention. Drug delivery through the biological barriers is a challenging task, which is highlighted by the example of transdermal method of drug administration. In this paper, nonionic surfactants are primarily discussed, including their application for the fabrication of nanocarriers, their surfactant-skin interactions, the mechanisms of modulating their permeability, and the factors controlling drug encapsulation, release, and targeted delivery. Different types of nanocarriers are covered, including niosomes, transfersomes, invasomes and chitosomes, with their morphological specificity, beneficial characteristics and limitations discussed.

How Science Can Contribute to the Remedial Conservation of Cultural Heritage

Colloid science is contributing solutions to counteract the degradation of artifacts, favoring their transfer to future generations. Advanced materials such as nanoparticles, coatings, gels and microemulsions have been assessed in conservation, spanning from archeological sites to modern and contemporary art. We give an overview of the fundamental milestones and latest innovations in conservation science, targeting solutions and tools for remedial conservation based on green nanomaterials and hybrid systems. Future perspectives and outstanding challenges in this exciting field are then outlined.

Advanced Materials in Cultural Heritage Conservation

Cultural Heritage is a crucial socioeconomic resource; yet, recurring degradation processes endanger its preservation. Serendipitous approaches in restoration practice need to be replaced by systematically addressing conservation issues through the development of advanced materials for the preservation of the artifacts. In the last few decades, materials and colloid science have provided valid solutions to counteract degradation, and we report here the main highlights in the formulation and application of materials and methodologies for the cleaning, protection and consolidation of works of art. Several types of artifacts are addressed, from murals to canvas paintings, metal objects, and paper artworks, comprising both classic and modern/contemporary art. Systems, such as nanoparticles, gels, nanostructured cleaning fluids, composites, and other functional materials, are reviewed. Future perspectives are also commented, outlining open issues and trends in this challenging and exciting field.

What dominates the interfacial properties of extended surfactants: Amphipathicity or surfactant shape?

HYPOTHESIS

The properties of conventional surfactants (c-surfactants) are generally accepted to be amphipathicity-dominated, but extended surfactants (e-surfactants) are additionally polypropylene oxide (PPO)-dependent; this additional property makes us wonder how an intramolecular PPO spacer would be "extended" at various interfaces and what is responsible for the excellent all-round properties of e-surfactants.

EXPERIMENTS

A series of novel sodium medium alkyl chain PPO-b-PEO sulfates (2-ethylhexyl polypropylene oxide-block-polyethylene oxide sulfates, C₈P_pE_eS) were designed, synthesized and structurally identified. Tensiometry was applied to estimate the surfactant shape at the air/water surface. Surface tension, interfacial tension, emulsifying power, electrolyte tolerance, adsorption onto oil sands and thermal hydrolysis stability were measured to evaluate the effect of the PPO coil on the interfacial and micellar properties of the e-surfactants.

FINDINGS

On the basis of obtaining greater values for e-surfactants than c-surfactants for both surface area (a_m) per surfactant molecule and the corresponding shape factor (S), we were surprised to find that e-surfactants form a rugby ball shape not only at the air/water surface but also at the oil/water interface; this result is potentially explained by the PPO spacer coiling and collapsing to produce dense packing at the monolayer adsorption, which is rationally borrowed by other interfaces. Many positive or negative correlations were observed between the interfacial/micellar properties of C₈P_pE_eS and a_m values, which seems that the surfactant shape dominants the properties of the e-surfactants. In fact, the properties of C₈P_pE_eS are dominated by the dynamic amphipathicity and assisted by the rugby ball shape of the molecules because of both being driven by the dynamic biphasic affinity of the PPO coil in response to the external environment; these findings provide soft interfacial materials specially adapted for surfactant flooding.

Comparative Study of Conventional/Ethoxylated/Extended n-Alkylsulfate Surfactants

A series of novel anionic e-surfactants n-C _cP _pS was molecular designed and synthesized from long-chain fatty alcohols by polypropoxylation and sulfation followed by neutralization. Excellent all-round performance of extended surfactants (e-surfactants) interests us how a simple polypropylene oxide (PPO) spacer has great effects on properties. By a comparative study of conventional/ethoxylated/extended n-alkylsulfate surfactants, we were surprised to find that e-surfactants are in an obvious rugby shape at the air/water surface according to molecular surface area ( a_m), and it comes down to the intramolecular PPO spacer coiling and surface-induced collapse. On the basis of the interfacial properties of the e-surfactants, it is found that the PPO spacer can provide both hydrophilic and lipophilic contributions to an e-surfactant molecule. The synergism between PPO spacers and alkyl chains indicates that a certain PPO spacer can adjust the contributions in view of different alkyl chain lengths. Therefore, it is both the rugby-shaped molecular geometry of e-surfactants and the dynamic amphipathicity of a PPO spacer that makes e-surfactants behave with excellent interfacial and solution properties for household cleaning. Therefore, this work gives us a hint that the molecular geometry of surfactants plays a vital role in interfacial and solution properties similar to molecular amphipathicity.