Exploration of the Conformational Scenario for α-, ß-, and γ-Cyclodextrins in Dry and Wet Conditions, from Monomers to Crystal Structures: A Quantum-Mechanical Study.

Cyclodextrins (CDs) constitute a class of cyclic oligosaccharides that are well recognized and largely applied in the drug delivery field, thanks to their biocompatibility, low cost, and the possibility to be derivatized in order to tune and optimize the complexation/release of the specific drug. The conformational flexibility of these systems is one of their key properties and requires a cost-effective methodology to be studied by combining the accuracy of results with the possibility of exploring a large set of conformations. In the present paper, we have explored the conformational potential energy surface of the monomers and dimers of α-, ß-, and γ-cyclodextrins (i.e., 6, 7, and 8 monomeric units, respectively) by means of fast but accurate semiempirical methods, which are then refined by state-of-the-art DFT functionals. Moreover, the crystal structure is considered for a more suitable comparison with the IR spectrum experimentally recorded. Calculations are carried out in the gas phase and in water environments, applying both implicit and explicit treatments. We show that the conformation of the studied molecules changes from the gas phase to the water, even if treated implicitly, thus modifying their complexation capability.

On the Interactions of Melatonin/ß-Cyclodextrin Inclusion Complex: A Novel Approach Combining Efficient Semiempirical Extended Tight-Binding (xTB) Results with Ab Initio Methods.

Melatonin (MT) is a molecule of paramount importance in all living organisms, due to its presence in many biological activities, such as circadian (sleep-wake cycle) and seasonal rhythms (reproduction, fattening, molting, etc.). Unfortunately, it suffers from poor solubility and, to be used as a drug, an appropriate transport vehicle has to be developed, in order to optimize its release in the human tissues. As a possible drug-delivery system, ß-cyclodextrin (ßCD) represents a promising scaffold which can encapsulate the melatonin, releasing when needed. In this work, we present a computational study supported by experimental IR spectra on inclusion MT/ßCD complexes. The aim is to provide a robust, accurate and, at the same time, low-cost methodology to investigate these inclusion complexes both with static and dynamic simulations, in order to study the main actors that drive the interactions of melatonin with ß-cyclodextrin and, therefore, to understand its release mechanism.

EPR study of the relationship between ultra high molecular weight polyethylene structure and radicals formed during irradiation with high energy sources.

Three different samples of ultra high molecular weight polyethylene have been irradiated with a high energy source (electron beam), and radicals have been generated. Different radical species have been assigned on the basis of their electron paramagnetic resonance spectra. Electron paramagnetic resonance data have been used also to evaluate the amount of each kind of radical that has been generated on different starting materials. The structure of the polymer (number of double bonds or crystallinity) is strictly connected to the response of the sample itself to the irradiation. A rationalization between these different parameters has been performed in order to evaluate the stability of polymer samples toward high energy irradiation processes.

Evaluation of Aging Effect on the Durability of Antibacterial Treatments Applied on Textile Materials for the Automotive Industry.

The automotive industry is always seeking novel solutions to improve the durability and the performance of textile materials used in vehicles. Indeed, especially after the coronavirus pandemic, antibacterial treatments have gained interest for their potential of ensuring cleanliness and safety toward microbial contamination within vehicles. This study gives a panoramic view of the durability of antibacterial treatments applied on textile materials in the automotive industry, focusing on their performance after experiencing accelerated aging processes. Two different textile materials, a fabric and a synthetic leather, both treated with antibacterial agents, were tested according to ISO 22196 and ISO 20743 standards, respectively, using two model microorganisms, Escherichia coli and Staphylococcus aureus. The impact of mechanical, thermal, and solar aging on the antibacterial properties has been evaluated. In addition, scanning electron microscope (SEM) analysis was performed to investigate the surface morphology of the materials before and after aging. Furthermore, contact angle measurements were conducted. The results suggest that neither mechanical nor thermal aging processes determined diminished antibacterial action. It was determined, instead, that the most damaging stressor for both textile materials was UV aging, causing severe surface alterations and a reduction in antibacterial activity.

Properties and Performance of Epoxy Resin/Boron Acid Composites.

This research study focused on the effect of adding boric acid to epoxy resin in order to obtain a composite material with improved properties and performance. To this end, a fine powder of boric acid (H3BO3) was introduced into epoxy resin in different amounts, i.e., 0.5 g, 1.0 g, and 1.5 g. As the matrix of the epoxy composites, styrene-modified epoxy resin based on bisphenol A (BPA) (Epidian 53) was used. It was cross-linked with two types of curing agents, i.e., an amine (ET) and a polyamide (PAC). The mechanical properties of the obtained epoxy composites (in terms of compressive strength, compressive modulus, and compressive strain) were determined at room temperature in order to assess the effect of the addition of boron acid and of the type of curing agent employed to cure the epoxy on these characteristics. Calorimetric measurements were made to highlight any changes in the glass transition temperature (Tg) as a result of the addition of boric acid to epoxy resin. Finally, flammability tests were performed on both Epidian 53/PAC and Epidian 53/ET epoxy composites to analyze their fire behavior and consequently establish the effectiveness of the selected additive as a flame retardant.

Unveiling the synergy: a combined experimental and theoretical study of ß-cyclodextrin with melatonin.

Melatonin (MT) is a vital hormone controlling biorhythms, and optimizing its release in the human body is crucial. To address MT's unfavorable pharmacokinetics, we explored the inclusion complexes of MT with ß-cyclodextrin (ß-CD). Nano spray drying was applied to efficiently synthesize these complexes in three molar ratios (MT : ß-CD = 1 : 1, 2 : 1, and 1 : 2), reducing reagent use and expediting inclusion. The complex powders were characterized through thermal analyses (TGA and DSC), Fourier transform infrared spectroscopy (FTIR), and in vitro MT release measurements via high-performance liquid chromatography (HPLC). In parallel, computational studies were conducted, examining the stability of MT : ß-CD complexes by means of unbiased semi-empirical conformational searches refined by DFT, which produced a distribution of MT : ß-CD binding enthalpies. Computational findings highlighted that these complexes are stabilized by specific hydrogen bonds and non-specific dispersive forces, with stronger binding in the 1 : 1 complex, which was corroborated by in vitro release data. Furthermore, the alignment between simulated and experimental FTIR spectra demonstrated the quality of both the structural model and computational methodology, which was crucial to enhance our comprehension of optimizing MT's release for therapeutic applications.

Modification of Epoxides with Metallic Fillers-Mechanical Properties after Ageing in Aqueous Environments.

The aim of this research was a comparative analysis of selected mechanical properties of epoxy compounds that were modified with metallic fillers and aged in aqueous environments. The tested epoxy compounds consisted of three components: styrene modified epoxy resin based on Bisphenol A, triethylenetetramine curing agent (resin/curing agent ratio of 100:10) and two types of metallic fillers in the form of particles: aluminum alloy (EN AW-2024-AlCu4Mg1) and tin-phosphor bronze (CuSn10P). Samples were subjected to ageing in 4 water environments: low-, medium- and high-mineralized natural water and in a sugar-containing solution for 1, 2 and 3 months. The epoxy samples were subjected to compressive strength tests in accordance with the ISO 604:2002 standard. It was observed that, among others, the compositions seasoned in low-mineralized water usually achieved the highest average compressive strength. As for filler type, using the bronze filler (CuSn10P) usually achieved the highest average compressive strength results.

Improving Sustainability through Covalent Adaptable Networks in the Recycling of Polyurethane Plastics.

The global plastic waste problem has created an urgent need for the development of more sustainable materials and recycling processes. Polyurethane (PU) plastics, which represent 5.5% of globally produced plastics, are particularly challenging to recycle owing to their crosslinked structure. Covalent adaptable networks (CANs) based on dynamic covalent bonds have emerged as a promising solution for recycling PU waste. CANs enable the production of thermoset polymers that can be recycled using methods that are traditionally reserved for thermoplastic polymers. Reprocessing using hot-pressing techniques, in particular, proved to be more suited for the class of polyurethanes, allowing for the efficient recycling of PU materials. This Review paper explores the potential of CANs for improving the sustainability of PU recycling processes by examining different types of PU-CANs, bond types, and fillers that can be used to optimise the recycling efficiency. The paper concludes that further research is needed to develop more cost-effective and industrial-friendly techniques for recycling PU-CANs, as they can significantly contribute to sustainable development by creating recyclable thermoset polymers.

Cyclodextrins for Lithium Batteries Applications.

Due to their high energy and power density, lithium-ion batteries (LIBs) have gained popularity in response to the demand for effective energy storage solutions. The importance of the electrode architecture in determining battery performance highlights the demand for optimization. By developing useful organic polymers, cyclodextrin architectures have been investigated to improve the performance of Li-based batteries. The macrocyclic oligosaccharides known as cyclodextrins (CDs) have relatively hydrophobic cavities that can enclose other molecules. There are many industries where this "host-guest" relationship has been found useful. The hydrogen bonding and suitable inner cavity diameter of CD have led to its selection as a lithium-ion diffusion channel. CDs have also been used as solid electrolytes for solid-state batteries and as separators and binders to ensure adhesion between electrode components. This review gives a general overview of CD-based materials and how they are used in battery components, highlighting their advantages.

A Comparison between the Molecularly Imprinted and Non-Molecularly Imprinted Cyclodextrin-Based Nanosponges for the Transdermal Delivery of Melatonin.

Melatonin is a neurohormone that ameliorates many health conditions when it is administered as a drug, but its drawbacks are its oral and intravenous fast release. To overcome the limitations associated with melatonin release, cyclodextrin-based nanosponges (CD-based NSs) can be used. Under their attractive properties, CD-based NSs are well-known to provide the sustained release of the drug. Green cyclodextrin (CD)-based molecularly imprinted nanosponges (MIP-NSs) are successfully synthesized by reacting ß-Cyclodextrin (ß-CD) or Methyl-ß Cyclodextrin (M-ßCD) with citric acid as a cross-linking agent at a 1:8 molar ratio, and melatonin is introduced as a template molecule. In addition, CD-based non-molecularly imprinted nanosponges (NIP-NSs) are synthesized following the same procedure as MIP-NSs without the presence of melatonin. The resulting polymers are characterized by CHNS-O Elemental, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric (TGA), Differential Scanning Calorimetry (DSC), Zeta Potential, and High-Performance Liquid Chromatography (HPLC-UV) analyses, etc. The encapsulation efficiencies are 60-90% for MIP-NSs and 20-40% for NIP-NSs, whereas melatonin loading capacities are 1-1.5% for MIP-NSs and 4-7% for NIP-NSs. A better-controlled drug release performance (pH = 7.4) for 24 h is displayed by the in vitro release study of MIP-NSs (30-50% released melatonin) than NIP-NSs (50-70% released melatonin) due to the different associations within the polymeric structure. Furthermore, a computational study, through the static simulations in the gas phase at a Geometry Frequency Non-covalent interactions (GFN2 level), is performed to support the inclusion complex between ßCD and melatonin with the automatic energy exploration performed by Conformer-Rotamer Ensemble Sampling Tool (CREST). A total of 58% of the CD/melatonin interactions are dominated by weak forces. CD-based MIP-NSs and CD-based NIP-NSs are mixed with cream formulations for enhancing and sustaining the melatonin delivery into the skin. The efficiency of cream formulations is determined by stability, spreadability, viscosity, and pH. This development of a new skin formulation, based on an imprinting approach, will be of the utmost importance in future research at improving skin permeation through transdermal delivery, associated with narrow therapeutic windows or low bioavailability of drugs with various health benefits.

HYSCORE and Davies ENDOR study of irradiated ultra high molecular weight polyethylene.

Ultra high molecular weight polyethylene (UHMWPE) has been studied with different magnetic resonance techniques to elicit information on the nature and the location of radicals generated during high energy irradiation. Field swept electron paramagnetic resonance, pulsed Davies electron nuclear double resonance and hyperfine sublevel correlation spectroscopic measurements allowed extracting for the first time the full (1) H hyperfine coupling tensors of the most abundant radical, i.e. a secondary alkyl radical and to ascertain the formation of allyl radicals in the first stages of the irradiation process. The (1) H hyperfine coupling tensors are analogous to those reported for single crystal irradiated polyethylene, suggesting that radicals generated in UHMWPE are located in the crystalline region of the polymer.

Functional Piezoresistive Polymer Composites Based on CO2 Laser-Irradiated Graphene Oxide-Loaded Polyurethane: Morphology, Structure, Electrical and Piezoresistive Properties.

Nanocomposite materials have recently attracted great attention for their wide range of applications, such as in smart materials, flexible electronics, and deformation sensing applications. Such materials make it possible to combine a polymer with functional fillers. In this study, flexible artificial leathers, exhibiting insulating properties and containing 1.5 or 2wt.% of graphene oxide (GO) in the polyurethane (PU) layer, were electrically activated via CO2 laser irradiation to obtain conductive paths at the surface exposed to the laser beam. As the material retained its insulating properties out of the irradiation areas, the laser scribing method allowed, at least in principle, a printed circuit to be easily and quickly fabricated. Combining a variety of investigation methods, including scanning electron microscopy (SEM), optical profilometry, IR and Raman spectroscopies, and direct current (DC) and alternate current (AC) electrical measurements, the effects of the laser irradiation were investigated, and the so-obtained electrical properties of laser-activated GO/PU regions were elucidated to unveil their potential use in both static and dynamic mechanical conditions. In more detail, it was shown that under appropriate CO2 laser irradiation, GO sheets into the GO/PU layer were locally photoreduced to form reduced-GO (RGO) sheets. It was verified that the RGO sheets were entangled, forming an accumulation path on the surface directly exposed to the laser beam. As the laser process was performed along regular paths, these RGO sheets formed electrically conductive wires, which exhibited piezoresistive properties when exposed to mechanical deformations. It was also verified that such piezoresistive paths showed good reproducibility when subjected to small flexural stresses during cyclic testing conditions. In brief, laser-activated GO/PU artificial leathers may represent a new generation of metal-free materials for electrical transport applications of low-current signals and embedded deformation sensors.

Recycling of EPDM via Continuous Thermo-Mechanical Devulcanization with Co-Rotating Twin-Screw Extruder.

Devulcanization represents the recycling of choice for a homogenous rubber waste stream because it allows revulcanization of samples previously devulcanized, making the life of the rubber virtually endless, according to the principles of circular economy. Among the many devulcanization processes, the thermo-mechanical one is the most appealing because it is a continuous process, easy to be industrialized. In this paper a comprehensive set of analyses (FTIR, TGA, DSC, elemental analyses, Py-GC/MS, swelling tests) were carried out on a post-industrial ethylene propylene diene monomer (EPDM), thermo-mechanical devulcanized in a co-rotating twin-screw extruder with different process parameters (thermal and screw profile, rpm). Results of the swelling test according to the Flory-Rehner theory and Horikx analyses show that the higher the thermal profile and the higher the rpm, the higher is the percentage of devulcanization. The quality of the devulcanized sample in terms of sol fraction and percentage of random scissions depends on the process conditions. The screw profile concurs to the efficiency of the devulcanization: the different number of kneading elements and more in general the screw profile composition affects the percentage of devulcanization, making the results in some tests more dependent on the screw speed.

Electron beam radiation effects on UHMWPE: an EPR study.

Electron paramagnetic resonance (EPR) technique has been employed to detect and characterise a series of different radical species generated in ultra-high molecular weight polyethylene (UHMWPE) via electron beam irradiation. Three different radical species have been found and assigned on the basis of their EPR spectra and of the related computer simulations. A secondary alkyl species, the prevalent one, is present immediately after irradiation, an allyl species appears only 24 h after irradiation when the alkyl species disappears.The third species, clearly visible at high microwave power only, has been observed for the first time and assigned to a tertiary alkyl carbon radical, whose formation is strictly connected with a Y-shape crosslink and a migration of the unpaired electron on a carbon atom localised in an adjacent position.

Thermal, Morphological, Electrical Properties and Touch-Sensor Application of Conductive Carbon Black-Filled Polyamide Composites.

Polyamide 66 (PA66) is a well-known engineering thermoplastic polymer, primarily employed in polymer composites with fillers and additives of different nature and dimensionality (1D, 2D and 3D) used as alternatives to metals in various technological applications. In this work, carbon black (CB), a conductive nanofiller, was used to reinforce the PA66 polymer in the 9-27 wt. % CB loading range. The reason for choosing CB was intrinsically associated with its nature: a nanostructured carbon filler, whose agglomeration characteristics affect the electrical properties of the polymer composites. Crystallinity, phase composition, thermal behaviour, morphology, microstructure, and electrical conductivity, which are all properties engendered by nanofiller dispersion in the polymer, were investigated using thermal analyses (thermogravimetry and differential scanning calorimetry), microscopies (scanning electron and atomic force microscopies), and electrical conductivity measurements. Interestingly, direct current (DC) electrical measurements and conductive-AFM mapping through the samples enable visualization of the percolation paths and the ability of CB nanoparticles to form aggregates that work as conductive electrical pathways beyond the electrical percolation threshold. This finding provides the opportunities to investigate the degree of filler dispersion occurring during the transformation processes, while the results of the electrical properties also contribute to enabling the use of such conductive composites in sensor and device applications. In this regard, the results presented in this paper provide evidence that conductive carbon-filled polymer composites can work as touch sensors when they are connected with conventional low-power electronics and controlled by inexpensive and commercially available microcontrollers.

The Effect of Ageing in Water Solution Containing Iron Sulfate on the Mechanical Properties of Epoxy Adhesives.

This study investigates the effect of operating factors such as seasoning in water solution containing iron (II) sulfate-FeSO4 (5 different water solution variants were tested) on the mechanical properties of an adhesive compound made of epoxy resin and amine curing agent, in a ratio of 100 g resin to 12 g curing agent. Strength tests of cured adhesive compound samples were performed on the Zwick/Roell Z150 testing machine in compliance with the EN ISO 604 standard. During the tests, compression modulus, compressive strength and compressive strain were measured. Obtained results served as a basis for analyzing the effect of a water environment containing iron sulfate on a given adhesive compound. It has been found that too high iron sulfate content in water has a negative effect on the mechanical properties of adhesive compound samples.

Poly (N-isopropylacrylamide) based hydrogels as novel precipitation and stabilization media for solid lipid nanoparticles (SLNs).

In this work, poly(N-isopropylacrylamide) (PNIPAM) based chemically cross-linked hydrogels are used as novel precipitation and stabilization media for solid lipid nanoparticles (SLNs) for the first time. The hydrogels and the hybrid thermoresponsive composite hydrogels with SLNs were characterized by SEM, DSC, DLS and rheometric analysis. The results showed that the SLNs obtained directly in the gel matrix by the newly devised method were well-dispersed and remained stable for one month. A remarkable advantage of this approach is that it yields the thermoresponsive nanocomposite hydrogels in a single step. This approach is a significant advancement in the preparation of hybrid thermoresponsive nanocomposite systems based on smart gels and SLNs for their use in biomedical applications.

Ocular Drug Delivery: A Special Focus on the Thermosensitive Approach.

The bioavailability of ophthalmic therapeutics is reduced because of the presence of physiological barriers whose primary function is to hinder the entry of exogenous agents, therefore also decreasing the bioavailability of locally administered drugs. Consequently, repeated ocular administrations are required. Hence, the development of drug delivery systems that ensure suitable drug concentration for prolonged times in different ocular tissues is certainly of great importance. This objective can be partially achieved using thermosensitive drug delivery systems that, owing to their ability of changing their state in response to temperature variations, from room to body temperature, may increase drug bioavailability. In the case of topical instillation, in situ forming gels increase pre-corneal drug residence time as a consequence of their enhanced adhesion to the corneal surface. Otherwise, in the case of intraocular and periocular, i.e., subconjunctival, retrobulbar, peribulbar administration, among others, they have the undoubted advantage of being easily injectable and, owing to their sudden thickening at body temperature, have the ability to form an in situ drug reservoir. As a result, the frequency of administration can be reduced, also favoring the patient's adhesion to therapy. In the main section of this review, we discuss some of the most common treatment options for ocular diseases, with a special focus on posterior segment treatments, and summarize the most recent improvement deriving from thermosensitive drug delivery strategies. Aside from this, an additional section describes the most widespread in vitro models employed to evaluate the functionality of novel ophthalmic drug delivery systems.

Thermosensitive Nanocomposite Hydrogels for Intravitreal Delivery of Cefuroxime.

Endophthalmitis is a rare, but serious, intravitreal inflammatory disorder that can arise after cataract surgery. The intracameral injection of 1 mg cefuroxime (CEF) followed by three-times daily antibiotic topical administration for a week is generally recognized as the routine method of prophylaxis after cataract surgery. This procedure is controversial because of both the low efficacy and the low adherence to therapy by elderly patients. A unique slow release antibiotic intravitreal injection could solve these problems. The objective of the present study was to design ophthalmic nanocomposite delivery systems based on in situ gelling formulations that undergo sol-to-gel transition upon change in temperature to prolong the effect of CEF. Oil in water (O/W) microemulsion (µE) and solid lipid nanoparticles (SLN), obtained with an innovative formulation technology called cold microemulsion dilution, were evaluated as ocular drug delivery systems for CEF. Drug entrapment efficiency up to 80% was possible by esterifying CEF with 1-dodecanol to obtain dodecyl-CEF (dCEF). Both dCEF-loaded SLN and µE were then added with Pluronic®F127 (20% w/v) to obtain a nanocomposite hydrogel-based long acting system. The prepared thermosensitive formulations were evaluated for their physical appearance, drug content, gelation temperature, injectability and rheological properties, in vitro release studies and stability studies. Moreover, cell proliferation assays on human retinal pigment epithelial ARPE-19 cells were performed to evaluate the influence of this innovative system on the cellular viability. In addition, minimal inhibitory concentration (MIC) was assessed for both CEF and dCEF, revealing the need of dCEF hydrolysis for the antimicrobial activity. Although further experimental investigations are required, the physico-chemical characterization of the nanocomposite hydrogels and the preliminary in vitro release studies highlighted the potential of these systems for the sustained release of CEF.

Poly(NIPAM-co-MPS)-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system.

Hybrid drug delivery systems (DDS) have been prepared by grafting poly(NIPAM-co-MPS) chains on multimodal porous silica nanoparticles having an inner mesoporous structure and an outer thin layer of micropores. The hybrid thermoresponsive DDS were fully characterized and loaded with a model drug. The in vitro drug release tests are carried out at below and above the lower critical solution temperature (LCST) of the copolymer. The results have revealed that due to the presence of small diameter (~1.3 nm) micropores at the periphery of the particles, the collapsed globules of the thermoresponsive copolymer above its LCST hinders the complete release of the drug which resulted in a reverse thermoresponsive drug release profile by the hybrid DDS.