The rapid increase of antimicrobial resistance forces researchers to find new therapeutic molecules for replacing the available antibiotics, no longer effective.
Recently, we reported the antibacterial activity against Gram-negative species, including multi-drugs-resistant Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter baumannii, of some amino acids-modified cationic dendrimers (CDs) [1]. The lysine-containing dendrimer displayed very low MIC values, thus establishing the key role of lysine in conferring a potent antibacterial activity to the devices [1]. In order to develop new antibacterial agents active against other resistant bacterial species, we reconsidered six cationic dendrimer complexes (UOACDs), synthesized to make water-soluble and administrable in vivo a mixture of ursolic and oleanolic acids (UOA) [2, 3]. Due to their cationic features and to the presence of UOA, known for having antibacterial properties particularly against Gram-positive species [4,5], the UOACDs were considered excellent candidates to achieve the goal. We selected three UOACDs, having particle size and drug loading in the ranges of 16.1-24.9 nm and 5.0-12.7 % (wt/wt) respectively, and their antibacterial behavior was preliminary assessed against Escherichia coli and Klebsiella pneumoniae, establishing their inactivity on these species. Otherwise, UOACDs displayed significant antibacterial activity against 12 strains of the genera Enterococcus and Staphylococcus. To clarify UOA contribute to the antibacterial effects observed, free UOA was also investigated. Interestingly, it was established that the antibacterial activity reported for UOACDs, depended strongly on the number of cationic groups and on the type of amino acids present on CDs, and that it was attributable only to the CDs themselves and not to the presence of UOA. Lysine was critical for the antibacterial potency, whereas arginine was pivotal for redirecting the activity against Gram-positive species. A high cationic character, associated with a balanced lysine/arginine content, resulted in high antimicrobial effects (MICs = 0.5-8.7 µM). More in-depth investigations are underway to better define the antibacterial characteristics of the developed arginine-containing CDs.

References

1. Schito, A.M.; Alfei, S. Antibacterial activity of non-cytotoxic, amino acid-modified polycationic dendrimers against Pseudomonas aeruginosa and other non-fermenting Gram-negative bacteria. Polymers 2020, 12, 1818.
2. Bisio, A.; Romussi, G.; Russo, E.; Cafaggi, S.; Schito, A. M.; Repetto, B.; De Tommasi, N. Antimicrobial activity of the ornamental species salvia corrugata, a potential new crop for extractive purposes. Agric. Food Chem. 2008, 56, 10468−10472.
3. Alfei, S.; Taptue, G.B.; Catena, S.; et al. Synthesis of Water-soluble, Polyester-based Dendrimer Prodrugs for Exploiting Therapeutic Properties of Two Triterpenoid Acids. J. Polym. Sci. 2018, 36, 999–1010, https://doi.org/10.1007/s10118-018-2124-9.
4. Do Nascimento, P.G.; Lemos, T.L.; Bizerra, A.M.; Arriaga, Â.M.; Ferreira, D.A.; Santiago, G.M.; Braz-Filho, R.; Costa, J.G.M. Antibacterial and Antioxidant Activities of Ursolic Acid and Derivatives. Molecules 2014, 19, 1317-1327.
5. Wolska, K.I.; Grudniak, A.M.; Fiecek, B.; Kraczkiewicz-Dowjat, A.; Kurek, A. Antibacterial activity of oleanolic and ursolic acids and their derivatives. Central Eur. J. Biol. 2010, 5, 543–553, doi:10.2478/s11535-010-0045-x.

New materials for thermoresistive applications in flexible electronics can be obtained by combining dielectric polymeric substrates with electrically conductive coatings. In this work, graphite platelet (GP) films were obtained by spraying a commercial graphite lacquer on low-density polyethylene (LDPE) substrates. According to the scanning electron microscopy investigation and X-ray diffraction analysis, the deposited films are composed of graphite platelets uniformly covering the substrate surface. The graphite platelets are composed of crystallites with an average size of 14 nm. The thermoresistive behavior of the GP on LDPE samples was investigated from 20 °C to 120 °C. The resistance of the samples increases considerably in the 20-100 °C range and decreases sharply for temperatures above 100 °C. The resistance behavior is dominated by the thermal properties of the polymeric substrate. The study confirms that GP on LDPE can be a promising and inexpensive material to use in thermoresistive devices.

n this study, we exploit films of multiwalled carbon nanotubes (MWCNTs) as the sensing element of new and low-cost sensors for temperature, pressure and humidity.

Aqueous solutions of functionalized MWCNTs are vacuum filtered to produce freestanding films of randomly oriented MWCNTs, known as buckypaper, with thickness in the range 200-500 µm. The electric resistance of the buckypaper, patterned in strips with width of few mm and length up to few cm, is investigated as a function of temperature, pressure and humidity.

The electric resistance of the buckypaper shows a monotonic decrease for increasing temperature over the 4.2 - 420 K range. This feature is exploited to fabricate temperature sensors with high sensitivity and fast response. Owing to the high porosity, the buckypaper structure can be changed by the application of a force. A compressive force applied over the buckypaper surface improves the electric contact between the MWCNTs and results in a decrease of the electric resistance. It has been observed that the change can be reversible over a certain pressure range, thus enabling the use of the buckypaper as a pressure sensor. The exposure of the buckypaper to liquid or vapour water increases its electric resistivity. Hence, a MWCNT film is also suitable as humidity sensing purposes.

The experimental data presented in this work confirm that the electrical conduction of a buckypaper is highly sensitive the environmental conditions and that the buckypaper is an interesting material with promising applications in a variety of sensors.

Carbon-based materials have shown captivated applications in water-purification technology, and one of them includes disinfection. The microbial safety of water has remained a challenging task despite being equipped with many technologies. Traditional disinfection methods, including chlorination, ozonation, and ultraviolet radiation, suffer limitations in terms of high chemical dosage and cost. The viability of these processes gets hindered when the generation of disinfection-by-products comes into play, which exhibits carcinogenic activity. Electrochemical disinfection is an excellent technology for its non-hostile operation, low cost, and residual effect. However, it still suffers from low oxygen overvoltage, charge reversibility, and lower current efficiencies. The mediation of nanomaterials enhances its capability due to their large surface area. Carbon-based nanomaterials, due to their nanometer size, possess excellent surface properties along with high conductivity, which makes them a versatile agent for electrochemical disinfection-based applications. The nanomaterials, including graphene, carbon nanotubes, fullerenes, nano-diamonds, have shown excellent antimicrobial properties over a broad range of microbes. Their action ranges from cutting, penetration to the generation of reactive oxygen species (ROS). Laser-Induced-Graphene (LIG), a recently discovered 3-D nanomaterial, had shown excellent surface properties and conductivity, which, when employed for electrochemical disinfection applications as membrane filters, manifested positive results against bacteria. Its facile one-step approach of preparation by laser scribing on any carbonaceous surface makes it a versatile material for long term disinfection applications. In this work, significant challenges with the conventional disinfection systems are highlighted and how electrochemical disinfection techniques could overcome that with the intervention of carbon-based nanomaterials.

As the diversity of nanomaterials is wide and their size can vary by 2 orders of magnitude (1−100 nm), the development of new and advanced analytical tools is of paramount importance for their in-depth characterization, allowing a fundamental understanding of their structure, further alteration and degree of chemical surface functionalization. Herein, we present a new strategy for characterisation of gold nanorods (GNRs) that are of specific interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared spectral region. More precisely, we characterized GNRs conjugated with short and long synthetic glycopolymers in terms of particle size, coating thickness, and/or mobility properties used as a diagnostic biosensing platform for lectin detection and compared it to the bare GNRs. This endeavour requires a multidisciplinary approach including a new comprehensive set of fit-for-purpose analytical tools being high resolution single-particle inductively coupled plasma-mass spectrometry (HR-spICP-MS) and electrical asymmetric-flow field-flow-fractionation hyphenated to the multi angle light scattering (EAF4-MALS). GNRs were separated and characterized via EAF4-MALS regarding their size and charge, while HR-spICP-MS provided information on the particle number density, size, size distribution, and the dimensional characterisation. In addition, EAF4-MALS appears to offer suitable approach for estimating coating thickness of glycoconjugated GNRs.

Acknowledgment – MV is a senior postdoctoral researcher of the Research Foundation – Flanders (FWO project number 12ZD120N). AP, PGG, IN and MIG thank the European Union’s Horizon 2020 research and innovation programme under GA 814236 (NanoCarb).

Gene therapy has been considered as a promising strategy for the treatment of several inherited disesases and acquired complex disorders . One important challenge yet to be solved to ensure the success of the nanomaterials in the delivery of gene therapies is their ability to escape from endosomes. To address this issue, we previously developed magnetite nanoparticles conjugated with the antimicrobial peptide Buforin II, which showed potent translocating and endosomal escape abilities in several cell lines. In this work, we propose the development of new cell-penetrating nanoplatforms by interfacing graphene oxide (GO) with potent translocating peptides to take advantage of already tested and new peptides as well as the distinctive interactions of GO with the phospholipids of membranes and endosomes. GO was prepared by the modified Hummers’ method through the oxidation of graphite sheets. Next, functionalization of GO was carried out by mixing tetramethylammonium hydroxide (TMAH) 25% (v/v), pure acetic acid and (3-Aminopropyl) triethoxysilane (APTES) 10% (v/v). Thermogravimetric analysis (TGA) and Fourier-Transform Infrared spectroscopy were used to characterize the nanoplatform. FTIR analysis exhibited the peaks related to the characteristic carboxyl groups of GO as well as the Si-O bonds after silanization. TGA allowed us to estimate a silanization efficiency of about 35%. Future work will be focused on conjugating Buforin II and assessing translocation efficiency by conducting uptake assays in liposomes and various cell lines. Additionally, endosomal escape will be determined via confocal microscopy by labeling the peptide with fluorescent molecules and looking at colocalization with the fluorescent probe lysotracker. By taking advantage of the exceptional qualities in terms of physicochemical, electrical and optical properties of GO, this study might provide novel strategies to overcome limitations commonly faced such as low stability of the translocating biomolecules and endosomal entrapment.

One of the main challenges in gene therapy is the transport of genetic material into target cells because it has several obstacles like rapid degradation of genetic material by the physiological environment, low endosomal escape and limited cell uptake. A meaningful way to increase the efficacy of genetic material delivery is to incorporate magnetic nanomaterials with the ability to transport biomolecules with easy handling and high biocompatibility. One of them is magnetite, which has been widely used in biomedicine as drug delivery vehicles due to the possibility of controlled fate by magnetic fields and the excretion as ferritin. This study aims to develop a nanostructured platform for the immobilization and intracellular release of nucleic acids with application in gene therapy. The nanobioconjugate was based on surface functionalization of magnetite with an organosilane molecule followed by a surface spacer and a molecule with a reducible disulfide linker to facilitate conjugation of aa thiolated tag, which is complementary to a non-encoding sequence within the delivery vector. In addition, a potent translocating and endosome escaping protein was co-immobilized on the surface to increase the efficiency of biologically active genetic material effectively reaching the nuclei. Once the nanobioconjugate reaches the intracellular space, the disulfide bond is reduced, and the cargo nucleotide is delivered. The delivery of the conjugated material was first tested in vitro with the aid of reducing agents. The conjugated rhodamine was tracked via a time evolution of the delivered molecules with the aid of spectrofluorimetry. Based on our results,we decided to deliver to neuroblastoma, and Vero cells to confirm an endosomal escape of about 85% as calculated by colocalization. Future experiments will be focused on the hybridization of a gene sequence for the expression of the fluorescent protein mCherry. The obtained nanobioconjugate will be also delivered to cells to evaluate transfection efficiencies.

Resonant modes are important characteristics of the optical properties of photonic crystals since they are responsible for the features in the transmission and reflection spectra, as well as the emissivity of quantum emitters inside such structures. We present a resonant modes expansion method applied to a problem of radiating dipoles inside of a photonic crystal. In stacked photonic crystal slabs there is a coupling between resonances of distinct subsystems and Fabry-Perot resonances. We propose a technique to calculate coefficients of resonant mode expansion based on the scattering matrix formalism of the Fourier modal method (FMM). The method appears to be convenient since it does not require rigorous normalization of resonant fields or application of perfectly matched layers. Then we demonstrate the agreement between the resonant modes expansion results and exact FMM solutions.

Lanthanide-doped upconversion nanoparticles (UCNPs) are capable of converting multiple near-infrared (NIR) photons into shorter-wavelength one by utilizing real long-lived, ladder-like energy levels of lanthanide ions. Such unique anti-Stokes emissions are immune to the auto-fluorescence background interference and derive from moderate irradiation compared to conventional multi-photon fluorescence, ideally suitable for imaging applications, coupled with improved imaging depth by NIR excitation light, excellent photostability, multicolor sharp-band emissions and tunable long emission lifetimes. However, the critical concentration quenching on upconversion luminescence generally observed in UCNPs sets barriers to obtain bright high doping UCNPs at low excitation power density, which hampers this promising luminescence probe applying to long-term live cell imaging. We explore the mechanism of Tm³⁺ concentration quenching from ensemble and single-particle levels to design the new generation sub-25-nm ultra-bright highly Tm³⁺-doped UCNPs for high-contrast imaging at limited excitation power density condition. This achievement provides a new strategy for developing small-sized bright highly activator-doped UCNPs and will broaden the applications of UCNPs in microscopic imaging.

Lead halide perovskite has attracted great attentions for the applications in perovskite solar cells and LED devices and it also has the great potential in photocatalytic applications due to high extinction coefficients, and long electron-hole diffusion lengths. However, the rapid recombination rate of photogenerated electron-hole pairs still limits the photocatalytic activity. Herein, a novel CsPbBr₃ quantum dots/S doping g-C₃N₄ ultrathin nanosheet 0D/2D heterojunctions photocatalyst are prepared by loading perovskite quantum dots onto ultrathin doped g-C₃N₄. The strategy of S element doping improved the properties of in g-C₃N₄ ultra-thin structure providing more adsorption and reaction sites for photocatalytic activity. And the type II band alignment structure of CsPbBr₃ / g-C₃N₄ heterostructure effectively improved the separation and transmission of photogenerated carriers and inhibit the recombination of photogenerated carriers, thus improving the photocatalytic CO₂ reduction performance. This study provides a facile and effective method for synthesis of halide perovskite based photocatalysts, which holds the potential for further application in environmental and energy field.