Hydrophobic Composites Designed by a Nonwoven Cellulose-Based Material and Polymer/CaCO3 Patterns with Biomedical Applications.

Herein, we report a simple method to obtain hydrophobic surfaces by surface modification with calcium carbonate via diffusion-controlled crystallization using a cheap, versatile, and super-hydrophilic cellulose-based nonwoven material (NWM) as the substrate. To control the CaCO3 crystal growth, the ammonium carbonate diffusion method was applied in the presence of polyanions [poly(acid acrylic), poly(2-acrylamido-2-methylpropanesulfonic acid), and a copolymer which contains 55 mol % 2-acrylamido-2-methylpropanesulfonic acid and 45 mol % acrylic acid] or nonstoichiometric polyelectrolyte complexes with polycations [poly(allylamine hydrochloride) and chitosan] on a pristine NWM and on polycation-treated surfaces. The surface morphology obtained by calcite growth under surface or environmental functional groups' influence and the hydrophilic/hydrophobic character of the composite materials were followed and compared to that of the starting material. The obtained composite materials become hydrophobic, having a contact angle in the range of 110-135°. The capacity of tetracycline sorption and release by selected modified surfaces were followed and compared to the untreated NWM. Also, the biological properties were evaluated in terms of biocompatibility, antibacterial activity, and antifouling capability.

Injectable Thixotropic ß-Cyclodextrin-Functionalized Hydrogels Based on Guanosine Quartet Assembly.

Facile method for the preparation of ß-cyclodextrin-functionalized hydrogels based on guanosine quartet assembly was described. A series of seven hydrogels were prepared by linking ß-cyclodextrin molecules with guanosine moieties in different ratios through benzene-1,4-diboronic acid linker in the presence of potassium hydroxide. The potassium ions acted as a reticulation agent by forming guanosine quartets, leading to the formation of self-sustained transparent hydrogels. The ratios of the ß-cyclodextrin and guanosine components have a significant effect on the internal structuration of the components and, correspondingly, on the mechanical properties of the final gels, offering a tunablity of the system by varying the components ratio. The insights into the hydrogels' structuration were achieved by circular dichroism, scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Rheological measurements revealed self-healing and thixotropic properties of all the investigated samples, which, in combination with available cyclodextrin cavities for active components loading, make them remarkable candidates for specific applications in biomedical and pharmaceutical fields. Moreover, all the prepared samples displayed selective antimicrobial properties against S. aureus in planktonic and biofilm phase, the activity also depending on the guanosine and cyclodextrin ratio within the hydrogel structure.

Antibacterial Polysiloxane Polymers and Coatings for Cochlear Implants.

Within this study, new materials were synthesized and characterized based on polysiloxane modified with different ratios of N-acetyl-l-cysteine (NAC) and crosslinked via UV-assisted thiol-ene addition, in order to obtain efficient membranes able to resist bacterial adherence and biofilm formation. These membranes were subjected to in vitro testing for microbial adherence against S. pneumoniae using standardized tests. WISTAR rats were implanted for 4 weeks with crosslinked siloxane samples without and with NAC. A set of physical characterization methods was employed to assess the chemical structure and morphological aspects of the new synthetized materials before and after contact with the microbiological medium.

Chitosan Derivatives in Macromolecular Co-assembly Nanogels with Potential for Biomedical Applications.

Maleoyl-chitosan/poly(aspartic acid) nanogels were developed and characterized in order to assess its suitability for biomedical applications. Thus, the physicochemical properties were investigated and correlated with the composition of the new structures. Dynamic light scattering measurements, correlated with transmission electron microscopy images, demonstrated that nanogels size distribution was narrow with average diameter between 186 and 246 nm, and presented positive zeta potential values. The sensitivity of nanogels at pH and temperature was also evaluated. Nanogels loaded with amoxicillin showed a controlled release profile dependent on nanogel content. The formulations loaded with amoxicillin had antibacterial properties, and the cytotoxicity tests indicated good in vivo biocompatibility. In conclusion, the new synthesized polyelectrolyte nanogels, which can provide a stable environment for the encapsulated drugs, can be used as a multifunctional platform for administration of antimicrobial agents from the spectrum of antibiotics that have a very poor biodistribution.

Duodenoscope-Associated Infections beyond the Elevator Channel: Alternative Causes for Difficult Reprocessing.

OBJECTIVES: Duodenoscopes have been widely used for both diagnostic and therapeutic endoscopic retrograde cholangiopancreatography (ERCP) procedures, but recently, numerous outbreaks of multidrug-resistant organisms (MDRO) infections have been reported which has led to extensive research for their possible causes. Consequently, the aim of this study is to search for possible duodenoscope surface damages that could provide an alternative and plausible source of infections. MATERIALS AND METHODS: In order to assess both outer and inner surfaces, a duodenoscope was dismantled and samples were taken from the outer resin polymer and from the air/water, elevator, and working (biopsy) channels that were characterized by FTIR, DSC, TGA, AFM, SEM techniques and the antimicrobial activity were tested. RESULTS: Alterations were noticed on both the coating and working channel polymers, with external alterations increasing progressively from the proximal sample to the distal sample near the tip of the scope. However, the results showed that the coating surface was still efficient against bacterial adhesion. Changes in surface texture and also morphological changes were shown. CONCLUSIONS: The study describes the impact of routine procedural use and reprocessing cycles on the duodenoscope, showing that these may possibly make it susceptible to bacterial contamination and MDRO biofilm formation due to difficult reprocessing of the altered surfaces.

In vitro activity of echinocandins against 562 clinical yeast isolates from a Romanian multicentre study.

The study presents the echinocandin susceptibility profile of a multi-centre collection of pathogenic yeast isolates from Romanian tertiary hospitals. The 562 isolates were identified using ID32C strips, MALDI-TOF MS and DNA sequencing. Minimal inhibitory concentrations (MICs) of caspofungin (CAS), micafungin (MCA), and anidulafungin (ANI) were assessed and interpreted according to EUCAST guidelines. Minimal fungicidal concentrations (MFC) were determined by plating content from the clear MIC wells. The activity was considered fungicidal at MFC/MIC ≤ 4. The three echinocandins had strongly correlated MICs and high percentages of MIC essential agreement. Most often, MCA had the lowest MICs, followed by CAS and ANI. Against C. parapsilosis and C. kefyr, CAS had the lowest MIC values. The MIC50 values were between 0.03 and 0.25 mg/l, except C. parapsilosis. The MIC90 values were usually one dilution higher. MFCs and MICs were weakly correlated. ANI and MCA had the lowest MFC values. The MFC50 values were between 0.06 and 0.5 mg/l, except C. parapsilosis, C. guilliermondii, and C. dubliniensis. The MFC90 values were usually two dilutions higher. Based on EUCAST breakpoints, 47 isolates (8.4%) were resistant to at least one echinocandin, most often ANI. Most resistant isolates were of C. albicans, C. glabrata, and C. krusei. There were 17 isolates (3%) resistant to echinocandins and fluconazole and most belonged to the same three species. MCA and ANI had the highest rates of fungicidal activity. The high rates of echinocandin resistance and significant multidrug resistance make prophylaxis and empiric therapy difficult.

Etiologic Agents and Antifungal Susceptibility of Oral Candidosis from Romanian patients with HIV-infection or type 1 diabetes mellitus.

This is the first Romanian investigation of oral candidosis in patients suffering of HIV-infection or type 1 diabetes mellitus (T1DM). Candida albicans was the dominant species in both types of isolates: n = 14 (46.7%) in T1DM, n = 60 (69.8%) in HIV. The most frequent non-albicans Candida spp. were Candida kefyr (n = 6; 20%) in T1DM and Candida dubliniensis (n = 8; 9.3%) in HIV. Resistance to fluconazole was detected only in the HIV non-albicans Candida group (n = 8; 9.3%). All isolates were susceptible to VOR. The experimental drug MXP had MIC values equal or close to the ones of VOR. Echinocandin resistance was more frequent than azole resistance.

Enhancing Flucytosine Anticandidal Activity Using PEGylated Squalene Nanocarrier.

There is an emerging necessity for improved therapies against Candida-related infections, with significant implications for global healthcare. Current antifungal agents, limited in number, target specific pathways, but resistance remains a concern. Flucytosine (5FC) exhibits antifungal activity, particularly against Candida. However, monotherapy efficacy is limited, necessitating combination treatments. Herein, we report PEGylated squalene-based nanocarriers for 5FC loading, aiming to enhance its monotherapy efficacy against Candida strains. The loading of 5FC within micelles was achieved using the ultrasound-assisted solvent evaporation method. The 5FC-loaded micelles, together with non-loaded micelles, were thoroughly characterized and analyzed. STEM and DLS analysis confirmed the core-shell morphology with nanometric dimensions along with improved colloidal stability. The quantification of drug loading efficiency and drug loading capacity was calculated using the UV-Vis technique. The in vitro drug-release studies in simulated physiological conditions showed sustained release within 48 hours. Moreover, the release kinetics calculated using mathematical models showed a Fickian diffusion drug release mechanism in simulated physiological conditions with a slower diffusion rate. The in vitro antifungal activity was tested on Candida albicans, Candida glabrata, and Candida parapsilosis. The results showed improved antifungal activity for the nanotherapeutic and unchanged in vitro toxicity toward normal cells, suggesting promising advancements in 5FC therapy.

Chitosan nanofibers encapsulating copper oxide nanoparticles: A new approach towards multifunctional ecological membranes with high antimicrobial and antioxidant efficiency.

This paper focuses on the preparation of chitosan-based nanofibers embedding copper oxide nanoparticles to create multifunctional materials that meet the demands of contemporary applications. To this end, a mixture of chitosan, quaternized chitosan and poly (ethylene glycol) was used as polymeric matrix, considering their own contribution to the final material's properties and their ability to stabilize the copper oxide nanoparticles. An exhaustive investigation of the nanofibers was done in order to assess their composition and morphology (FTIR, 1H NMR, WXRD, TGA, SEM, TEM, POM, UV-vis) and to study their mechanical, antimicrobial and antioxidant properties, air and water permeability and ability for air filtration. It was shown that the copper oxide nanoparticles were anchored into the polymeric matrix via strong hydrogen bonding and electrostatic interactions, which induced the improvement of the mechanical properties and antioxidant activity. The copper oxide nanoparticles favored the thinning of the fibers during electrospinning process and improved the antibacterial activity and dust filtration capacity. Besides, the fibers displayed air permeability and vapor water transmission rate similar to synthetic nanofibers, while being biodegradable. All these performances recommend the new materials for developing antibacterial eco-materials with good breathability to be used as hygienic textiles, masks, or air filters.

Biocompatible hydrogels based on quaternary ammonium salts of chitosan with high antimicrobial activity as biocidal agents for disinfection.

The paper reports new hydrogels based on quaternary ammonium salts of chitosan designed as biocidal products. The chitosan derivative was crosslinked with salicylaldehyde via reversible imine bonds and supramolecular self-assemble to give dynamic hydrogels which respond to environmental stimuli. The crosslinking mechanism was demonstrated by 1H NMR and FTIR spectroscopy, and X-ray diffraction and polarized light microscopy. The hydrogel nature, self-healing and thixotropy were proved by rheological investigation and visual observation, and their morphology was assessed by scanning electron microscopy. The relevant properties for application as biocidal products, such as swelling, dissolution, bioadhesiveness, antimicrobial activity and ex-vivo hemocompatibility and in vivo local toxicity and biocompatibility on experimental mice were measured and analyzed in relationship with the imination degree and the influence of each component. It was found that the hydrogels are superabsorbent, have good adhesivity to skin and various surfaces and antimicrobial activity against relevant gram-positive and gram-negative bacteria, while being hemocompatible and biocompatible. Besides, the hydrogels are easily biodegraded in soil. All these properties recommend the studied hydrogels as ecofriendly biocidal agents for living tissues and surfaces, but also open the perspectives of their use as platform for in vivo applications in tissue engineering, wound healing, or drug delivery systems.

Photothermal Hydrogel Composites Featuring G4-Carbon Nanomaterial Networks for Staphylococcus aureus Inhibition.

Microbial infections represent a significant health risk, often leading to severe complications and, in some cases, even fatalities. As a result, there is an urgent need to explore innovative drug delivery systems and alternative therapeutic techniques. The photothermal therapy has emerged as a promising antibacterial approach and is the focus of this study. Herein, we report the successful synthesis of two distinct supramolecular composite hydrogels by incorporating graphene oxide (GO) and single-walled carbon nanotubes (SWNTs) into guanosine quadruplex (G4) based hydrogels containing covalently bound ß-cyclodextrin (ß-CD). The G4 matrix was synthesized through a two-step process, establishing a robust network between G4 and ß-CDs, followed by the encapsulation of either GO or SWNTs. Comprehensive characterization of these composite hydrogels were conducted using analytical techniques, including circular dichroism, Raman spectroscopy, rheological investigations, X-ray diffraction, and scanning electron microscopy. A notable discovery from the conducted research is the differential photothermal responses exhibited by the hydrogels when exposed to near-infrared laser irradiation. Specifically, SWNT-based hydrogels demonstrated superior photothermal performance, achieving a remarkable temperature increase of up to 52 °C, in contrast to GO-based hydrogels, which reached a maximum of 34 °C. These composite hydrogels showed good cytotoxicity evaluation results and displayed synergistic antibacterial activity against Staphylococcus aureus, positioning them as promising candidates for antibacterial photothermic platforms, particularly in the context of wound treatment. This study offers a valuable contribution to the development of advanced and combined therapeutic strategies for combating microbial infections and highlights the potential of carbon nanomaterial-enhanced supramolecular hydrogels in photothermal therapy applications.

Zein/Polysaccharide Nanoscale Electrostatic Complexes: Preparation, Drug Encapsulation and Antibacterial Properties.

Characterization of zein aqueous solutions, as a function of the ethanol content and pH, was performed, giving information on the zein aggregation state for the construction of complexes. The aggregation state and surface charge of zein was found to depend on the mixed solvent composition and pH. Nonstoichiometric complex nanoparticles (NPECs) were prepared by electrostatically self-assembling zein, as the polycation, and sodium alginate or chondroitin sulfate, as the polyanions, at a pH of 4. A wide range of parameters were investigated: the alcohol-water content in the zein solutions, the charge molar ratios, the solution addition order and the addition rate. The resulting nanoparticles were characterized by dynamic and electrophoretic light scattering, circular dichroism and scanning electron microscopy. The smallest size for the NPECs (100 nm) was obtained when the polysaccharides acted as the titrate with an addition rate of 0.03 mL·min-1. The NPECs with the best characteristics were selected for loading with ciprofloxacin and then deposited on a cellulosic material in order to evaluate their antibacterial activity. Substantial drug encapsulation with desired drug release profiles were found together with notable antibacterial efficiency, showing the tunability of the properties for both the zein and its complexes with polysaccharides, together with their application potential in the biomedical field.

Dextran coated iron oxide nanoparticles loaded with protocatechuic acid as multifunctional therapeutic agents.

Nowadays, there is a growing interest in multifunctional therapeutic agents as valuable tools to improve and expand the applicability field of traditional bioactive compounds. In this context, the synthesis and main characteristics of dextran-coated iron oxide nanoparticles (IONP-Dex) loaded with both an antioxidant, protocatechuic acid (PCA), and an antibiotic, ceftazidime (CAZ) or levofloxacin (LEV) are herein reported for the first time, with emphasis on the potentiation effect of PCA on drugs activity. All nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, differential scanning calorimetry and dynamic light scattering. As evidenced by DPPH method, IONP-Dex loaded with PCA and LEV had similar antioxidant activity like those with PCA only, but higher than PCA and CAZ loaded ones. A synergy of action between PCA and each antibiotic co-loaded on IONP-Dex has been highlighted by an enhanced activity against reference bacterial strains, such as S. aureus and E. coli after 40 min of incubation. It was concluded that PCA, which is the main cause of the antioxidative properties of loaded nanoparticles, further improves the antimicrobial activity of IONP-Dex nanoparticles when was co-loaded with CAZ or LEV antibiotics. All constructs also showed a good biocompatibility with normal human dermal fibroblasts.

Biogenic Synthesis of Silver Nanoparticles Mediated by Aronia melanocarpa and Their Biological Evaluation.

In the present study, two A. melanocarpa berry extracts were used for the synthesis of silver nanoparticles (AgNPs). After the optimization of synthesis, the AgNPs were characterized using UV-Vis, FTIR, EDX, DLS, and STEM analyses. The stability in different media, phytotoxicity, as well as antimicrobial and antioxidant activities were also evaluated. The ideal synthesis conditions were represented by a 3 mM AgNO3 concentration, 1:9 extract:AgNO3 volume ratio, alkaline medium, and stirring at 40 °C for 120 min. The synthesis was confirmed by the surface plasmon resonance (SPR) peak at 403 nm, and the strong signal at 3 keV from the EDX spectra. FTIR analysis indicated that polyphenols, polysaccharides, and amino acids could be the compounds responsible for synthesis. Stability tests and the negative zeta potential values showed that phytocompounds also play a role in the stabilization and capping of AgNPs. The preliminary phytotoxicity studies on T. aestivum showed that both the extracts and their corresponding AgNPs had an impact on the growth of roots and shoots as well as on the microscopic structure of leaves. The synthesized AgNPs presented antimicrobial activity against S. aureus, E. coli, and C. albicans. Moreover, considering the results obtained in the lipoxygenase inhibition, the DPPH and hydroxyl scavenging activities, and the ferrous ion chelating assay, AgNPs exhibit promising antioxidant activity.

Preparation and Characterization of Polymeric Microparticles Based on Poly(ethylene brassylate-co-squaric Acid) Loaded with Norfloxacin.

In recent years, increasing interest has been accorded to polyester-based polymer microstructures, driven by their promising potential as advanced drug delivery systems. This study presents the preparation and characterization of new polymeric microparticles based on poly(ethylene brassylate-co-squaric acid) loaded with norfloxacin, a broad-spectrum antibiotic. Polymacrolactone was synthesised in mild conditions through the emulsion polymerization of bio-based and renewable monomers, ethylene brassylate, and squaric acid. The microparticles were obtained using the precipitation technique and subsequently subjected to comprehensive characterization. The impact of the copolymer/drug ratio on various properties of the new system was systematically evaluated, confirming the structure of the copolymer and the encapsulation of norfloxacin. The microspheres are approximately spherical and predominantly homogeneously distributed. The average hydrodynamic diameter of the microparticles falls between 400 and 2000 nm, a decrease that is observed with the increase in norfloxacin content. All samples showed good encapsulation efficiency and drug loading capacity, with the highest values obtained for microparticles synthesised using an equal ratio of copolymer and drug. In vitro drug release results disclose that norfloxacin molecules are released in a sustained biphasic manner for up to 24 h. Antimicrobial activity was also studied, with samples showing very good activity against E. coli and moderate activity against S. aureus and E. faecalis. In addition, HDFA human fibroblast cell cultures demonstrated the cytocompatibility of the microparticles.

New Hydrogels and Formulations Based on Piperonyl-Imino-Chitosan Derivatives.

Candida infections have been always a serious healcare related problem. The present study reports the preparation of hydrogels and formulations based on piperonyl-imino-chitosan derivatives and Amphotericin B drug for the treatment of Candida infections. The hydrogels were obtained by the imination reaction of chitosan with piperonal monoaldehyde, followed by the self-assembling of the resulted imines, while the formulations were obtained by an in situ hydrogelation method of chitosan with piperonal in the presence of Amphotericin B antifungal drug. The structural characterization of both hydrogels and formulations by Fourier transform infrared spectroscopy and Nuclear magnetic resonance spectroscopy revealed the formation of imine units between the reagents, while their supramolecular characterization using polarized optical microscopy and wide angle X-ray diffraction demonstrated that hydrophilic/hydrophobic segregation is the process which governed the formation of gel like systems. The systems were further investigated from the point of view of their further applications revealing that they were biodegradable, presented high swelling ability and were able to release the antifungal drug in a sustained manner, presenting promising antifungal activity against five Candida strains.

Temperature Induced Gelation and Antimicrobial Properties of Pluronic F127 Based Systems.

Different formulations containing Pluronic F127 and polysaccharides (chitosan, sodium alginate, gellan gum, and κ-carrageenan) were investigated as potential injectable gels that behave as free-flowing liquid with reduced viscosity at low temperatures and displayed solid-like properties at 37 °C. In addition, ZnO nanoparticles, lysozyme, or curcumin were added for testing the antimicrobial properties of the thermal-sensitive gels. Rheological investigations evidenced small changes in transition temperature and kinetics of gelation at 37 °C in presence of polysaccharides. However, the gel formation is very delayed in the presence of curcumin. The antimicrobial properties of Pluronic F127 gels are very modest even by adding chitosan, lysozyme, or ZnO nanoparticles. A remarkable enhancement of antimicrobial activity was observed in the presence of curcumin. Chitosan addition to Pluronic/curcumin systems improves their viscoelasticity, antimicrobial activity, and stability in time. The balance between viscoelastic and antimicrobial characteristics needs to be considered in the formulation of Pluronic F127 gels suitable for biomedical and pharmaceutical applications.

Drug delivery based on a supramolecular chemistry approach by using chitosan hydrogels.

Microbial infections are a serious healthcare related problem, causing several complications and even death. That is why, the development of new drug delivery systems with prolonged effect represents an interesting research topic. This study presents the synthesis and characterization of new hydrogels based on chitosan and three halogenated monoaldehydes. Further, the hydrogels were used as excipients for the development of drug delivery systems (DDS) by the incorporation of fluconazole, an antifungal drug. The systems were structurally characterized by Fourier Transformed Infrared Spectroscopy and Nuclear Magnetic Resonance, both methods revealing the formation of the imine linkages between chitosan and the aldehydes. The samples presented a high degree of ordering at supramolecular level, as demonstrated by WXRD and POM and a good water-uptake, reaching a maximum of 1.6 g/g. The obtained systems were biodegradable, loosing between 38 and 49 % from their initial mass in the presence of lysozyme in 21 days. The ability to release the antifungal drug in a sustained manner for seven days, along with the high values of the inhibition zone diameter, reaching a maximum of 64 mm against Candida parapsilosis for the chlorine containing sample, recommend these systems as promising materials for bioapplications.

Surface Degradation of DGEBA Epoxy Resins Cured with Structurally Different Amine Hardeners: Effects of UV Radiation.

In this study, the effects of three diamine curing agents (aromatic, cycloaliphatic, aliphatic) on the photochemical behavior of bisphenol A diglycidyl ether networks were comparatively examined. In order to monitor structural changes and study the curing agents' action mode, the cured epoxy resins were characterized before and after photoirradiation by means of Fourier-transform infrared spectroscopy, contact angle, differential scanning calorimetry, scanning electron microscopy, and energy-dispersive X-ray analysis, mass loss, and color modification measurements. Water absorption tests were also conducted. The cured epoxy resins are to be used in different multicomponent polymer materials for outdoor protection. The presence of the cycloaliphatic hardener led to reduced water absorption, and after UV irradiation, an increase in the glass transition temperature and lowest mass loss of the corresponding cured epoxy resin compared to the ones cured with aromatic and aliphatic hardener.

Thermosensitive Polyurethane-Based Hydrogels as Potential Vehicles for Meloxicam Delivery.

Meloxicam (MX) is a nonsteroidal anti-inflammatory drug (NSAID) used mainly to reduce pain, inflammation, and fever. In the present study, thermosensitive polyurethane (PU)-based hydrogels with various excipients (PEG, PVP, HPC, and essential oil) were prepared and loaded with MX. Rheological investigations were carried out on the PU-based formulations in various shear regimes, and their viscoelastic characteristics were determined. The average size of the PU micelles was 35.8 nm at 37 °C and slightly increased at 37 nm in the presence of MX. The zeta potential values of the hydrogels were between -10 mV and -11.5 mV. At pH = 6 and temperature of 37 °C, the formulated PU-based hydrogels loaded with MX could deliver significant amounts of the active substance, between 60% and 80% over 24-48 h and more than 90% within 2 weeks. It was found that anomalous transport phenomena dominated MX's release mechanism from the PU-based networks. The results are encouraging for further studies aiming to design alternative carriers to commercial dosage forms of nonsteroidal anti-inflammatory drugs.