miR-21/Gemini surfactant-capped gold nanoparticles as potential therapeutic complexes: Synthesis, characterization and in vivo nanotoxicity probes

Au@16-pH-16/miR-21 mimic nanosystem: An efficient treatment for obesity through browning and thermogenesis induction

Despite the abundance of registered clinical trials worldwide, the availability of effective drugs for obesity treatment is limited due to their associated side effects. Thus, there is growing interest in therapies that stimulate energy expenditure in white adipose tissue. Recently, we demonstrated that the delivery of a miR-21 mimic using JetPEI effectively inhibits weight gain in an obese mouse model by promoting metabolism, browning, and thermogenesis, suggesting the potential of miR-21 mimic as a treatment for obesity. Despite these promising results, the implementation of more advanced delivery system techniques for miR-21 mimic would greatly enhance the advancement of safe and efficient treatment approaches for individuals with obesity in the future. Our objective is to explore whether a new delivery system based on gold nanoparticles and Gemini surfactants (Au@16-ph-16) can replicate the favorable effects of the miR-21 mimic on weight gain, browning, and thermogenesis. We found that dosages as low as 0.2 μg miR-21 mimic /animal significantly inhibited weight gain and induced browning and thermogenic parameters. This was evidenced by the upregulation of specific genes and proteins associated with these processes, as well as the biogenesis of beige adipocytes and mitochondria. Significant increases in miR-21 levels were observed in adipose tissue but not in other tissue types. Our data indicates that Au@16-ph-16 could serve as an effective delivery system for miRNA mimics, suggesting its potential suitability for the development of future clinical treatments against obesity.

Synergistic Antibacterial Effects of Amoxicillin and Gold Nanoparticles: A Therapeutic Option to Combat Antibiotic Resistance

Compacted Au@16-mph-16/DNA-AMOX (NSi) nanosystems were prepared from amoxicillin (AMOX) and precursor Au@16-mph-16 gold nanoparticles (Ni) using a Deoxyribonucleic acid (DNA) biopolymer as a glue. The synthesized nanocarrier was tested on different bacterial strains of Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae to evaluate its effectiveness as an antibiotic as well as its internalization. Synthesis of the nanosystems required previous structural and thermodynamic studies using circular dichroism (CD) and UV-visible techniques to guarantee optimal complex formation and maximal DNA compaction, characteristics which facilitate the correct uptake of the nanocarrier. Two nanocomplexes with different compositions and structures, denoted NS1 and NS2, were prepared, the first involving external Au@16-mph-16 binding and the second partial intercalation. The Ni and NSi nanosystems obtained were characterized via transmission electron microscopy (TEM), zeta potential, and dynamic light scattering (DLS) techniques to measure their charge, aggregation state and hydrodynamic size, and to verify their presence inside the bacteria. From these studies, it was concluded that the zeta potential values for gold nanoparticles, NS1, and NS2 nanosystems were 67.8, -36.7, and -45.1 mV. Moreover, the particle size distribution of the Au@16-mph-16 gold nanoparticles and NS2 nanoformulation was found to be 2.6 nm and 69.0 nm, respectively. However, for NS1 nanoformulation, a bimodal size distribution of 44 nm (95.5%) and 205 nm (4.5%) was found. Minimal inhibitory concentration (MIC) values were determined for the bacteria studied using a microdilution plates assay. The effect on Escherichia coli bacteria was notable, with MIC values of 17 µM for both the NS1 and NS2 nanosystems. The Staphylococcus aureus chart shows a greater inhibition effect of NS2 and NP2 in non-diluted wells, and clearly reveals a great effect on Streptococcus pneumoniae, reaching MIC values of 0.53 µM in more diluted wells. These results are in good agreement with TEM internalization studies of bacteria that reveal significant internalization and damage in Streptococcus pneumoniae. In all the treatments carried out, the antibiotic capacity of gold nanosystems as enhancers of amoxicillin was demonstrated, causing both the precursors and the nanosystems to act very quickly, and thus favoring microbial death with a small amount of antibiotic. Therefore, these gold nanosystems may constitute an effective therapy to combat resistance to antibiotics, in addition to avoiding the secondary effects derived from the administration of high doses of antibiotics.

Multiheaded Cationic Surfactants with Dedicated Functionalities: Design, Synthetic Strategies, Self-Assembly and Performance

Contemporary research concerning surfactant science and technology comprises a variety of requirements relating to the design of surfactant structures with widely varying architectures to achieve physicochemical properties and dedicated functionality. Such approaches are necessary to make them applicable to modern technologies, such as nanostructure engineering, surface structurization or fine chemicals, e.g., magnetic surfactants, biocidal agents, capping and stabilizing reagents or reactive agents at interfaces. Even slight modifications of a surfactant's molecular structure with respect to the conventional single-head-single-tail design allow for various custom-designed products. Among them, multicharge structures are the most intriguing. Their preparation requires specific synthetic routes that enable both main amphiphilic compound synthesis using appropriate step-by-step reaction strategies or coupling approaches as well as further derivatization toward specific features such as magnetic properties. Some of the most challenging aspects of multicharge cationic surfactants relate to their use at different interfaces for stable nanostructures formation, applying capping effects or complexation with polyelectrolytes. Multiheaded cationic surfactants exhibit strong antimicrobial and antiviral activity, allowing them to be implemented in various biomedical fields, especially biofilm prevention and eradication. Therefore, recent advances in synthetic strategies for multiheaded cationic surfactants, their self-aggregation and performance are scrutinized in this up-to-date review, emphasizing their applications in different fields such as building blocks in nanostructure engineering and their use as fine chemicals.

Gold Nanosystems Covered with Doxorubicin/DNA Complexes: A Therapeutic Target for Prostate and Liver Cancer

Different gold nanosystems covered with DNA and doxorubicin (Doxo) were designed and synthesized for cancer therapy, starting from Au@16-Ph-16 cationic nanoparticles and DNA-Doxo complexes prepared under saturation conditions. For the preparation of stable, biocompatible, and small-sized compacted Au@16-Ph-16/DNA-Doxo nanotransporters, the conditions for the DNA-Doxo compaction process induced by gold nanoparticles were first explored using fluorescence spectroscopy, circular dichroism and atomic force microscopy techniques. The reverse process, which is fundamental for Doxo liberation at the site of action, was found to occur at higher C_Au@16-Ph-16 concentrations using these techniques. Zeta potential, dynamic light scattering and UV-visible spectroscopy reveal that the prepared compacted nanosystems are stable, highly charged and of adequate size for the effective delivery of Doxo to the cell. This fact is verified by in vitro biocompatibility and internalization studies using two prostate cancer-derived cell lines (LNCaP and DU145) and one hepatocellular carcinoma-derived cell line (SNU-387), as well as a non-tumor prostate (PNT2) cell line and a non-hepatocarcinoma hepatoblastoma cell line (Hep-G2) model used as a control in liver cells. However, the most outstanding results of this work are derived from the use of the C_I+N_I combined treatments which present strong action in cancer-derived cell lines, while a protective effect is observed in non-tumor cell lines. Hence, novel therapeutic targets based on gold nanoparticles denote high selectivity compared to conventional treatment based on free Doxo at the same concentration. The results obtained show the viability of both the proposed methodology for internalization of compacted nanocomplexes inside the cell and the effectiveness of the possible treatment and minimization of side effects in prostate and liver cancer.

Use of Nanoparticles to Prevent Resistance to Antibiotics-Synthesis and Characterization of Gold Nanosystems Based on Tetracycline

Antimicrobial resistance (AMR) is a serious public health problem worldwide which, according to the World Health Organization (WHO), requires research into new and more effective drugs. In this work, both gold nanoparticles covered with 16-3-16 cationic gemini surfactant (Au@16-3-16) and DNA/tetracycline (DNA/TC) intercalated complexes were prepared to effectively transport tetracycline (TC). Synthesis of the Au@16-3-16 precursor was carried out by using trihydrated gold, adding sodium borohydride as a reducing agent and the gemini surfactant 16-3-16 as stabilizing agent. Circular dichroism and atomic force microscopy techniques were then used to ascertain the optimal R range of the relationship between the concentrations of Au@16-3-16 and the DNA/TC complex (R = CAu@16-3-16/CDNA) that allow the obtainment of stable and compact nanosystems, these characteristics being fundamental for their use as antibiotic transporters. Stability studies over time were carried out for distinct selected Au@16-3-16 and Au@16-3-16/DNA-TC nanoformulations using the ultraviolet−visible spectrophotometry technique, checking their stability for at least one month. In addition, in order to know the charge and size distribution of the nanocomplexes, DLS and zeta potential measurements were performed in the solution. The results showed that the characterized nanosystems were highly charged, stable and of a reduced size (<100 nm) that allows them to cross bacterial membranes effectively (>1 μm). Once the different physicochemical characteristics of the gold nanosystems were measured, Au@16-3-16 and Au@16-3-16/DNA-TC were tested on Escherichia coli and Staphylococcus aureus to study their antibacterial properties and internalization capacity in microbes. Differences in the interaction of the precursors and the compacted nanosystems generated were observed in Gram-positive and Gram-negative bacteria, possibly due to membrane damage or electrostatic interaction with internalization by endocytosis. In the internalization experiments, depending on the treatment application time, the greatest bacterial destruction was observed for all nanoformulations explored at 18 h of incubation. Importantly, the results obtained demonstrate that both new nanosystems based on TC and Au@16-3-16 precursors have optimal antimicrobial properties and would be beneficial for use in patients, avoiding possible side effects.

Biocompatible DNA/5-Fluorouracil-Gemini Surfactant-Functionalized Gold Nanoparticles as Promising Vectors in Lung Cancer Therapy

The design and preparation of novel nanocarriers to transport cancer drugs for chemotherapy purposes is an important line of research in the medical field. A new 5-fluorouracil (5-Fu) transporter was designed based on the use of two new biocompatible gold nanosystems: (i) a gold nanoparticle precursor, Au@16-Ph-16, stabilized with the positively charged gemini surfactant 16-Ph-16, and (ii) the compacted nanocomplexes formed by the precursor and DNA/5-Fu complexes, Au@16-Ph-16/DNA-5-Fu. The physicochemical properties of the obtained nanosystems were studied by using UV-visible spectroscopy, TEM, dynamic light scattering, and zeta potential techniques. Method tuning also requires the use of circular dichroism, atomic force microscopy, and fluorescence spectroscopy techniques for the prior selection of the optimal relative Au@16-Ph-16 and DNA concentrations (R = CAu@16-Ph-16/CDNA), biopolymer compaction/decompaction, and 5-Fu release from the DNA/5-Fu complex. TEM experiments revealed the effective internalization of the both precursor and Au@16-Ph-16/DNA-5-Fu-compacted nanosystems into the cells. Moreover, cytotoxicity assays and internalization experiments using TEM and confocal microscopy showed that the new strategy for 5-Fu administration enhanced efficacy, biocompatibility and selectivity against lung cancer cells. The differential uptake among different formulations is discussed in terms of the physicochemical properties of the nanosystems.