The New Strategy for Studying Drug-Delivery Systems with Prolonged Release: Seven-Day In Vitro Antibacterial Action.

The new method of antibacterial-drug-activity investigation in vitro is proposed as a powerful strategy for understanding how carriers affect drug action during long periods (7 days). In this paper, we observed fluoroquinolone moxifloxacin (MF) antibacterial-efficiency in non-covalent complexes, with the sulfobutyl ether derivative of ß-cyclodextrin (SCD) and its polymer (SCDpol). We conducted in vitro studies on two Escherichia coli strains that differed in surface morphology. It was found that MF loses its antibacterial action after 3-4 days in liquid media, whereas the inclusion of the drug in SCD led to the increase of MF antibacterial activity by up to 1.4 times within 1-5 days of the experiment. In the case of MF-SCDpol, we observed a 12-fold increase in the MF action, and a tendency to prolonged antibacterial activity. We visualized this phenomenon (the state of bacteria, cell membrane, and surface morphology) during MF and MF-carrier exposure by TEM. SCD and SCDpol did not change the drug's mechanism of action. Particle adsorption on cells was the crucial factor for determining the observed effects. The proteinaceous fimbriae on the bacteria surface gave a 2-fold increase of the drug carrier adsorption, hence the strains with fimbriae are more preferable for the proposed treatment. Furthermore, the approach to visualize the CD polymer adsorption on bacteria via TEM is suggested. We hope that the proposed comprehensive method will be useful for the studies of drug-delivery systems to uncover long-term antibacterial action.

Poly(Ethylene Glycol) Interacts with Hyaluronan in Aqueous Media.

We report here the first evidence for the interaction of poly(ethylene glycol) (PEG) with hyaluronan (HA) in aqueous solutions. PEG-HA complexes (Kapp = 45,000 ± 8000 M-1) contained about 3.3 ± 0.1 of ethylene glycol units per disaccharide of HA. The carboxyl of the D-glucuronic acid and the amide of the N-acetyl-D-glucosamine did not participate in PEG binding. Similar experiments performed with dextran and monosaccharides showed that multiple free primary hydroxyls regularly distributed along the polysaccharide chain are necessary for PEG binding. Another novelty of our study is contraction of HA upon PEG binding. The effect was observed with HA in solution or adsorbed on positively charged liposomes. The thickness of the HA layer on the liposomes decreased 2-fold upon PEG addition. HA compaction induced by PEG may underlie the changes in the plasma membrane properties and resealing of mechanical injuries induced by Pluronics.

Interaction of Ionenes with Lipid Membrane: Unusual Impact of Charge Density.

Synthetic water-soluble polymers are increasingly used for gene delivery, stabilization, and delivery of proteins, and as prospective antimicrobial and antiviral agents. Therefore, study of their interaction with lipid membranes is of special importance. Herein, we studied interaction of aliphatic cationic ionenes (recently tested for gene delivery efficiency) differed in the length of spacer between charged groups (and therefore in charge density) with anionic lipid membrane. A range of approaches such as measurement of particle size and electrophoretic mobility, liposome integrity, ATR-FTIR spectroscopy, isothermal titration calorimetry as well as atomistic molecular modeling was used. Ionene with a spacer of 10 methylene groups has been shown to be incorporated into membrane and interact with its inner hydrophobic part in contrast to ionenes with shorter spacer, which interacted only with outer polar head groups of lipids staying at the water-membrane interface. It affects membrane integrity and results in a different behavior of the polymer-liposome complexes. These findings are relevant for potential biomedical application of ionenes, including creation of composite polymer-liposome systems for drug delivery.

Magnetic nanorods for remote disruption of lipid membranes by non-heating low frequency magnetic field.

This work presents direct evidence of disordering of liposomal membranes by magnetic nanoparticles during their exposures to non-heating alternating Extremely Low Frequency Magnetic Field (ELF MF). Changes in the lipid membrane structure were demonstrated by the Attenuated total reflection Fourier Transform Infrared and fluorescence spectroscopy. Specifically, about 50% of hydrophobic chains became highly mobile under the action of ELF MF. Magnetic field-induced increase in the membrane fluidity was accompanied by an increase in membrane permeability and release of solutes entrapped in liposomes. The effect of ELF MF on the membrane fluidity was greater in case of 70 × 12 nm magnetite nanorods adsorbed on the liposomes surface compared to liposomes with ~7 nm spherical MNPs embedded within lipid membranes. A physical model of this process explaining experimental data is suggested. The obtained results open new horizons for the development of systems for triggered drug release without dangerous heating and overheating of tissues.

Engineering macrophage-derived exosomes for targeted paclitaxel delivery to pulmonary metastases: in vitro and in vivo evaluations.

Exosomes have recently emerged as a promising drug delivery system with low immunogenicity, high biocompatibility, and high efficacy of delivery. We demonstrated earlier that macrophage-derived exosomes (exo) loaded with a potent anticancer agent paclitaxel (PTX) represent a novel nanoformulation (exoPTX) that shows high anticancer efficacy in a mouse model of pulmonary metastases. We now report the manufacture of targeted exosome-based formulations with superior structure and therapeutic indices for systemic administration. Herein, we developed and optimized a formulation of PTX-loaded exosomes with incorporated aminoethylanisamide-polyethylene glycol (AA-PEG) vector moiety to target the sigma receptor, which is overexpressed by lung cancer cells. The AA-PEG-vectorized exosomes loaded with PTX (AA-PEG-exoPTX) possessed a high loading capacity, profound ability to accumulate in cancer cells upon systemic administration, and improved therapeutic outcomes. The combination of targeting ability with the biocompatibility of exosome-based drug formulations offers a powerful and novel delivery platform for anticancer therapy.

Lanthanide Fluorobenzoates as Bio-Probes: a Quest for the Optimal Ligand Fluorination Degree.

The thorough study of fluorinated benzoates of lanthanides (Eu, Tb, Nd, Er, Yb, Gd, La, Lu) is reported. Their composition in single crystal and powder state revealed two predominant structural motifs. An in-depth luminescence study has been performed on the reported fluorobenzoates, showing, that terbium and europium complexes in solid state possess high luminescence intensity with the quantum yield of up to 69 %. High solubility in most organic solvents, as well as in water, combined with the high luminescence intensity in water solution and non-toxicity allowed the testing of europium complexes as bioprobes in cellulo. Among all tested fluorobenzoates, europium 2-fluorobenzoate dihydrate combined the best luminescent properties, thermodynamic stability, aqueous solubility, and non-toxicity, and was shown to be a viable bio-marker.

Thermodynamics and molecular insight in guest-host complexes of fluoroquinolones with ß-cyclodextrin derivatives, as revealed by ATR-FTIR spectroscopy and molecular modeling experiments.

ß-Сyclodextrin (CD) is a perspective class of excipients used in pharmaceutical formulations to enhance solubility, bioavailability, and pharmacokinetics of various poorly soluble drugs, forming a non-covalent guest-host complex. However, the development of such formulations is usually a very laborious and time-consuming process due to lack of appropriate analytical tools to directly track and study the detailed molecular mechanism of such complex formation. Here, using guest-host complexes of fluoroquinolones (FQ) with CDs, as an example, we demonstrate the utility of ATR-FTIR to determine the thermodynamic stability, as well as structural features associated with complex formation, including involvement of certain functional groups. Furthermore, varying the CD's side groups, we were able to tailor the CD's geometry and binding surface to make FQ-CD interactions strong enough to potentially affect its pharmacokinetics and justify development of a new sustained-release drug formulation (dissociation constant decreased from 5 * 10-3 M to 10-5 M). 3D molecular modeling with energy optimization supports the findings and conclusions made on the basis of ATR-FTIR data analysis and explains the observed difference in dissociation constants.

Novel Prodrug of Doxorubicin Modified by Stearoylspermine Encapsulated into PEG-Chitosan-Stabilized Liposomes.

Here, we report a new modification of doxorubicin based on an amphiphilic stearoylspermine anchor, enabling loading into liposomal membranes. Doxorubicin is coupled with stearoylspermine through an acid-labile hydrazone linker to ensure the release of the drug in the acidic interstitium of tumors. Using ATR-FTIR spectroscopy (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy), the mechanism of interaction of doxorubicin with the anionic liposomal membrane was studied: incorporation of stearoyl chains leads to an increase in local microfluidity, and the amino groups of spermine interact with the phosphate groups of lipids. To stabilize liposomes against aggregation, we applied the copolymer PEG-chitosan as a coating: complex formation leads to charge neutralization, and the liposomes grow in size. According to MTT tests and confocal microscopy for cell lines A459 and Caco-2, PEG-chitosan-coated liposomes are as effective as neutral liposomes but are much more stable.

Development of exosome-encapsulated paclitaxel to overcome MDR in cancer cells.

Exosomes have recently come into focus as "natural nanoparticles" for use as drug delivery vehicles. Our objective was to assess the feasibility of an exosome-based drug delivery platform for a potent chemotherapeutic agent, paclitaxel (PTX), to treat MDR cancer. Herein, we developed different methods of loading exosomes released by macrophages with PTX (exoPTX), and characterized their size, stability, drug release, and in vitro antitumor efficacy. Reformation of the exosomal membrane upon sonication resulted in high loading efficiency and sustained drug release. Importantly, incorporation of PTX into exosomes increased cytotoxicity more than 50 times in drug resistant MDCKMDR1 (Pgp+) cells. Next, our studies demonstrated a nearly complete co-localization of airway-delivered exosomes with cancer cells in a model of murine Lewis lung carcinoma pulmonary metastases, and a potent anticancer effect in this mouse model. We conclude that exoPTX holds significant potential for the delivery of various chemotherapeutics to treat drug resistant cancers. FROM THE CLINICAL EDITOR: Exosomes are membrane-derived natural vesicles of ~40 - 200 nm size. They have been under extensive research as novel drug delivery vehicles. In this article, the authors developed exosome-based system to carry formulation of PTX and showed efficacy in the treatment of multi-drug resistant cancer cells. This novel system may be further developed to carry other chemotherapeutic agents in the future.

Antioxidant activity of an inclusion complex between rutin and ß-cyclodextrin: experimental and quantum chemical studies.

This study aims to synthesize a guest-host complex derived from rutin (Rut) and ß-cyclodextrin (ß-CD) (denoted as [Rut⊂ß-CD]). The obtained substance was characterized by the FT-IR and DSC methods, signifying the formation of an inclusion complex between Rut and ß-CD. Complex formation increased the antioxidant activity of rutin corresponding to the decrease of EC50 values from 1.547 × 10-5 mol L-1 to 1.227 × 10-5 mol L-1 according to the DPPH free radical scavenging test. The rutin-ß-CD interaction energies were calculated in the vacuum and various solvents (e.g., water, ethanol, and dimethylsulfoxide) utilizing an accurate and broadly parametrized self-consistent tight-binding quantum chemical method (GFN2-xTB). The calculation results reveal the influence of solvent on the structural formation of the rutin-ß-CD complex. In both the vacuum and aqueous solution, rutin can enter into the small-sized empty cavity of ß-CD, albeit through different terminals, resulting in distinct preferential structures. The presence of organic solvents appears to reduce the interaction between rutin and ß-CD, with the interaction strength following the order: water > ethanol > dimethyl sulfoxide.

Conjugates of Chitosan with ß-Cyclodextrins as Promising Carriers for the Delivery of Levofloxacin: Spectral and Microbiological Studies.

In this work, we synthesized chitosan 5 kDa conjugates with ß-cyclodextrins with various substituents as promising mucoadhesive carriers for the delivery of fluoroquinolones using the example of levofloxacin. The obtained conjugates were comprehensively characterized by spectral methods (UV-Vis, ATR-FTIR, 1H NMR, SEM). The physico-chemical properties of the complex formations were studied by IR, UV, and fluorescence spectroscopy. The dissociation constants of complexes with levofloxacin were determined. Complexation with conjugates provided four times slower drug release in comparison with plain CD and more than 20 times in comparison with the free drug. The antibacterial activity of the complexes was tested on model microorganisms Gram-negative bacteria Escherichia coli ATCC 25922 and Gram-positive Bacillus subtilis ATCC 6633. The complex with the conjugate demonstrated the same initial levofloxacin antibacterial activity but provided significant benefits, e.g., prolonged release.

The Solubility Studies and the Complexation Mechanism Investigations of Biologically Active Spiro[cyclopropane-1,3'-oxindoles] with ß-Cyclodextrins.

In this work, we first improved the aqueous solubility of biologically active spiro[cyclopropane-1,3'-oxindoles] (SCOs) via their complexation with different ß-cyclodextrins (ß-CDs) and proposed a possible mechanism of the complex formation. ß-CDs significantly increased the water solubility of SCOs (up to fourfold). Moreover, the nature of the substituents in the ß-CDs influenced the solubility of the guest molecule (MßCD > SBEßCD > HPßCD). Complexation preferably occurred via the inclusion of aromatic moieties of SCOs into the hydrophobic cavity of ß-CDs by the numerous van der Waals contacts and formed stable supramolecular systems. The phase solubility technique and optical microscopy were used to determine the dissociation constants of the complexes (Kc~102 M−1) and reveal a significant decrease in the size of the formed crystals. FTIR-ATR microscopy, PXRD, and 1H-1H ROESY NMR measurements, as well as molecular modeling studies, were carried out to elucidate the host−guest interaction mechanism of the complexation. Additionally, in vitro experiments were carried out and revealed enhancements in the antibacterial activity of SCOs due to their complexation with ß-CDs.

Combined System for the Simultaneous Delivery of Levofloxacin and Rifampicin: Structural and Functional Properties and Antibacterial Activity.

The therapy of resistant forms of tuberculosis requires the simultaneous use of several drugs, in particular, a combination of rifampicin and levofloxacin. In this paper, we aimed to design a combined system for the simultaneous delivery of these drugs for potential inhalation administration. A feature of this system is the incorporation of rifampicin into optimized liposomal vesicles capable of forming a multipoint non-covalent complex with chitosan-ß-cyclodextrin conjugates. Levofloxacin is incorporated into cyclodextrin tori by forming a host-guest complex. Here, a comprehensive study of the physicochemical properties of the obtained systems was carried out and special attention was paid to the kinetics of cargo release for individual drugs and in the combined system. The release of levofloxacin in combined system is slow and is described by the Higuchi model in all cases. The release of rifampicin from liposomes during the formation of complexes with polymeric conjugates is characterized by the change of the Higuchi model to the Korsmeyer-Peppas model with the main type of diffusion against Fick's law. Microbiological studies in solid and liquid growth media a consistently high antibacterial activity of the obtained systems was shown against B. subtilis and E. coli.

Cyclodextrins and Their Polymers Affect Human Serum Albumin's Interaction with Drugs Used in the Treatment of Pulmonary Infections.

Respiratory infectious diseases have challenged medical communities and researchers. Ceftriaxone, meropenem and levofloxacin are widely used for bacterial infection treatment, although they possess severe side effects. To overcome this, we propose cyclodextrin (CD) and CD-based polymers as a drug delivery system for the drugs under consideration. CD polymers demonstrate higher binding affinity for levofloxacin (Ka ≈ 105 M) compared to drug-CD complexes. CDs slightly alter the drugs' affinity for human serum albumin (HSA), whereas CD polymers increase the drugs' binding affinity up to 100 times. The most significant effect was observed for more the hydrophilic drugs ceftriaxone and meropenem. The drug's encapsulation in CD carriers leads to a decrease in the degree of change in the protein's secondary structure. The drug-CD carrier-HSA complexes demonstrate satisfying antibacterial activity in vitro, and even a high binding affinity does not decrease the drug's microbiological properties after 24 h. The proposed carriers are promising for a drug form with a prolonged drug release.

pH-Sensitive Liposomes with Embedded 3-(isobutylamino)cholan-24-oic Acid: What Is the Possible Mechanism of Fast Cargo Release?

pH-sensitive liposomes have great potential for biomedical applications, in particular as nanocontainers for the delivery of biologically active compounds to specific areas of the human body. In this article, we discuss the possible mechanism of fast cargo release from a new type of pH-sensitive liposomes with embedded ampholytic molecular switch (AMS, 3-(isobutylamino)cholan-24-oic acid) with carboxylic anionic groups and isobutylamino cationic ones attached to the opposite ends of the steroid core. AMS-containing liposomes demonstrated the rapid release of the encapsulated substance when altering the pH of an outer solution, but the exact mechanism of the switch action has not yet been accurately determined. Here, we report on the details of fast cargo release based on the data obtained using ATR-FTIR spectroscopy as well as atomistic molecular modeling. The findings of this study are relevant to the potential application of AMS-containing pH-sensitive liposomes for drug delivery.

Liposomal Forms of Fluoroquinolones and Antifibrotics Decorated with Mannosylated Chitosan for Inhalation Drug Delivery.

The severe course of COVID-19 leads to the long-terming pulmonary diseases, such as bacterial pneumonia and post-COVID-19 pulmonary fibrosis. Thus, the essential task of biomedicine is a design of new effective drug formulations, including those for inhalation administration. In this work, we propose an approach to the creation of lipid-polymer delivery systems for fluoroquinolones and pirfenidone based on liposomes of various compositions decorated with mucoadhesive mannosylated chitosan. A generalizing study on the physicochemical patterns of the interactions of drugs with bilayers of various compositions was carried out, and the main binding sites were identified. The role of the polymer shell in the stabilization of vesicles and the delayed release of the contents has been demonstrated. For the liquid-polymer formulation of moxifloxacin, a prolonged accumulation of the drug in lung tissues was found after a single endotracheal administration to mice, significantly exceeding the control intravenous and endotracheal administration of the drug.

Spectroscopy Study of Albumin Interaction with Negatively Charged Liposome Membranes: Mutual Structural Effects of the Protein and the Bilayers.

Liposomes as drug carriers are usually injected into the systemic circulation where they are instantly exposed to plasma proteins. Liposome-protein interactions can affect both the stability of liposomes and the conformation of the associated protein leading to the altered biodistribution of the carrier. In this work, mutual effects of albumin and liposomal membrane in the course of the protein's adsorption were examined in terms of quantity of bound protein, its structure, liposome membrane permeability, and changes in physicochemical characteristics of the liposomes. Fluorescence spectroscopy methods and Fourier transform infrared spectroscopy (ATR-FTIR), which provides information about specific groups in lipids involved in interaction with the protein, were used to monitor adsorption of albumin with liposomes based on egg phosphatidylcholine with various additives of negatively charged lipidic components, such as phosphatidylinositol, ganglioside GM1, or the acidic lipopeptide. Less than a dozen of the protein molecules were tightly bound to a liposome independently of bilayer composition, yet they had a detectable impact on the bilayer. Albumin conformational changes during adsorption were partially related to bilayer microhydrophobicity. Ganglioside GM1 showed preferable features for evading undesirable structural changes.

Modulation of α-Chymotrypsin Conjugated to Magnetic Nanoparticles by the Non-Heating Low-Frequency Magnetic Field: Molecular Dynamics, Reaction Kinetics, and Spectroscopy Analysis.

Enzymes conjugated to magnetic nanoparticles (MNPs) undergo changes in the catalytic activity of the non-heating low-frequency magnetic field (LFMF). We apply in silico simulations by molecular dynamics (MD) and in vitro spectroscopic analysis of the enzyme kinetics and secondary structure to study α-chymotrypsin (CT) conjugated to gold-coated iron oxide MNPs. The latter are functionalized by either carboxylic or amino group moieties to vary the points of enzyme attachment. The MD simulation suggests that application of the stretching force to the CT globule by its amino or carboxylic groups causes shrinkage of the substrate-binding site but little if any changes in the catalytic triad. Consistent with this, in CT conjugated to MNPs by either amino or carboxylic groups, LFMF alters the Michaelis-Menten constant but not the apparent catalytic constant k cat (= V max/[E]o). Irrespective of the point of conjugation to MNPs, the CT secondary structure was affected with nearly complete loss of α-helices and increase in the random structures in LFMF, as shown by attenuated total reflection Fourier transformed infrared spectroscopy. Both the catalytic activity and the protein structure of MNP-CT conjugates restored 3 h after the field exposure. We believe that such remotely actuated systems can find applications in advanced manufacturing, nanomedicine, and other areas.

Cyclodextrins and Their Polymers Affect the Lipid Membrane Permeability and Increase Levofloxacin's Antibacterial Activity In Vitro.

Cyclodextrins (CDs) are promising drug carriers that are used in medicine. We chose CDs with different substituents (polar/apolar, charged/neutral) to obtain polymers (CDpols) with different properties. CDpols are urethanes with average Mw of ~120 kDa; they form nanoparticles 100-150 nm in diameter with variable ζ-potential. We studied the interaction of CD and CDpols with model (liposomal) and bacterial membranes. Both types of CD carriers cause an increase in the liposomal membrane permeability, and for polymers, this effect was almost two times stronger. The formation of CD/CDpols complexes with levofloxacin (LV) enhances LV's antibacterial action 2-fold in vitro on five bacterial strains. The most pronounced effect was determined for LV-CD complexes. LV-CDs and LV-CDpols adsorb on bacteria, and cell morphology influences this process dramatically. According to TEM studies, the rough surface and proteinaceous fimbria of Gram-negative E. coli facilitate the adsorption of CD particles, whereas the smooth surface of Gram-positive bacteria impedes it. In comparison with LV-CDs, LV-CDpols are adsorbed 15% more effectively by E. coli, 2.3-fold better by lactobacilli and 5-fold better in the case of B. subtilis. CDs and CDpols are not toxic for bacterial cells, but may cause mild defects that, in addition to LV-CD carrier adsorption, improve LV's antibacterial properties.

Effect of cross-linking on the inclusion complex formation of derivatized ß-cyclodextrins with small-molecule drug moxifloxacin.

Derivatized ß-cyclodextrins (CDs), cyclic oligomers of glucose with inner cavity, are able to form the inclusion complex with many poorly soluble lipophilic organic molecules, including drugs, thus improving their solubility in aqueous solutions and drug bioavailability. Here, we have studied the effect of cross-linking of derivatized CDs with different substituent nature, on their binding with antibacterial drug moxifloxacin (MF) which served as a model small molecule drug. Cross-linking of derivatized CDs with 1,6-hexamethylene diisocyanate (HMD) yielded 100-200 nm nanoparticles with distinct binding properties, strongly depending on the nature of the CD substituent, degree of oligomerization, and the nanoparticle's charge. Interestingly, substituent that improved MF binding to monomeric CDs the most (methyl moiety), had reverse effect in the case of cross-linked CD. Whereas the substituent that had only limited effect on the monomeric CD (sulfobutyl ether moiety), improved binding of cross-linked CD by almost two orders of magnitude. Further, we show that the cross-linked CD complexes with MF perform better in vitro antibacterial assay on E.coli, compared to both free MF and monomeric CD-MF. Overall, this data indicates the potential utility of CD cross-linking and derivatization to develop small molecule drug formulations with improved pharmacological properties.