Colistin-entrapped liposomes driven by the electrostatic interaction: Mechanism of drug loading and in vivo characterization

Enhancing the Encapsulation Performances of Liposomes for Amphiphilic Copolymers by Computer Simulations

Liposomes, which encapsulate drugs into an inner aqueous core and demonstrate high drug-loading capacity, have attracted considerable interest in the field of drug delivery. Herein, the encapsulation processes for amphiphilic copolymers within liposomes have been investigated systematically to enhance the encapsulation capacity and optimize the structures using dissipative particle dynamics simulations. The results indicate that the physicochemical properties of lipids, receptors, and amphiphilic copolymers collectively determine the encapsulation behaviors of liposomes. Adjusting the hydrophobic interaction between hydrophobic tails of lipids (receptors) and hydrophobic blocks of copolymers, along with modulating the specific interaction between ligands and the functional head groups of receptors, can lead to various encapsulation capacities. Significantly, a medium hydrophobic interaction strength or a strong specific interaction is conducive to achieving a higher degree of encapsulation for amphiphilic copolymers. Furthermore, varying the key parameters, such as the hydrophobic interaction, the specific interaction, as well as the concentrations of lipids and receptors, can induce seven typical aggregate structures: heterogeneous, fully encapsulated, partially encapsulated, saturated-encapsulated, unsaturated-encapsulated, multilamellar, and column-like structures. The final phase diagrams are also constructed to provide a guideline for designing various structures of liposomes encapsulated with amphiphilic copolymers. These results significantly contribute to the illumination of strategies for the rational construction of the self-assembly system that facilitates the efficient encapsulation of amphiphilic copolymers within the inner aqueous core of liposomes, thereby providing valuable insights into the optimal design of liposome carriers for future biomedical applications.

Colistin- and amikacin-loaded lipid-based drug delivery systems for resistant gram-negative lung and wound bacterial infections

Antimicrobial resistance (AMR) is a global health issue, which needs to be tackled without further delay. The World Health Organization(WHO) has classified three gram-negative bacteria, Pseudomonas aeruginosa, Klebsiella pneumonia and Acinetobacter baumannii, as the principal responsible for AMR, mainly causing difficult to treat nosocomial lung and wound infections. In this regard, the need for colistin and amikacin, the re-emerged antibiotics of choice for resistant gram-negative infections, will be examined as well as their associated toxicity. Thus, current but ineffective clinical strategies designed to prevent toxicity related to colistin and amikacin will be reported, highlighting the importance of lipid-based drug delivery systems (LBDDSs), such as liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), as efficient delivery strategies for reducing antibiotic toxicity. This review reveals that colistin- and amikacin-NLCs are promising carriers with greater potential than liposomes and SLNs to safely tackle AMR, especially for lung and wound infections.

An evolving perspective on novel modified release drug delivery systems for inhalational therapy

INTRODUCTION

Drugs delivered via the lungs are predominantly used to treat various respiratory disorders, including asthma, chronic obstructive pulmonary diseases, respiratory tract infections and lung cancers, and pulmonary vascular diseases such as pulmonary hypertension. To treat respiratory diseases, targeted, modified or controlled release inhalation formulations are desirable for improved patient compliance and superior therapeutic outcome.

AREAS COVERED

This review summarizes the important factors that have an impact on the inhalable modified release formulation approaches with a focus toward various formulation strategies, including dissolution rate-controlled systems, drug complexes, site-specific delivery, drug-polymer conjugates, and drug-polymer matrix systems, lipid matrix particles, nanosystems, and formulations that can bypass clearance via mucociliary system and alveolar macrophages.

EXPERT OPINION

Inhaled modified release formulations can potentially reduce dosing frequency by extending drug's residence time in the lungs. However, inhalable modified or controlled release drug delivery systems remain unexplored and underdeveloped from the commercialization perspective. This review paper addresses the current state-of-the-art of inhaled controlled release formulations, elaborates on the avenues for developing newer technologies for formulating various drugs with tailored release profiles after inhalational delivery and explains the challenges associated with translational feasibility of modified release inhalable formulations.

Sensitive Tumor Cell Line for Annonaceous Acetogenins and High Therapeutic Efficacy at a Low Dose for Choriocarcinoma Therapy

Annonaceous acetogenins (ACGs) have attracted much attention because of excellent antitumor activity. However, the lack of selectivity and the accompanying serious toxicity have eventually prevented ACGs from entering clinical application. To decrease the side effects of ACGs, the cytotoxicity of ACGs on 10 types of tumor cell lines was investigated by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) test to identify one that was very sensitive to ACGs. Meanwhile, ACGs nanoparticles (ACGs-NPs) were prepared using poloxamer 188 (P188) as an excipient so as to solve the problem of poor solubility and the in vivo delivery of ACGs. ACG-NPs were 163.9±2.5 nm in diameter, negatively charged, and spherical with a high drug loading content (DLC) of 44.9±1.2%. MTS assays demonstrated that ACGs had strong cytotoxicity against JEG-3, HeLa, SiHa, MCF-7, A375, A2058, A875, U-118MG, LN- 229, and A431 cells, among which JEG-3 cell line was extremely sensitive to ACGs with a 50% inhibitory concentration (IC50) value of 0.26 ng/mL, a very encouraging discovery. ACGs-NPs demonstrated very good dose-dependent antitumor efficacy in a broad range of 45?1200 μg/kg on JEG-3 tumor-bearing mice. At a very low dose (1200 μg/kg), ACGs-NPs achieved a high tumor inhibition rate (TIR) of 77.6% through oral administration, displaying a significant advantage over paclitaxel (PTX) injections that are currently used as first-line anti-choriocarcinoma drugs. In the acute toxicity study, the half lethal dose (LD50) of ACGs-NPs was 135.5 mg/kg, which was over 100 times as of the effective antitumor dose, indicating good safety of ACGs-NPs. ACGs-NPs show promise as a new type of and potent anti-choriocarcinoma drug in the future.

Pharmaceutical strategies to extend pulmonary exposure of inhaled medicines

Pulmonary administration route has been extensively exploited for the treatment of local lung diseases such as asthma, chronic obstructive pulmonary diseases and respiratory infections, and systemic diseases such as diabetes. Most inhaled medicines could be cleared rapidly from the lungs and their therapeutic effects are transit. The inhaled medicines with extended pulmonary exposure may not only improve the patient compliance by reducing the frequency of drug administration, but also enhance the clinical benefits to the patients with improved therapeutic outcomes. This article systematically reviews the physical and chemical strategies to extend the pulmonary exposure of the inhaled medicines. It starts with an introduction of various physiological and pathophysiological barriers for designing inhaled medicines with extended lung exposure, which is followed by recent advances in various strategies to overcome these barriers. Finally, the applications of the inhaled medicines with extended lung exposure for the treatment of various diseases and the safety concerns associated to various strategies to extend the pulmonary exposure of the inhaled medicines are summarized.

Effect of sodium deoxycholate sulfate on outer membrane permeability and neutralization of bacterial lipopolysaccharides by polymyxin B formulations

We demonstrated binding interactions of polymyxin B (PMB), PMB formulations in the mole ratios of 1:2 and 1:3 of PMB:sodium deoxycholate sulfate (SDCS) and a commercial PMB formulation (CPMB) with lipopolysaccharides (LPS). The 1:2 PMB formulation (78.5-135.2 nM) exhibited a lower number of binding sites to the tested LPS compared to CPMB (112.6-140.9 nM) whereas 1:3 PMB formulation exhibited a higher number of binding sites (143.9-340.2 nM). Similarly, in the presence of LPS, the 1:2 PMB formulation (163.8-221.4 nm) exhibited smaller particle sizes compared to PMB, CPMB and 1:3 PMB formulation (248.8-603.5 nm). Molecular docking simulation suggested that the fatty acyl tails of LPS wrap together to produce a pseudo-globular structure of PMB-LPS complex, and among those 1:2 PMB formulation formed a more stable structure. The primary forces behind this complex are hydrogen bonds and salt bridges among the LPS, PMB, and SDCS. This study revealed that the PMB, CPMB, and PMB formulations inserted into the LPS micelles to disrupt the LPS membrane, whereas the SDCS may induce aggregation. The 1:2 PMB formulation also had higher bacterial uptake than other PMB formulations. The 1:2 PMB formulation neutralized the LPS micelles and was effective against Escherichia coli and Pseudomonas aeruginosa.

Synthetic macromolecules as therapeutics that overcome resistance in cancer and microbial infection

Synthetic macromolecular antimicrobials have shown efficacy in the treatment of multidrug resistant (MDR) pathogens. These synthetic macromolecules, inspired by Nature's antimicrobial peptides (AMPs), mitigate resistance by disrupting microbial cell membrane or targeting multiple intracellular proteins or genes. Unlike AMPs, these polymers are less prone to degradation by proteases and are easier to synthesize on a large scale. Recently, various studies have revealed that cancer cell membrane, like that of microbes, is negatively charged, and AMPs can be used as anticancer agents. Nevertheless, efforts in developing polymers as anticancer agents has remained limited. This review highlights the recent advancement in the development of synthetic biodegradable antimicrobial polymers (e.g. polycarbonates, polyesters and polypeptides) and anticancer macromolecules including peptides and polymers. Additionally, strategies to improve their in vivo bioavailability and selectivity towards bacteria and cancer cells are examined. Lastly, future perspectives, including use of artificial intelligence or machine learning, in the development of antimicrobial and anticancer macromolecules are discussed.

Octopus-like Flexible Vector for Noninvasive Intraocular Delivery of Short Interfering Nucleic Acids

Gene therapy is promising for chronic posterior ocular diseases, which are causal factors for severe vision impairment and even blindness worldwide. However, the inherent absorption barriers of the eye restrict intraocular delivery of therapeutic nucleic acids via topical instillation. Safe and efficient nonviral vectors for ocular gene therapy are still unmet clinical desires. Herein, an octopus-like flexible multivalent penetratin (MVP) was designed to facilitate condensation and delivery of therapeutic nucleic acids using multiarm polyethylene glycol (PEG) as a core and conjugating penetratin at each end of the PEG arms as outspread tentacles. Among the MVPs, 8-valent penetratin (8VP) stably compacted nucleic acids into positively charged polyplexes smaller than 100 nm, promoting cellular uptake efficiency (approaching 100%) and transfection rate (over 75%). After being instilled into the conjunctival sac, 8VP enabled rapid (<10 min) and prolonged (>6 h) distribution of nucleic acids in the retina via a noncorneal pathway. In a retinoblastoma-bearing mice model, topical instillation of 8VP/siRNA efficiently inhibited the protein expression of intraocular tumor without toxicity. MVP is advantageous over the commercial transfection reagent in safety and efficiency, and therefore provides a promising vector for noninvasive intraocular gene delivery.

Proliposomes for oral delivery of total biflavonoids extract from Selaginella doederleinii: formulation development, optimization, and in vitro-in vivo characterization

Purpose

Amentoflavone, robustaflavone, 2'',3''-dihydro-3',3'''-biapigenin, 3',3'''-binaringenin and delicaflavone are five major active ingredients in the total biflavonoids extract from Selaginella doederleinii (TBESD) with favorable anticancer properties. However, the natural-derived potent antitumor agent of TBESD is undesirable due to its poor solubility. The present study was to develop and optimize a proliposomal formulation of TBESD (P-TBESD) to improve its solubility, oral bioavailability and efficacy.

Materials and methods

P-TBESD containing a bile salt, a protective hydrophilic isomalto-oligosaccharides (IMOs) coating, were successfully prepared by thin film dispersion-sonication method. The physicochemical and pharmacokinetic properties of P-TBESD were characterized, and the antitumor effect was evaluated using the HT-29 xenograft-bearing mice models in rats.

Results

Compared with TBESD, the relative bioavailability of amentoflavone, robustaflavone, 2'',3''-dihydro-3',3'''-biapigenin, 3',3'''-binaringenin and delicaflavone from P-TBESD were 669%, 523%, 761%, 955% and 191%, respectively. The results of pharmacodynamics demonstrated that both TBESD and P-TBESD groups afforded antitumor effect without systemic toxicity, and the antitumor effect of P-TBESD was significantly superior to that of raw TBESD, based on the tumor growth inhibition and histopathological examination.

Conclusion

Hence, IMOs-modified proliposomes have promising potential for TBESD solving the problem of its poor solubility and oral bioavailability, which can serve as a practical oral preparation for TBESD in the future cancer therapy.

Binding interactions of bacterial lipopolysaccharides to polymyxin B in an amphiphilic carrier 'sodium deoxycholate sulfate'

This work presents the outcomes of a comparative study of molecular interactions of polymyxin B (PMB) and F12 and F13 formulations in the mole ratios of 1:2 and 1:3 of PMB:sodium deoxycholate sulfate (SDCS), respectively, and a commercial PMB formulation (CPMB) with lipopolysaccharides (LPS). Several spectroscopic and interfacial studies were performed to obtain LPS-peptide interactions at a molecular level. The fluorescence titrimetry method revealed that the F12 formulation (325 nM) exhibited a lower number of binding sites to the LPS compared to CPMB and F13 as well as PMB alone (537 nM). Similarly, in the presence of LPS, the F12 formulation (88 nm) exhibited smaller particle sizes in the dynamic light scattering study compared to PMB (116 nm), CPMB, and the F13 formulation. An interfacial study and circular dichroism spectroscopy revealed PMB and CPMB insertion into the LPS micelles to destabilize and disrupt the LPS membrane, whereas the F12 and F13 formulations may induce pseudo-aggregation. The NMR and IR studies showed that the presence of SDCS, the hydrophobicity of PMB increased by hydrogen bonding and electrostatic interactions and formed stabilized PMB-SDCS micelles. The PMB-SDCS formulation is likely to release PMB for easy penetration into the lipid membrane and cause disruption of the complex LPS micelles. Furthermore, the PMB-SDCS formulations neutralized and detoxified the LPS micelles with minimal toxicity to normal kidney tubular cells as well as an immortalised kidney cell line. The antimicrobial properties of PMBloaded SDCS nanomicelles were effective against a resistant strain of Pseudomonas aeruginosa.

Co-Delivery of Ciprofloxacin and Colistin in Liposomal Formulations with Enhanced In Vitro Antimicrobial Activities against Multidrug Resistant Pseudomonas aeruginosa

PURPOSE

This study aims to develop liposomal formulations containing synergistic antibiotics of colistin and ciprofloxacin for the treatment of infections caused by multidrug-resistant Pseudomonas aeruginosa.

METHODS

Colistin (Col) and ciprofloxacin (Cip) were co-encapsulated in anionic liposomes by ammonium sulfate gradient. Particle size, encapsulation efficiency, in vitro drug release and in vitro antibiotic activities were evaluated.

RESULTS

The optimized liposomal formulation has uniform sizes of approximately 100 nm, with encapsulation efficiency of 67.0% (for colistin) and 85.2% (for ciprofloxacin). Incorporation of anionic lipid (DMPG) markedly increased encapsulation efficiency of colistin (from 5.4 to 67.0%); however, the encapsulation efficiency of ciprofloxacin was independent of DMPG ratio. Incorporation of colistin significantly accelerated the release of ciprofloxacin from the DMPG anionic liposomes. In vitro release of ciprofloxacin and colistin in the bovine serum for 2 h were above 70 and 50%. The cytotoxicity study using A549 cells showed the liposomal formulation is as non-toxic as the drug solutions. Liposomal formulations of combinations had enhanced in vitro antimicrobial activities against multidrug resistant P. aeruginosa than the monotherapies.

CONCLUSIONS

Liposomal formulations of two synergistic antibiotics was promising against multidrug resistant P. aeruginosa infections.

Dual-responsive core-crosslinked polyphosphoester-based nanoparticles for pH/redox-triggered anticancer drug delivery

"Intelligent" crosslinked nanoparticles (NPs) provide great advantages in enhancing drug bioavailability and reducing side effects in anticancer therapeutics. In this study, a novel biodegradable polyphosphoester-based functional copolymer prodrug PTX-(PBYP-g-MPA)-b-PEEP was prepared to construct pH/redox dual-responsive core-crosslinked nanoparticles (DOX/CCL NPs), in which paclitaxel (PTX) was conjugated to the polyphosphoester to form an amphiphilic prodrug and doxorubicin (DOX) was encapsulated inside the prodrug NPs. At first, PTX was used as an initiator to polymerize 2-(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane (BYP) and 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EOP) by one-pot sequential ring-opening polymerization, yielding a biodegradable polymeric prodrug PTX-PBYP-b-PEEP. Subsequently, a radical-mediated thiol-yne "click" reaction was performed between the alkynyl groups on the PBYP segment and the thiol group of 3-mercaptopropionic acid (MPA) to form a functional carboxyl group at the side chain. The potential positively charged DOX·HCl can be physically encapsulated via electrostatic interaction with the carboxyl group and hydrophobic interaction. Afterwards, the DOX/CCL NPs with cleavable disulfide (S-S) linkages can be formed by partial crosslinking through amidation between the pendant carboxyl groups and cystamine. These NPs possess multifunctional characteristics used for in vitro drug release. Notably, a redox-responsive crosslinker, cystamine dihydrochloride, and synergetic non-covalent interactions not only stabilize the nanoparticles, achieve high DOX-loading capacity of drug loading content (DLC, 14.6%) and drug loading efficiency (DLE, 73.1%), but also endow the DOX/CCL NPs with controlled drug release capacity, which is due to the cleavage of S-S bonds in the presence of 10 mM glutathione (GSH) and weakened electrostatic interaction caused by the protonation of carboxyl groups at a lower pH (5.0). Moreover, these pH/redox dual-responsive DOX/CCL NPs can be steadily internalized by HeLa cells, exhibiting high-efficiency cellular proliferation inhibition. This study presents a promising strategy for controlled intracellular drug release in cancer therapy.

An innovative method for preparation of hydrophobic ion-pairing colistin entrapped poly(lactic acid) nanoparticles: Loading and release mechanism study

Hydrophobic ion-pairing (HIP) complexation has emerged as an efficient approach to enhance the entrapment of therapeutic peptides in the biodegradable polymer matrix. In the present study, we developed an innovative extraction method for preparation of HIP-colistin (CST, a polycationic peptide) using various water-insoluble anionic lipids. To determine the loading mechanism of HIP-CST entrapped poly(lactic acid) (PLA) nanoparticles (HIP-CST-PLA-NPs), the effects of anionic lipids and PLA molecular weight (Mw) on the unentrapped fraction (uf) of CST in PLA-NPs were investigated. And CST release mechanism from HIP-CST-PLA-NPs was also investigated by evaluating their release behavior and NP swelling. It is showed that HIP-CST retention in the PLA-NPs was imposed by their physical localization in the networks of the PLA chains, rather than the electrostatic attraction between anionic lipid and CST in serum. And HIP-CST-PLA-NPs in serum exhibited the swelling-controlled release behavior with a substantially accelerated release and NP swelling observed in comparison with that in phosphate buffer. Our results can effectively guide the preparation of biodegradable polymer based modified drug release systems with desired properties for peptides delivery.