A promising drug controlled-release system based on diacetylene/phospholipid polymerized vesicles

Stimuli-Responsive Liposomes of 5-Fluorouracil: Progressive Steps for Safe and Effective Treatment of Colorectal Cancer

5-Fluorouracil (5-FU) has become one of the most widely employed antimetabolite chemotherapeutic agents in recent decades to treat various types of cancer. It is considered the standard first-line treatment for patients with metastatic colorectal cancer. Unfortunately, traditional chemotherapy with 5-FU presents many limitations, such as a short half-life, a low bioavailability, and a high cytotoxicity, affecting both tumor tissue and healthy tissue. In order to overcome the drawbacks of 5-FU and enhance its therapeutic effectiveness against colorectal cancer, many studies have focused on designing new delivery systems to successfully deliver 5-FU to tumor sites. Liposomes have gained attention as a well-accepted nanocarrier for several chemotherapeutic agents. These amphipathic spherical vesicles consist of one or more phospholipid bilayers, showing promise for the drug delivery of both hydrophobic and hydrophilic components in addition to distinctive properties, such as biodegradability, biocompatibility, a low toxicity, and non-immunogenicity. Recent progress in liposomes has mainly focused on chemical and structural modifications to specifically target and activate therapeutic actions against cancer within the proximity of tumors. This review provides a comprehensive overview of both internal-stimuli-responsive liposomes, such as those activated by enzymes or pH, and external-stimuli-responsive liposomes, such as those activated by the application of a magnetic field, light, or temperature variations, for the site-specific delivery of 5-FU in colorectal cancer therapy, along with the future perspectives of these smart-delivery liposomes in colorectal cancer. In addition, this review critically highlights recent innovations in the literature on various types of stimuli-responsive liposomal formulations designed to be applied either exogenously or endogenously and that have great potential in delivering 5-FU to colorectal cancer sites.

Design of oleic acid/alkyl glycoside composite vesicles as cosmetics carrier: stability, skin permeability and antioxidant activity

Biocompatible fatty acids are natural biological materials which exhibit widespread biomedical applications. Nevertheless, their application in vesicle forms is hampered by strong pH sensitivity and poor stability to changes in ionic strength, temperature, and storage. In the investigation, the incorporation of alkyl glycoside (APG), a surfactant with non-ionic properties, into the oleic acid (OA) vesicles was undertaken as a means to address this issue. The newly formed OA/APG composite vesicles form in a pH range of between 5.4 and 7.4, which is close to the pH range of the physiological environment. The stability studies results showed that the OA/APG composite vesicles have excellent stability in terms of ionic strengths, temperature and storage. The formation of NAR-loaded OA/APG composite vesicles was demonstrated through FT-IR, DSC and XRD. In vitro topical delivery and skin retention studies confirmed that the composite vesicles improve skin permeation rate and have better skin permeation behavior. Antioxidant activity experiments confirmed that the antioxidant effect composite vesicles were significantly increased as compared to the naringenin (NAR). This finding has theoretical implications for the use of drug-loaded fatty acid vesicles in cosmetics industries and topical delivery systems.

Improving the anti-inflammatory efficacy of dexamethasone in the treatment of rheumatoid arthritis with polymerized stealth liposomes as a delivery vehicle

Rheumatoid arthritis (RA) is an autoimmune disease that causes chronic inflammation of the joints of the body. Although liposomes are a promising drug delivery vehicle, there is still a challenge of using conventional liposomes for the treatment of RA due to their short circulation time and physicochemical instability in blood vessels. Here, we report the formation of polymerized stealth liposomes composed of 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) and 1,2-distearoyl-sn-glycero-3-phospho-ethanolamine-poly(ethyleneglycol) (DSPE-PEG2000) with a thin-film hydration method, in which DC8,9PC molecules are cross-linked in the bilayer of the liposomes by UV irradiation and the PEG chains present at the surface of the liposomes provide a stealth layer. We demonstrate that the polymerized stealth liposomes are stable and show long circulation time in blood vessels. They can be internalized by cells without significant toxicity. After being injected into arthritic rats, the polymerized stealth liposomes with loaded dexamethasone (Dex) show long blood circulation time and accumulate preferentially in inflamed joints, consequently suppressing the level of proinflammatory cytokines (TNF-α and IL-1β) in joint tissues, reducing the swelling of inflamed joints and alleviating the progression of RA. We believe that polymerized stealth liposomes can be used as a promising drug delivery vehicle for various therapeutic applications.

Nanoformulation strategies for improving intestinal permeability of drugs: A more precise look at permeability assessment methods and pharmacokinetic properties changes

The therapeutic efficacy of orally administered drugs is often restricted by their inherent limited oral bioavailability. Low water solubility, limited permeability through the intestinal barrier, instability in harsh environment of the gastrointestinal (GI) tract and being substrate of the efflux pumps and the cytochrome P450 (CYP) can impair oral drug bioavailability resulting in erratic and variable plasma drug profile. As more drugs with low membrane permeability are developed, new interest is growing to enhance their intestinal permeability and bioavailability. A wide variety of nanosystems have been developed to improve drug transport and absorption. Sufficient evidence exists to suggest that nanoparticles are able to increase the transepithelial transport of drug molecules. However, key questions remained unanswered. What types of nanoparticles are more efficient? What are preclinical (or clinical) achievements of each type of nanoformulation in terms of pharmacokinetic (PK) parameters? Addressing this issue in this paper, we have reviewed the current literature regarding permeability enhancement, permeability assessment methods and changes in PK parameters following administration of various nanoformulations. Although permeability enhancement by various nanoformulations holds great promise for oral drug delivery, many challenges still need to be addressed before development of more clinically successful nanoproducts.

Phase Change Ultrasound Contrast Agents with a Photopolymerized Diacetylene Shell

Phase change contrast agents for ultrasound (US) imaging consist of nanodroplets (NDs) with a perfluorocarbon (PFC) liquid core stabilized with a lipid or a polymer shell. Liquid ↔ gas transition, occurring in the core, can be triggered by US to produce acoustically active microbubbles (MBs) in a process named acoustic droplet vaporization (ADV). MB shells containing polymerized diacetylene moiety were considered as a good trade off between the lipid MBs, showing optimal attenuation, and the polymeric ones, displaying enhanced stability. This work reports on novel perfluoropentane and perfluorobutane NDs stabilized with a monolayer of an amphiphilic fatty acid, i.e. 10,12-pentacosadiynoic acid (PCDA), cured with ultraviolet (UV) irradiation. The photopolymerization of the diacetylene groups, evidenced by the appearance of a blue color due to the conjugation of ene-yne sequences, exhibits a chromatic transition from the nonfluorescent blue color to a fluorescent red color when the NDs are heated or the pH of the suspension is basic. An estimate of the molecular weights reached by the polymerized PCDA in the shell, poly(PCDA), has been obtained using gel permeation chromatography and MALDI-TOF mass spectrometry. The poly(PCDA)/PFC NDs show good biocompatibility with fibroblast cells. ADV efficiency and acoustic properties before and after the transition were tested using a 1 MHz probe, revealing a resonance frequency between 1 and 2 MHz similar to other lipidic MBs. The surface of PCDA shelled NDs can be easily modified without influencing the stability and the acoustic performances of droplets. As a proof of concept we report on the conjugation of cyclic RGD and PEG chains of the particles to support targeting ability toward endothelial cells.

Surfactant Aggregates Encapsulating and Modulating: An Effective Way to Generate Selective and Discriminative Fluorescent Sensors

The heterogeneous structure and dynamic balancing nature of surfactant aggregates make them attractive in developing fluorescent sensors. They can provide a number of advantages, e.g., enhanced fluorescence stability and quantum yield, detection capability in aqueous solutions, and easy operation. Thus, various strategies have been used to construct surfactant aggregate-based fluorescent sensors. Surfactant aggregates play various roles in different strategies and realize multiple sensing behaviors. Many new functions have been discovered for surfactant aggregates in constructing fluorescent sensors. In this feature article, we briefly summarize the development of surfactant aggregate-based fluorescent sensors and their applications in three different types of sensing: selective sensing, multiple analyte sensing, and cross-reactive sensing. For each type of sensing, the design strategies and the roles of surfactant aggregates are particularly introduced. An understanding of these aspects will help to expand the applications of surfactant assemblies in the sensing field.

Stimuli-responsive liposomes for drug delivery

The ultimate goal of drug delivery is to increase the bioavailability and reduce the toxic side effects of the active pharmaceutical ingredient (API) by releasing them at a specific site of action. In the case of antitumor therapy, association of the therapeutic agent with a carrier system can minimize damage to healthy, nontarget tissues, while limit systemic release and promoting long circulation to enhance uptake at the cancerous site due to the enhanced permeation and retention effect (EPR). Stimuli-responsive systems have become a promising way to deliver and release payloads in a site-selective manner. Potential carrier systems have been derived from a wide variety of materials, including inorganic nanoparticles, lipids, and polymers that have been imbued with stimuli-sensitive properties to accomplish triggered release based on an environmental cue. The unique features in the tumor microenvironment can serve as an endogenous stimulus (pH, redox potential, or unique enzymatic activity) or the locus of an applied external stimulus (heat or light) to trigger the controlled release of API. In liposomal carrier systems triggered release is generally based on the principle of membrane destabilization from local defects within bilayer membranes to effect release of liposome-entrapped drugs. This review focuses on the literature appearing between November 2008-February 2016 that reports new developments in stimuli-sensitive liposomal drug delivery strategies using pH change, enzyme transformation, redox reactions, and photochemical mechanisms of activation. WIREs Nanomed Nanobiotechnol 2017, 9:e1450. doi: 10.1002/wnan.1450 For further resources related to this article, please visit the WIREs website.

Dual-Targeting Lactoferrin-Conjugated Polymerized Magnetic Polydiacetylene-Assembled Nanocarriers with Self-Responsive Fluorescence/Magnetic Resonance Imaging for In Vivo Brain Tumor Therapy

Maintaining a high concentration of therapeutic agents in the brain is difficult due to the restrictions of the blood-brain barrier (BBB) and rapid removal from blood circulation. To enable controlled drug release and enhance the blood-brain barrier (BBB)-crossing efficiency for brain tumor therapy, a new dual-targeting magnetic polydiacetylene nanocarriers (PDNCs) delivery system modified with lactoferrin (Lf) is developed. The PDNCs are synthesized using the ultraviolet (UV) cross-linkable 10,12-pentacosadiynoic acid (PCDA) monomers through spontaneous assembling onto the surface of superparamagnetic iron oxide (SPIO) nanoparticles to form micelles-polymerized structures. The results demonstrate that PDNCs will reduce the drug leakage and further control the drug release, and display self-responsive fluorescence upon intracellular uptake for cell trafficking and imaging-guided tumor treatment. The magnetic Lf-modified PDNCs with magnetic resonance imaging (MRI) and dual-targeting ability can enhance the transportation of the PDNCs across the BBB for tracking and targeting gliomas. An enhanced therapeutic efficiency can be obtained using Lf-Cur (Curcumin)-PDNCs by improving the retention time of the encapsulated Cur and producing fourfold higher Cur amounts in the brain compared to free Cur. Animal studies also confirm that Lf targeting and controlled release act synergistically to significantly suppress tumors in orthotopic brain-bearing rats.

Polymer-lipid hybrid systems: merging the benefits of polymeric and lipid-based nanocarriers to improve oral drug delivery

INTRODUCTION

A number of biobarriers limit efficient oral drug absorption; both polymer-based and lipid-based nanocarriers have demonstrated properties and delivery mechanisms to overcome these biobarriers in preclinical settings. Moreover, in order to address the multifaceted oral drug delivery challenges, polymer-lipid hybrid systems are now being designed to merge the beneficial features of both polymeric and lipid-based nanocarriers.

AREAS COVERED

Recent advances in the development of polymer-lipid hybrids with a specific focus on their viability in oral delivery are reviewed. Three classes of polymer-lipid hybrids have been identified, i.e. lipid-core polymer-shell systems, polymer-core lipid-shell systems, and matrix-type polymer-lipid hybrids. We focus on their application to overcome the various biological barriers to oral drug absorption, as exemplified by selected preclinical studies.

EXPERT OPINION

Numerous studies have demonstrated the superiority of polymer-lipid hybrid systems to their non-hybrid counterparts in providing improved drug encapsulation, modulated drug release, and improved cellular uptake. These features have encouraged their applications in the delivery of chemotherapeutics, proteins, peptides, and vaccines. With further research expected to optimize the manufacturing and scaling up processes and in-depth pre-clinical pharmacological and toxicological assessments, these multifaceted drug delivery systems will have significant clinical impact on the oral delivery of pharmaceuticals and biopharmaceuticals.

Chromatic response of polydiacetylene vesicle induced by the permeation of methotrexate

The noble vesicular system of polydiacetylene showed a red shift using two types of detecting systems. One of the systems involves the absorption of target materials from the outer side of the vesicle, and the other system involves the permeation through the vesicular layers from within the vesicle. The chromatic mixed vesicles of N-(2-aminoethyl)pentacosa-10,12-diynamide (AEPCDA) and dimethyldioctadecylammonium chloride (DODAC) were fabricated by sonication, followed by polymerization by UV irradiation. The stability of monomeric vesicles was observed to increase with the polymerization of the vesicles. Methotrexate was used as a target material. The polymerized mixed vesicles having a blue color were exposed to a concentration gradient of methotrexate, and a red shift was observed indicating the adsorption of methotrexate on the polydiacetylene bilayer. In order to check the chromatic change by the permeation of methotrexate, we separated the vesicle portion, which contained methotrexate inside the vesicle, and checked chromatic change during the permeation of methotrexate through the vesicle. The red shift apparently indicates the disturbance in the bilayer induced by the permeation of methotrexate. The maximum contrast of color appeared at the equal molar ratio of AEPCDA and DODAC, indicating that the formation of flexible and deformable vesicular layers is important for red shift. Therefore, it is hypothesized that the system can be applicable for the chromatic detection of the permeation of methotrexate through the polydiacetylene layer.

Magainin II modified polydiacetylene micelles for cancer therapy

Polydiacetylene (PDA) micelles have been widely used to deliver anticancer drugs in the treatment of a variety of tumours and for imaging living cells. In this study, we developed an effective strategy to directly conjugate magainin II (MGN-II) to the surface of PDA micelles using a fluorescent dye. These stable and well-defined PDA micelles had high cytotoxicity in cancer cell lines, and were able to reduce the tumour size in mice. The modified PDA micelles improved the anticancer effects of MGN-II in the A549 cell line only at a concentration of 16.0 μg mL(-1) (IC50). In addition, following irradiation with UV light at 254 nm, the PDA micelles gave rise to an energy transfer from the fluorescent dye to the backbone of PDA micelles to enhance the imaging of living cells. Our results demonstrate that modified PDA micelles can not only be used in the treatment of tumors in vitro and in vivo in a simple and directed way, but also offer a new platform for designing functional liposomes to act as anticancer agents.

Cross-linkable liposomes stabilize a magnetic resonance contrast-enhancing polymeric fastener

Liposomes are commonly used to deliver drugs and contrast agents to their target site in a controlled manner. One of the greatest obstacles in the performance of such delivery vehicles is their stability in the presence of serum. Here, we demonstrate a method to stabilize a class of liposomes that load gadolinium, a magnetic resonance (MR) contrast agent, as a model cargo on their surfaces. We hypothesized that the sequential adsorption of a gadolinium-binding chitosan fastener on the liposome surface followed by covalent cross-linking of the lipid bilayer would provide enhanced stability and improved MR signal in the presence of human serum. To investigate this hypothesis, liposomes composed of diyne-containing lipids were assembled and functionalized via chitosan conjugated with a hydrophobic anchor and diethylenetriaminepentaacetic acid (DTPA). This postadsorption cross-linking strategy served to stabilize the thermodynamically favorable association between liposome and polymeric fastener. Furthermore, the chitosan-coated, cross-linked liposomes proved more effective as delivery vehicles of gadolinium than uncross-linked liposomes due to the reduced liposome degradation and chitosan desorption. Overall, this study demonstrates a useful method to stabilize a broad class of particles used for systemic delivery of various molecular payloads.

Nano-antibiotics in chronic lung infection therapy against Pseudomonas aeruginosa

Antibiotic encapsulation into nanoparticle carriers has emerged as a promising inhaled antibiotic formulation for treatment of chronic Pseudomonas aeruginosa lung infection prevalent in chronic obstructive pulmonary diseases. Attributed to their prolonged lung retention, sustained antibiotic release, and mucus penetrating ability, antibiotic nanoparticles, or nano-antibiotics in short, can address the principal weakness of inhaled antibiotic solution, i.e. low antibiotic exposure in the vicinity of P. aeruginosa biofilm colonies resulting in diminished anti-pseudomonal efficacy after repeated uses. This review details the current state of development and limitations of the two most widely studied forms of nano-antibiotics, i.e. liposomes and polymer nanoparticles. Factors in their formulation that influence the anti-pseudomonal efficacy in vitro and in vivo, such as liposome's membrane rigidity, surface charge, size, and polymer hydrophobicity, are discussed. This review reveals that the superior anti-pseudomonal efficacy of liposomal antibiotics to free antibiotics has been clearly established when they are correctly formulated, with several liposomal antibiotic formulations are currently undergoing clinical trials. Liposomal antibiotics, nevertheless, are not without limitation due to their weak physicochemical stability. In contrast, only mucus penetrating ability of the more stable polymeric nano-antibiotics has been established, while their anti-pseudomonal efficacy has only been examined in vitro from which their superiority to free antibiotics has not been ascertained. Lastly, future research needs to bring liposome and polymer-based nano-antibiotics closer to their clinical realization are identified.

Vesicular self-assembly of a natural triterpenoid arjunolic acid in aqueous medium: study of entrapment properties and in situ generation of gel–gold nanoparticle hybrid material

Formation of vesicular gel and gel–gold nanoparticle hybrid material from arjunolic acid extractable from the saw-dust of Terminalia arjuna.

Multifunctional polydiacetylene-liposome with controlled release and fluorescence tracing

A multifunctional polydiacetylene-liposome (PDA-liposome) was prepared by self-assembly, which can be characterized with controlled drug release and fluorescence tracing.

Liposomes with double-stranded DNA anchoring the bilayer to a hydrogel core

Liposomes are important biomolecular nanostructures for handling membrane-associated molecules in the lab and delivering drugs in the clinic. In addition to their biomedical applications, they have been widely used as model cell membranes in biophysical studies. Here we present a liposome-based model membrane that mimics the attachment of membrane-resident molecules to the cytoskeleton. To facilitate this attachment, we have developed a lipid-based hybrid nanostructure in which the liposome bilayer membrane is covalently anchored to a biocompatible poly(ethylene) glycol (PEG) hydrogel core using short double-stranded DNA (dsDNA) linkers. The dsDNA linkers connect cholesterol groups that reside in the bilayer to vinyl groups that are incorporated in the cross-linked hydrogel backbone. Size exclusion chromatography (SEC) of intact and surfactant-treated nanoparticles confirms the formation of anchored hydrogel structures. Transmission electron microscopy (TEM) shows ~100 nm nanoparticles even after removal of unanchored phospholipids. The location of dsDNA groups at the hydrogel-bilayer interface is confirmed with a fluorescence assay. Using DNA as a linker between the bilayer and a hydrogel core allows for temperature-dependent release of the anchoring interaction, produces polymer nanogels with addressible hybridization sites on their surface, and provides a prototype structure for potential future oligonucleotide drug delivery applications.

Thermal and photic stimuli-responsive polydiacetylene liposomes with reversible fluorescence

A novel reversible fluorescent switch of a polydiacetylene liposome (PDA liposome) was realized by alternating heating and UV irradiation processes. The reversible fluorescence switching of the PDA liposome was mainly caused by the microstructural changes of the PDA backbone in the PDA liposomes under the alternating conditions of heating and UV irradiation.

Nanohybrid systems of non-ionic surfactant inserting liposomes loading paclitaxel for reversal of multidrug resistance

Three new nanohybrid systems of non-ionic surfactant inserting liposomes loading paclitaxel (PTX) (NLPs) were prepared to overcome multidrug resistance (MDR) in PTX-resistance human lung cancer cell line. Three non-ionic surfactants, Solutol HS 15 (HS-15), pluronic F68 (PF-68) and cremophor EL (CrEL) were inserted into liposomes by film hydration method to form NLPs with an average size of around 110, 180 and 110 nm, respectively. There was an obvious increase of rhodamin 123 (Rh123) accumulation in A549/T cells after treated with nanohybrid systems loading Rh123 (NLRs) when compared with free Rh123 or liposomes loading Rh123 without surfactants (LRs), which indicated the significant inhibition effects of NLRs on drug efflux. The P-gp detection and ATP determination demonstrated that BNLs could not only interfere P-gp expression on the membrane of drug resistant cells, but also decrease ATP level in the cells. The cytotoxicity of NLPs against A549/T cells was higher than PTX loaded liposomes without surfactants (LPs), and the best result was achieved after treated with NLPs2. The apoptotic assay and the cell cycle analysis showed that NLPs could induce more apoptotic cells in drug resistant cells when compared with LPs. These results suggested that NLPs could overcome MDR by combination of drug delivery, P-gp inhibition and ATP depletion, and showed potential for treatment of MDR.

Partially polymerized liposomes: stable against leakage yet capable of instantaneous release for remote controlled drug delivery

A critical issue for current liposomal carriers in clinical applications is their leakage of the encapsulated drugs that are cytotoxic to non-target tissues. We have developed partially polymerized liposomes composed of polydiacetylene lipids and saturated lipids. Cross-linking of the diacetylene lipids prevents the drug leakage even at 40 °C for days. These inactivated drug carriers are non-cytotoxic. Significantly, more than 70% of the encapsulated drug can be instantaneously released by a laser that matches the plasmon resonance of the tethered gold nanoparticles on the liposomes, and the therapeutic effect was observed in cancer cells. The remote activation feature of this novel drug delivery system allows for precise temporal and spatial control of drug release.

Localization of antimicrobial peptides on polymerized liposomes leading to their enhanced efficacy against Pseudomonas aeruginosa

Antimicrobial peptide IG-25 (a truncated version of LL-37 of the cathelicidin family) tethering an azido-capped poly(ethylene glycol) chain at the N-terminus was site-specifically attached to alkynyl-terminated polymerized liposomes using copper catalyzed "click" reaction, leading to an 18 fold enhancement in efficacy against Pseudomonas aeruginosa when compared to LL-37 without any increase in cytotoxicity to human corneal epithelial cells.