Polydopamine-Modified Liposomes: Preparation and Recent Applications in the Biomedical Field

Polydopamine (PDA) is a bioinspired polymer that has unique and desirable properties for emerging applications in the biomedical field, such as extraordinary adhesiveness, extreme ease of functionalization, great biocompatibility, large drug loading capacity, good mucopenetrability, strong photothermal capacity, and pH-responsive behavior. Liposomes are consolidated and attractive biomimetic nanocarriers widely used in the field of drug delivery for their biocompatibility and biodegradability, as well as for their ability to encapsulate hydrophobic, hydrophilic, and amphiphilic compounds, even simultaneously. In addition, liposomes can be decorated with appropriate functionalities for targeted delivery purposes. Thus, combining the interesting properties of PDA with those of liposomes allows us to obtain multifunctional nanocarriers with enhanced stability, biocompatibility, and functionality. In this review, a focus on the most recent developments of liposomes modified with PDA, either in the form of polymer layers trapping multiple vesicles or in the form of PDA-coated nanovesicles, is proposed. These innovative PDA coatings extend the application range of liposomes into the field of biomedical applications, thereby allowing for easier functionalization with targeting ligands, which endows them with active release capabilities and photothermal activity and generally improves their interaction with biological fluids. Therefore, hybrid liposome/PDA systems are proposed for surface-mediated drug delivery and for the development of nanocarriers intended for systemic and oral drug delivery, as well as for multifunctional nanocarriers for cancer therapy. The main synthetic strategies for the preparation of PDA-modified liposomes are also illustrated. Finally, future prospects for PDA-coated liposomes are discussed, including the suggestion of potential new applications, deeper evaluation of side effects, and better personalization of medical treatments.

Spotlight on the protein corona of liposomes

Although an established drug delivery platform, liposomes have not fulfilled their true potential. In the body, interactions of liposomes are mediated by the layer of plasma proteins adsorbed on the surface, the protein corona. The review aims to collect the data of the last decade on liposome protein corona, tracing the path from interactions of individual proteins to the effects mediated by the protein corona in vivo. It offers a classification of the approaches to exploitation of the protein corona-rather than elimination thereof-based on the bilayer composition-corona composition-molecular interactions-biological performance framework. The multitude of factors that affect each level of this relationship urge to the widest implementation of bioinformatics tools to predict the most effective liposome compositions relying on the data on protein corona. Supplementing the picture with new pieces of accurately reported experimental data will contribute to the accuracy and efficiency of the predictions. STATEMENT OF SIGNIFICANCE: The review focuses on liposomes as an established nanomedicine platform and analyzes the available data on how the protein corona formed on liposome surface in biological fluids affects performance of the liposomes. The review offers a rigorous account of existing literature and critical analysis of methodology currently applied to the assessment of liposome-plasma protein interactions. It introduces a classification of the approaches to exploitation of the protein corona and tailoring liposome carriers to advance the field of nanoparticulate drug delivery systems for the benefit of patients.

Turning Toxic Nanomaterials into a Safe and Bioactive Nanocarrier for Co-delivery of DOX/pCRISPR

Hybrid bioactive inorganic-organic carbon-based nanocomposites of reduced graphene oxide (rGO) nanosheets enlarged with multi-walled carbon nanotubes (MWCNTs) were decorated to provide a suitable space for in situ growth of CoNi₂S₄ and green-synthesized ZnO nanoparticles. The ensuing nanocarrier supplied π-π interactions between the DOX drug and a stabilizing agent derived from leaf extracts on the surface of ZnO nanoparticles and hydrogen bonds; gene delivery of (p)CRISPR was also facilitated by chitosan and alginate renewable macromolecules. Also, these polymers can inhibit the potential interactions between the inorganic parts and cellular membranes to reduce the potential cytotoxicity. Nanocomposite/nanocarrier analyses and sustained DOX delivery (cytotoxicity analyses on HEK-293, PC12, HepG2, and HeLa cell lines after 24, 48, and 72 h) were indicative of an acceptable cell viability of up to 91.4 and 78.8% after 48 at low and high concentrations of 0.1 and 10 μg/mL, respectively. The MTT results indicate that by addition of DOX to the nanostructures, the relative cell viability increased after 72 h of treatment; since the inorganic compartments, specifically CoNi₂S₄, are toxic, this is a promising route to increase the bioavailability of the nanocarrier before reaching the targeted cells. Nanosystems were tagged with (p)CRISPR for co-transfer of the drug/genes, where confocal laser scanning microscopy (CLSM) pictures of the 4',6-diamidino-2-phenylindole (DAPI) were indicative of appropriate localization of DOX into the nanostructure with effective cell and drug delivery at varied pH. Also, the intrinsic toxicity of CoNi₂S₄ does not affect the morphology of the cells, which is a breakthrough. Furthermore, the CLSM images of the HEK-293 and HeLa cell displayed effective transport of (p)CRISPR into the cells with an enhanced green fluorescent protein (EGFP) of up to 8.3% for the HEK-293 cell line and 21.4% for the HeLa cell line, a record. Additionally, the specific morphology of the nanosystems before and after the drug/gene transport events, via images by TEM and FESEM, revealed an intact morphology for these biopolymers and their complete degradation after long-time usage.

Probing cell-nanoparticle (cubosome) interactions at the endothelial interface: do tissue dimension and flow matter?

In the research field of nanostructured systems for biomedical applications, increasing attention has been paid to using biomimetic, dynamic cellular models to adequately predict their bio-nano behaviours. This work specifically evaluates the biointeractions of nanostructured lipid-based particles (cubosomes) with human vascular cells from the aspects of tissue dimension (conventional 2D well plate versus 3D dynamic tubular vasculature) and shear flow effect (static, venous and arterial flow-mimicking conditions). A glass capillary-hosted, 3D tubular endothelial construct was coupled with circulating luminal fluid flow to simulate the human vascular systems. In the absence of fluid flow, the degree of cell-cubosome association was not significantly different between the 2D planar and the 3D tubular systems. Under flow conditions simulating venous (0.8 dynes per cm²) and arterial (10 dynes per cm²) shear stresses, the cell-cubosome association notably declined by 50% and 98%, respectively. This highlights the significance of shear-guided biointeractions of non-targeted nanoparticles in the circulation. Across all 2D and 3D cellular models with and without flow, cubosomes had little effect on the cell-cell contact based on the unchanged immunoexpression of the endothelial-specific intercellular junction marker PECAM-1. Interestingly, there were dissimilar nanoparticle distribution patterns between the 2D planar (showing discrete punctate staining) and the 3D tubular endothelium (with a more diffused, patchy fashion). Taken together, these findings highlight the importance of tissue dimension and shear flow in governing the magnitude and feature of cell-nanoparticle interactions.

Evaluating nanomedicine with microfluidics

Nanomedicines are engineered nanoscale structures that have an extensive range of application in the diagnosis and therapy of many diseases. Despite the rapid progress in and tremendous potential of nanomedicines, their clinical translational process is still slow, owing to the difficulty in understanding, evaluating, and predicting their behavior in complex living organisms. Microfluidic techniques offer a promising way to resolve these challenges. Carefully designed microfluidic chips enable in vivo microenvironment simulation and high-throughput analysis, thus providing robust platforms for nanomedicine evaluation. Here, we summarize the recent developments and achievements in microfluidic methods for nanomedicine evaluation, categorized into four sections based on their target systems: single cell, multicellular system, organ, and organism levels. Finally, we provide our perspectives on the challenges and future directions of microfluidics-based nanomedicine evaluation.

Formation and characterization of Langmuir and Langmuir-Blodgett films of Newkome-type dendrons in presence and absence of a therapeutic compound, for the development of surface mediated drug delivery systems

Organic macromolecules with dendrimeric architectures are polymeric materials potentially useful as nanocarriers for therapeutic drugs. In this work, we evaluate a series of Newkome-type dendrons in Langmuir and Langmuir-Blodgett films as platforms capable of interacting with a potential antitumoral agent. The nanocomposite is proposed as model for the development of surface mediated drug delivery systems. We were successful in the formation and characterization of pure (dendrons) and composite (drug-dendron) stable and reproducible monolayers, and their transfer to solid substrates. A detailed study of topographic characteristics of the generated surfaces by atomic force microscopy was conducted. Furthermore, we probed dendron monolayer films as anchorage surfaces for mammalian cells. Normal cell attachment and proliferation on the surfaces were observed. No evident cytotoxic effects were detected, demonstrating the adequate biocompatibility of the surfaces.

A novel biocompatible antibacterial product: Nanoliposomes loaded with poly(hexamethylene biguanide chloride)

In this study, nanoliposome-loaded poly(hexamethylene biguanide) is introduced as a novel biocompatible antibacterial product with higher activity than microliposomes. Soy lecithin as a clean product was used to prepare various nanoliposomes through sonication, high-pressure homogenizer, and normal homogenizer and also microliposomes through two methods of lipid film hydration and incubation methods. The nanoliposomes were formed under sonication with the size of 50 nm. The prepared liposomes were then loaded with poly(hexamethylene biguanide chloride) and the inclusion percentage was measured. The release profile of liposomes in buffer showed a release of 92% for poly(hexamethylene biguanide) during 24 h. The loaded liposomes were characterized with particle size analyzer, nuclear magnetic resonance, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The antibacterial properties of different micro and nanoliposomes were investigated against a Gram-negative ( Escherichia coli) and a Gram-positive ( Staphylococcus aureus) bacteria. The poly(hexamethylene biguanide)–loaded nanoliposomes indicated higher antibacterial activities than microliposomes. Nanoliposomes have the potential to entrap lower poly(hexamethylene biguanide) dosages while retaining optimum therapeutic efficacy in the target site having lower cytotoxicity with lower side effects. The cytotoxicity of poly(hexamethylene biguanide) entrapped in liposomes was studied in human dermal fibroblasts and compared with free poly(hexamethylene biguanide) and blank liposomes. The maximum cytotoxicity was observed for free poly(hexamethylene biguanide) that is substantially decreased through loading within liposomes structure. Overall, the encapsulation of poly(hexamethylene biguanide) in liposomes improved the biocompatibility and safety of the product introducing a useful biocompatible antibacterial polymer for treatments of infectious diseases.

Subcompartmentalized Nanoreactors as Artificial Organelle with Intracellular Activity

Cell mimicry is an approach which aims at substituting missing or lost activity. In this context, the goal of artificial organelles is to provide intracellularly active nanoreactors to affect the cellular performance. So far, only a handful of reports discuss concepts addressing this challenge based on single-component reactors. Here, the assembly of nanoreactors equipped with glucose oxidase (GOx)-loaded liposomal subunits coated with a poly(dopamine) polymer layer and RGD targeting units is reported. When comparing different surface modifications, the uptake of the nanoreactors by endothelial cells and macrophages with applied shear stress is confirmed without inherent cytotoxicity. Furthermore, the encapsulation and preserved activity of GOx within the nanoreactors is shown. The intracellular activity is demonstrated by exposing macrophages with internalized nanoreactors to glucose and assessment of the cell viability after 6 and 24 h. The macrophage viability is found to be reduced due to the intracellularly produced hydrogen peroxide by GOx. This report on the first intracellular active subcompartmentalized nanoreactors is a considerable step in therapeutic cell mimicry.

Physicochemical evaluation of DEAE-Dx coated liposomes for long alkyl chain lipids

The purpose of this work was to study the potential of diethylaminoethyl dextran (DEAE-Dx) coated liposomes as drug carriers.

Recent developments in poly(dopamine)-based coatings for biomedical applications

The success of polymer coatings for biomedical applications is undeniable. Among the very successful examples are poly(dopamine) (PDA) films due to their simplicity in deposition and beneficial interaction with biomolecules and cells. The aim of this review is to highlight the findings and achievement of PDA in nanomedicine since 2011. We discuss the progress that has been made to elucidate the structure of PDA and novel aspects considering the assembly of PDA-based films on diverse substrates. We highlight the newest results considering the biological evaluation PDA-based coatings to control cell behavior and the use of PDA in biosensing. The popularity of PDA remains unchanged, but the research efforts start to be consolidated toward more specific aims and clinical applications.

Interaction between drug delivery vehicles and cells under the effect of shear stress

Over the last decades, researchers have developed an ever greater and more ingenious variety of drug delivery vehicles (DDVs). This has made it possible to encapsulate a wide selection of therapeutic agents, ranging from proteins, enzymes, and peptides to hydrophilic and hydrophobic small drugs while, at the same time, allowing for drug release to be triggered through a diverse range of physical and chemical cues. While these advances are impressive, the field has been lacking behind in translating these systems into the clinic, mainly due to low predictability of in vitro and rodent in vivo models. An important factor within the complex and dynamic human in vivo environment is the shear flow observed within our circulatory system and many other tissues. Within this review, recent advances to leverage microfluidic devices to better mimic these conditions through novel in vitro assays are summarized. By grouping the discussion in three prominent classes of DDVs (lipidic and polymeric particles as well as inorganic nanoparticles), we hope to guide researchers within drug delivery into this exciting field and advance a further implementation of these assay systems within the development of DDVs.

Phospholipid-polymer amphiphile hybrid assemblies and their interaction with macrophages

Recently, the combination of lipids and block copolymers has become an alternative to liposomes and polymersomes as nano-sized drug carriers. We synthesize novel block copolymers consisting of poly(cholesteryl acrylate) as the hydrophobic core and poly(N-isopropylacrylamide) (PNIPAAm) as the hydrophilic extensions. Their successful phospholipid-assisted assembly into vesicles is demonstrated using the evaporation-hydration method. The preserved thermo-responsive property of the lipid-polymer hybrids is shown by a temperature dependent adsorption behaviour of the vesicles to poly(l lysine) coated surfaces. As expected, the vesicle adsorption is found to be higher at elevated temperatures. The cellular uptake efficiency of hybrids is assessed using macrophages with applied shear stress. The amount of adhering macrophages is affected by the time and level of applied shear stress. Further, it is found that shorter PNIPAAm extensions lead to higher uptake of the assemblies by the macrophages with applied shear stress. No inherent cytotoxicity is observed at the tested conditions. Taken together, this first example of responsive lipid-polymer hybrids, and their positive biological evaluation makes them promising nano-sized drug carrier candidates.

Mixed poly(dopamine)/poly(L-lysine) (composite) coatings: from assembly to interaction with endothelial cells

Engineered polymer films are of significant importance in the field of biomedicine. Poly(dopamine) (PDA) is becoming more and more a key player in this context. Herein, we deposited mixed films consisting of PDA and poly(L-lysine) (PLL) of different molecular weights. The coatings were characterized by quartz crystal microbalance with dissipation monitoring, atomic force microscopy, and X-ray photoelectron spectroscopy. The protein adsorption to the mixed films was found to decrease with increasing amounts of PLL. PDA/PLL capsules were also successfully assembled. Higher PLL content in the membranes reduced their thickness while the ζ-potential increased. Further, endothelial cell adhesion and proliferation over 96 h were found to be independent of the type of coating. Using PDA/PLL in liposome-containing composite coatings showed that sequential deposition of the layers yielded higher liposome trapping compared to one-step adsorption except for negatively charged liposomes. Association/uptake of fluorescent cargo by adherent endothelial cells was found to be different for PDA and PDA/PLL films. Taken together, our findings illustrate the potential of PDA/PLL mixed films as coatings for biomedical applications.