Novel Biomimetic Surfactant: Synthesis and Micellar Characteristics

A Thermo-Responsive Polymer Micelle with a Liquid Crystalline Core

An amphiphilic diblock copolymer (PChM-PNIPAM), composed of poly(cholesteryl 6-methacryloyloxy hexanoate) (PChM) and poly(N-isopropyl acrylamide) (PNIPAM) blocks, was prepared via reversible addition-fragmentation chain transfer radical polymerization. The PChM and PNIPAM blocks exhibited liquid crystalline behavior and a lower critical solution temperature (LCST), respectively. PChM-PNIPAM formed water-soluble polymer micelles in water below the LCST because of hydrophobic interactions of the PChM blocks. The PChM and PNIPAM blocks formed the core and hydrophilic shell of the micelles, respectively. With increasing temperature, the molecular motion of the pendant cholesteryl groups increased, and a liquid crystalline phase transition occurred from an amorphous state in the core. With further increases in temperature, the PNIPAM block in the shell exhibited the LCST and dehydrated. Hydrophobic interactions of the PNIPAM shells resulted in inter-micellar aggregation above the LCST.

Modeling Polyzwitterion-Based Drug Delivery Platforms: A Perspective of the Current State-of-the-Art and Beyond

Drug delivery platforms are anticipated to have biocompatible and bioinert surfaces. PEGylation of drug carriers is the most approved method since it improves water solubility and colloid stability and decreases the drug vehicles' interactions with blood components. Although this approach extends their biocompatibility, biorecognition mechanisms prevent them from biodistribution and thus efficient drug transfer. Recent studies have shown (poly)zwitterions to be alternatives for PEG with superior biocompatibility. (Poly)zwitterions are super hydrophilic, mainly stimuli-responsive, easy to functionalize and they display an extremely low protein adsorption and long biodistribution time. These unique characteristics make them already promising candidates as drug delivery carriers. Furthermore, since they have highly dense charged groups with opposite signs, (poly)zwitterions are intensely hydrated under physiological conditions. This exceptional hydration potential makes them ideal for the design of therapeutic vehicles with antifouling capability, i.e., preventing undesired sorption of biologics from the human body in the drug delivery vehicle. Therefore, (poly)zwitterionic materials have been broadly applied in stimuli-responsive "intelligent" drug delivery systems as well as tumor-targeting carriers because of their excellent biocompatibility, low cytotoxicity, insignificant immunogenicity, high stability, and long circulation time. To tailor (poly)zwitterionic drug vehicles, an interpretation of the structural and stimuli-responsive behavior of this type of polymer is essential. To this end, a direct study of molecular-level interactions, orientations, configurations, and physicochemical properties of (poly)zwitterions is required, which can be achieved via molecular modeling, which has become an influential tool for discovering new materials and understanding diverse material phenomena. As the essential bridge between science and engineering, molecular simulations enable the fundamental understanding of the encapsulation and release behavior of intelligent drug-loaded (poly)zwitterion nanoparticles and can help us to systematically design their next generations. When combined with experiments, modeling can make quantitative predictions. This perspective article aims to illustrate key recent developments in (poly)zwitterion-based drug delivery systems. We summarize how to use predictive multiscale molecular modeling techniques to successfully boost the development of intelligent multifunctional (poly)zwitterions-based systems.

Steroid-Based Liquid Crystalline Polymers: Responsive and Biocompatible Materials of the Future

Steroid-based liquid crystal polymers and co-polymers have come a long way, with new and significant advances being made every year. This paper reviews some of the recent key developments in steroid-based liquid crystal polymers and co-polymers. It covers the structure–property relationship between cholesterol and sterol-based compounds and their corresponding polymers, and the influence of chemical structure and synthesis conditions on the liquid crystalline behaviour. An overview of the nature of self-assembly of these materials in solvents and through polymerisation is given. The role of liquid crystalline properties in the applications of these materials, in the creation of nano-objects, drug delivery and biomedicine and photonic and electronic devices, is discussed.

Association Behavior of Amphiphilic ABA Triblock Copolymer Composed of Poly(2-methoxyethyl acrylate) (A) and Poly(ethylene oxide) (B) in Aqueous Solution

Poly(2-methoxyethyl acrylate) (PMEA) and poly(ethylene oxide) (PEO) have protein-antifouling properties and blood compatibility. ABA triblock copolymers (PMEAl-PEO11340-PMEAm (MEOMn; n is average value of l and m)) were prepared using single-electron transfer-living radical polymerization (SET-LRP) using a bifunctional PEO macroinitiator. Two types of MEOMn composed of PMEA blocks with degrees of polymerization (DP = n) of 85 and 777 were prepared using the same PEO macroinitiator. MEOMn formed flower micelles with a hydrophobic PMEA (A) core and hydrophilic PEO (B) loop shells in diluted water with a similar appearance to petals. The hydrodynamic radii of MEOM85 and MEOM777 were 151 and 108 nm, respectively. The PMEA block with a large DP formed a tightly packed core. The aggregation number (Nagg) of the PMEA block in a single flower micelle for MEOM85 and MEOM777 was 156 and 164, respectively, which were estimated using a light scattering technique. The critical micelle concentrations (CMCs) for MEOM85 and MEOM777 were 0.01 and 0.002 g/L, respectively, as determined by the light scattering intensity and fluorescence probe techniques. The size, Nagg, and CMC for MEOM85 and MEOM777 were almost the same independent of hydrophobic DP of the PMEA block.

Glioma-derived exosomes hijack the blood-brain barrier to facilitate nanocapsule delivery via LCN2

Exosomes are small extracellular vehicles which could transport genetic materials and proteins between cells. Although there are reports about exosomes crossing the blood-brain barrier (BBB), the underlying mechanisms still need further study. We found that exosomes from primary brain tumors could upregulate the expression of Lipocalin-2 (LCN2) in bEnd.3 brain microvascular endothelial cells (BMVECs). Furthermore, exosomes increased the membrane fluidity of bEnd.3 cells in an LCN2 dependent manner. Both intraperitoneal injection and caudal vein injection of LCN2 increased the number of nanocapsules crossing the BBB. Evans Blue staining revealed that LCN2 does not interrupt the integrity of the BBB, as observed in the traumatic brain injury model. Tandem mass tags quantitative proteomics and bioinformatics analysis revealed that LCN2 is upregulated by exosomes via the JAK-STAT3 pathway, but not delivered from exosomes. Knocking down LCN2 in bEnd.3 cells significantly abrogated the effect of exosomes on BMVEC membrane fluidity. Previously, we have reported that 2-methacryloyloxyethyl phosphorylcholine (MPC) and a peptide crosslinker could encapsulate mAbs to achieve nanocapsules. The nanocapsules containing choline analogs could effectively penetrate the BBB to deliver therapeutic monoclonal antibodies (tAbs) to the glioma. However, the delivered tAbs could be significantly reduced by blocking the release of exosomes from the gliomas. Application of tAb nanocapsules prior to treatment with MK2206, an AKT pathway inhibitor that has been shown to inhibit the production of exosomes, resulted in a better combination. Insights from this study provide a mechanistic framework with regard to how glioblastomas hijack BMVECs using exosomes. In addition, we provide a strategy for maximizing the effect of the choline-containing nanocapsules and MK2206 combination. These results also demonstrate the therapeutic role of tAbs in glioblastoma and brain tumor metastasis, by shedding new light on strategies that can be used for BBB-penetrating therapies.

Emerging Phospholipid Nanobiomaterials for Biomedical Applications to Lab-on-a-Chip, Drug Delivery, and Cellular Engineering

The design of advanced nanobiomaterials to improve analytical accuracy and therapeutic efficacy has become an important prerequisite for the development of innovative nanomedicines. Recently, phospholipid nanobiomaterials including 2-methacryloyloxyethyl phosphorylcholine (MPC) have attracted great attention with remarkable characteristics such as resistance to nonspecific protein adsorption and cell adhesion for various biomedical applications. Despite many recent reports, there is a lack of comprehensive review on the phospholipid nanobiomaterials from synthesis to diagnostic and therapeutic applications. Here, we review the synthesis and characterization of phospholipid nanobiomaterials focusing on MPC polymers and highlight their attractive potentials for applications in micro/nanofabricated fluidic devices, biosensors, lab-on-a-chip, drug delivery systems (DDSs), COVID-19 potential usages for early diagnosis and even treatment, and artificial extracellular matrix scaffolds for cellular engineering.

Polymeric Drug Delivery Systems Bearing Cholesterol Moieties: A Review

This review aims to provide an overview of polymers comprising cholesterol moiety/ies designed to be used in drug delivery. Over the last two decades, there have been many papers published in this field, which are summarized in this review. The primary focus of this article is on the methods of synthesis of polymers bearing cholesterol in the main chain or as side chains. The data related to the composition, molecular weight, and molecular weight distribution of polymers are presented. Moreover, other aspects, such as forms of carriers, types of encapsulated drugs, encapsulation efficiency and capacity, are also included.

Gold embedded chitosan nanoparticles with cell membrane mimetic polymer coating for pH-sensitive controlled drug release and cellular fluorescence imaging

In this work, gold embedded chitosan nanoparticles (Au@CS NPs) were fabricated by a one-pot method. The benzaldehyde-terminated poly[(2-methacryloyloxy) ethyl phosphorylcholine] (PMPC) was applied to modification of the gold doped chitosan nanoparticles. The obtained Au@CS-PMPC NPs had the diameter of 135 nm with a narrow distribution. The size of the Au@CS-PMPC NPs, as well as the size of the embedded gold NPs, might be well-controlled by adjusting the feeding ratio between chitosan and HAuCl₄. Furthermore, the Au@CS-PMPC NPs showed increased colloidal stability, high drug loading content, pH-responsive drug release, excellent biocompatibility and bright fluorescence emission. The results demonstrated that Au@CS-PMPC NPs showed a great potential for tumor therapy via the combination advantages of pH-sensitive controlled drug release and cellular fluorescence imaging.

Recent advances of biomimetic nano-systems in the diagnosis and treatment of tumor

The lack of effective methods of diagnosis and treatment presents a major barrier to combat against tumor. The biomimetic concept is an emerging field that expresses great application potential in tumor fighting. Strategy for combining nano-systems with biomimetic technology has gained increasing attention that is proved bioinspired, environmentally benign, and promising. Herein, we provide an up-to-date review of biomimetic nano-systems as well as their applications in tumor therapy. In addition, the challenges and future directions of biomimetic nano-systems to achieve clinical translation are also pointed out.

Polymeric micelles: Basic research to clinical practice

Rapidly developing polymeric micelles as potential targeting carriers has intensified the need for better understanding of the underlying principles related to the selection of suitable delivery materials for designing, characterizing, drug loading, improving stability, targetability, biosafety and efficacy. The emergence of advanced analytical tools such as fluorescence resonance energy transfer and dissipative particle dynamics has identified new dimensions of these nanostructures and their behavior in much greater details. This review summarizes recent efforts in the development of polymeric micelles with respect to their architecture, formulation strategy and targeting possibilities along with their preclinical and clinical aspects. Literature of the past decade is discussed critically with special reference to the chemistry involved in the formation and clinical applications of these versatile materials. Thus, our main objective is to provide a timely update on the current status of polymeric micelles highlighting their applications and the important parameters that have led to successful delivery of drugs to the site of action.

An Amphiphilic Fluorescent Probe Designed for Extracellular Visualization of Nitric Oxide Released from Living Cells

Nitric oxide (NO) is an intracellular and intercellular messenger involved in numerous physiological and pathophysiological processes. Small-molecule fluorescent probes coupled with fluorescence microscopy provide excellent tools for real-time detection of NO in situ. However, most probes are designed for imaging intracellular NO, which cannot reflect the release behavior of endogenously produced NO. In order to visualize extracellular NO released from living cells, we report herein a particularly designed amphiphilic fluorescent probe, disodium 2,6-disulfonate-1,3-dimethyl-5-hexadecyl-8-(3,4-diaminophenyl)-4,4'-difluoro-4-bora-3a,4a-diaza-s-indacene (DSDMHDAB), in which hydrophilic groups are introduced to keep the fluorophore and recognition domain outside the cell and a hydrophobic C16 alkyl chain acts as the membrane anchor. Based on this design, NO released out of the cells has been visualized on the outer surface of the plasma membrane. Using RAW 264.7 cells and ECV-304 cells as models, the diffusion of NO across the plasma membrane has been directly observed. The amphiphilic design strategy of fluorescent probes holds great promise for developing fluorescent imaging probes to study the release behaviors of other endogenous gasotransmitters.

Polymersomes from Amphiphilic Glycopolymers Containing Polymeric Liquid Crystal Grafts

For the first time, polymersomes were obtained by self-assembly in water of amphiphilic grafted glycopolymers based on dextran polysaccharidic backbone and polymeric liquid crystal grafts (poly(diethylene glycol cholesteryl ether acrylate), PDEGCholA). After measuring the properties of these glycopolymers in term of surfactancy, the influence of their structural parameters on their self-assemblies once dispersed in water was investigated by static and dynamic light scattering and by cryogenic transmission electron microscopy (cryo-TEM). Based on the results, a proper design of Dex-g^N-PDEGCholA^F leads to hollow vesicular structure formulation known as polymersome.

Nanoprecipitation of polymeric nanoparticle micelles based on 2-methacryloyloxyethyl phosphorylcholine (MPC) with 2-(diisopropylamino)ethyl methacrylate (DPA), for intracellular delivery applications

Biodistribution of nanoparticle-based intracellular delivery systems is mediated primarily by particle size and physicochemical properties. As such, overcoming the rapid removal of these by the reticuloendothelial system remains a significant challenge. To date, a number of copolymer nanoparticle systems based on 2-methacryloyloxyethyl phosphorylcholine (MPC) with 2-(diisopropylamino)ethyl methacrylate (DPA), displaying biomimetic and pH responsive properties, have been published, however these have been predominately polymersome based, whilst micelle systems have remained relatively unexplored. This study utilised nanoprecipitation to investigate the effects of solvent and buffer choice upon micelle size and polydispersity, and found using methanol produced monodisperse micelles of circa 70 nm diameter, whilst ethanol produced polydisperse systems with nanoparticles of circa 128 nm diameter. The choice of aqueous buffer, dialysis of the systems, extended storage, and exposure to a wide temperature range (5-70 °C) had no significant effect on micelle size, and the systems were highly resistant to dilution, indicating excellent colloidal stability. Optimisation of the nanoprecipitation process, post precipitation, was investigated, and model drugs successfully loaded whilst maintaining system stability. Subsequent in vitro studies suggested that the micelles were of negligible cellular toxicity, and an apparent cellular uptake was observed via confocal laser scanning microscopy. This paper presents the first report of an optimised nanoprecipitation methodology for the formation of MPC-DPA nanoparticle micelles, and in doing so achieved monodisperse systems with the size and physicochemical characteristics seen as desirable for long circulating therapeutic delivery vehicles.

Bolaamphiphiles: a pharmaceutical review

The field of drug discovery is ever growing and excipients play a major role in it. A novel class of amphiphiles has been discussed in the review. The review focuses on natural as well as synthetic bolaamphiphiles, their chemical structures and importantly, their ability to self assemble rendering them of great use to pharmaceutical industry. Recent reports on their ability to be used in fabrication of suitable nanosized carriers for drug as well as genes to target site, has been discussed substantially to understand the potential of bolaamphiphiles in field of drug delivery.

Cholesterol--a biological compound as a building block in bionanotechnology

Cholesterol is a molecule with many tasks in nature but also a long history in science. This feature article highlights the contribution of this small compound to bionanotechnology. We discuss relevant chemical aspects in this context followed by an overview of its self-assembly capabilities both as a free molecule and when conjugated to a polymer. Further, cholesterol in the context of liposomes is reviewed and its impact ranging from biosensing to drug delivery is outlined. Cholesterol is and will be an indispensable player in bionanotechnology, contributing to the progress of this potent field of research.

Cell membrane-inspired phospholipid polymers for developing medical devices with excellent biointerfaces

This review article describes fundamental aspects of cell membrane-inspired phospholipid polymers and their usefulness in the development of medical devices. Since the early 1990s, polymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) units have been considered in the preparation of biomaterials. MPC polymers can provide an artificial cell membrane structure at the surface and serve as excellent biointerfaces between artificial and biological systems. They have also been applied in the surface modification of some medical devices including long-term implantable artificial organs. An MPC polymer biointerface can suppress unfavorable biological reactions such as protein adsorption and cell adhesion - in other words, specific biomolecules immobilized on an MPC polymer surface retain their original functions. MPC polymers are also being increasingly used for creating biointerfaces with artificial cell membrane structures.

Novel bolaamphiphilic pyrimidinophane as building block for design of nanosized supramolecular systems with concentration-dependent structural behavior

A new macrocyclic bolaamphiphile with thiocytosine fragments in the molecule (B1) has been synthesized and advanced as perspective platform for the design of soft supramolecular systems. Strong concentration-dependent structural behavior is observed in the water-DMF (20% vol) solution of B1 as revealed by methods of tensiometry, conductometry, dynamic light scattering, and atomic force microscopy. Two breakpoints are observed in the surface tension isotherms. The first one, around 0.002 M, is identified as a critical micelle concentration (cmc), whereas the second critical concentration of 0.01 M is a turning point between the two models of the association involved. Large aggregates of ca. 200 nm are mostly formed beyond the cmc, whereas small micelle-like aggregates exist above 0.01 M. The growth of aggregates between these critical points occurs, resulting in a gel-like behavior. An unusual decrease in the solution pH with concentration takes place, which is assumed to originate from the steric hindrance around the B1 head groups. Because of controllable structural behavior, B1 is assumed to be a candidate for the development of biomimetic catalysts, nanocontainers, drug and gene carriers, etc.

Polymers Comprising Cholesterol: Synthesis, Self-Assembly, and Applications

This article reviews the current status of self-assembling liquid crystalline polymers comprising cholesterol. This article will focus on synthesis, structure-property relationships and strategies to direct ordering and packing of meso- and nanostructures of cholesterol polymers in the neat- or melt state and in solution. The applications of these self-assembled structures will be presented.

A novel biomimetic polymer as amphiphilic surfactant for soluble and biocompatible carbon nanotubes (CNTs)

Novel amphiphilic diblock copolymer, cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (CPMPC), which has poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) as hydrophilic segment and cholesterol as hydrophobic segment, was specially designed as amphiphilic surfactant to achieve water-soluble and biocompatible carbon nanotubes (CNTs). The pristine CNTs were facilely dispersed via non-covalently binding the zwitterionic phosphorylcholine-based amphiphile onto the surfaces of the CNTs. It is interesting to find that CPMPC shows better CNTs solubilizing ability compared with the surfactant of pyrene-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (PPMPC). The biocompatibility of the CPMPC stabilized CNTs was evaluated using cholesterol-end-capped poly(2-(dimethylamino) ethyl methacrylate) (CPDMAEMA), cholesterol-end-capped poly(acrylic acid) (CPAA) and cholesterol-end-capped poly(ethylene oxide) (CPEG) as surfactants for CNTs as controls. While CPDMAEMA stabilized CNTs and CPAA stabilized CNTs showed obvious cytotoxicity, cytotoxicity of this novel zwitterionic phosphorylcholine-based amphiphile stabilized CNTs was not observed as indicated by cell culture. The biocompatible CNTs represent an excellent nano-object for potential biomedical applications.

Zwitterionic phosphorylcholine as a better ligand for stabilizing large biocompatible gold nanoparticles

Zwitterionic phosphorylcholine showed better stabilization than oligo(ethylene glycol) in protecting big gold nanoparticles.

Water-soluble dendritic core-shell-type architectures based on polyglycerol for solubilization of hydrophobic drugs

Since many potential drugs are poorly water soluble, there is a high demand for solubilization agents. Here, we describe the synthesis of dendritic core-shell-type architectures based on hyperbranched polyglycerol for the solubilization of hydrophobic drugs. Amphiphilic macromolecules containing hydrophobic biphenyl groups in the core were synthesized in an efficient three- or four-step procedure by employing Suzuki-coupling reactions. These species were then used to solubilize the commercial drug nimodipine, a calcium antagonist used for the treatment of heart diseases and neurological deficits. Pyrene was also used as a hydrophobic model compound. It turned out that the transport properties of the dendritic polyglycerol derivatives, which are based on hydrophobic host-guest interactions, depend strongly on the degree and type of core functionalization. In the case of the multifunctional nimodipine, additional specific polymer-drug interactions could be tailored by this flexible core design, as detected by UV spectroscopy. The enhancement of solubilization increased 300-fold for nimodipine and 6000-fold for pyrene at a polymer concentration of 10 wt%. The sizes of the polymer-drug complexes were determined by both dynamic light scattering (DLS) experiments and transmission electron microscopy (TEM), and extremely well-defined aggregates with diameters of approximately 10 nm in the presence of a drug were observed. These findings together with a low critical aggregate concentration of 4x10(-6) mol L-1 indicate the controlled self-assembly of the presented amphiphilic dendritic core-shell-type architectures rather than a unimolecular transport behavior.

Novel biomimetic polymersomes as polymer therapeutics for drug delivery

Novel amphiphilic diblock copolymers, cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (CMPC), which have poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) as hydrophilic segment and cholesterol as hydrophobic segment, was specially designed as drug delivery systems. Fluorescence probe technique and transmission electron microscope (TEM) characterizations indicated that this novel amphiphilic copolymer formed micelles structure in water and the critical micelle concentration (CMC) was determined to be 1.57 x 10(-7) mol/l. A commercial obtained polymeric amphiphiles, Cholesterol end capped PEO (CPEO), which had a similar structure with CMPC, was used as a control in the cytotoxicity test. While CPEO showed obvious cytotoxicity, cytotoxicity of this novel amphiphiles was not observed as indicated by cell culture. Anti-cancer drug adriamycin (ADR) was incorporated into the micelles by oil-in-water method. The size of the drug-containing micelles was less than 200 nm, and the size distribution of the drug-containing micelles showed a narrow and monodisperse unimodal pattern. The release rate of ADR from the nanosphere was slow and the release continued over 7 days and the release rate decreased with the increase of molecular weights of the copolymer and the amount of the drug entrapped. These experimental results suggested that the nanoparticles prepared from CMPC block copolymers could be a good candidate for injectable drug delivery carrier.