Strategies to improve micelle stability for drug delivery

Determination of Critical Micelle Concentration from the Diffusion-Driven Dilution of Micellar Aqueous Mixtures

Micellization is a phenomenon of central importance in surfactant solutions. Here, we demonstrate that the diffusion-based spreading of the free boundary between a micellar aqueous solution and pure water yields a one-dimensional spatial profile of surfactant concentration that can be used to identify the critical micelle concentration, here denoted as C*. This can be achieved because dilution of micelles into water leads to their dissociation at a well-defined position along the concentration profile and an abrupt increase in the diffusion coefficient. Rayleigh interferometry was successfully employed to determine C* values for three well-known surfactants in water at 25 °C: Triton X-100 (TX-100), sodium dodecyl sulfate (SDS), and poly(oxyethylene)(4)Lauryl Ether (Brij-30). The dependence of C* on salt concentration was also characterized for TX-100 in the presence of Na₂SO₄, NaCl, and NaSCN. Accurate values of C* can be directly identified by visual inspection of the corresponding concentration-gradient profiles. To apply the method of least squares to experimental concentration profiles, a mathematical expression was derived from Fick's law and the pseudophase separation model of micellization with the inclusion of appropriate modifications. While Rayleigh interferometry was employed in our experiments, this approach can be extended to any experimental technique that yields one-dimensional profiles of surfactant concentration. Moreover, diffusion-driven surfactant disaggregation is precise, noninvasive, requires single-sample preparation, and applies to both nonionic and ionic surfactants. Thus, this work provides the foundation of diffusion-driven dilution methods, thereby representing a valuable addition to existing techniques for the determination of C*.

Polymeric micelles in drug delivery: An insight of the techniques for their characterization and assessment in biorelevant conditions

Polymeric micelles, i.e. aggregation colloids formed in solution by self-assembling of amphiphilic polymers, represent an innovative tool to overcome several issues related to drug administration, from the low water-solubility to the poor drug permeability across biological barriers. With respect to other nanocarriers, polymeric micelles generally display smaller size, easier preparation and sterilization processes, and good solubilization properties, unfortunately associated with a lower stability in biological fluids and a more complicated characterization. Particularly challenging is the study of their interaction with the biological environment, essential to predict the real in vivo behavior after administration. In this review, after a general presentation on micelles features and properties, different characterization techniques are discussed, from the ones used for the determination of micelles basic characteristics (critical micellar concentration, size, surface charge, morphology) to the more complex approaches used to figure out micelles kinetic stability, drug release and behavior in the presence of biological substrates (fluids, cells and tissues). The techniques presented (such as dynamic light scattering, AFM, cryo-TEM, X-ray scattering, FRET, symmetrical flow field-flow fractionation (AF4) and density ultracentrifugation), each one with their own advantages and limitations, can be combined to achieve a deeper comprehension of polymeric micelles in vivo behavior. The set-up and validation of adequate methods for micelles description represent the essential starting point for their development and clinical success.

Polymeric Micelles in Cancer Immunotherapy

Cancer immunotherapies have generated some miracles in the clinic by orchestrating our immune system to combat cancer cells. However, the safety and efficacy concerns of the systemic delivery of these immunostimulatory agents has limited their application. Nanomedicine-based delivery strategies (e.g., liposomes, polymeric nanoparticles, silico, etc.) play an essential role in improving cancer immunotherapies, either by enhancing the anti-tumor immune response, or reducing their systemic adverse effects. The versatility of working with biocompatible polymers helps these polymeric nanoparticles stand out as a key carrier to improve bioavailability and achieve specific delivery at the site of action. This review provides a summary of the latest advancements in the use of polymeric micelles for cancer immunotherapy, including their application in delivering immunological checkpoint inhibitors, immunostimulatory molecules, engineered T cells, and cancer vaccines.

CD44 Targeted Nanomaterials for Treatment of Triple-Negative Breast Cancer

Identified as the second leading cause of cancer-related deaths among American women after lung cancer, breast cancer of all types has been the focus of numerous research studies. Even though triple-negative breast cancer (TNBC) represents 15-20% of the number of breast cancer cases worldwide, its existing therapeutic options are fairly limited. Due to the pivotal role of the presence/absence of specific receptors to luminal A, luminal B, HER-2+, and TNBC in the molecular classification of breast cancer, the lack of these receptors has accounted for the aforementioned limitation. Thereupon, in an attempt to participate in the ongoing research endeavors to overcome such a limitation, the conducted study adopts a combination strategy as a therapeutic paradigm for TNBC, which has proven notable results with respect to both: improving patient outcomes and survivability rates. The study hinges upon an investigation of a promising NPs platform for CD44 mediated theranostic that can be combined with JAK/STAT inhibitors for the treatment of TNBC. The ability of momelotinib (MMB), which is a JAK/STAT inhibitor, to sensitize the TNBC to apoptosis inducer (CFM-4.16) has been evaluated in MDA-MB-231 and MDA-MB-468. MMB + CFM-4.16 combination with a combination index (CI) ≤0.5, has been selected for in vitro and in vivo studies. MMB has been combined with CD44 directed polymeric nanoparticles (PNPs) loaded with CFM-4.16, namely CD44-T-PNPs, which selectively delivered the payload to CD44 overexpressing TNBC with a significant decrease in cell viability associated with a high dose reduction index (DRI). The mechanism underlying their synergism is based on the simultaneous downregulation of P-STAT3 and the up-regulation of CARP-1, which has induced ROS-dependent apoptosis leading to caspase 3/7 elevation, cell shrinkage, DNA damage, and suppressed migration. CD44-T-PNPs showed a remarkable cellular internalization, demonstrated by uptake of a Rhodamine B dye in vitro and S0456 (NIR dye) in vivo. S0456 was conjugated to PNPs to form CD44-T-PNPs/S0456 that simultaneously delivered CFM-4.16 and S0456 parenterally with selective tumor targeting, prolonged circulation, minimized off-target distribution.

The wormlike micelles formed using an ionic liquid surfactant and polar organic solvents at low temperature without additives and their lubricant properties

Wormlike micelles (or reverse wormlike micelles) are flexible cylindrical chains that are normally formed in water (or a nonpolar organic solvent) at 25.0 °C or above; the formation of wormlike micelles at lower temperatures is rare. Here, we have reported wormlike micelles formed at low temperature using an ionic liquid surfactant (1-octadecyl-3-nonyl imidazolium bromide) in polar organic solvents (including 1,3-propanediol, 1,2-propylene glycol, N,N-dimethylformamide, and glycerol/1,2-propylene glycol mixture) in the absence of any additives. The viscoelasticity and morphology of the wormlike micelles were studied using rheology, small-angle X-ray scattering, and cryo-transmission electron microscopy. The viscoelastic properties of the wormlike micelles in polar solvents are affected by the solvent type (or the weight ratio of glycerol to 1,2-propylene glycol), surfactant concentration, and temperature. Moreover, the G' and G'' crossover twice in the dynamic curves, which is different from the case in water. The first crossover (at low frequency) corresponds to the relaxation time for the alkyl chains to disentangle from the transient network, and the second crossover (at high frequency) is related to the segmental motion of the chains. Furthermore, the tribological performance of these wormlike micelles is investigated at low temperature. It is found that the protective film (formed by the physical adhesion of the wormlike micelles on the surface of friction disk pair) and the tribochemical reaction together lead to good antifriction and antiwear performance, which indicates the application prospects of these wormlike micelles in low-temperature lubrication.

Challenges of Dissolution Methods Development for Soft Gelatin Capsules

Recently, the development of soft gelatin capsules (SGCs) dosage forms has attracted a great deal of interest in the oral delivery of poorly water-soluble drugs. This is attributed to the increased number of poorly soluble drugs in the pipeline, and hence the challenges of finding innovative ways of developing bioavailable and stable dosage forms. Encapsulation of these drugs into SGCs is one of the approaches that is utilized to deliver the active ingredients to the systemic circulation to overcome certain formulation hurdles. Once formulated, encapsulated drugs in the form of SGCs require suitable in vitro dissolution test methods to ensure drug product quality and performance. This review focuses on challenges facing dissolution test method development for SGCs. A brief discussion of the physicochemical and formulation factors that affect the dissolution properties of SGCs will be highlighted. Likewise, the influence of cross-linking of gelatin on the dissolution properties of SGCs will also be discussed.

Microstructures of encapsulates and their relations with encapsulation efficiency and controlled release of bioactive constituents: A review

Vitamins, peptides, essential oils, and probiotics are examples of health beneficial constituents, which are nevertheless heat-sensitive and possess poor chemical stability. Various encapsulation methods have been applied to protect these constituents against thermal and chemical degradations. Encapsulates prepared by different methods and/or at different conditions exhibit different microstructures, which in turn differently influence the encapsulation efficiency as well as retention of encapsulated core materials. This review provides a summary of various microstructures resulted from the use of selected encapsulation methods or systems, namely, spray coating; co-extrusion; emulsion-, micelle-, and liposome-based; coacervation; and ionic gelation encapsulation, at different conditions. Subsequent effects of the different microstructures on encapsulation efficiency and retention of encapsulated core materials are mentioned and discussed. Encapsulates having compact microstructures resulted from the use of low-surface tension and low-viscosity encapsulants, high-stability encapsulation systems, lower loads of core materials to total solids of encapsulants and appropriate solidification conditions have proved to exhibit higher encapsulation efficiencies and better retention of encapsulated core materials. Encapsulates with hollow, dent, shrunken microstructures or thinner walls resulted from inappropriate solidification conditions and higher loads of core materials, on the other hand, possess lower encapsulation efficiencies and protection capabilities. Encapsulates having crack, blow-hole or porous microstructures resulted from the use of high-viscosity encapsulants and inappropriate solidification conditions exhibit the lowest encapsulation efficiencies and poorest protection capabilities. Compact microstructures and structures formed between ionic biopolymers could be used to regulate the release of encapsulated cores.

Chol-Dex nanomicelles: Synthesis, characterization and evaluation as efficient drug carriers for colon targeting

Core-shell structures obtained from amphiphilic molecules on self-assembly in a medium have emerged as an important tool in the area of biomedical sciences. Here, we have synthesized cholesteryl-dextran (Chol-Dex) amphiphiles in sufficiently high yields via conjugation of cholesteryl hemisuccinate to dextran in two different concentrations (5 and 10%). After physicochemical and spectral analysis, the nanomicelles were subjected to size measurements. DLS and TEM confirmed the formation of core-shell type of nanomicelles. Hydrophobic drug-entrapped formulations (Metronidazole and Rifampicin) displayed sustained release behaviour of drugs from them. Sustained release at neutral pH demonstrated usefulness of the non-toxic delivery system for colon specific diseases.

Cationic nanoparticles self-assembled from amphiphilic chitosan derivatives containing poly(amidoamine) dendrons and deoxycholic acid as a vector for co-delivery of doxorubicin and gene

Combination treatment through the co-delivery of drugs and genes by nanoformulations may achieve a synergistic effect. In our previous study, poly(amidoamine) dendronized chitosan derivative (PAMAM-Cs) showed good gene transfection efficiency and low cytotoxicity. Here, we incorporated hydrophobic deoxycholic acid (DCA) onto the chitosan backbone of PAMAM-Cs to obtain an amphiphilic derivative-PAMAM-Cs-DCA, which could self-assemble into cationic nanoparticles (NPs). The resulting NPs with diameters of 140-220 nm can encapsulate the hydrophobic anticancer drug doxorubicin (DOX) in the core while bind pDNA via the positively charged PAMAM shell. PAMAM-Cs-DCA NPs could completely complex with pDNA at a ratio of nitrogen to phosphorous (N/P) low as 1 and the complexes achieved a transfection efficiency up to 74 % at N/P 20. Moreover, low-dose co-delivered DOX could enhance the transgene expression, showing a synergistic effect. These results suggest that PAMAM-Cs-DCA NPs hold great promise to co-deliver chemotherapeutics and nucleic acid drugs.

CC Chemokine Receptor 2-Targeting Copper Nanoparticles for Positron Emission Tomography-Guided Delivery of Gemcitabine for Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with dire prognosis due to aggressive biology, lack of effective tools for diagnosis at an early stage, and limited treatment options. Detection of PDAC using conventional radiographic imaging is limited by the dense, hypovascular stromal component and relatively scarce neoplastic cells within the tumor microenvironment (TME). The CC motif chemokine 2 (CCL2) and its cognate receptor CCR2 (CCL2/CCR2) axis are critical in fostering and maintaining this kind of TME by recruiting immunosuppressive myeloid cells such as the tumor-associated macrophages, thereby presenting an opportunity to exploit this axis for both diagnostic and therapeutic purposes. We engineered CCR2-targeting ultrasmall copper nanoparticles (Cu@CuOx) as nanovehicles not only for targeted positron emission tomography imaging by intrinsic radiolabeling with 64Cu but also for loading and delivery of the chemotherapy drug gemcitabine to PDAC. This 64Cu-radiolabeled nanovehicle allowed sensitive and accurate detection of PDAC malignancy in autochthonous genetically engineered mouse models. The ultrasmall Cu@CuOx showed efficient renal clearance, favorable pharmacokinetics, and minimal in vivo toxicity. Systemic administration of gemcitabine-loaded Cu@CuOx effectively suppressed the progression of PDAC tumors in a syngeneic xenograft mouse model and prolonged survival. These CCR2-targeted ultrasmall nanoparticles offer a promising image-guided therapeutic agent and show great potential for translation.

Challenge to overcome current limitations of cell-penetrating peptides

The penetration of biological membranes is a prime obstacle for the delivery of pharmaceutical drugs. Cell-penetrating peptide (CPP) is an efficient vehicle that can deliver various cargos across the biological membranes. Since the discovery, CPPs have been rigorously studied to unveil the underlying penetrating mechanism as well as to exploit CPPs for various biomedical applications. This review will focus on the various strategies to overcome current limitations regarding stability, selectivity, and efficacy of CPPs.

Direct synthesis of light-emitting triblock copolymers from RAFT polymerization

We introduce a straightforward and clean method to synthesize semiconducting triblockcopolymers (tri-BCPs) using RAFT polymerization.

Synthesis and self-assembly of amphiphilic precision glycomacromolecules

Amphiphilic precision glycomacromolecules (APG) are synthesized using solid-phase synthesis and studied for their self-assembly behavior and as inhibitors of bacterial adhesion.

Polymeric nanoparticles for RNA delivery

As exemplified by recent clinical approval of RNA drugs including the latest COVID-19 mRNA vaccines, RNA therapy has demonstrated great promise as an emerging medicine. Central to the success of RNA therapy is the delivery of RNA molecules into the right cells at the right location. While the clinical success of nanotechnology in RNA therapy has been limited to lipid-based nanoparticles currently, polymers, due to their tunability and robustness, have also evolved as a class of promising material for the delivery of various therapeutics including RNAs. This article overviews different types of polymers used in RNA delivery and the methods for the formulation of polymeric nanoparticles and highlights recent progress of polymeric nanoparticle-based RNA therapy.

Cationic (Co)polymers Based on N-Substituted Polyacrylamides as Carriers of Bio-macromolecules: Polyplexes, Micelleplexes, and Spherical Nucleic Acidlike Structures

Novel N-substituted polyacrylamides bearing a cycle with two tertiary amines, poly(4-methyl-piperazin-1-yl)-propenone (PMPP) and its block copolymers with polylactide (PMPP-b-PLA), are synthesized and characterized. The homopolymers are water-soluble, whereas the block copolymers self-assemble in aqueous solution into a small size (R_h around 30 nm), are narrowly distributed, and exhibit core-shell micelles with good colloidal stability. Both the homopolymers and copolymer micelles are positively charged (ζ-potentials in the 13.8-17.6 mV range), which are employed for formation of electrostatic complexes with oppositely charged DNA. Complexes (polyplexes, micelleplexes, and spherical nucleic acidlike structures) in a wide range of N/P (amino to phosphate groups) ratios are prepared with short (115 bp) and long (2000 bp) DNA. The behavior and physicochemical properties of the resulting nanocarriers of DNA are strongly dependent on the polymer/polymer micelles' characteristics and the DNA chain length. All systems exhibit low cytotoxicity and good cellular uptake ability and show promise for gene delivery and regulation.

Covalent Organic Polymer as a Carborane Carrier for Imaging-Facilitated Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is an atomic targeted radiotherapy that shows fantastic suppression impact on locally intrusive threatening tumors. One key factor for effective BNCT is to aggregate an adequate concentration (>20 ppm) of ¹⁰B in the cytoplasm of the tumor. Carborane-loaded polymer nanoparticles are promising because of their outstanding biocompatibility and plasma steadiness. In this study, a new class of carborane-loaded nanoscale covalent organic polymers (BCOPs) was prepared by a Schiff base condensation reaction, and their solubility was greatly improved in common solvents via alkyl chain engineering and size tailoring. The obtained BCOP-5T was further functionalized by biocompatible 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene-glycol)-2000] (DSPE-PEG, molecular weight 2000) to form stable aqueous-phase nanoparticles with a hydrodynamic diameter of around 100 nm. After chelating with radioactive copper-64, DSPE-BCOP-5T was tracked by positron emission tomography (PET) imaging and showed significant accumulation in the tumor. DSPE-BCOP-5T + neutron radiation showed remarkable tumor suppression in 4T1 tumor-bearing mice (murine breast cancer). No obvious physical tissue damage and abnormal behavior were observed, demonstrating that the boron delivery was successful and tumor-selective. To conclude, this study presents a theranostic COP-based platform with a well-defined composition, good biocompatibility, and satisfactory tumor accumulation, which is promising for PET imaging, drug delivery, and BNCT.

The Therapeutic Efficacy of Dendrimer and Micelle Formulations for Breast Cancer Treatment

Breast cancer is among the most common types of cancer in women and it is the cause of a high rate of mortality globally. The use of anticancer drugs is the standard treatment approach used for this type of cancer. However, most of these drugs are limited by multi-drug resistance, drug toxicity, poor drug bioavailability, low water solubility, poor pharmacokinetics, etc. To overcome multi-drug resistance, combinations of two or more anticancer drugs are used. However, the combination of two or more anticancer drugs produce toxic side effects. Micelles and dendrimers are promising drug delivery systems that can overcome the limitations associated with the currently used anticancer drugs. They have the capability to overcome drug resistance, reduce drug toxicity, improve the drug solubility and bioavailability. Different classes of anticancer drugs have been loaded into micelles and dendrimers, resulting in targeted drug delivery, sustained drug release mechanism, increased cellular uptake, reduced toxic side effects of the loaded drugs with enhanced anticancer activity in vitro and in vivo. This review article reports the biological outcomes of dendrimers and micelles loaded with different known anticancer agents on breast cancer in vitro and in vivo.

Molecular Stereocomplexation for Enhancing the Stability of Nanoparticles Encapsulated in Polymeric Micelles for Magnetic Resonance Imaging

A generalizable approach for improving the stability of polylactide-based (PLA-based) micelles for encapsulating nanoparticles (NPs) is demonstrated, using stereocomplexation between a pair of poly (ethylene glycol)-b-poly(d-lactide)/poly(ethylene glycol)-b-poly(l-lactide) block copolymer blends. Three different superparamagnetic ferrite-based NPs with distinct nanostructures are first prepared by the high-temperature pyrolysis method, including spherical MnFe₂O₄, cubic MnFe₂O₄, and core-shell MnFe₂O₄@Fe₃O₄. The diameters of these NPs are approximately 7-10 nm as revealed by transmission electron microscopy. These hydrophobic NPs can be encapsulated within self-assembled, stereocomplexed PLA (sc-PLA) micelles. All sc-PLA micelle systems loaded with three different NPs exhibit enhanced stability at elevated temperatures (20-60 °C) and with extended storage time (∼96 h) compared with analogous samples without stereocomplex formation, confirmed by dynamic light scattering measurements. The magnetic NP-loaded micelles with mean diameters of approximately 150 nm show both biocompatibility and superparamagnetic property. Under a 1.5 T magnetic field, cubic MnFe₂O₄ (c-MnFe₂O₄)-loaded micelles exhibit an excellent negative contrast enhancement of MR signals (373 mM^-1·s^-1), while core-shell MnFe₂O₄@Fe₃O₄-loaded micelles show a slightly lower signal for MR imaging (275 mM^-1·s^-1). These results suggest the potential of using sc-PLA-based polymer micelles as universal carriers for magnetic resonance imaging contrast agents with improved stability for different applications such as cancer diagnosis.

Miktoarm Star Polymers with Environment-Selective ROS/GSH Responsive Locations: From Modular Synthesis to Tuned Drug Release through Micellar Partial Corona Shedding and/or Core Disassembly

Branched architectures with asymmetric polymeric arms provide an advantageous platform for the construction of tailored nanocarriers for therapeutic interventions. Simple and adaptable synthetic methodologies to amphiphilic miktoarm star polymers have been developed in which spatial location of reactive oxygen species (ROS) and glutathione (GSH) responsive entities is articulated to be on the corona shell surface or inside the core. The design of such architectures is facilitated through versatile building blocks and selected combinations of ring-opening polymerization, Steglich esterification, and alkyne-azide click reactions. Soft nanoparticles from aqueous self-assembly of these stimuli responsive miktoarm stars have low critical micelle concentrations and high drug loading efficiencies. Partial corona shedding upon response to ROS is accompanied by an increase in drug release, without significant changes to overall micelle morphology. The location of the GSH responsive unit at the core leads to micelle disassembly and complete drug release. Curcumin loaded soft nanoparticles show higher efficiencies in preventing ROS generation in extracellular and cellular environments, and in ROS scavenging in human glioblastoma cells. The ease in synthetic elaboration and an understanding of structure-property relationships in stimuli responsive nanoparticles offer a facile venue for well-controlled drug delivery, based on the extra- and intracellular concentrations of ROS and GSH.

Reduction-responsive polymers for drug delivery in cancer therapy-Is there anything new to discover?

Among various types of stimuli-responsive drug delivery systems, reduction-responsive polymers have attracted great interest. In general, these systems have high stability in systemic circulation, however, they can respond quickly to differences in the concentrations of reducing species in specific physiological sites associated with a pathology. This is a particularly relevant strategy to target diseases in which hypoxic regions are present, as polymers which are sensitive to in-situ expressed antioxidant species can, through a local response, release a therapeutic at high concentration in the targeted site, and thus, improve the selectivity and efficacy of the treatment. At the same time, such reduction-responsive materials can also decrease the toxicity and side effects of certain drugs. To date, polymers containing disulfide linkages are the most investigated of the class of reduction-responsive nanocarriers, however, other groups such as selenide and diselenide have also been used for the same purpose. In this review article, we discussed the rationale behind the development of reduction-responsive polymers as drug delivery systems and highlight examples of recent progress. We include the most popular design methods to generate reduction-responsive polymeric carriers and their applications in cancer therapy, and question what areas may still need to be explored in a field with already a very large number of research articles. Finally, we consider the main challenges associated with the clinical translation of these nanocarriers and the future perspectives in this area. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

ROS Responsive Nanoplatform with Two-Photon AIE Imaging for Atherosclerosis Diagnosis and "Two-Pronged" Therapy

Atherosclerosis, characterized by endothelial injury, progressive inflammation, and lipid deposition, can cause cardiovascular diseases. Although conventional anti-inflammatory drugs reveal a certain amount of therapeutic effect, more reasonable design on plaque targeting, local anti-inflammation, and lipid removal are still required for comprehensive atherosclerosis therapy. In this work, a theranostic nanoplatform is developed for atherosclerosis recognition and inhibition. A two-photon aggregation-induced emission (AIE) active fluorophore (TP) developed is linked to β-cyclodextrin (CD) with a ROS responsive bond, which can carry prednisolone (Pred) in its entocoele via supramolecular interaction to build a diagnosis-therapy compound two-photon fluorophore-cyclodextrin/prednisolone complexes (TPCDP). With TPCDP packaged by nanosized micelles based on a ROS sensitive copolymer poly (2-methylthio ethanol methacrylate)-poly (2-methacryloyloxyethyl phosphorylcholine), the TPCDP@PMM can accumulate in atherosclerotic tissue through the damaged vascular endothelium. Activated by the local overexpressed ROS and rich lipid, the micelles are interrupted and TPCDP is further disintegrated with Pred release due to the relatively stronger interaction of lipid with CD, resulting in anti-inflammatory activity and lipid removal for atherosclerosis inhibition. Besides, labeled with the TP, TPCDP@PMM indicates a distinct two-photon AIE imaging on atherosclerosis recognition. The "two-pronged" therapeutic effect and plaque location ability has been confirmed in vivo on ApoE^-/- mice, holding TPCDP@PMM a great promise for atherosclerosis theranostics.

A selective drug delivery system based on phospholipid-type nanobubbles for lung cancer therapy

Aim: To develop a micelle-type nanobubble decorated with fluorescein-5-isothiocyanate-conjugated transferrin, with encapsulation of paclitaxel (PTX@FT-NB) for lung cancer treatment. Materials & methods: PTX@FT-NBs were characterized to determine their physicochemical properties, structural stability and cytotoxicity. Lung cancer cell and mouse xenograft tumor models were used to evaluate the therapeutic effectiveness of PTX@FT-NB. Results: The PTX@FT-NBs not only showed selective targeting to lung cancer cells but also inhibited tumor growth significantly via paclitaxel release. Furthermore, paclitaxel-induced microtubule stabilization demonstrated the release of the drug from PTX@FT-NB in the targeted tumor cell both in vitro and in vivo. Conclusion: PTX@FT-NB has the potential as an anticancer nanocarrier against lung cancer cells because of its specific targeting and better drug delivery capacity.

Evaluation of Cytotoxic Effect of Cholesterol End-Capped Poly(N-Isopropylacrylamide)s on Selected Normal and Neoplastic Cells

Purpose

Efficient intracellular delivery of a therapeutic compound is an important feature of smart drug delivery systems (SDDS). Modification of a carrier structure with a cell-penetrating ligand, ie, cholesterol moiety, is a strategy to improve cellular uptake. Cholesterol end-capped poly(N-isopropylacrylamide)s offer a promising foundation for the design of efficient thermoresponsive drug delivery systems.

Methods

A series of cholesterol end-capped poly(N-isopropylacrylamide)s (PNIPAAm) with number-average molar masses ranging from 3200 to 11000 g·mol^–1 were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization from original xanthate-functionalized cholesterol and self-assembled into micelles. The physicochemical characteristics and cytotoxicity of cholesterol end-capped poly(N-isopropylacrylamide)s have been thoroughly investigated.

Results

Phase transition temperature dependence on the molecular weight and hydrophilic/hydrophobic ratio in the polymers were observed in water. Biological test results showed that the obtained materials, both in disordered and micellar form, are non-hemolytic, highly compatible with fibroblasts, and toxic to glioblastoma cells. It was found that the polymer termini dictates the mode of action of the system.

Conclusion

The cholesteryl moiety acts as a cell-penetrating agent, which enables disruption of the plasma membrane and in effect leads to the restriction of the tumor growth. Cholesterol end-capped PNIPAAm showing in vitro anticancer efficacy can be developed not only as drug carriers but also as components of combined/synergistic therapy.

Interface cisplatin-crosslinked doxorubicin-loaded triblock copolymer micelles for synergistic cancer therapy

Combination chemotherapy is an effective way to improve the therapeutic efficiency in anticancer treatment. Herein, we synthesized a novel amphiphilic triblock copolymer via a two-step ring-opening polymerization (ROP) followed by post-modification. Doxorubicin (DOX) was encapsulated into the copolymeric micelles through hydrophobic interactions, cisplatin (CDDP) was employed to in situ crosslink the interface of DOX-loaded micelles through Pt-carboxyl coordination interaction. The CDDP-mediated crosslinking improved the stability of the micelles and also reduced the release of DOX at physiological pH. After being taken up into the endosome/lysosome, the low environmental pH weakened the Pt-carboxyl coordination interactions, resulting in the destruction of the micelles and the release of CDDP and DOX. Moreover, these micelles loaded with dual drugs enabled a synergistic anticancer effect, showing promise as a potential drug delivery platform for cancer therapy.

Development and evaluation of polymeric micelle containing tablet formulation for poorly water-soluble drug: tamoxifen citrate

Poor aqueous solubility is one of the key reasons for slow dissolution rate and poor intestinal absorption and finally that causes low therapeutic efficacy of many existing drugs. Tamoxifen citrate (TMX) (BCS Class II drug) with low water solubility has poor oral bioavailability in the range of 20%-30%, therefore, high doses are required for treatment with TMX. Self-assemblage of amphiphilic polymers leads to the formation of polymeric micelles which makes them unique nano-carriers with excellent biocompatibility, low toxicity, enhanced blood circulation time, and solubilization of poorly water-soluble drugs. In this study poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) triblock copolymer, which has been approved by FDA for oral application was used to benefit its micellar solubilization effect. Self-assembled micelles were prepared for the delivery of TMX and this way TMX solubility was increased approximately 60 times. TMX-treated cells showed 38.06 ± 1.5% viability at 50 µM concentration for 24 h; 66.71 ± 11.6% viability at 25 µM concentration for 48 h, at the same conditions TMX-loaded micelles exhibited 24.994 ± 0.25% and 43.36 ± 4.37% cell viability, respectively (p < 0.05). These results showed that the encapsulation of TMX into PEG-PPG-PEG micelles facilitated the cellular uptake, which led to an increased cytotoxicity in MCF-7 cancer cells. Tablet formulation containing lyophilized TMX-loaded micelles was showed an improved dissolution than commercial TMX tablet (Tamoxifen^® TEVA). It can be reasonably expected that the obtained drug dissolution rate and increased cytotoxicity to tumor cells will result in an increase of TMX bioavailability and tolerability associated with an important dose reduction and decreased side effects.

Combination Therapy with Doxorubicin-Loaded Reduced Albumin Nanoparticles and Focused Ultrasound in Mouse Breast Cancer Xenografts

Because chemotherapeutic drugs are often associated with serious side effects, the central topic in modern drug delivery is maximizing the localization of drugs at the target while minimizing non-specific drug interactions at unwanted regions. To address this issue, biocompatible nanoparticles have been developed to enhance the drug half-life while minimizing the associated toxicity. Nevertheless, relying solely on the enhanced half-life and enhanced permeability and retention (EPR) effects has been ineffective, and designing stimulus-sensitive nanoparticles to introduce the precise control of drug release has been desired. In this paper, we introduce a pH-sensitive, reduced albumin nanoparticle in combination with focused ultrasound treatment. Not only did these nanoparticles have superior therapeutic efficacy and toxicity profiles when compared to the free drugs in xenograft mouse models, but we were also able to show that the albumin nanoparticles reported in this paper were more suitable than other types of non-reduced albumin nanoparticles as vehicles for drug delivery. As such, we believe that the albumin nanoparticles presented in this paper with desirable characteristics including the induction of strong anti-tumor response, precise control, and superior safety profiles hold strong potential for preclinical and clinical anticancer therapy.

Polymer Capsules with Hydrophobic Liquid Cores as Functional Nanocarriers

Recent developments in the fabrication of core-shell polymer nanocapsules, as well as their current and future applications, are reported here. Special attention is paid to the newly introduced surfactant-free fabrication method of aqueous dispersions of nanocapsules with hydrophobic liquid cores stabilized by amphiphilic copolymers. Various approaches to the efficient stabilization of such vehicles, tailoring their cores and shells for the fabrication of multifunctional, navigable nanocarriers and/or nanoreactors useful in various fields, are discussed. The emphasis is placed on biomedical applications of polymer nanocapsules, including the delivery of poorly soluble active compounds and contrast agents, as well as their use as theranostic platforms. Other methods of fabrication of polymer-based nanocapsules are briefly presented and compared in the context of their biomedical applications.

Miktoarm Star Polymers: Branched Architectures in Drug Delivery

Delivering active pharmaceutical agents to disease sites using soft polymeric nanoparticles continues to be a topical area of research. It is becoming increasingly evident that the composition of amphiphilic macromolecules plays a significant role in developing efficient nanoformulations. Branched architectures with asymmetric polymeric arms emanating from a central core junction have provided a pivotal venue to tailor their key parameters. The build-up of miktoarm stars offers vast polymer arm tunability, aiding in the development of macromolecules with adjustable properties, and allows facile inclusion of endogenous stimulus-responsive entities. Miktoarm star-based micelles have been demonstrated to exhibit denser coronae, very low critical micelle concentrations, high drug loading contents, and sustained drug release profiles. With significant advances in chemical methodologies, synthetic articulation of miktoarm polymer architecture, and determination of their structure-property relationships, are now becoming streamlined. This is helping advance their implementation into formulating efficient therapeutic interventions. This review brings into focus the important discoveries in the syntheses of miktoarm stars of varied compositions, their aqueous self-assembly, and contributions their formulations are making in advancing the field of drug delivery.

Micelles of Progesterone for Topical Eye Administration: Interspecies and Intertissues Differences in Ex Vivo Ocular Permeability

Progesterone (PG) may provide protection to the retina during retinitis pigmentosa, but its topical ocular supply is hampered by PG poor aqueous solubility and low ocular bioavailability. The development of efficient topical ocular forms must face up to two relevant challenges: Protective barriers of the eyes and lack of validated ex vivo tests to predict drug permeability. The aims of this study were: (i) To design micelles using Pluronic F68 and Soluplus copolymers to overcome PG solubility and permeability; and (ii) to compare drug diffusion through the cornea and sclera of three animal species (rabbit, porcine, and bovine) to investigate interspecies differences. Micelles of Pluronic F68 (3–4 nm) and Soluplus (52–59 nm) increased PG solubility by one and two orders of magnitude, respectively and exhibited nearly a 100% encapsulation efficiency. Soluplus systems showed in situ gelling capability in contrast to the low viscosity Pluronic F68 micelles. The formulations successfully passed the hen’s egg-chorioallantoic membrane test (HET-CAM) test. PG penetration through rabbit cornea and sclera was faster than through porcine or bovine cornea, although the differences were also formulation-dependent. Porcine tissues showed intermediate permeability between rabbit and bovine. Soluplus micelles allowed greater PG accumulation in cornea and sclera whereas Pluronic F68 promoted a faster penetration of lower PG doses.

Acid-sensitive PEGylated paclitaxel prodrug nanoparticles for cancer therapy: Effect of PEG length on antitumor efficacy

Paclitaxel is one of the most widely used anticancer agents, but strong side effects and low bioavailability limit its clinical efficacy. The use of tumor microenvironment-responsive prodrugs is promising to solve these problems, and a smart linkage is crucial to achieve the efficient release of paclitaxel from such prodrugs in tumor. Herein, an acid-responsive acetone-based acyclic ketal linkage is used to construct paclitaxel prodrugs with different length of poly(ethylene glycol) (PEG). The PEGylated acetone-based acyclic-ketal-linked prodrugs of paclitaxel (PKPs) self-assembled into nanoparticles that were stable in normal physiological environment but released paclitaxel rapidly in mildly acidic environment in tumor. The length of PEG had considerable impact on size and critical micelle concentration of PKP nanoparticles, thereby affecting prodrug hydrolysis kinetics, pharmacokinetics, biodistribution, and antitumor activity for PKP nanoparticles. In an A2780 xenograft mouse model, PKP nanoparticles displayed improved pharmacokinetics and superior antitumor efficacy against Taxol. Our results demonstrate that acyclic-ketal-based prodrugs are useful for the development of acid-responsive anticancer nanomedicines.

Lipid-oligonucleotide conjugates for bioapplications

Lipid-oligonucleotide conjugates (LONs) are powerful molecular-engineering materials for various applications ranging from biosensors to biomedicine. Their unique amphiphilic structures enable the self-assembly and the conveyance of information with high fidelity. In particular, LONs present remarkable potential in measuring cellular mechanical forces and monitoring cell behaviors. LONs are also essential sensing tools for intracellular imaging and have been employed in developing cell-surface-anchored DNA nanostructures for biomimetic-engineering studies. When incorporating therapeutic oligonucleotides or small-molecule drugs, LONs hold promise for targeted therapy. Moreover, LONs mediate the controllable assembly and fusion of vesicles based on DNA-strand displacements, contributing to nanoreactor construction and macromolecule delivery. In this review, we will summarize the general synthesis strategies of LONs, provide some characterization analysis and emphasize recent advances in bioanalytical and biomedical applications. We will also consider the relevant challenges and suggest future directions for building better functional LONs in nanotechnology and materials-science applications.

Towards Robust Delivery of Antimicrobial Peptides to Combat Bacterial Resistance

Antimicrobial peptides (AMPs), otherwise known as host defence peptides (HDPs), are naturally occurring biomolecules expressed by a large array of species across the phylogenetic kingdoms. They have great potential to combat microbial infections by directly killing or inhibiting bacterial activity and/or by modulating the immune response of the host. Due to their multimodal properties, broad spectrum activity, and minimal resistance generation, these peptides have emerged as a promising response to the rapidly concerning problem of multidrug resistance (MDR). However, their therapeutic efficacy is limited by a number of factors, including rapid degradation, systemic toxicity, and low bioavailability. As such, many strategies have been developed to mitigate these limitations, such as peptide modification and delivery vehicle conjugation/encapsulation. Oftentimes, however, particularly in the case of the latter, this can hinder the activity of the parent AMP. Here, we review current delivery strategies used for AMP formulation, focusing on methodologies utilized for targeted infection site release of AMPs. This specificity unites the improved biocompatibility of the delivery vehicle with the unhindered activity of the free AMP, providing a promising means to effectively translate AMP therapy into clinical practice.

Photosensitive Supramolecular Micelle-Mediated Cellular Uptake of Anticancer Drugs Enhances the Efficiency of Chemotherapy

The development of stimuli-responsive supramolecular micelles with high drug-loading contents that specifically induce significant levels of apoptosis in cancer cells remains challenging. Herein, we report photosensitive uracil-functionalized supramolecular micelles that spontaneously form via self-assembly in aqueous solution, exhibit sensitive photo-responsive behavior, and effectively encapsulate anticancer drugs at high drug-loading contents. Cellular uptake analysis and double-staining flow cytometric assays confirmed the presence of photo-dimerized uracil groups within the irradiated micelles remarkably enhanced endocytic uptake of the micelles by cancer cells and subsequently led to higher levels of apoptotic cell death, and thus improved the therapeutic effect in vitro. Thus, photo-dimerized uracil-functionalized supramolecular micelles may potentially represent an intelligent nanovehicle to improve the safety, efficacy, and applicability of cancer chemotherapy, and could also enable the development of nucleobase-based supramolecular micelles for multifunctional biomaterials and novel biomedical applications.

Designer Nanoparticles as Robust Superlubrication Vectors

Phosphatidylcholine lipid bilayers or liposomes at interfaces in aqueous environments can provide extremely efficient lubrication. This is attributed to the hydration lubrication mechanism acting at the highly hydrated phosphocholine-headgroup layers exposed at the outer surface of each bilayer. Micelles exposing such phosphocholine groups could be an attractive alternative to liposomes due to their much easier preparation and structure control, but all studies to date of surfactant micelles have revealed that at relatively low normal stresses the surface layers rupture and friction increases abruptly. Here, we examine surface interactions between three kinds of phosphocholine-exposing micelles with different designed structures: single-tail surfactant micelles, homo-oligomeric micelles, and block copolymer micelles. Normal and shear forces between mica surfaces immersed in solutions of these micelles were measured using a surface force balance. The adsorbed layers on the mica were imaged using atomic force microscope, revealing surface structures ranging from wormlike to spherical micelles. The block copolymer micelles showed relatively low coverage arising from their stabilizing corona and consequently poor lubrication (μ ∼ 10-1). In contrast, the surfactant and homo-oligomeric micelles fully covered the mica surface and demonstrated excellent lubrication (μ ∼ O(10-3)). However, while the boundary layer of single-tailed surfactant micelles degraded under moderate pressure, the homo-oligomeric micellar boundary layer was robust at all applied contact pressures in our study (up to about 5 MPa). We attribute the difference to the much greater energy required to remove a homo-oligomeric molecule from its micelle, resulting in far greater stability under pressure and shear.

Development and evaluation of TPGS/PVA-based nanosuspension for enhancing dissolution and oral bioavailability of ticagrelor

In this study, we developed ticagrelor-dispersed nanosuspension (TCG-NSP) to enhance the dissolution and oral bioavailability of ticagrelor (TCG) through a statistical design approach. TCG, a reversible P2Y₁₂ receptor antagonist, is classified as a biopharmaceutics classification system (BCS) class IV drug with low solubility and permeability, resulting in low oral bioavailability. Nanosuspension (NSP) is an efficient pharmaceutical technique for overcoming the disadvantages. First, we optimized TCG-NSP consisting of D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) and polyvinyl alcohol (PVA), which exhibited homogeneously dispersed TCG particle (233 nm) and low precipitation (3%). Characterization studies demonstrated that TCG-NSP provided amorphous TCG particles and supersaturation effect, resulting in higher dissolution than a commercial product. In addition, everted gut sac and pharmacokinetic studies confirmed that TCG-NSP improved the gastrointestinal permeation of TCG by 2.8-fold compared to commercial product, thereby enhancing the oral bioavailability (2.2-fold). These results suggested that TCG-NSP could be successfully used as an efficient pharmaceutical formulation to achieve the enhanced dissolution and oral bioavailability of TCG.

Nanomedicines for the delivery of glucocorticoids and nucleic acids as potential alternatives in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects 0.5-1% of the world population. Current treatments include on one hand non-steroidal anti-inflammatory drugs and glucocorticoids (GCs) for treating pain and on the other hand disease-modifying anti-rheumatic drugs such as methotrexate, Janus kinase inhibitors or biologics such as antibodies targeting mainly cytokine expression. More recently, nucleic acids such as siRNA, miRNA, or anti-miRNA have shown strong potentialities for the treatment of RA. This review discusses the way nanomedicines can target GCs and nucleic acids to inflammatory sites, increase drug penetration within inflammatory cells, achieve better subcellular distribution and finally protect drugs against degradation. For GCs such a targeting effect would allow the treatment to be more effective at lower doses and to reduce the administration frequency as well as to induce much fewer side-effects. In the case of nucleic acids, particularly siRNA, knocking down proteins involved in RA, could importantly be facilitated using nanomedicines. Finally, the combination of both siRNA and GCs in the same carrier allowed for the same cell to target both the GCs receptor as well as any other signaling pathway involved in RA. Nanomedicines appear to be very promising for the delivery of conventional and novel drugs in RA therapeutics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

A Novel pH-Tunable Secondary Conformation Containing Mixed Micellar System in Anticancer Treatment

In this study, for the first time, we precisely assembled the poly-γ-benzyl-l-glutamate and an amphiphilic copolymer d-α-tocopherol polyethylene glycol succinate into a mixed micellar system for the embedment of the anticancer drug doxorubicin. Importantly, the intracellular drug-releasing behaviors could be controlled by changing the secondary structures of poly-γ-benzyl-l-glutamate via the precise regulation of the buffer’s pH value. Under neutral conditions, the micellar architectures were stabilized by both α-helix secondary structures and the microcrystalline structures. Under acidic conditions (pH 4.0), the interior structures transformed into a coil state with a disordered alignment, inducing the release of the loaded drug. A remarkable cytotoxicity of the Dox-loaded mixed micelles was exhibited toward human lung cancer cells in vitro. The internalizing capability into the cancer cells, as well as the intracellular drug-releasing behaviors, were also identified and observed. The secondary structures containing Dox-loaded mixed micelles had an outstanding antitumor efficacy in human lung cancer A549 cells-bearing nude mice, while little toxicities occurred or interfered with the hepatic or renal functions after the treatments. Thus, these pH-tunable α-helix-containing mixed micelles are innovative and promising for controlled intracellular anticancer drug delivery.

Nanomedicine Fight against Antibacterial Resistance: An Overview of the Recent Pharmaceutical Innovations

Based on the recent reports of World Health Organization, increased antibiotic resistance prevalence among bacteria represents the greatest challenge to human health. In addition, the poor solubility, stability, and side effects that lead to inefficiency of the current antibacterial therapy prompted the researchers to explore new innovative strategies to overcome such resilient microbes. Hence, novel antibiotic delivery systems are in high demand. Nanotechnology has attracted considerable interest due to their favored physicochemical properties, drug targeting efficiency, enhanced uptake, and biodistribution. The present review focuses on the recent applications of organic (liposomes, lipid-based nanoparticles, polymeric micelles, and polymeric nanoparticles), and inorganic (silver, silica, magnetic, zinc oxide (ZnO), cobalt, selenium, and cadmium) nanosystems in the domain of antibacterial delivery. We provide a concise description of the characteristics of each system that render it suitable as an antibacterial delivery agent. We also highlight the recent promising innovations used to overcome antibacterial resistance, including the use of lipid polymer nanoparticles, nonlamellar liquid crystalline nanoparticles, anti-microbial oligonucleotides, smart responsive materials, cationic peptides, and natural compounds. We further discuss the applications of antimicrobial photodynamic therapy, combination drug therapy, nano antibiotic strategy, and phage therapy, and their impact on evading antibacterial resistance. Finally, we report on the formulations that made their way towards clinical application.

Nanocarriers as Magic Bullets in the Treatment of Leukemia

Leukemia is a type of hematopoietic stem/progenitor cell malignancy characterized by the accumulation of immature cells in the blood and bone marrow. Treatment strategies mainly rely on the administration of chemotherapeutic agents, which, unfortunately, are known for their high toxicity and side effects. The concept of targeted therapy as magic bullet was introduced by Paul Erlich about 100 years ago, to inspire new therapies able to tackle the disadvantages of chemotherapeutic agents. Currently, nanoparticles are considered viable options in the treatment of different types of cancer, including leukemia. The main advantages associated with the use of these nanocarriers summarized as follows: i) they may be designed to target leukemic cells selectively; ii) they invariably enhance bioavailability and blood circulation half-life; iii) their mode of action is expected to reduce side effects. FDA approval of many nanocarriers for treatment of relapsed or refractory leukemia and the desired results extend their application in clinics. In the present review, different types of nanocarriers, their capability in targeting leukemic cells, and the latest preclinical and clinical data are discussed.