PEG length effect of peptide-functional liposome for blood brain barrier (BBB) penetration and brain targeting

Nanoparticles, in particular PEGylated, show great potential for in vivo brain targeted drug delivery. Nevertheless, how polyethylene glycol (PEG) length of nanoparticles affects their blood brain barrier (BBB) penetration or brain targeting is still unclear. In this study, we investigated the power of PEG chain-lengths (2, 3.4, 5, 10 kDa) in BBB penetration and brain targeting using Angiopep-2 peptide decorated liposomes. We found that PEG chain-length is critical, where the shorter PEG enabled the Angiopep-2 decorated liposomes to display more potent in vitro cell uptake via endocytosis. In contrast, their in vitro BBB penetration via transcytosis was much weaker relative to the liposomes with longer PEG chains, which result from their ineffective BBB exocytosis. Interestingly, the in vivo brain targeting aligns with the in vitro BBB penetration, as the long chain PEG-modified liposomes exerted superior brain accumulation both in normal or orthotropic glioblastoma (GBM) bearing mice, which could be ascribed to the combinational effect of prolonged circulation and enhanced BBB penetration of long chain PEG attached liposomes. These results demonstrate the crucial role of PEG length of nanoparticles for BBB penetration and brain targeting, providing guidance for PEG length selection in the design of nanocarrier for brain diseases treatment.

Structural Optimization of Carboxy-Terminal Phenylalanine-Modified Dendrimers for T-Cell Association and Model Drug Loading

Dendrimers are potent nanocarriers in drug delivery systems because their structure can be precisely controlled. We previously reported that polyamidoamine (PAMAM) dendrimers that were modified with 1,2-cyclohexanedicarboxylic acid (CHex) and phenylalanine (Phe), PAMAM-CHex-Phe, exhibited an effective association with various immune cells, including T-cells. In this study, we synthesized various carboxy-terminal Phe-modified dendrimers with different linkers using phthalic acid and linear dicarboxylic acids to determine the association of these dendrimers with Jurkat cells, a T-cell model. PAMAM-n-hexyl-Phe demonstrated the highest association with Jurkat T-cells. In addition, dendri-graft polylysine (DGL) with CHex and Phe, DGL-CHex-Phe, was synthesized, and its association with Jurkat cells was investigated. The association of DGL-CHex-Phe with T-cells was higher than that of PAMAM-CHex-Phe. However, it was insoluble in water and thus it is unsuitable as a drug carrier. Model drugs, such as protoporphyrin IX and paclitaxel, were loaded onto these dendrimers, and the most model drug molecules could be loaded into PAMAM-CHex-Phe. PTX-loaded PAMAM-CHex-Phe exhibited cytotoxicity against Jurkat cells at a similar level to free PTX. These results suggest that PAMAM-CHex-Phe exhibited both efficient T-cell association and drug loading properties.

T Cell-Association of Carboxy-Terminal Dendrimers with Different Bound Numbers of Phenylalanine and Their Application to Drug Delivery

T cells play important roles in various immune reactions, and their activation is necessary for cancer immunotherapy. Previously, we showed that polyamidoamine (PAMAM) dendrimers modified with 1,2-cyclohexanedicarboxylic acid (CHex) and phenylalanine (Phe) underwent effective uptake by various immune cells, including T cells and their subsets. In this study, we synthesized various carboxy-terminal dendrimers modified with different bound numbers of Phe and investigated the association of these dendrimers with T cells to evaluate the influence of terminal Phe density. Carboxy-terminal dendrimers conjugating Phe at more than half of the termini exhibited a higher association with T cells and other immune cells. The carboxy-terminal Phe-modified dendrimers at 75% Phe density tended to exhibit the highest association with T cells and other immune cells, which was related to their association with liposomes. A model drug, protoporphyrin IX (PpIX), was encapsulated into carboxy-terminal Phe-modified dendrimers, which were then used for drug delivery into T cells. Our results suggest the carboxy-terminal Phe-modified dendrimers are useful for delivery into T cells.

Poly (β amino esters) copolymers: Novel potential vectors for delivery of genes and related therapeutics

The unique properties of polymers have performed an essential contribution to the drug delivery system by providing an outstanding platform for the delivery of macromolecules and genes. However, the block copolymers have been the subject of many recently published works whose results have demonstrated excellent performance in drug targeting. Poly(β-amino esters) (PβAEs) copolymers are the synthetic cationic polymers that are tailored by chemically joining PβAEs with other additives to demonstrate extraordinary efficiency in designing pre-defined and pre-programmed nanostructures, site-specific delivery, andovercoming the distinct cellular barriers. Different compositional and structural libraries could be generated by combinatorial chemistry and by the addition of various novel functional additives that fulfill the multiple requirements of targeted delivery. These intriguing attributes allow PβAE-copolymers to have customized therapeutic functions such as excellent encapsulation capacity, high stability, and stimuli-responsive release. Here, we give an overview of PβAE copolymers-based formulations along with focusing on most notable improvements such as structural modifications, bio-conjugations, and stimuli-responsive approaches, for safe and effective nucleic acids delivery.

Artificial cell membrane camouflaged immunomagnetic nanoparticles for enhanced circulating tumor cells isolation

Precise and specific circulating tumor cells (CTCs) isolation is heavily interfered by blood cells and proteins. Though satisfactory results have been achieved by some cell membrane-derived platforms, following limitations have...

Protein Removal from Hydrogels through Repetitive Surface Degradation

Suppression of protein adsorption is a necessary property for materials used in the living body. In this study, thermoresponsive and degradable hydrogels were prepared by the radical polymerization of 2-methylene-1,3-dioxepane, 2-hydroxyethyl acrylate (HEA), and poly(ethylene glycol) monomethacrylate (PEGMA). The prepared hydrogels re-exposed PEG-grafted chains to the interface through surface degradation, which was confirmed by the maintenance of the chemical composition of the hydrogel surfaces after hydrolysis. Notably, adsorbed proteins can be removed from the hydrogel surfaces through hydrogel surface degradation at least thrice.

Quantifying the effect of PEG architecture on nanoparticle ligand availability using DNA-PAINT

The importance of PEG architecture on nanoparticle (NP) functionality is known but still difficult to investigate, especially at a single particle level. Here, we apply DNA Point Accumulation for Imaging in Nanoscale Topography (DNA-PAINT), a super-resolution microscopy (SRM) technique, to study the surface functionality in poly(lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) NPs with different PEG structures. We demonstrated how the length of the PEG spacer can influence the accessibility of surface chemical functionality, highlighting the importance of SRM techniques to support the rational design of functionalized NPs.

Chemo-physical Strategies to Advance the in Vivo Functionality of Targeted Nanomedicine: The Next Generation

The past few decades have witnessed an evolution of nanomedicine from biologically inert entities to more smart systems, aimed at advancing in vivo functionality. However, we should recognize that most systems still rely on reasonable explanation-including some over-explanation-rather than definitive evidence, which is a watershed radically determining the speed and extent of advancing nanomedicine. Probing nano-bio interactions and desirable functionality at the tissue, cellular, and molecular levels is most frequently overlooked. Progress toward answering these questions will provide instructive insight guiding more effective chemo-physical strategies. Thus, in the next generation, we argue that much effort should be made to provide definitive evidence for proof-of-mechanism, in lieu of creating many new and complicated systems for similar proof-of-concept.

Ligand-Installed Nanocarriers toward Precision Therapy

Development of drug-delivery systems that selectively target neoplastic cells has been a major goal of nanomedicine. One major strategy for achieving this milestone is to install ligands on the surface of nanocarriers to enhance delivery to target tissues, as well as to enhance internalization of nanocarriers by target cells, which improves accuracy, efficacy, and ultimately enhances patient outcomes. Herein, recent advances regarding the development of ligand-installed nanocarriers are introduced and the effect of their design on biological performance is discussed. Besides academic achievements, progress on ligand-installed nanocarriers in clinical trials is presented, along with the challenges faced by these formulations. Lastly, the future perspectives of ligand-installed nanocarriers are discussed, with particular emphasis on their potential for emerging precision therapies.

Multivalent nanoparticles for personalized theranostics based on tumor receptor distribution behavior

It is acknowledged that the targeting ability of multivalent ligand-modified nanoparticles (MLNs) strongly depends on the ligand spatial presentation determined by ligand valency. However, the receptor overexpression level varies between different types or stages of tumors. Thus, it is essential to explore the influence of ligand valency on the targeting ability of MLNs to tumors with different levels of receptor overexpression. In this study, a dual-acting agent raltitrexed was used as a ligand to target the folate receptor (FR). Different copies of the raltitrexed-modified multivalent dendritic polyethyleneimine ligand cluster PRn (n = 2, 4, and 8) were conjugated onto magnetic nanoparticles to form multivalent magnetic NPs (MMNs) with different valences. The in vitro studies demonstrated that Fe-PR4 was the most effective valency in the treatment of high FR overexpressing KB cells with a decentralized receptor distribution, owing to the fact that Fe-PR2 was negative in statistical rebinding and Fe-PR8 could induce steric hindrance in the limited binding area. Instead, in moderate FR overexpressing HeLa cells with clustered receptor display, the extra ligands on Fe-PR8 would facilitate statistical rebinding more beneficially. Furthermore, in in vivo tumor inhibition and targeted magnetic resonance imaging (MRI) of KB tumors and another moderate FR expressing H22 tumor, similar results were obtained with the cell experiments. Overall, the optimizable treatment effect of Fe-PRn by modulating the ligand valency based on the overexpressing tumor receptor distribution behavior supports the potential of Fe-PRn as a nanomedicine for personalized theranostics.

Screening of pH-responsive long-circulating polysaccharide–drug conjugate nanocarriers for antitumor applications

Schematic illustration of the development of long-circulating pH-responsive polysaccharide–DOX prodrug nanoparticles for antitumor applications.

A study of polyethylene glycol backfilling for enhancing target recognition using QCM-D and DPI

Polyethylene glycol (PEG) is a promising candidate for protein resistance and preserving protein function in biomedical applications. In this study, a PEG-based bifunctional platform with antifouling for plasma proteins and high sensitivity for biomolecules was designed. Long PEG chains (PEG₂₄) were used to install functional biomolecules, and short PEG chains (PEG₄) served as a protective layer to backfill the surface and suppress nonspecific protein adsorption. Quartz crystal microbalance with dissipation (QCM-D) and dual polarization interferometry (DPI) were combined to investigate the dynamic process of PEG₄ backfilling and the recognition capacity of biomolecules with different ratios of PEG₄ and PEG₂₄ in real time. The amount of PEG₄ chain backfilling affected the flexibility of PEG₂₄ and exposed sites. The recognition capacity was improved by increasing the ratios of PEG₄ to PEG₂₄. Therefore, when the feeding ratio of PEG₄ to PEG₂₄ was 9 : 1, a highly efficient and sensitive platform was constructed for immobilization of antibodies and recognition of antigens either in pure PBS or in a complex biological environment.

Fine tuning neuronal targeting of nanoparticles by adjusting the ligand grafting density and combining PEG spacers of different length

Poly(ethylene glycol) (PEG) has been extensively used to coat the surface of nanocarriers to improve their physicochemical properties and allow the grafting of targeting moieties. Still, to date there is no common agreement on the ideal PEG coverage-density or length to be used for optimum vector performance. In this study, we aimed to investigate the impact of both PEG density and length on the vectoring capacity of neuron-targeted gene-carrying trimethyl chitosan nanoparticles. The non-toxic fragment from the tetanus toxin (HC) was coupled to a 5 kDa heterobifunctional PEG (HC-PEG_5k) reactive for the thiol groups inserted into the polymer backbone and grafted at different densities onto the nanoparticles. Internalization and transfection studies on neuronal versus non-neuronal cell lines allowed to determine the PEG density of 2 mol% of PEG chains per mol of primary amine groups as the one with superior biological performance. To enhance HC exposure and maximize cell-nanoparticle specific interaction, NPs containing different ratios of HC-PEG_5k and 2 kDa methoxy-PEG at the same grafting density were produced. By intercalating HC-PEG_5k with methoxy-PEG_2k we attained the best performance in terms of internalization (higher payload delivery into cells) and transfection efficiency, using twice lower amount of HC. This outcome highlights the need for fine-tuning of PEG-modified nanoparticles towards the achievement of optimal targeting.

STATEMENT OF SIGNIFICANCE

The amount and exposure of targeting moieties at a nanoparticle surface are critical parameters regarding the targeting potential of nanosized delivery vectors. However, to date, few studies have considered fundamental aspects impacting the ligand-receptor pair interaction, such as the effect of spacer chain length, flexibility or conformation. By optimizing the PEG spacer density and chain length grafted into nanoparticles, we were able to establish the formulation that maximizes cell-nanoparticle specific interaction and has superior biological performance. Our work shows that the precise adjustment of the PEG coverage-density presents a significant impact on the selectivity and bioactivity of the developed formulation, emphasizing the need for the fine-tuning of PEG-modified nanoparticles for the successful development of the next-generation nanomedicines.

Block Copolymer Micelles in Nanomedicine Applications

Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. This Review focuses on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs, proteins, or nucleic acids as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are described in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing on the chemistry and engineering of the block copolymers. By shaping these features, polymeric micelles have been propitious for delivering a wide range of therapeutics through effective sensing of targets in the body and adjustment of their properties in response to particular stimuli, modulating the activity of the loaded drugs at the targeted sites, even at the subcellular level. Finally, the future perspectives and imminent challenges for polymeric micelles as nanomedicines are discussed, anticipating to spur further innovations.

Membrane proteins significantly restrict exosome mobility

Exosomes are membrane nanovesicles implicated in cell-to-cell signaling in which they transfer their molecular cargo from the parent to the recipient cells. This role essentially depends on the exosomes' small size, which is the prerequisite for their rapid migration through the crowded extracellular matrix and into and out of circulation. Here we report much lower exosome mobility than expected from the size of their vesicles, implicate membrane proteins in a substantially impeded rate of migration, and suggest an approach to quantifying the impact. The broadly distributed excess hydrodynamic resistance provided by surface proteins produces a highly heterogeneous and microenvironment-dependent hindrance to exosome mobility. The implications of the findings on exosome-mediated signaling are discussed.

Atomic-level characterization and cilostazol affinity of poly(lactic acid) nanoparticles conjugated with differentially charged hydrophilic molecules

Nanotherapeutics is a promising field for numerous diseases and represents the forefront of modern medicine. In the present work, full atomistic computer simulations were applied to study poly(lactic acid) (PLA) nanoparticles conjugated with polyethylene glycol (PEG). The formation of this complex system was simulated using the reactive polarizable force field (ReaxFF). A full picture of the morphology, charge and functional group distribution is given. We found that all terminal groups (carboxylic acid, methoxy and amino) are randomly distributed at the surface of the nanoparticles. The surface design of NPs requires that the charged groups must surround the surface region for an optimal functionalization/charge distribution, which is a key factor in determining physicochemical interactions with different biological molecules inside the organism. Another important point that was investigated was the encapsulation of drugs in these nanocarriers and the prediction of the polymer-drug interactions, which provided a better insight into structural features that could affect the effectiveness of drug loading. We employed blind docking to predict NP-drug affinity testing on an antiaggregant compound, cilostazol. The results suggest that the combination of molecular dynamics ReaxFF simulations and blind docking techniques can be used as an explorative tool prior to experiments, which is useful for rational design of new drug delivery systems.

Sugared biomaterial binding lectins: achievements and perspectives

Lectins, a distinct group of glycan-binding proteins, play a prominent role in the immune system ranging from pathogen recognition and tuning of inflammation to cell adhesion or cellular signalling. The possibilities of their detailed study expanded along with the rapid development of biomaterials in the last decade. The immense knowledge of all aspects of glycan-lectin interactions both in vitro and in vivo may be efficiently used in bioimaging, targeted drug delivery, diagnostic and analytic biological methods. Practically applicable examples comprise photoluminescence and optical biosensors, ingenious three-dimensional carbohydrate microarrays for high-throughput screening, matrices for magnetic resonance imaging, targeted hyperthermal treatment of cancer tissues, selective inhibitors of bacterial toxins and pathogen-recognising lectin receptors, and many others. This review aims to present an up-to-date systematic overview of glycan-decorated biomaterials promising for interactions with lectins, especially those applicable in biology, biotechnology or medicine. The lectins of interest include galectin-1, -3 and -7 participating in tumour progression, bacterial lectins from Pseudomonas aeruginosa (PA-IL), E. coli (Fim-H) and Clostridium botulinum (HA33) or DC-SIGN, receptors of macrophages and dendritic cells. The spectrum of lectin-binding biomaterials covered herein ranges from glycosylated organic structures, calixarene and fullerene cores over glycopeptides and glycoproteins, functionalised carbohydrate scaffolds of cyclodextrin or chitin to self-assembling glycopolymer clusters, gels, micelles and liposomes. Glyconanoparticles, glycan arrays, and other biomaterials with a solid core are described in detail, including inorganic matrices like hydroxyapatite or stainless steel for bioimplants.

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non-invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state-of-the-art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half-life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio-nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi-modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.

Cancer Nanomedicines Stabilized by π-π Stacking between Heterodimeric Prodrugs Enable Exceptionally High Drug Loading Capacity and Safer Delivery of Drug Combinations

Combination therapy using distinct mode-of-action drugs has sparked a rapidly growing interest because this paradigm holds promise for improving the therapeutic efficacy of anticancer therapy. However, the current drug combination therapy refers to administering individual drugs together, which is far from a perfect regimen for cancer patients. The aim of this work was to demonstrate that synergistic delivery of two chemotherapeutic drugs in a single nanoparticle reservoir could be achieved through the rational chemical ligation of the drugs followed by supramolecular nano-assembly via blending of the drugs with a minimal amount of matrix. Choosing 7-ethyl-10-hydroxycamptothecin and taxanes, which are rich in aromatic structures, as model compounds, we show that the heterodimeric conjugates of the two agents are miscible with lipids to form systemically injectable nanomedicines. The compatibility between the prodrug conjugates and lipid carriers is substantially augmented by the intermolecular π-π stacking and alleviated polarity, thus enabling an exceptionally high drug loading (DL) capacity (~92%) and a gratifyingly long drug retention time within the micellar core. We further observed superior therapeutic outcomes in a mouse tumor model without detecting accompanying systemic toxicity. This structure-based, self-assembled cancer nanomedicine increased the potency and drug tolerability in animals and thus offers a robust strategy for simultaneously formulating two or more drugs in single nanovehicles.

Shedding PEG Palisade by Temporal Photostimulation and Intracellular Reducing Milieu for Facilitated Intracellular Trafficking and DNA Release

The dilemma of poly(ethylene glycol) surface modification (PEGylation) inspired us to develop an intracellularly sheddable PEG palisade for synthetic delivery systems. Here, we attempted to conjugate PEG to polyethylenimine (PEI) through tandem linkages of disulfide-bridge susceptible to cytoplasmic reduction and an azobenzene/cyclodextrin inclusion complex responsive to external photoirradiation. The subsequent investigations revealed that facile PEG detachment could be achieved in endosomes upon photoirradiation, consequently engendering exposure of membrane-disruptive PEI for facilitated endosome escape. The liberated formulation in the cytosol was further subjected to complete PEG detachment relying on disulfide cleavage in the reductive cytosol, thus accelerating dissociation of electrostatically assembled PEI/DNA polyplex to release DNA by means of polyion exchange reaction with intracellularly charged species, ultimately contributing to efficient gene expression.

Non-conjugated polyurethane polymer dots based on crosslink enhanced emission (CEE) and application in Fe3+ sensing

A novel non-conjugated polymer dot sensor is developed for Fe³⁺ detection based on crosslink enhanced emission.