Regulating the surface poly(ethylene glycol) density of polymeric nanoparticles and evaluating its role in drug delivery in vivo

Fluorine-modified polymers reduce the adsorption of immune-reactive proteins to PEGylated gold nanoparticles

Aim: To investigate the influence of fluorine in reducing the adsorption of immune-reactive proteins onto PEGylated gold nanoparticles. Methods: Reversible addition fragmentation chain transfer polymerization, the Turkevich method and ligand exchange were used to prepare polymer-coated gold nanoparticles. Subsequent in vitro physicochemical and biological characterizations and proteomic analysis were performed. Results: Fluorine-modified polymers reduced the adsorption of complement and other immune-reactive proteins while potentially improving circulatory times and modulating liver toxicity by reducing apolipoprotein E adsorption. Fluorine actively discouraged phagocytosis while encouraging the adsorption of therapeutic targets, CD209 and signaling molecule calreticulin. Conclusion: This study suggests that the addition of fluorine in the surface coating of nanoparticles could lead to improved performance in nanomedicine designed for the intravenous delivery of cargos.

Nanoparticle-mediated blockade of CXCL12/CXCR4 signaling enhances glioblastoma immunotherapy: Monitoring early responses with MRI radiomics

The limited therapeutic efficacy of checkpoint blockade immunotherapy against glioblastoma is closely related to the blood-brain barrier (BBB) and tumor immunosuppressive microenvironment, where the latter is driven primarily by tumor-associated myeloid cells (TAMCs). Targeting the C-X-C motif chemokine ligand-12/C-X-C motif chemokine receptor-4 (CXCL12/CXCR4) signaling orchestrates the recruitment of TAMCs and has emerged as a promising approach for alleviating immunosuppression. Herein, we developed an iRGD ligand-modified polymeric nanoplatform for the co-delivery of CXCR4 antagonist AMD3100 and the small-molecule immune checkpoint inhibitor BMS-1. The iRGD peptide facilitated superior BBB crossing and tumor-targeting abilities both in vitro and in vivo. In mice bearing orthotopic GL261-Luc tumor, co-administration of AMD3100 and BMS-1 significantly inhibited tumor proliferation without adverse effects. A reprogramming of immunosuppression upon CXCL12/CXCR4 signaling blockade was observed, characterized by the reduction of TAMCs and regulatory T cells, and an increased proportion of CD8+T lymphocytes. The elevation of interferon-γ secreted from activated immune cells upregulated PD-L1 expression in tumor cells, highlighting the synergistic effect of BMS-1 in counteracting the PD-1/PD-L1 pathway. Finally, our research unveiled the ability of MRI radiomics to reveal early changes in the tumor immune microenvironment following immunotherapy, offering a powerful tool for monitoring treatment responses. STATEMENT OF SIGNIFICANCE: The insufficient BBB penetration and immunosuppressive tumor microenvironment greatly diminish the efficacy of immunotherapy for glioblastoma (GBM). In this study, we prepared iRGD-modified polymeric nanoparticles, loaded with a CXCR4 antagonist (AMD3100) and a small-molecule checkpoint inhibitor of PD-L1 (BMS-1) to overcome physical barriers and reprogram the immunosuppressive microenvironment in orthotopic GBM models. In this nanoplatform, AMD3100 converted the "cold" immune microenvironment into a "hot" one, while BMS-1 synergistically counteracted PD-L1 inhibition, enhancing GBM immunotherapy. Our findings underscore the potential of dual-blockade of CXCL12/CXCR4 and PD-1/PD-L1 pathways as a complementary approach to maximize therapeutic efficacy for GBM. Moreover, our study revealed that MRI radiomics provided a clinically translatable means to assess immunotherapeutic efficacy.

Nanoscale Surface Topography of Polyethylene Glycol-Coated Nanoparticles Composed of Bottlebrush Block Copolymers Prolongs Systemic Circulation and Enhances Tumor Uptake

Improving the performance of nanocarriers remains a major challenge in the clinical translation of nanomedicine. Efforts to optimize nanoparticle formulations typically rely on tuning the surface density and thickness of stealthy polymer coatings, such as poly(ethylene glycol) (PEG). Here, we show that modulating the surface topography of PEGylated nanoparticles using bottlebrush block copolymers (BBCPs) significantly enhances circulation and tumor accumulation, providing an alternative strategy to improve nanoparticle coatings. Specifically, nanoparticles with rough surface topography achieve high tumor cell uptake in vivo due to superior tumor extravasation and distribution compared to conventional smooth-surfaced nanoparticles based on linear block copolymers. Furthermore, surface topography profoundly impacts the interaction with serum proteins, resulting in the adsorption of fundamentally different proteins onto the surface of rough-surfaced nanoparticles formed from BBCPs. We envision that controlling the nanoparticle surface topography of PEGylated nanoparticles will enable the design of improved nanocarriers in various biomedical applications.

Regulating Size and Charge of Liposomes in Microneedles to Enhance Intracellular Drug Delivery Efficiency in Skin for Psoriasis Therapy

The stratum corneum (SC) and cell membrane are two major barriers that hinder the therapeutic outcomes of transdermal drug delivery for the treatment of skin diseases. While microneedles (MNs) can efficiently penetrate the SC to deliver nanomedicines, the optimization of physicochemical properties of nanomedicines in MNs to enhance their in vivo cellular delivery efficiency remains unclear. Here, how the size and surface charge of drug-loaded liposomes in MNs influence the retention time and cellular delivery in psoriatic skin is systematically investigated. The results indicate that while 100 nm negatively-charged liposomes in MNs show higher cellular uptake in vitro, 250 and 450 nm liposomes could enhance skin retention and the long-term in vivo cellular delivery efficiency of drugs. Moreover, 250 nm cationic liposomes with a stronger positive charge show an extraordinarily long skin retention time of 132 h and significantly higher in vivo cellular internalization. In the treatment study, dexamethasone (dex)-loaded cationic liposomes-integrated MNs show better therapeutic outcomes than dex-loaded anionic liposomes-integrated MNs in a psoriasis-like animal model. The design principles of liposomes in MN drug delivery systems explored in the study hold the potential for enhancing the therapeutic outcomes of psoriasis and are instrumental for successful translation.

Polyethylene glycol crosslinked decellularized single liver lobe scaffolds with vascular endothelial growth factor promotes angiogenesis in vivo

BACKGROUND

Improving the mechanical properties and angiogenesis of acellular scaffolds before transplantation is an important challenge facing the development of acellular liver grafts. The present study aimed to evaluate the cytotoxicity and angiogenesis of polyethylene glycol (PEG) crosslinked decellularized single liver lobe scaffolds (DLSs), and establish its suitability as a graft for long-term liver tissue engineering.

METHODS

Using mercaptoacrylate produced by the Michael addition reaction, DLSs were first modified using N-succinimidyl S-acetylthioacetate (SATA), followed by cross-linking with PEG as well as vascular endothelial growth factor (VEGF). The optimal concentration of agents and time of the individual steps were identified in this procedure through biomechanical testing and morphological analysis. Subsequently, human umbilical vein endothelial cells (HUVECs) were seeded on the PEG crosslinked scaffolds to detect the proliferation and viability of cells. The scaffolds were then transplanted into the subcutaneous tissue of Sprague-Dawley rats to evaluate angiogenesis. In addition, the average number of blood vessels was evaluated in the grafts with or without PEG at days 7, 14, and 21 after implantation.

RESULTS

The PEG crosslinked DLS maintained their three-dimensional structure and were more translucent after decellularization than native DLS, which presented a denser and more porous network structure. The results for Young's modulus proved that the mechanical properties of 0.5 PEG crosslinked DLS were the best and close to that of native livers. The PEG-VEGF-DLS could better promote cell proliferation and differentiation of HUVECs compared with the groups without PEG cross-linking. Importantly, the average density of blood vessels was higher in the PEG-VEGF-DLS than that in other groups at days 7, 14, and 21 after implantation in vivo.

CONCLUSIONS

The PEG crosslinked DLS with VEGF could improve the biomechanical properties of native DLS, and most importantly, their lack of cytotoxicity provides a new route to promote the proliferation of cells in vitro and angiogenesis in vivo in liver tissue engineering.

The interplay between PEGylated nanoparticles and blood immune system

During the last two decades, an increasing number of reports have pointed out that the immunogenicity of polyethylene glycol (PEG) may trigger accelerated blood clearance (ABC) and hypersensitivity reaction (HSR) to PEGylated nanoparticles, which could make PEG modification counterproductive. These phenomena would be detrimental to the efficacy of the load and even life-threatening to patients. Consequently, further elucidation of the interplay between PEGylated nanoparticles and the blood immune system will be beneficial to developing and applying related formulations. Many groups have worked to unveil the relevance of structural factors, dosing schedule, and other factors to the ABC phenomenon and hypersensitivity reaction. Interestingly, the results of some reports seem to be difficult to interpret or contradict with other reports. In this review, we summarize the physiological mechanisms of PEG-specific immune response. Moreover, we speculate on the potential relationship between the induction phase and the effectuation phase to explain the divergent results in published reports. In addition, the role of nanoparticle-associated factors is discussed based on the classification of the action phase. This review may help researchers to develop PEGylated nanoparticles to avoid unfavorable immune responses based on the underlying mechanism.

Hydrophilic nanofibers with aligned topography modulate macrophage-mediated host responses via the NLRP3 inflammasome

Successful biomaterial implantation requires appropriate immune responses. Macrophages are key mediators involved in this process. Currently, exploitation of the intrinsic properties of biomaterials to modulate macrophages and immune responses is appealing. In this study, we prepared hydrophilic nanofibers with an aligned topography by incorporating polyethylene glycol and polycaprolactone using axial electrospinning. We investigated the effect of the nanofibers on macrophage behavior and the underlying mechanisms. With the increase of hydrophilicity of aligned nanofibers, the inflammatory gene expression of macrophages adhering to them was downregulated, and M2 polarization was induced. We further presented clear evidence that the inflammasome NOD-like receptor thermal protein domain associated protein 3 (NLRP3) was the cellular sensor by which macrophages sense the biomaterials, and it acted as a regulator of the macrophage-mediated response to foreign bodies and implant integration. In vivo, we showed that the fibers shaped the implant-related immune microenvironment and ameliorated peritendinous adhesions. In conclusion, our study demonstrated that hydrophilic aligned nanofibers exhibited better biocompatibility and immunological properties.

FRET-based analysis on the structural stability of polymeric micelles: Another key attribute beyond PEG coverage and particle size affecting the blood clearance

Various attributes of micelles, such as PEG density and particle size, are considered to be related to blood clearance. The structural stability of micelles is another key attribute that will affect the in vivo fate. This study employed fluorescence resonance energy transfer (FRET) analysis to guide the preparation of polymeric micelles with different structural stability. Micelles prepared using copolymers with longer hydrophobic blocks showed higher structural stability; emulsification was a better method than nanoprecipitation to prepare stable micelles. The fast chain exchange kinetics and the high-water content of micellar cores explained the low structural stability of those micelles. Moreover, this study highlighted the importance of structural stability that affected blood clearance in concert with PEG length and particle size. One-third of the small and stable micelles were detected in the blood 24 h after injection. While unstable micelles would be cleared from the circulation within 4 h. Notably, there would be a threshold of structural stability. Micelles with structural stability below this threshold were quickly cleared even if they possessed a longer PEG length and a smaller size. In contrast, higher structural stability allowed polymeric micelles to maintain higher integrity in vivo and enhance tumor accumulation and anti-tumor efficacy. In conclusion, this study systematically analyzed the importance of the structural stability of micelles on the in vivo fate.

Polymeric core-crosslinked particles prepared via a nanoemulsion-mediated process: from particle design and structural characterization to in vivo behavior in chemotherapy

Various polymeric nanoparticles have been used as drug carriers in drug delivery systems (DDSs). Most of them were constructed from dynamic self-assembly systems formed via hydrophobic interactions and from structures that are unstable in an in vivo environment owing to their relatively weak formation forces. As a solution to this issue, physically stabilized core-crosslinked particles (CP) with chemically crosslinked cores have received attention as alternatives to the dynamic nanoparticles. This focused review summarizes recent advances in the construction, structural characterization, and in vivo behavior of polymeric CPs. First, we introduce a nanoemulsion-mediated method to create polyethylene glycol (PEG)-bearing CPs and their structural characterization. The relationship between the PEG chain conformations in the particle shell and the in vivo fate of the CPs is also discussed. After that, the development and advantages of zwitterionic amino acid-based polymer (ZAP)-bearing CPs are presented to address the poor penetration and the internalization of PEG-based CPs into tumor tissues and cells, respectively. Finally, we conclude and discuss prospects for application of polymeric CPs in the DDS field.

Role of Micelle Size in Cell Transcytosis-Based Tumor Extravasation, Infiltration, and Treatment Efficacy

Transcytosis-based active transport of cancer nanomedicine has shown great promise for enhancing its tumor extravasation and infiltration and antitumor activity, but how the key nanoproperties of nanomedicine, particularly particle size, influence the transcytosis remains unknown. Herein, we used a transcytosis-inducing polymer, poly[2-(N-oxide-N,N-diethylamino)ethyl methacrylate] (OPDEA), and fabricated stable OPDEA-based micelles with different sizes (30, 70, and 140 nm in diameter) from its amphiphilic block copolymer, OPDEA-block-polystyrene (OPDEA-PS). The study of the micelle size effects on cell transcytosis, tumor extravasation, and infiltration showed that the smallest micelles (30 nm) had the fastest transcytosis and, thus, the most efficient tumor extravasation and infiltration. So, the 7-ethyl-10-hydroxyl camptothecin (SN38)-conjugated OPDEA micelles of 30 nm had much enhanced antitumor activity compared with the 140 nm micelles. These results are instructive for the design of active cancer nanomedicine.

Tuning the corona-core ratio of polyplex micelles for selective oligonucleotide delivery to hepatocytes or hepatic immune cells

Targeted delivery of oligonucleotides or small molecular drugs to hepatocytes, the liver's parenchymal cells, is challenging without targeting moiety due to the highly efficient mononuclear phagocyte system (MPS) of the liver. The MPS comprises Kupffer cells and specialized sinusoidal endothelial cells, efficiently clearing nanocarriers regardless of their size and surface properties. Physiologically, this non-parenchymal shield protects hepatocytes; however, these local barriers must be overcome for drug delivery. Nanocarrier structural properties strongly influence tissue penetration, in vivo pharmacokinetics, and biodistribution profile. Here we demonstrate the in vivo biodistribution of polyplex micelles formed by polyion complexation of short interfering (si)RNA with modified poly(ethylene glycol)-block-poly(allyl glycidyl ether) (PEG-b-PAGE) diblock copolymer that carries amino moieties in the side chain. The ratio between PEG corona and siRNA complexed PAGE core of polyplex micelles was chemically varied by altering the degree of polymerization of PAGE. Applying Raman-spectroscopy and dynamic in silico modeling on the polyplex micelles, we determined the corona-core ratio (CCR) and visualized the possible micellar structure with varying CCR. The results for this model system reveal that polyplex micelles with higher CCR, i.e., better PEG coverage, exclusively accumulate and thus allow passive cell-type-specific targeting towards hepatocytes, overcoming the macrophage-rich reticuloendothelial barrier of the liver.

Impact of Polyethylene Glycol (PEG) Conformations on the In Vivo Fate and Drug Release Behavior of PEGylated Core-Cross-Linked Polymeric Nanoparticles

In cancer chemotherapy, core-cross-linked particles (CCPs) are a promising drug carrier due to their high structural stability in an in vivo environment, resulting in improved tumor delivery. A biocompatible polymer of polyethylene glycol (PEG) is often utilized to coat the surface of CCPs to avoid nonspecific adsorption of proteins in vivo. The PEG density and conformation on the particle surface are important structural factors that determine the in vivo fate of such PEGylated nanoparticles, including their pharmacokinetics and pharmacodynamics. However, contrary to expectations, we found no significant differences in the in vivo pharmacokinetics and pharmacodynamics of the PEGylated CCPs with the different PEG densities including mushroom, brush, and dense brush conformations. On the contrary, the in vivo release kinetics of hydrophilic and hydrophobic model drugs from the PEGylated CCPs was strongly dependent on the PEG conformation and the drug polarity. This may be related to the water-swelling degree in the particle PEG layer, which promotes and inhibits the diffusion of hydrophilic and hydrophobic drugs, respectively, from the particle core to the water phase. Our results provide guidelines for the design of cancer-targeting nanomedicine based on PEGylated CCPs.

Polyglycerol and Poly(ethylene glycol) exhibit different effects on pharmacokinetics and antibody generation when grafted to nanoparticle surfaces

Poly(ethylene glycol) (PEG) is widely employed for passivating nanoparticle (NP) surfaces to prolong blood circulation and enhance localization of NPs to target tissue. However, the immune response of PEGylated NPs-including anti-PEG antibody generation, accelerated blood clearance (ABC), and loss of delivery efficacy-is of some concern, especially for treatments that require repeat administrations. Although polyglycerol (PG), which has the same ethylene oxide backbone as PEG, has received attention as an alternative to PEG for NP coatings, the pharmacokinetic and immunogenic impact of PG has not been studied systematically. Here, linear PG, hyperbranched PG (hPG), and PEG-coated polylactide (PLA) NPs with varying surface densities were studied in parallel to determine the pharmacokinetics and immunogenicity of PG and hPG grafting, in comparison with PEG. We found that linear PG imparted the NPs a stealth property comparable to PEG, while hPG-grafted NPs needed a higher surface density to achieve the same pharmacokinetic impact. While linear PG-grafted NPs induced anti-PEG antibody production in mice, they exhibited minimal accelerated blood clearance (ABC) effects due to the poor interaction with anti-PEG immunoglobulin M (IgM). Further, we observed no anti-polymer IgM responses or ABC effects for hPG-grafted NPs.

Nanoparticles with dense poly(ethylene glycol) coatings with near neutral charge are maximally transported across lymphatics and to the lymph nodes

Lymphatic vessels have recently been shown to effectively deliver immune modulatory therapies to the lymph nodes, which enhances their therapeutic efficacy. Prior work has shown that lymphatics transport 10-250 nm nanoparticles from peripheral tissues to the lymph node. However, the surface chemistry required to maximize this transport is poorly understood. Here, we determined the effect of surface poly(ethylene glycol) (PEG) density and size on nanoparticle transport across lymphatic endothelial cells (LECs) by differentially PEGylated model polystyrene nanoparticles. Using an established in-vitro lymphatic transport model, we found PEGylation improved the transport of 100 and 40 nm nanoparticles across LECs 50-fold compared to the unmodified nanoparticles and that transport is maximized when the PEG is in a dense brush conformation or high grafting density (Rf/D = 4.9). We also determined that these trends are not size-dependent. PEGylating 40 nm nanoparticles improved transport efficiency across LECs 68-fold compared to unmodified nanoparticles. We also found that PEGylated 100 nm and 40 nm nanoparticles accumulate in lymph nodes within 4 h after intradermal injection, while unmodified nanoparticles accumulated minimally. Densely PEGylated nanoparticles traveled the furthest distance from the injection site and densely PEGylated 40 nm nanoparticles had maximum accumulation in the lymph nodes compared to low density PEGylated and unmodified nanoparticles. Finally, we determined that nanoparticles are transported via both paracellular and transcellular mechanisms, and that PEG conformation modulates the cellular transport mechanisms. Our results suggest that PEG conformation is crucial to maximize nanoparticle transport across LECs and into lymphatic vessels, making PEG density a crucial design. Optimizing PEG density on nanoparticle formulations has the potential to enhance immunotherapeutic and vaccine outcomes. STATEMENT OF SIGNIFICANCE: Lymphatic vessels are an emerging target for drug delivery both in the context of modulating immune responses and enhancing bioavailability by avoiding first pass hepatic metabolism after oral delivery. Lymphatic vessels are the natural conduits from peripheral tissues to the lymph nodes, where the adaptive immune response is shaped, and eventually to systemic circulation via the thoracic duct. Lymphatics can be targeted via nanoparticles, but the surface chemistry required to maximize nanoparticle transport by lymphatics vessels remains poorly understood. Here, we demonstrate that coating nanoparticles with hydrophilic polyethylene glycol (PEG) effectively enhances their transport across lymphatic endothelial cells in vitro and in vivo and that both paracellular and micropinocytosis mechanisms underly this transport. We found that dense PEG coatings maximize lymphatic transport of nanoparticles, thus providing new material design criteria for lymphatic targeted drug delivery.

Biomedical polymers: synthesis, properties, and applications

Biomedical polymers have been extensively developed for promising applications in a lot of biomedical fields, such as therapeutic medicine delivery, disease detection and diagnosis, biosensing, regenerative medicine, and disease treatment. In this review, we summarize the most recent advances in the synthesis and application of biomedical polymers, and discuss the comprehensive understanding of their property-function relationship for corresponding biomedical applications. In particular, a few burgeoning bioactive polymers, such as peptide/biomembrane/microorganism/cell-based biomedical polymers, are also introduced and highlighted as the emerging biomaterials for cancer precision therapy. Furthermore, the foreseeable challenges and outlook of the development of more efficient, healthier and safer biomedical polymers are discussed. We wish this systemic and comprehensive review on highlighting frontier progress of biomedical polymers could inspire and promote new breakthrough in fundamental research and clinical translation.

Poly(ϵ-Caprolactone)-Methoxypolyethylene Glycol (PCL-MPEG)-Based Micelles for Drug-Delivery: The Effect of PCL Chain Length on Blood Components, Phagocytosis, and Biodistribution

Background

The main challenge of polymeric micelles as drug delivery systems is that the actual delivery efficiency is not as high as expected, which is closely related with the interactions with the complex biological environments such as blood components, phagocytosis, and biodistribution. Herein, we expect to understand these concerns for the clinically relevant micelles that composed of methoxypolyethylene glycol (MPEG) with identical chain length And poly(ε-caprolactone) (PCL) with tunable chain length (PCL_n-MPEG) (n=20, 30, and 40) wherein doxorubicin was encapsulated as a model drug.

Methods

The doxorubicin-loaded PCL_n-MPEG micelles were prepared by a dialysis method and characterized by dynamic light scattering and transmission electron microscopy. The surface PEG density and chain conformation were investigated by dissipative particle dynamics simulation. The stability of the micelles was detected by nanoparticle tracking analysis. The effects of PCL chain length on the blood components, phagocytosis, and biodistribution were assayed in vitro and in vivo.

Results

The micelles exhibited spherical morphology with a diameter about 30nm. The PEG chain conformation from “mushroom-like” to “brush-like” was evident. The micelles have no remarkable effect on the red blood cells, blood coagulation, and platelet activation. Interestingly, the protein adsorption was affected and dependent on the chain conformation, with lowest adsorption for PCL₃₀-MPEG, which also has the loWest phagocytosis. The stability of the micelles was in the order of PCL₄₀-MPEG>PCL₃₀-MPEG>PCL₂₀-MPEG which was dependent on the PCL chain length. The micelles mainly accumulated in liver, with the order consistent with their stability, indicating that, besides the phagocytosis, the stability of the micelle plays an important role in biodistribution as well. The related mechanisms were proposed and discussed.

Conclusion

Manipulating the PEG/PCL ratio of the micelle is an effective approach to modulate the protein adsorption, phagocytosis, and biodistribution, which may be a prerequisite for clinical applications.

Tailoring the physicochemical properties of nanomaterials for immunomodulation

Immunomodulation is poised to revolutionize the treatment of cancer, autoimmune diseases, and many other inflammation-related disorders. The immune system in these conditions can be either activated or suppressed by nanocarriers loaded with bioactive molecules. Although immunomodulation via these therapeutics has long been recognized, and a broad range of nanocarriers have been designed to accommodate varied usages, less studies have focused on the effects of nanomaterial physicochemical properties on immune responses, especially the immunity altered by nanocarrier materials alone. Conclusions are sometimes seemly inconsistent due to the complexities of nanomaterials and the immune system. An in-depth understanding of the nanocarrier-induced immune responses is essential for clinical applications. In this review, we summarize recent studies of the immune responses influenced by nanomaterial physicochemical properties with an emphasis on the intrinsic features of nanomaterials that modulate the innate and adaptive immunities. We then provide our perspectives on the design of nanomaterials for immunomodulation.

Progress and Principle of Drug Nanocrystals for Tumor Targeted Delivery

Drugs are referred to as drug nanocrystals when they exist as nanoscale crystal structures. This kind of nanocarrier has been widely utilized to increase the solubility and absorption for poorly aqueous soluble drugs after oral administration, or prolong the drug circulation when intravenous administration. The systemic cytotoxicity caused by antitumor drugs usually come from the nonspecific drug distribution. To solve the disadvantage of poor targetability, drug nanocrystals for tumor targeted delivery have been developed in recent years. In this review, the targeting mechanisms of various surface modified drug nanocrystals are introduced with the focus on passive targeting, active targeting and stimuli-responsive targeting in details. Function and application of common surface modified materials are also discussed.

Size-dependent chemosensitization of doxorubicin-loaded polymeric nanoparticles for malignant glioma chemotherapy

Chemotherapy is a traditional treatment method in clinical cancer treatment. However, it is limited due to the large toxic side effects of chemotherapeutics. Nanomedicines have shown great potential in the application of tumor therapy. The size of nanoparticles as a crucial factor in the enhanced permeability and retention (EPR) effect can be regulated for the enhanced chemotherapy. Therefore, we believe that regulation of nanoparticle size can be used as an effective sensitizer to enhance the therapeutic effect of chemotherapy drugs on tumors. Here, we prepared several nanoparticles of different hydrodynamic diameters commonly found in nanomedical applications by the diblock copolymer of methoxy polyethylene glycol-poly (ϵ -caprolactone) (mPEG-PCL). The blood circulation effect and organ distribution in blood were detected by fluorescence labeled nanoparticles. We found that the small-sized nanoparticles exhibited much longer blood circulation time than the large-sized nanoparticles in vivo, and thus the nanoparticle concentration in the tumor tissue was relatively high. Systematic injection of the doxorubicin (DOX) loaded nanoparticles can effectively inhibit tumor growth. Compared to the free drug, tumor cells were much more sensitive to DOX loaded nanoparticles of small size. Our nano-drug delivery system has been proven to be safe and nontoxic in vivo and was suitable for use as a sensitizer in clinical oncology chemotherapy.

Surface Topography of Polyethylene Glycol Shell Nanoparticles Formed from Bottlebrush Block Copolymers Controls Interactions with Proteins and Cells

Although poly(ethylene glycol) (PEG) is commonly used in nanoparticle design, the impact of surface topography on nanoparticle performance in biomedical applications has received little attention, despite showing significant promise in the study of inorganic nanoparticles. Control of the surface topography of polymeric nanoparticles is a formidable challenge due to the limited conformational control of linear polymers that form the nanoparticle surface. In this work, we establish a straightforward method to precisely tailor the surface topography of PEGylated polymeric nanoparticles based on tuning the architecture of shape-persistent amphiphilic bottlebrush block copolymer (BBCP) building blocks. We demonstrate that nanoparticle formation and surface topography can be controlled by systematically changing the structural parameters of BBCP architecture. Furthermore, we reveal that the surface topography of PEGylated nanoparticles significantly affects their performance. In particular, the adsorption of a model protein and the uptake into HeLa cells were closely correlated to surface roughness and BBCP terminal PEG block brush width. Overall, our work elucidates the importance of surface topography in nanoparticle research as well as provides an approach to improve the performance of PEGylated nanoparticles.

Synergistic chemo-photothermal cancer therapy of pH-responsive polymeric nanoparticles loaded IR825 and DTX with charge-reversal property

IR825 is a kind of near-infrared (NIR) small molecule cyanine dye and has distinct near-infrared absorbance and excellent thermal conversion performance. Due to poor stability and insufficient therapy efficacy, various nano-systems have been developed as delivery vehicles for NIR dyes to improve their application in tumor treatment. Herein, we developed an intelligent polymer drug vehicle (Mal-PAH-PEG-DMMA/ poly (ethylene imine) - poly(ε-caprolactone) block polymers, MPPD/PEI-PCL) based on pH-responsive charge-reversal to deliver docetaxel (DTX) and photosensitizer (IR825) for chemo-photothermal combination therapy (MPPD@IR825/DTX NPs). MPPD@IR825/DTX NPs could undergo charge conversion in a slightly acidic microenvironment (pH 6.8), resulted in strong electrostatic repulsion to withdraw the shell of the polymer nanoparticles (MPPD), enhanced cellular uptake and increased drug release. MPPD@IR825/DTX NPs demonstrated nanoscale in size with good mono-dispersity and stability, triggered DTX release in response to acid environment and NIR stimulation, in the same time providing excellent photothermal conversion efficiency. In vitro and In vivo experiments confirmed that charge-reversal polymeric nanoparticles improved antitumor efficiency in 4T1 tumor cell modal than non-charge-reversal polymeric nanoparticles. Furthermore, in comparison with chemotherapy or photothermal therapy in a single treatment mode, chemo-photothermal combination therapy of MPPD@IR825/DTX NPs with laser irradiation showed highly efficient tumor ablation. In addition, the polymeric nanoparticles exhibited good biocompatibility and safety. Therefore, the design of charge-reversal polymeric nanoparticles (MPPD@IR825/DTX NPs) provides a new strategy and promising application for targeting and synergistic chemo-photothermal combination therapy.

Safety Evaluation of Nanotechnology Products

Nanomaterials are now being used in a wide variety of biomedical applications. Medical and health-related issues, however, have raised major concerns, in view of the potential risks of these materials against tissue, cells, and/or organs and these are still poorly understood. These particles are able to interact with the body in countless ways, and they can cause unexpected and hazardous toxicities, especially at cellular levels. Therefore, undertaking in vitro and in vivo experiments is vital to establish their toxicity with natural tissues. In this review, we discuss the underlying mechanisms of nanotoxicity and provide an overview on in vitro characterizations and cytotoxicity assays, as well as in vivo studies that emphasize blood circulation and the in vivo fate of nanomaterials. Our focus is on understanding the role that the physicochemical properties of nanomaterials play in determining their toxicity.

The Fate of Nanoparticles In Vivo and the Strategy of Designing Stealth Nanoparticle for Drug Delivery

Nano-drug delivery systems (Nano-DDS) offer powerful advantages in drug delivery and targeted therapy for diseases. Compared to the traditional drug formulations, Nano-DDS can increase solubility, biocompatibility, and reduce off-targeted side effects of free drugs. However, they still have some disadvantages that pose a limitation in reaching their full potential in clinical use. Protein adsorption in blood, activation of the complement system, and subsequent sequestration by the mononuclear phagocyte system (MPS) consequently result in nanoparticles (NPs) to be rapidly cleared from circulation. Therefore, NPs have low drug delivery efficiency. So, it is important to develop stealth NPs for reducing bio-nano interaction. In this review, we first conclude the interaction between NPs and biological environments, such as blood proteins and MPS, and factors influencing each other. Next, we will summarize the new strategies to reduce NPs protein adsorption and uptake by the MPS based on current knowledge of the bio-nano interaction. Further directions will also be highlighted for the development of biomimetic stealth nano-delivery systems by combining targeted strategies for a better therapeutic effect.

Smart On-Site Immobilizable Near-Infrared II Fluorescent Nanoprobes for Ultra-Long-Term Imaging-Guided Tumor Surgery and Photothermal Therapy

Accurate diagnosis and efficient treatment of tumors are highly significant in battling cancer. Near-infrared II (NIR-II) fluorescence imaging shows big promise for deep tumor visualization in living systems due to high temporal and spatial resolution and deep tissue penetration capability, whereas the development of efficient NIR-II probes for tumor theranostics still faces a huge challenge. Herein, we have designed and constructed intelligent mPEG₅₀₀₀-PCL₃₀₀₀-encapsulated NIR-II nanoprobe ZM1068-NPs that showed great chemical stability and excellent biocompatibility. With the merits of the strong fluorescence in the NIR-II region and prominent optical-thermal conversion efficiency, this probe was successfully used for NIR-II imaging-guided surgery and photothermal therapy of breast carcinoma in living mice. More notably, it was for the first time found that ZM1068 dyes could be covalently on-site-immobilized within tumors through the thiol-chlor nucleophilic substitution reaction, resulting in improved tumor accumulation and retention time. We thus envision that this probe may provide an attractive means for precise cancer diagnosis and treatment.

In vivo protein corona on nanoparticles: does the control of all material parameters orient the biological behavior?

Nanomaterials have a huge potential in research fields from nanomedicine to medical devices. However, surface modifications of nanoparticles (NPs) and thus of their physicochemical properties failed to predict their biological behavior. This requires investigating the "missing link" at the nano-bio interface. The protein corona (PC), the set of proteins binding to the NPs surface, plays a critical role in particle recognition by the innate immune system. Still, in vitro incubation offers a limited understanding of biological interactions and fails to explain the in vivo fate. To date, several reports explained the impact of PC in vitro but its applications in the clinical field have been very limited. Furthermore, PC is often considered as a biological barrier reducing the targeting efficiency of nano vehicles. But the protein binding can actually be controlled by altering PC both in vitro and in vivo. Analyzing PC in vivo could accordingly provide a deep understanding of its biological effect and speed up the transfer to clinical applications. This review demonstrates the need for clarifications on the effect of PC in vivo and the control of its behavior by changing its physicochemical properties. It unfolds the recent in vivo developments to understand mechanisms and challenges at the nano-bio interface. Finally, it reports recent advances in the in vivo PC to overcome and control the limitations of the in vitro PC by employing PC as a boosting resource to prolong the NPs half-life, to improve their formulations and thereby to increase its use for biomedical applications.

Tailor-made oligonucleotide-loaded lipid-polymer nanosystems designed for bone gene therapy

Gene therapy has emerged as a tool for the treatment of systemic metabolic disorders as osteoporosis (OP). However, the design of a suitable vehicle able to efficiently load and release the genetic material on the target cells is still a challenge. Moreover, the internalization pathway of nanosystems has been described to be dependent on their surface characteristics and the cell type evaluated. In this study, we aim at obtaining PEGylated lipid-PLGA nanoparticles (NPs) with variable surface charge able to incorporate GapmeRs (single-strand antisense oligonucleotides) for OP treatment. Nanoparticles showing negative, positive, and neutral surface charge were obtained by modulating the lipid composition. All formulations showed a remarkably low polydispersity index with adequate size. NPs were loaded with GapmeRs showing a high encapsulation efficiency and a surface charge-independent oligonucleotide loading. All the formulations were adequately internalized by MSCs. Future experiments will be devoted to use the developed formulations to clarify if the intracellular distribution of hybrid NPs on mesenchymal stem cells (MSCs) is dependent on surface charge. This portfolio of NPs will serve as a tool to analyze the effect of NP surface charge on gene therapy efficiency.

Effect of Poly(ethylene glycol) (PEG) Surface Density on the Fate and Antitumor Efficacy of Redox-Sensitive Hybrid Nanoparticles

The effects of poly(ethylene glycol) (PEG) on improving the biological compatibility and circulation time of nanocarriers are determined by the surface density of PEG on nanoparticles. PEG with high surface density on nanocarriers has greater accumulation in tumor tissues. However, this impairs the release of drugs loaded in the nanoparticles in the tumor tissues. The relations and internal regularities between the controlled stripping of PEG of nanoparticles and its fate and antitumor efficacy in vivo remain unsolved. Redox-sensitive hybrid nanoparticles coated with varied PEG densities were prepared by blending a redox-sensitive polymer of DLPE-SS-MPEG. To keep identical nanoproperties, these nanoparticles were prepared with a similar size distribution of around 100 nm. The effects of controlled stripping of PEG on antitumor activities of nanoparticles were then investigated. As the PEG surface density increased, lower cellular internalization by tumor cells was observed. However, nanoparticles with higher controlled stripping of PEG showed greater accumulation in tumor tissues and advanced antitumor activities in vivo.

Investigation of the in vivo integrity of polymeric micelles via large Stokes shift fluorophore-based FRET

Polymeric micelles hold great potential for anticancer drug delivery. Sufficient integrity of polymeric micelles after intravenous injection is critical for successful drug delivery to solid tumors, but accurate measurement of the in vivo micellar integrity remains challenging. Methods based on Förster resonance energy transfer (FRET) to monitor the in vivo micellar integrity are frequently used. However, the self-quenching effect of these FRET fluorophores used has been improperly ignored and has caused inaccurate measurements. Herein, we report a FRET-based approach using the large Stokes shift (LSS) fluorophores NBD-X and MS735 as the donor and acceptor, respectively, to investigate the integrity of polyethylene glycol-block-poly(ε-caprolactone) (PEG-PCL) micelles. We established a mathematical formula for the integrity calculation, and an in vitro verification experiment showed that the formula results exactly matched the simulated results. Our results demonstrated that PEG-PCL micelles gradually dissociated in blood circulation, but approximately 60% of the micelles in plasma remained intact 72 h after intravenous (i.v.) injection. This LSS fluorophore-based FRET approach can be used to accurately monitor the integrity of nanoparticles, and this study demonstrates that most of PEG-PCL micelles maintain their aggregation state during blood circulation for anticancer drug delivery.

Protein Binding Affinity of Polymeric Nanoparticles as a Direct Indicator of Their Pharmacokinetics

Polymeric nanoparticles (NPs) are an important category of drug delivery systems, and their in vivo fate is closely associated with delivery efficacy. Analysis of the protein corona on the surface of NPs to understand the in vivo fate of different NPs has been shown to be reliable but complicated and time-consuming. In this work, we establish a simple approach for predicting the in vivo fate of polymeric NPs. We prepared a series of poly(ethylene glycol)-block-poly(d,l-lactide) (PEG-b-PLA) NPs with different protein binding behaviors by adjusting their PEG densities, which were determined by analyzing the serum protein adsorption. We further determined the protein binding affinity, denoted as the equilibrium association constant (K_A), to correlate with in vivo fate of NPs. The in vivo fate, including blood clearance and Kupffer cell uptake, was studied, and the maximum concentration (C_max), the area under the plasma concentration-time curve (AUC), and the mean residence time (MRT) were negatively linearly dependent, while Kupffer cell uptake was positively linearly dependent on K_A. Subsequently, we verified the reliability of the approach for in vivo fate prediction using poly(methoxyethyl ethylene phosphate)-block-poly(d,l-lactide) (PEEP-b-PLA) and poly(vinylpyrrolidone)-block-poly(d,l-lactide) (PVP-b-PLA) NPs, and the linear relationship between the K_A value and their PK parameters further suggests that the protein binding affinity of polymeric NPs can be a direct indicator of their pharmacokinetics.

Meta-Analysis of Nanoparticle Delivery to Tumors Using a Physiologically Based Pharmacokinetic Modeling and Simulation Approach

Numerous studies have engineered nanoparticles with different physicochemical properties to enhance the delivery efficiency to solid tumors, yet the mean and median delivery efficiencies are only 1.48% and 0.70% of the injected dose (%ID), respectively, according to a study using a nonphysiologically based modeling approach based on published data from 2005 to 2015. In this study, we used physiologically based pharmacokinetic (PBPK) models to analyze 376 data sets covering a wide range of nanomedicines published from 2005 to 2018 and found mean and median delivery efficiencies at the last sampling time point of 2.23% and 0.76%ID, respectively. Also, the mean and median delivery efficiencies were 2.24% and 0.76%ID at 24 h and were decreased to 1.23% and 0.35%ID at 168 h, respectively, after intravenous administration. While these delivery efficiencies appear to be higher than previous findings, they are still quite low and represent a critical barrier in the clinical translation of nanomedicines. We explored the potential causes of this poor delivery efficiency using the more mechanistic PBPK perspective applied to a subset of gold nanoparticles and found that low delivery efficiency was associated with low distribution and permeability coefficients at the tumor site (P < 0.01). We also demonstrate how PBPK modeling and simulation can be used as an effective tool to investigate tumor delivery efficiency of nanomedicines.

Transforming Complexity to Simplicity: Protein-Like Nanotransformer for Improving Tumor Drug Delivery Programmatically

It was difficult for nanodrugs to simultaneously meet the contradictory requirements of prolonged circulation time, augmented cellular uptake, rapid lysosome escape, precise drug release, and tumor penetration in tumor drug delivery. We prepared a nanotransformer (DTIG) through assembling doxorubicin, tannic acid, and indocyanine green to overcome this dilemma. Hydrophilic DTIG showed prolonged blood circulation time. Besides, DTIG could be efficiently internalized by tumor cells through transforming into hydrophobic particles in an acidic tumor microenvironment. Subsequently, oversized hydrophobic particles were further formed in acidic lysosomes to escape from it through rupturing the lysosome. These hydrophobic DTIGs could rapidly revert to a smaller hydrophilic nanoassembly and release the payloads in cytoplasm. Similar to denaturation and renaturation of protein, these high-efficiency instantaneous transformations were activated by proton. Besides, photothermal therapy of DTIG promoted drug penetration efficiency in tumor. This optimized drug delivery process of DTIG finally offered potent antitumor efficacy and an obvious advantage on prognosis.

Rapid transport of germ-mimetic nanoparticles with dual conformational polyethylene glycol chains in biological tissues

Polyethylene glycols (PEGs) can improve the diffusivity of nanoparticles (NPs) in biological hydrogels, while extended PEG chains severely impede cellular uptake of NPs. Inspired by invasive germs with flagellum-driven mucus-penetrating and fimbriae-mediated epithelium-adhering abilities, we developed germ-mimetic NPs (GMNPs) to overcome multiple barriers in mucosal and tumor tissues. In vitro studies and computational simulations revealed that the tip-specific extended PEG chains on GMNP functioned similarly to flagella, facilitating GMNP diffusion (up to 83.0-fold faster than their counterparts). Meanwhile, the packed PEG chains on the bodies of GMNP mediated strong adhesive interactions with cells similarly to the fimbriae, preserving cellular uptake efficiency. The in vivo results proved the superior tumor permeability and improved oral bioavailability provided by the GMNP (21.9-fold over administration of crystalline drugs). These findings offer useful guidelines for the rational design of NPs by manipulating surface polymer conformation to realize multiple functions and to enhance delivery efficacy.

MOF-derived novel porous Fe3O4@C nanocomposites as smart nanomedical platforms for combined cancer therapy: magnetic-triggered synergistic hyperthermia and chemotherapy

Smart Fe₃O₄@C-PVP@DOX nanomedical platforms hold great potential application in the precise treatments of clinical cancer.

Metal-Organic Framework (MOF)-based Nanomaterials for Biomedical Applications

BACKGROUND

Metal-organic frameworks (MOFs), as a new class of porous organic-inorganic crystalline hybrid materials that governed by the self-assembled of metal atoms and organic struts have attracted tremendous attention because of their special properties. Recently, some more documents have reported different types of nanoscale metal-organic frameworks (NMOFs) as biodegradable and physiological pH-responsive systems for photothermal therapy and radiation therapy in the body.

DISCUSSION

In this review paper aims at describing the benefits of using MOF nanoparticles in the field of biomedicine, and putting into perspective their properties in the context of the ones of other NPs. The first section briefly reviews the biomaterial scaffolds of MOFs. The second section presents the main types of stimuli-responsive mechanisms and strategies from two categories: intrinsic (pH, redox state) and extrinsic (temperature, light irradiation and magnetic field) ones. The combinations of photothermal therapy and radiation therapy have been concluded in detail. Finally, clinical applications of MOFs, future challenges and perspectives are also mentioned.

CONCLUSION

This review outlines the most recent advances MOFs design and biomedical applications, from different synthesis to their use as smart drug delivery systems, bioimaging technology or a combination of both.

An inhalable nanoparticulate STING agonist synergizes with radiotherapy to confer long-term control of lung metastases

Mounting evidence suggests that the tumor microenvironment is profoundly immunosuppressive. Thus, mitigating tumor immunosuppression is crucial for inducing sustained antitumor immunity. Whereas previous studies involved intratumoral injection, we report here an inhalable nanoparticle-immunotherapy system targeting pulmonary antigen presenting cells (APCs) to enhance anticancer immunity against lung metastases. Inhalation of phosphatidylserine coated liposome loaded with STING agonist cyclic guanosine monophosphate–adenosine monophosphate (NP-cGAMP) in mouse models of lung metastases enables rapid distribution of NP-cGAMP to both lungs and subsequent uptake by APCs without causing immunopathology. NP-cGAMP designed for enhanced cytosolic release of cGAMP stimulates STING signaling and type I interferons production in APCs, resulting in the pro-inflammatory tumor microenvironment in multifocal lung metastases. Furthermore, fractionated radiation delivered to one tumor-bearing lung synergizes with inhaled NP-cGAMP, eliciting systemic anticancer immunity, controlling metastases in both lungs, and conferring long-term survival in mice with lung metastases and with repeated tumor challenge.

Successful anticancer immunotherapy should induce robust systemic immunity against metastases. Here, the authors engineer an inhalable nano-STING agonist, which synergizes with fractionated radiation to control lung metastases and confers long-term systemic antitumor immunity in mice.

Low density lipoprotein mimic nanoparticles composed of amphipathic hybrid peptides and lipids for tumor-targeted delivery of paclitaxel

BACKGROUND

Low density lipoprotein (LDL) has been regarded as a promising antitumor drug vehicle. However some problems, such as rare source, difficulty of large-scale production, and potential safety concerns, hinder its clinical application.

PURPOSE

The objective of this study is to develop a biomimetic LDL nanocarrier by replacing the native apolipoprotein B-100 (apoB-100) with an artificial amphipathic peptide and demonstrate its antitumor efficacy.

METHODS

The amphipathic hybrid peptide (termed as FPL) consisting of a lipid binding motif of apoB-100 (LBMapoB)-polyethylene glycol (PEG)-folic acid (FA) was synthesized and characterized by 1H NMR and circular dichroism. FPL decorated lipoprotein-mimic nanoparticles (termed as FPLM NPs) were prepared by a modified solvent emulsification method. Paclitaxel (PTX) was incorporated into NPs and its content was quantified by HPLC analysis. The morphology of NPs was observed by transmission electron microscopy (TEM), and the particle size and zeta potential of NPs were determined by dynamic light scattering (DLS). The colloidal stability of FPLM NPs was evaluated in PBS containing bovine serum albumin (BSA). In vitro release of PTX loaded FPLM NPs was evaluated using the dialysis method. Cellular uptake and cytotoxity assayswere evaluated on human cervical cancer cells (HeLa) and lung cancer cells (A549). Tumor inhibition in vivo was investigated in M109 tumor-bearing mice via tail vein injection of Taxol formulation and PTX loaded NPs.

RESULTS

The composition of FPLM NPs, including cholesteryl oleate, glyceryl trioleate, cholesterol, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and FPL peptides, was optimized to be 5:1:1:3:10 (w/w). FPLM NPs had a spherical shape with a mean diameter of 83 nm and a negative charge (-12 mV). FPLM NPs with optimum formulation had good colloidal stability in BSA solution.The release of PTX from FPLM NPs was slow and sustained. The uptake of FPLM NPs was higher in folate receptor (FR) overexpressing tumor cells (HeLa cells) than in FR deficient tumor cells (A549 cells). The intracellular distribution indicated that FPLM NPs had the lysosome escape capacity. The internalization mechanism of FPLM NPs was involved with clathrin- and caveolae-mediated endocytosis and FR played a positive role in the internalization of FPLM NPs. The CCK-8 assay demonstrated that FPLM NPs exhibited notably better anti-tumor effect than Taxol formulation in vitro. Moreover, PTX loaded FPLM NPs produced very marked anti-tumor efficiency in M109 tumor-bearing mice in vivo.

CONCLUSION

FPLM NPs is a promising nanocarrier which can improve the therapeutic effect and reduce the side effects of antitumor drugs.

Modulating Targeting of Poly(ethylene glycol) Particles to Tumor Cells Using Bispecific Antibodies

Low-fouling or "stealth" particles composed of poly(ethylene glycol) (PEG) display a striking ability to evade phagocytic cell uptake. However, functionalizing them for specific targeting is challenging. To address this challenge, stealth PEG particles prepared by a mesoporous silica templating method are functionalized with bispecific antibodies (BsAbs) to obtain PEG-BsAb particles via a one-step binding strategy for cell and tumor targeting. The dual specificity of the BsAbs-one arm binds to the PEG particles while the other targets a cell antigen (epidermal growth factor receptor, EGFR)-is exploited to modulate the number of targeting ligands per particle. Increasing the BsAb incubation concentration increases the amount of BsAb tethered to the PEG particles and enhances targeting and internalization into breast cancer cells overexpressing EGFR. The degree of BsAb functionalization does not significantly reduce the stealth properties of the PEG particles ex vivo, as assessed by their interactions with primary human blood granulocytes and monocytes. Although increasing the BsAb amount on PEG particles does not lead to the expected improvement in tumor accumulation in vivo, BsAb functionalization facilitates tumor cell uptake of PEG particles. This work highlights strategies to balance evading nonspecific clearance pathways, while improving tumor targeting and accumulation.

Development of "CLAN" Nanomedicine for Nucleic Acid Therapeutics

Nucleic acid-based macromolecules have paved new avenues for the development of therapeutic interventions against a spectrum of diseases; however, their clinical translation is limited by successful delivery to the target site and cells. Therefore, numerous systems have been developed to overcome delivery challenges to nucleic acids. From the viewpoint of clinical translation, it is highly desirable to develop systems with clinically validated materials and controllability in synthesis. With this in mind, a cationic lipid assisted PEG-b-PLA nanoparticle (CLAN) is designed that is capable of protecting nucleic acids via encapsulation inside the aqueous core, and delivers them to target cells, while maintaining or improving nucleic acid function. The system is formulated from clinically validated components (PEG-b-PLA and its derivatives) and can be scaled-up for large scale manufacturing, offering potential for its future use in clinical applications. Here, the development and working mechanisms of CLANs, the ways to improve its delivery efficacy, and its application in various disease treatments are summarized. Finally, a prospective for the further development of CLAN is also discussed.

Incorporation of a rhodamine B conjugated polymer for nanoparticle trafficking both in vitro and in vivo

A method to stably label and quantitatively detect self-assembled nanoparticles by the incorporation of rhodamine B-conjugated poly(ε-caprolactone) (PCL–RhoB).

Neutrophil-mediated and low density lipoprotein receptor-mediated dual-targeting nanoformulation enhances brain accumulation of scutellarin and exerts neuroprotective effects against ischemic stroke

Delivery of poorly permeable drugs across the blood-brain barrier (BBB) is a great challenge in the treatment of ischemic stroke.

Hydrophobicity-Adaptive Nanogels for Programmed Anticancer Drug Delivery

Reconciling the conflicting needs for a prolonged circulation time, enhanced cellular uptake by bulk tumor cells and cancer stem cells (CSCs), and extensive tumor tissue penetration remains a major challenge for current nano drug delivery systems. Here we describe smart poly( N-isopropylacrylamide)-based nanogels with a fast adaptive hydrophobicity to solve these contradictory requirements for enhanced cancer chemotherapy. The nanogels are hydrophilic in the blood to prolong their circulation time. Once they accumulate at tumor sites, they rapidly become hydrophobic in response to tumor extracellular acidity. The adaptive hydrophobicity of the nanogels facilitates tumor accumulation, deep tumor penetration, and efficient uptake by bulk tumor cells and CSCs, resulting in a greater in vivo enrichment in tumor cells and side population cells. Together with lysosomal pH-regulated charge reversal and redox-responsive intracellular drug release, the nanogels escape from lysosomes and release their cargo doxorubicin. Thus, the nanogels significantly improve the in vivo anticancer efficacy and decrease side effects of doxorubicin. Strikingly, the ratio of CSCs is greatly decreased after treatment with the nanogels loaded with doxorubicin. Our current study provides new insights into designing effective anticancer drug delivery systems.

Effective and Targeted Human Orthotopic Glioblastoma Xenograft Therapy via a Multifunctional Biomimetic Nanomedicine

Glioblastoma multiforme (GBM) is a fatal central nervous system tumor without effective treatment. Chemotherapeutic agents are mainstays in the treatment of glioblastoma. However, the effectiveness of these is seriously hindered by poor blood-brain-barrier (BBB) penetrance and tumor targeting, together with short biological half-life. Improved chemotherapy is thus urgently needed for GBM. Multifunctional nanoparticle delivery systems offer much promise in overcoming current limitations. Accordingly, a multifunctional biomimetic nanomedicine is developed by functionalizing the surface of red blood cell membranes (RBCms) with angiopep-2 and loading pH-sensitive nanoparticles (polymer, doxorubicin (Dox), and lexiscan (Lex)) using the functionalized cell membrane to generate the novel nanomedicine, Ang-RBCm@NM-(Dox/Lex). The studies toward orthotopic U87MG human glioblastoma tumor-bearing nude mice show that the Ang-RBCm@NM-(Dox/Lex) nanomedicine has much improved blood circulation time, superb BBB penetration, superior tumor accumulation and retention. Moreover, effective suppression of tumor growth and significantly improved medium survival time are also observed after Ang-RBCm@NM-(Dox/Lex) treatment. The results show that this biomimetic nanoplatform can serve as a flexible and powerful system for GBM treatment which can be readily adapted for the treatment of other central nervous system (CNS) disorders.

Biodegradable nanoparticles bearing amine groups as a strategy to alter surface features, biological identity and accumulation in a lung metastasis model

Polymer-based nanoparticles (NPs) with a cationic charge have emerged recently as a potent nanotool due to their unique ability to penetrate deeply inside tumor tissue and to interact preferentially with the plasma membrane of cancer cells. In this paper, we propose a general strategy to obtain biodegradable cationic NPs of poly(ε-caprolactone) (PCL) based on an amine terminated PCL (NH₂-PCL_4.2k) or its mixture with monomethoxypoly(ethylene glycol)-PCL (mPEG_1k-PCL_4k). Positively-charged NPs were obtained, switching to net negative values through adsorption of low molecular weight hyaluronan. NPs exposing both amine and PEG groups on the surface showed a larger fixed aqueous layer thickness as compared to fully PEGylated NPs, suggesting that PEG conformation/localization is affected by the presence of amino groups. The stability of the positively-charged NPs was affected by the presence of ions, while interaction with the human plasma protein pool indicated time-dependent protein corona formation imparting an overall negative charge. NP-induced haemolysis was low, while cytotoxicity against A549 and Calu-3 lung cancer cell lines was cell-specific as well as dose and time-dependent. Finally, the presence of amino groups greatly changed the in vivo biodistribution of the NPs in tumor-bearing mice (lung colonization of B16F10 cancer cells) allowing the amine/PEGylated NPs to accumulate mainly at the target organ. Overall, this study demonstrates that NPs with a mixed amine/PEGylated surface exhibit a peculiar biological identity that alters their interaction with the bioenvironment and are thus worthy of further investigation in the delivery of chemotherapeutics.