NIR-Light-Activated Ratiometric Fluorescent Hybrid Micelles for High Spatiotemporally Controlled Biological Imaging and Chemotherapy.

Intelligent-responsive imaging-therapy strategy has shown great significance for biomedicine. However, it is still a challenge to construct spatiotemporally controlled imaging-therapy systems triggered by near infrared (NIR) light. In this work, NIR-light-activated ratiometric fluorescent hybrid micelles (RFHM) are prepared via the co-assembly of upconversion nanoparticles (UCNPs), doxorubicin (DOX), and UV-light-responsive amphiphilic block copolymer for the spatiotemporally controlled imaging and chemotherapy. Upon NIR light irradiation, UCNPs can convert NIR light to UV light. The emitted UV light induces the photoreaction of copolymer to further trigger ratiometric fluorescence imaging and degradation of hybrid micelles, resulting in rapid DOX release from hybrid micelles for antitumor therapy. The animal experiments reveal that NIR light can not only remotely regulate the ratiometric fluorescence imaging of RFHM in tumor tissue, but also trigger DOX release from RFHM to inhibit tumor growth. Therefore, this study provides a new strategy to achieve high spatial-temporal-controlled biological imaging and chemotherapy.

Polymer-Upconverting Nanoparticle Hybrid Micelles for Enhanced Synergistic Chemo-Photodynamic Therapy: Effects of Emission-Absorption Spectral Match.

Chemo-photodynamic combined therapy is promising in cancer treatment, although low tissue penetration of visible light for activating photosensitizers (e.g., chlorin e6, Ce6) limited its broad applications. Combination of upcoverting nanoparticles (UCNPs) with the photosensitizers endows us with the possibility to utilize highly tissue penetrable near-infrared light; nevertheless, the mismatch between absorption of common photosensitizers (λabs, mainly red) and emission of UCNPs (λem, mainly green) resulted in low energy utilization and unsatisfied therapeutic efficacy in the current UCNP-PDT (photodymanic therapy) platforms. To resolve this problem, herein, we construct polymer-UCNP hybrid micelles (PUHMs) for codelivery of doxorubicin (DOX) and Ce6, and systemically studied the effects of spectral match between λem of UCNPs and λabs of Ce6 on efficiency of synergistic chemo-photodynamic therapy. Compared with spectrally mismatched PUHMs, the spectrally matched PUHMs can significantly enhance the utilization efficiency of upconverted emission energy to activate the photosensitizers and generate more reactive oxygen species (ROS) for enhanced photodynamic therapy. Meanwhile, as the assembled structure of PUHMs can be destroyed by the oxidation of ROS upon 980 nm laser irradiation because of the hydrophobic-hydrophilic transformation of poly(propylene sulfide) (PPS) segment, the spectrally matched PUHMs triggered faster release of DOX, thus resulting in more effective chemotherapy. As a result, the spectrally matched PUHMs induced more prominent cytotoxicity and superior synergistic therapeutic effect for cancer cells in vitro. Our results demonstrated that such spectrally matched PUHMs provide us with an effective strategy for photodynamic-chemo synergistic therapy.

Photothermal Effect-Triggered Drug Release from Hydrogen Bonding-Enhanced Polymeric Micelles.

Incorporation of noncovalent interactions into hydrophobic cores of polymeric micelles provides the micelles with enhanced physical stability and drug loading efficiency, however, it also creates obstacles for drug release due to the strong interactions between carriers and drugs. Herein, a series of amphiphilic block copolymers based on poly(ethylene glycol)- b-poly(l-lysine) (mPEG- b-PLL) with similar chemical structures, while different hydrogen bonding donors (urethane, urea, and thiourea groups) are synthesized, and their capacities for codelivery of anticancer drug (e.g., doxorubicin) and photothermal agent (e.g., indocyanine green) are investigated. The resulting hybrid micelles display decreased critical micelle concentrations (CMCs) and enhanced micelle stabilities due to the hydrogen bonding between urea groups in the polymers. Moreover, the strong hydrogen bonds between the urea/thiourea groups and drugs provide the carriers with enhanced drug loading efficiencies, decreased micelle sizes, however, slower drug release profiles as well. When exposed to the near-infrared laser irradiation, destabilization of the hydrogen bonding through photothermal effect triggers fast and controlled drug releases from the micelles, which dramatically promotes the aggregation of the drugs in the nuclei, resulting in an enhanced anticancer activity. These results demonstrate that the hydrogen bonding-enhanced micelles are promising carriers for controllable chemo-photothermal synergistic therapy.

Cascade-amplified self-immolative polymeric prodrug for cancer therapy by disrupting redox homeostasis.

The amplification of reactive oxygen species (ROS) generation and glutathione (GSH) depletion in cancer cells represents a promising strategy to disrupt redox homeostasis for cancer therapy. Quinone methide and its analogs (QM) have recently been recognized as potential GSH scavengers for anticancer applications; however, an effective QM prodrug is yet to be developed. In this study, we prepare a self-immolative polymeric prodrug (SPP), which could be selectively degraded to generate large quantities of QMs in cancer cells during the spontaneous stepwise head-to-tail degradation of SPP. The amphiphilic SPP is self-assembled into nano-sized micelles, allowing for encapsulating 2-methoxy-ß-estradiol (2ME), an anticancer drug that produces a large amount of intracellular ROS. When SPP@2ME, as the cascade-amplified prodrug, is treated on the cancer cells, 2ME is rapidly released at the ROS-rich intracellular environment by degradation of SPP, thus generating more ROS that triggers the degradation of more SPP chains. Such a domino-like cascade-amplified feedback loop significantly amplifies oxidative stress and disrupts the redox homeostasis in cancer cells. This unique strategy provides synergistic anticancer therapeutic efficacy and demonstrates an important perception in innovative and precise nanomedicine.

Self-immolative polymer-based immunogenic cell death inducer for regulation of redox homeostasis.

Doxorubicin (DOX), widely used as an anticancer drug, is considered an immunogenic cell death (ICD) inducer that enhances cancer immunotherapy. However, its extended application as an ICD inducer has been limited owing to poor antigenicity and inefficient adjuvanticity. To enhance the immunogenicity of DOX, we prepare a reactive oxygen species (ROS)-responsive self-immolative polymer (R-SIP) that can efficiently destroy redox homeostasis via self-immolation-mediated glutathione depletion in cancer cells. Owing to its amphiphilic nature, R-SIP self-assemble into nano-sized particles under aqueous conditions, and DOX is efficiently encapsulated inside the nanoparticles by a simple dialysis method. Interestingly, when treated with 4T1 cancer cells, DOX-encapsulated R-SIP (DR-SIP) induces the phosphorylation of eukaryotic translation initiation factor 2α and overexpression of ecto-calreticulin, resulting in endoplasmic reticulum-associated ICD. In addition, DR-SIP contributes to the maturation of dendritic cells by promoting the release of damage-associated molecular patterns (DAMPs) from cancer cells. When intravenously administered to tumor-bearing mice, DR-SIP remarkably inhibits tumor growth compared with DOX alone. Overall, DR-SIP may have the potential to elicit an immune response as an ICD inducer.

Transdermal delivery of rapamycin with poor water-solubility by dissolving polymeric microneedles for anti-angiogenesis.

Angiogenesis plays an important role in the occurrence and development of skin tumors and vascular anomalies (VAs). Many drugs have been adopted for the inhibition of angiogenesis, among which rapamycin (RAPA) possesses good application prospects. However, the clinical potential of RAPA for VAs is limited by its poor solubility, low bioavailability, and high cytotoxicity. To extend its application prospect for VAs treatment, in this study, we develop RAPA-loaded dissolving polymeric microneedles (RAPA DMNs) made of polyvinylpyrrolidone (PVP) due to its excellent solubilizing ability. RAPA DMNs are shown to have sufficient mechanical strength to overcome the skin barrier of the stratum corneum and could deliver RAPA to a depth of 200 µm. The microneedle shafts completely dissolve and 80% of the drug could be released within 10 min after insertion ex vivo. The DMNs-penetrated mice skin could repair itself within 4 h after the application of RAPA DMNs. RAPA DMNs also show good anti-angiogenic effect by inhibiting the growth of human umbilical vein endothelial cells (HUVECs) and decreasing the secretion of vascular endothelial growth factor (VEGF). Therefore, RAPA DMNs promisingly provide a safe and efficient approach for VAs treatment.

Polyethylenimine-based micro/nanoparticles as vaccine adjuvants.

Vaccines have shown great success in treating and preventing tumors and infections, while adjuvants are always demanded to ensure potent immune responses. Polyethylenimine (PEI), as one of the well-studied cationic polymers, has been used as a transfection reagent for decades. However, increasing evidence has shown that PEI-based particles are also capable of acting as adjuvants. In this paper, we briefly review the physicochemical properties and the broad applications of PEI in different fields, and elaborate on the intracellular processes of PEI-based vaccines. In addition, we sum up the proof of their in vivo and clinical applications. We also highlight some mechanisms proposed for the intrinsic immunoactivation function of PEI, followed by the challenges and future perspectives of the applications of PEI in the vaccines, as well as some strategies to elicit the desirable immune responses.

Guanidinated Thiourea-Decorated Polyethylenimines for Enhanced Membrane Penetration and Efficient siRNA Delivery.

RNA interference (RNAi) provides the promising treatments of gene-related diseases while hindered by the lack of highly efficient delivery platform with low cytotoxicity. Moreover, the intracellular fates of nonviral gene carriers are closely related to their internalization pathway, and eventually influence their RNAi efficiency. Herein, a series of guanidinated thiourea-modified polyethylenimines (PEI-MTU-Gs) are synthesized and utilized as the efficient carriers of small interfering RNA (siRNA) with up to 71.6% inhibition of luciferase activity in the luciferase-expressing cell lines (i.e., HeLa/Luc cells). The introduction of noncationic hydrogen bond donors, that is, thiourea groups, provides the carriers with much lower cytotoxicities and relatively looser complex structures that facilitate the intracellular release of siRNAs. Furthermore, the multiguanidino structures endow the PEI-MTU-G/siRNA complexes with the ability to directly penetrate cell membrane, which facilitates the cellular internalization while avoiding them suffering from the rigorous lysosomes. The results demonstrate PEI-MTU35 -Gs as promising siRNA carriers for further gene therapy.

miRNA oligonucleotide and sponge for miRNA-21 inhibition mediated by PEI-PLL in breast cancer therapy.

MicroRNA-21 (miR-21) inhibition is a promising biological strategy for breast cancer therapy. However its application is limited by the lack of efficient miRNA inhibitor delivery systems. As a cationic polymer transfection material for nucleic acids, the poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer combines the high transfection efficiency of polyethylenimine (PEI) and the good biodegradability of polyllysine (PLL). In this work, PEI-PLL was successfully synthesized and confirmed to transfect plasmid and oligonucleotide more effectively than PEI in MCF-7 cells (human breast cancer cells). In this regard, two kinds of miR-21 inhibitors, miR-21 sponge plasmid DNA (Sponge) and anti-miR-21 oligonucleotide (AMO), were transported into MCF-7 cells by PEI-PLL respectively. The miR-21 expression and the cellular physiology were determined post transfection. Compared with the negative control, PEI-PLL/Sponge or PEI-PLL/AMO groups exhibited lower miR-21 expression and cell viability. The anti-tumor mechanism of PEI-PLL/miR-21 inhibitors was further studied by cell cycle and western blot analyses. The results indicated that the miR-21 inhibition could induce the cell cycle arrest in G1 phase, upregulate the expression of Programmed Cell Death Protein 4 (PDCD4) and thus active the caspase-3 apoptosis pathway. Interestingly, the PEI-PLL/Sponge and PEI-PLL/AMO also sensitized the MCF-7 cells to anti-tumor drugs, doxorubicin (DOX) and cisplatin (CDDP). These results demonstrated that PEI-PLL/Sponge and PEI-PLL/AMO complexes would be two novel and promising gene delivery systems for breast cancer gene therapy based on miR-21 inhibition. STATEMENT OF SIGNIFICANCE: This work was a combination of the high transfection efficiency of polyethylenimine (PEI), the good biodegradability of polyllysine (PLL) and the breast cancer-killing effect of miR-21 inhibitors. The poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer was employed as the vector of miR-21 sponge plasmid DNA (Sponge) or anti-miR-21 oligonucleotide (AMO). PEI-PLL showed more transfection efficiency and lower cytotoxicity in human breast cancer cells than PEI. Moreover, the breast cancer cells exhibited significantly lower miR-21 expression and cell viability post transfection with sponge or AMO. Interestingly, the PEI-PLL/miR-21 inhibitor complexes also sensitized the cancer cells to anti-cancer chemotherapy drugs, doxorubicin (DOX) and cisplatin (CDDP). This synergistic effect provides a good application prospect of co-delivery miR-21 inhibitors and chemical drugs in breast cancer therapy.

A serum-tolerant hydroxyl-modified polyethylenimine as versatile carriers of pDNA/siRNA.

The polyethylenimine (PEI) derivatives (PTn) are prepared by treating PEI25k with Tris(hydroxymethyl) acrylamidomethane via the Michael addition. These PTns can effectively condense nucleic acids into nanosized particles with positive surface charges. The PTns show lower cytotoxicity and better serum-resistant capacity than PEI25k. Specially, the transfection efficiency of PT26/DNA is 29-fold higher than that of PEI25k in HeLa cells in serum-containing medium. The PTn/siRNA complexes show superior knockdown effect in CT26 cells in serum-containing medium. In addition, flow cytometry analysis shows that the PTns can efficiently mediate the entry of nucleic acids into the cell. Thus, PTns are potentially applicable as non-viral carriers of nucleic acids and warrant further development for use in gene therapy.