Size-adaptable and ligand (biotin)-sheddable nanocarriers equipped with avidin scavenging technology for deep tumor penetration and reduced toxicity

Phase-separating Pt(IV)-graft-glycopeptides sequentially sensing pH and redox for deep tumor penetration and targeting chemotherapy

Active-targeting nanomedicines have been widely employed in cancer treatment for increasing therapeutic index. However, the limited permeability caused by the binding site barrier (BSB) and size hindrances compromises their clinical antitumor efficacy in patients. Herein, learning from the liquid-liquid phase separation (LLPS) of bio-macromolecules, we report phase-separating glycopeptides (HEP) from polyhistidine (PHis) grafted hyaluronic acid (HA), which can sense the tumor extracellular pH and concomitantly overcome size and BSB dilemmas for enhanced tumor penetration. HEP aggregates into nanodroplets in solution at neutral pH. Upon reaching the acidic extracellular environment of tumors, the pH-responsive PHis triggers a phase separation, converting the coacervate nanodroplets into monomeric glycopeptides. This enables HEP conjugated with the platinum prodrug (HEPPt) to deeply penetrate into tumors by overcoming the BSB effect arising from the interaction between nanodroplets and cluster of differentiation 44 (CD44), as well as resolving the size challenges. Moreover, HEPPt in monomeric states exhibits promoted cellular uptake after pH-triggered phase separation, attributed to the transmembrane effect of exposed PHis. Subsequently, the rapid release of Pt(II), triggered by tumor intracellular reducing environment, exerts excellent antitumor activity. The phase-separating glycopeptides represent a promising platform for improving tumor penetration and intracellular delivery of therapeutic agents.

Flexible Site-Specific Labeling-Mediated Self-Assembly Sensor Based on Quantum Dots and LUMinescent AntiBody Sensor for Duplexed Detection of Antibodies

Over recent years, the LUMinescent AntiBody Sensor (LUMABS) system, utilizing bioluminescence resonance energy transfer (BRET), has emerged as a highly effective method for antibody detection. This system incorporates NanoLuc (Nluc) as the donor and fluorescent protein (FP) as the acceptor. However, the limited Stokes shift of FP poses a challenge, as it leads to significant spectral cross-talk between the excitation and emission spectra. This issue complicates the implementation of multiplexed detection. To address this challenge, we present an innovative enhancement to the LUMABS sensor with quantum dots (QDs) as the acceptor instead of FP. The use of QDs offers several advantages over those of traditional FP-based sensors. The biotin-avidin system facilitates the flexible interchangeability of QDs, allowing for a more convenient multicolor sensor construct. The new QD-LUMABS system overcomes the limitations of spectral cross-talk and provides better spectral separation. This breakthrough enables the successful implementation of multiplexed detection for multiple targets simultaneously. Results demonstrated that the wavelength-tunable QD-LUMABS sensors achieved picomolar-level detection limits for antibodies and that this sensor-construction strategy was generally applicable among various epitopes and their antibodies. Furthermore, this sensor displayed excellent duplexing capabilities. These features underscore its potential for future clinical disease diagnosis applications.

Recent advances, strategies, and future perspectives of peptide-based drugs in clinical applications

Peptide-based therapies have attracted considerable interest in the treatment of cancer, diabetes, bacterial infections, and neurodegenerative diseases due to their promising therapeutic properties and enhanced safety profiles. This review provides a comprehensive overview of the major trends in peptide drug discovery and development, emphasizing preclinical strategies aimed at improving peptide stability, specificity, and pharmacokinetic properties. It assesses the current applications and challenges of peptide-based drugs in these diseases, illustrating the pharmaceutical areas where peptide-based drugs demonstrate significant potential. Furthermore, this review analyzes the obstacles that must be overcome in the future, aiming to provide valuable insights and references for the continued advancement of peptide-based drugs.

Enzyme-responsive liposomes for controlled drug release

Compared to other nanovectors, liposomes exhibit unique advantages, such as good biosafety and high drug-loading capacity. However, slow drug release from conventional liposomes makes most payloads unavailable, restricting the therapeutic efficacy. Therefore, in the last ∼20 years, enzyme-responsive liposomes have been extensively investigated, which liberate drugs under the stimulation of enzymes overexpressed at disease sites. In this review, we elaborate on the research progress on enzyme-responsive liposomes. The involved enzymes mainly include phospholipases, particularly phospholipase A2, matrix metalloproteinases, cathepsins, and esterases. These enzymes can cleave ester bonds or specific peptide sequences incorporated in the liposomes for controlled drug release by disrupting the primary structure of liposomes, detaching protective polyethylene glycol shells, or activating liposome-associated prodrugs. Despite decades of efforts, there are still a lack marketed products of enzyme-responsive liposomes. Therefore, more efforts should be made to improve the safety and effectiveness of enzyme-responsive liposomes and address the issues associated with production scale-up.

Exploiting Nanotechnology for Drug Delivery: Advancing the Anti-Cancer Effects of Autophagy-Modulating Compounds in Traditional Chinese Medicine

Background

Cancer continues to be a prominent issue in the field of medicine, as demonstrated by recent studies emphasizing the significant role of autophagy in the development of cancer. Traditional Chinese Medicine (TCM) provides a variety of anti-tumor agents capable of regulating autophagy. However, the clinical application of autophagy-modulating compounds derived from TCM is impeded by their restricted water solubility and bioavailability. To overcome this challenge, the utilization of nanotechnology has been suggested as a potential solution. Nonetheless, the current body of literature on nanoparticles delivering TCM-derived autophagy-modulating anti-tumor compounds for cancer treatment is limited, lacking comprehensive summaries and detailed descriptions.

Methods

Up to November 2023, a comprehensive research study was conducted to gather relevant data using a variety of databases, including PubMed, ScienceDirect, Springer Link, Web of Science, and CNKI. The keywords utilized in this investigation included "autophagy", "nanoparticles", "traditional Chinese medicine" and "anticancer".

Results

This review provides a comprehensive analysis of the potential of nanotechnology in overcoming delivery challenges and enhancing the anti-cancer properties of autophagy-modulating compounds in TCM. The evaluation is based on a synthesis of different classes of autophagy-modulating compounds in TCM, their mechanisms of action in cancer treatment, and their potential benefits as reported in various scholarly sources. The findings indicate that nanotechnology shows potential in enhancing the availability of autophagy-modulating agents in TCM, thereby opening up a plethora of potential therapeutic avenues.

Conclusion

Nanotechnology has the potential to enhance the anti-tumor efficacy of autophagy-modulating compounds in traditional TCM, through regulation of autophagy.

Advances in the variations and biomedical applications of stimuli-responsive nanodrug delivery systems

Chemotherapy is an important cancer treatment modality, but the clinical utility of chemotherapeutics is limited by their toxic side effects, inadequate distribution and insufficient intracellular concentrations. Nanodrug delivery systems (NDDSs) have shown significant advantages in cancer diagnosis and treatment. Variable NDDSs that respond to endogenous and exogenous triggers have attracted much research interest. Here, we summarized nanomaterials commonly used for tumor therapy, such as peptides, liposomes, and carbon nanotubes, as well as the responses of NDDSs to pH, enzymes, magnetic fields, light, and multiple stimuli. Specifically, well-designed NDDSs can change in size or morphology or rupture when induced by one or more stimuli. The varying responses of NDDSs to stimulation contribute to the molecular design and development of novel NDDSs, providing new ideas for improving drug penetration and accumulation, inhibiting tumor resistance and metastasis, and enhancing immunotherapy.

Light controlled self-escape capability of non-cationic carbon nitride-based nanosheets in lysosomes for hepatocellular carcinoma targeting stimulus-responsive gene delivery

High positive charge-induced toxicity, easy lysosomal degradation of nucleic acid drugs, and poor lesion sites targeting are major problems faced in the development of gene carriers. Herein, we proposed the concept of self-escape non-cationic gene carriers for targeted delivery and treatment of photocontrolled hepatocellular carcinoma (HCC) with sufficient lysosome escape and multiple response capacities. Functional DNA was bound to the surface of biotin-PEG2000-modified graphitic carbon nitride (Bio-PEG-CN) nanosheets to form non-cationic nanocomplexes Bio-PEG-CN/DNA. These nanocomposites could actively target HCC tissue. Once these nanocomplexes were taken up by tumor cells, the accumulated reactive oxygen species (ROS) generated by Bio-PEG-CN under LED irradiation would disrupt the lysosome structure, thereby facilitating nanocomposites escape. Due to the acidic microenvironment and lipase in the HCC tissue, the reversible release of DNA could be promoted to complete the transfection process. Meanwhile, the fluorescence signal of Bio-PEG-CN could be monitored in real time by fluorescence imaging technology to investigate the transfection process and mechanism. In vitro and in vivo results further demonstrated that these nanocomplexes could remarkably upregulate the expression of tumor suppressor protein P53, increased tumor sensitivity to ROS generated by nanocarriers, and realized effective gene therapy for HCC via loading P53 gene.

Reactive oxygen species (ROS)-responsive size-reducible nanoassemblies for deeper atherosclerotic plaque penetration and enhanced macrophage-targeted drug delivery

Nanoparticle-based therapeutics represent potential strategies for treating atherosclerosis; however, the complex plaque microenvironment poses a barrier for nanoparticles to target the dysfunctional cells. Here, we report reactive oxygen species (ROS)-responsive and size-reducible nanoassemblies, formed by multivalent host-guest interactions between β-cyclodextrins (β-CD)-anchored discoidal recombinant high-density lipoprotein (NP³_ST) and hyaluronic acid-ferrocene (HA-Fc) conjugates. The HA-Fc/NP³_ST nanoassemblies have extended blood circulation time, specifically accumulate in atherosclerotic plaque mediated by the HA receptors CD44 highly expressed in injured endothelium, rapidly disassemble in response to excess ROS in the intimal and release smaller NP³_ST, allowing for further plaque penetration, macrophage-targeted cholesterol efflux and drug delivery. In vivo pharmacodynamicses in atherosclerotic mice shows that HA-Fc/NP³_ST reduces plaque size by 53%, plaque lipid deposition by 63%, plaque macrophage content by 62% and local inflammatory factor level by 64% compared to the saline group. Meanwhile, HA-Fc/NP³_ST alleviates systemic inflammation characterized by reduced serum inflammatory factor levels. Collectively, HA-Fc/NP³_ST nanoassemblies with ROS-responsive and size-reducible properties exhibit a deeper penetration in atherosclerotic plaque and enhanced macrophage targeting ability, thus exerting effective cholesterol efflux and drug delivery for atherosclerosis therapy.

•

HA-Fc/NP³_ST is designed for long blood circulation and deep plaque penetration.

•

Nanoassemblies are formed by multivalent host-guest interactions of β-CD/ferrocene.

•

Release of NP³_ST triggered by excess ROS aims for macrophage-targeted drug delivery.

•

FRET method is utilized to characterize the ROS-responsiveness of nanoassemblies.

•

Biomimic cell coculture model is constructed to simulate the atherosclerotic plaque.

Multifunctional ROS-Responsive and TME-Modulated Lipid-Polymer Hybrid Nanoparticles for Enhanced Tumor Penetration

PURPOSE

To enhance tumor penetration by formulation design and tumor microenvironment (TME) modulation, herein a novel reactive oxygen species (ROS)-responsive size/shape transformable lipid-polymer hybrid nanoparticle (LPN) has been fabricated for the co-delivery of an anticancer and collagen-inhibition drug.

METHODS

A ROS-responsive poly(D, L-lactide)-thioketal-polyethylene glycol (PLA-TK-PEG) co-polymer was synthesized. LPNs were then fabricated by encapsulation of losartan (LST)-loaded micelles as the core to support paclitaxel (PTX)-loaded liposomes. The PEG content in the lipid shell of LPNs was then adjusted to obtain the size-/shape-transformable LPNs (M/LST-Lip/PTX-PEG5%). The ROS-responsiveness was observed in vitro by transmission electron microscopy and the tumor-penetration of the LPNs was evaluated in 3D tumor spheroids by confocal laser scanning microscopy. Tumor-targeting, tumor-penetrating, and antitumor efficacies of the NPs in 4T1 tumor-bearing mice were determined by in vivo imaging.

RESULTS

ROS-responsive micellar core degradation and the transformation of spherical LPNs (120nm) to smaller 40 mm discoid nanoparticles (NP) were observed. The transformable LPNs exhibited enhanced capacity of penetration in contrast to the un-transformable preparations in three-dimensional (3D) tumor spheroids. Furthermore, synergetic penetrating enhancement was achieved by LST-loaded transformable LPNs in 4T1 and fibroblast cell mixed 3D tumor spheroids. The improved tumor penetration of LST-loaded transformable LPNs was observed in vivo, which could be due to their collagen inhibiting and size/shape transformable effect. Due to their enhanced penetrability, LST and PTX-loaded transformable LPNs demonstrated significant in vivo antitumor efficacy in comparison to other preparations.

CONCLUSION

The results confirmed the efficacy of M/LST-Lip/PTX-PEG5% in tumor targeting, collagen inhibition in TME, and enhanced tumor penetration. This novel drug delivery system can therefore play a substantial role in improving the therapeutic efficacy of antitumor drugs combined with TME-improving agents.

Dual Functionalized Liposomes for Selective Delivery of Poorly Soluble Drugs to Inflamed Brain Regions

Dual functionalized liposomes were developed to cross the blood−brain barrier (BBB) and to release their cargo in a pathological matrix metalloproteinase (MMP)-rich microenvironment. Liposomes were surface-functionalized with a modified peptide deriving from the receptor-binding domain of apolipoprotein E (mApoE), known to promote cargo delivery to the brain across the BBB in vitro and in vivo; and with an MMP-sensitive moiety for an MMP-triggered drug release. Different MMP-sensitive peptides were functionalized at both ends with hydrophobic stearate tails to yield MMP-sensitive lipopeptides (MSLPs), which were assembled into mApoE liposomes. The resulting bi-functional liposomes (i) displayed a < 180 nm diameter with a negative ζ-potential; (ii) were able to cross an in vitro BBB model with an endothelial permeability of 3 ± 1 × 10−5 cm/min; (iii) when exposed to functional MMP2 or 9, efficiently released an encapsulated fluorescein dye; (iv) showed high biocompatibility when tested in neuronal cultures; and (v) when loaded with glibenclamide, a drug candidate with poor aqueous solubility, reduced the release of proinflammatory cytokines from activated microglial cells.

Pt/DOX Nanomotors Enhance Penetration in the Deep Tumor by Positive Chemotaxis

Inefficient tumor penetration caused by the characteristics of tumor microenvironments is a primary obstacle to improving drug delivery efficiency, which restricts the chemotherapy drug efficacy. One such promising idea is to construct micro/nanomotors (MNMs) as an effective delivery vehicle by way of producing autonomous motion and converting exogenous stimuli or external energies from the surrounding environment into mechanical forces. In this research, the Pt/DOX nanomotor was prepared, and the enhanced diffusion and positive chemotaxis driven by substrates were verified in vitro, proof of the enhanced cellular uptake and deep penetration of Pt/DOX. As a novel nanovehicle, Pt/DOX potentially provides an intriguing approach to foster the tumor-deep penetration and enhance the drug delivery efficiency.

Strategies to enhance drug delivery to solid tumors by harnessing the EPR effects and alternative targeting mechanisms

The Enhanced Permeability and Retention (EPR) effect has been recognized as the central paradigm in tumor-targeted delivery in the last decades. In the wake of this concept, nanotechnologies have reached phenomenal levels in research. However, clinical tumors display a poor manifestation of EPR effect. Factors including tumor heterogeneity, complicating tumor microenvironment, and discrepancies between laboratory models and human tumors largely contribute to poor efficiency in tumor-targeted delivery and therapeutic failure in clinical translation. In this article, approaches for evaluation of EPR effect in human tumor were overviewed as guidance to employ EPR effect for cancer treatment. Strategies to augment EPR-mediated tumoral delivery are discussed in different dimensions including enhancement of vascular permeability, depletion of tumor extracellular matrix and optimization of nanoparticle design. Besides, the recent development in alternative tumor-targeted delivery mechanisms are highlighted including transendothelial pathway, endogenous cell carriers and non-immunogenic bacteria-mediated delivery. In addition, the emerging preclinical models better reflect human tumors are introduced. Finally, more rational applications of EPR effect in other disease and field are proposed. This article elaborates on fundamental reasons for the gaps between theoretical expectation and clinical outcomes, attempting to provide some perspective directions for future development of cancer nanomedicines in this still evolving landscape.

ZIF-based carbon dots with lysosome-Golgi transport property as visualization platform for deep tumour therapy via hierarchical size/charge dual-transform and transcytosis

The poor penetration of nanomaterials in solid tumours and difficulty in monitoring their penetration depth are major obstacles in their application for the treatment of solid tumours. Herein, pH-responsive carbon dots (ZCD) based on a zeolitic imidazolate framework (ZIF-8) were fabricated to achieve the deep delivery of the chemotherapeutic doxorubicin (DOX) via a hierarchical size/charge dual-transformation and transcytosis. The as-prepared ZCD accumulated in the solid tumour and the acidic tumour microenvironment further triggered its decomposition. Firstly, ZCD was decomposed by the weakly acidic extracellular microenvironment of the solid tumour, enabling it to transform into small and neutrally charged particles. Subsequently, these particles were endocytosed by lysosomes, and further disintegrated into smaller and positively charged particles, which could target the Golgi apparatus. Consequently, ZCD delivered DOX deep into the solid tumour via a size-shrinking strategy and Golgi-mediated transcytosis, thus significantly improving its antitumour efficacy. In addition, carbonization endowed ZCD with superior fluorescence property, which was enhanced in the acidic microenvironment, thus improving the sensitivity and accuracy of ex vivo monitoring of the penetration depth of the nanomedicine in real time. Collectively, our results confirmed that the carbon dots obtained via the direct carbonization of ZIF-8 simultaneously exhibited enhanced deep penetration into solid tumours and fluorescence, which could be monitored, and that the carbonization of functional materials is effective to enhance their fluorescence, and further broaden their applications.

Synergistic photothermal-photodynamic-chemotherapy toward breast cancer based on a liposome-coated core-shell AuNS@NMOFs nanocomposite encapsulated with gambogic acid

A multifunctional nanoplatform with core–shell structure was constructed in one-pot for the synergistic photothermal, photodynamic, and chemotherapy against breast cancer. In the presence of gambogic acid (GA) as the heat-shock protein 90 (HSP90) inhibitor and the gold nanostars (AuNS) as the photothermal reagent, the assembly of Zr⁴⁺ with tetrakis (4-carboxyphenyl) porphyrin (TCPP) gave rise to the nanocomposite AuNS@ZrTCPP-GA (AZG), which in turn, further coated with PEGylated liposome (LP) to enhance the stability and biocompatibility, and consequently the antitumor effect of the particle. Upon cellular uptake, the nanoscale metal − organic framework (NMOF) of ZrTCPP in the resulted AuNS@ZrTCPP-GA@LP (AZGL) could be slowly degraded in the weak acidic tumor microenvironment to release AuNS, Zr⁴⁺, TCPP, and GA to exert the synergistic treatment of tumors via the combination of AuNS-mediated mild photothermal therapy (PTT) and TCPP-mediated photodynamic therapy (PDT). The introduction of GA serves to reduce the thermal resistance of the cell to re-sensitize PTT and the constructed nanoplatform demonstrated remarkable anti-tumor activity in vitro and in vivo. Our work highlights a facile strategy to prepare a pH-dissociable nanoplatform for the effective synergistic treatment of breast cancer.

Anchoring β-CD on simvastatin-loaded rHDL for selective cholesterol crystals dissolution and enhanced anti-inflammatory effects in macrophage/foam cells

Macrophage/foam cells and cholesterol crystals (CCs) have been regarded as the central triggers of maladaptive inflammation in atherosclerotic plaque. Despite the tremendous progress of recombinant high-density lipoprotein (rHDL) serving for targeted drug delivery to alleviate inflammation in macrophage/foam cells, the active attempt to modulate/improve its CCs dissolution capacity remains poorly explored. The untreated CCs can seriously aggravate inflammation and threaten plaque stability. Based on the superb ability of β-cyclodextrin (β-CD) to bind CCs and promote cholesterol efflux, simvastatin-loaded discoidal-rHDL (ST-d-rHDL) anchored with β-CD (βCD-ST-d-rHDL) was constructed. We verified that βCD-ST-d-rHDL specifically bound and dissolved CCs extracellularly and intracellularly. Furthermore, anchoring β-CD onto the surface of ST-d-rHDL enhanced its cholesterol removal ability in RAW 264.7 cell-derived foam cells characterized by accelerated cholesterol efflux, reduced intracellular lipid deposition, and improved cell membrane fluidity/permeability. Finally, βCD-ST-d-rHDL exerted efficient drug delivery and effective anti-inflammatory effects in macrophage/foam cells. Collectively, anchoring β-CD onto the surface of ST-d-rHDL for selective CCs dissolution, accelerated cholesterol efflux, and improved drug delivery represents an effective strategy to enhance anti-inflammatory effects for the therapy of atherosclerosis.

A triple enhanced permeable gold nanoraspberry designed for positive feedback interventional therapy

Due to the unique microenvironment, nanoparticles cannot easily penetrate deeply into tumours, which decreases their therapeutic efficacy. Thus, new strategies should be developed to solve this problem and increase the efficacy of nanomedicine. In this study, gold nanoraspberries (GNRs) were constructed using ultrasmall gold nanospheres (UGNPs) with a matrix metalloproteinase (MMP)-2/9-sensitive peptide as a cross-linking agent. These UGNPs were then modified with trastuzumab (TRA) and mertansine derivatives (DM1) via the AuS bond. TRA targets the human epidermal growth factor receptor-2 (Her-2) which is overexpressed on Her-2⁺ breast cancer cells. The AuS bond in GNRs-DM1 can be replaced by the free sulfhydryl group of GSH, which could achieve GSH dependent redox responsive release of the drug. In the mouse model of Her-2⁺ breast cancer, a "positive feedback" triple enhanced penetration platform was construct to treat tumours. Firstly, near-infrared light-triggered photothermal conversion increased vascular permeability, resulting in nanoparticle penetration. Secondly, GNRs disintegrated into UGNPs in response to stimulation with MMPs. GNRs with larger particle sizes reached the tumour site through EPR effect and active targeting. Meanwhile, UGNPs with smaller particle sizes penetrated deeply into the tumour through diffusion. Thirdly, the UGNPs transformed activated cancer-associated fibroblasts to a quiescent state, which reduced intercellular pressure and promoted the penetration of the UGNPs into the interior of the tumour. In turn, an increase in the number of nanoparticles penetrating into the tumour led to a "positive feedback" loop of triple enhanced photothermal effects and further self-amplify the permeability in vivo. Interventional photothermal therapy (IPTT) was used to improve the therapeutic efficacy by reducing the laser power attenuation caused by percutaneous irradiation. The GNRs also showed excellent multimode imaging (computed tomography, photoacoustic imaging and photothermal imaging) capabilities and high anti-tumour efficacy due to efficient tumour targeting and triple enhanced deep penetration into the tumour site. Thus, these MMP-2/redox dual-responsive GNRs are promising carriers of drugs targeting human epidermal growth factor receptor 2+ breast cancer.

Tumor microenvironment-activated cancer cell membrane-liposome hybrid nanoparticle-mediated synergistic metabolic therapy and chemotherapy for non-small cell lung cancer

BACKGROUND

Biomimetic nanotechnology-based RNA interference (RNAi) has been successful in improving theranostic efficacy in malignant tumors. Its integration with hybrid biomimetic membranes made of natural cell membranes fused with liposomal membranes is mutually beneficial and extends their biofunctions. However, limited research has focused on engineering such biomimetics to endow them with unique properties and functions, in particular, those essential for a "smart" drug delivery system, such as a tumor microenvironment (TME)-activated multifunctional biomimetic nanoplatform.

RESULTS

Herein, we utilized an integrated hybrid nanovesicle composed of cancer cell membranes (Cm) and matrix metallopeptidase 9 (MMP-9)-switchable peptide-based charge-reversal liposome membranes (Lipm) to coat lipoic acid-modified polypeptides (LC) co-loaded with phosphoglycerate mutase 1 (PGAM1) siRNA (siPGAM1) and DTX. The nanovesicle presented a negatively charged coating (citraconic anhydride-grafted poly-L-lysine, PC) in the middle layer for pH-triggered charge conversion functionalization. The established chemotherapeutic drug (DTX) co-delivery system CLip-PC@CO-LC nanoparticles (NPs) have a particle size of ~ 193 nm and present the same surface proteins as the Cm. Confocal microscopy and flow cytometry results indicated a greater uptake of MMP-9-treated CLip-PC@CO-LC NPs compared with that of the CLip-PC@CO-LC NPs without MMP-9 pretreatment. The exposure to MMP-9 activated positively charged cell-penetrating peptides on the surface of the hybrid nanovesicles. Moreover, pH triggered membrane disruption, and redox triggered DTX and siRNA release, leading to highly potent target-gene silencing in glycolysis and chemotherapy with enhanced antiproliferation ability. The biodistribution results demonstrated that the CLip-PC@LC-DiR NPs accumulated in the tumor owing to a combination of long blood retention time, homologous targeting ability, and TME-activated characteristics. The CLip-PC@CO-LC NPs led to more effective tumor growth inhibition than the DTX and free siPGAM1 formulations.

CONCLUSIONS

TME-activated cancer cell membrane-liposome integrated hybrid NPs provide an encouraging nanoplatform that combines RNAi with chemotherapy for precise treatment of non-small cell lung cancer.

Brefeldin A delivery nanomicelles in hepatocellular carcinoma therapy: Characterization, cytotoxic evaluation in vitro, and antitumor efficiency in vivo

Hepatocellular carcinoma (HCC) is one of the major cancers with high mortality rate. Traditional drugs used in clinic are usually limited by the drug resistance and side effect and novel agents are still needed. Macrolide brefeldin A (BFA) is a well-known lead compound in cancer chemotherapy, however, with poor solubility and instability. In this study, to overcome these disadvantages, BFA was encapsulated in mixed nanomicelles based on TPGS and F127 copolymers (M-BFA). M-BFA was conferred high solubility, colloidal stability, and capability of sustained release of intact BFA. In vitro, M-BFA markedly inhibited the proliferation, induced G0/G1 phase arrest, and caspase-dependent apoptosis in human liver carcinoma HepG2 cells. Moreover, M-BFA also induced autophagic cell death via Akt/mTOR and ERK pathways. In HepG2 tumor-bearing xenograft mice, indocyanine green (ICG) as a fluorescent probe loaded in M-BFA distributed to the tumor tissue rapidly, prolonged the blood circulation, and improved the tumor accumulation capacity. More importantly, M-BFA (10 mg/kg) dramatically delayed the tumor progression and induced extensive necrosis of the tumor tissues. Taken together, the present work suggests that M-BFA has promising potential in HCC therapy.

Stimulus-responsive liposomes for biomedical applications

Liposomes are amphipathic lipidic supramolecular aggregates that are able to encapsulate and carry molecules of both hydrophilic and hydrophobic nature. They have been widely used as in vivo drug delivery systems for some time because they offer features such as synthetic flexibility, biodegradability, biocompatibility, low immunogenicity, and negligible toxicity. In recent years, the chemical modification of liposomes has paved the way to the development of smart liposome-based drug delivery systems, which are characterized by even more tunable and disease-directed features. In this review, we highlight the different types of chemical modification introduced to date, with a particular focus on internal stimuli-responsive liposomes and prodrug activation.

Morphology/Interstitial Fluid Pressure-Tunable Nanopomegranate Designed by Alteration of Membrane Fluidity under Tumor Enzyme and PEGylation

Up to now, insufficient drug accumulation in tumor remains a major challenge for nanochemotherapy. However, the spherical nanocarriers with large diameter, which are beneficial for blood circulation and tumor extravasation, cannot travel deep in a tumor. Additionally, high tumor interstitial fluid pressure (IFP) in the tumor microenvironment may promote the efflux of the penetrable nanodrugs. Therefore, the size and shape of nanocarriers as well as the tumoral IFP can be regulated synchronously for improved tumor penetration and combined chemotherapy. Herein, a novel dual-functional polymer-polypeptide (Biotin-PEG₂₀₀₀-GKGPRQITITK) for both verified tumor targeting and responsiveness was synthesized to construct the "peel" of nanopomegranate-like nanovectors (DI-MPL), in which docetaxel-loaded micelles was encapsulated as "seeds". Interestingly, DI-MPL was endowed multi-abilities of tunable size/shape switch and controlled release of IFP alleviator imatinib (IM), which were developed with one and the same strategy-alteration of membrane fluidity under the cleavage of polymer-polypeptide and PEGylation. As a result, the peel of DI-MPL could turn into small pieces with the seed scattered out in response to matrix metalloproteinase-9 (MMP-9), making nanopomegranate (180 nm) switch into spheres/disks (40 nm), during which IM is released to reduce IFP synchronously. With prominent tumor penetration ability in both multicellular tumor spheroids (MCTS) and tumor tissue, DI-MPL exhibited optimal inhibition of MCTS growth and the enhanced chemotherapy in comparison to other preparations. Meanwhile, the improved penetrability of DI-MPL in tumor tissue was found to be related to the reduced IFP, which is achieved via inhibiting expression of phosphorylated platelet-derived growth factor receptor-β (p-PDGFR-β) by IM. Altogether, the bilateral adjusting strategies from nanocarrier size/shape and tumoral IFP with a single enzyme-responsive material could provide a potential combined chemotherapy to improve tumor penetration.

Single- versus Dual-Targeted Nanoparticles with Folic Acid and Biotin for Anticancer Drug Delivery

Cancer is one of the major causes of death worldwide and its treatment remains very challenging. The effectiveness of cancer therapy significantly depends upon tumour-specific delivery of the drug. Nanoparticle drug delivery systems have been developed to avoid the side effects of the conventional chemotherapy. However, according to the most recent recommendations, future nanomedicine should be focused mainly on active targeting of nanocarriers based on ligand-receptor recognition, which may show better efficacy than passive targeting in human cancer therapy. Nevertheless, the efficacy of single-ligand nanomedicines is still limited due to the complexity of the tumour microenvironment. Thus, the NPs are improved toward an additional functionality, e.g., pH-sensitivity (advanced single-targeted NPs). Moreover, dual-targeted nanoparticles which contain two different types of targeting agents on the same drug delivery system are developed. The advanced single-targeted NPs and dual-targeted nanocarriers present superior properties related to cell selectivity, cellular uptake and cytotoxicity toward cancer cells than conventional drug, non-targeted systems and single-targeted systems without additional functionality. Folic acid and biotin are used as targeting ligands for cancer chemotherapy, since they are available, inexpensive, nontoxic, nonimmunogenic and easy to modify. These ligands are used in both, single- and dual-targeted systems although the latter are still a novel approach. This review presents the recent achievements in the development of single- or dual-targeted nanoparticles for anticancer drug delivery.

Nanodrug Delivery Systems Modulate Tumor Vessels to Increase the Enhanced Permeability and Retention Effect

The use of nanomedicine for antitumor therapy has been extensively investigated for a long time. Enhanced permeability and retention (EPR) effect-mediated drug delivery is currently regarded as an effective way to bring drugs to tumors, especially macromolecular drugs and drug-loaded pharmaceutical nanocarriers. However, a disordered vessel network, and occluded or embolized tumor blood vessels seriously limit the EPR effect. To augment the EPR effect and improve curative effects, in this review, we focused on the perspective of tumor blood vessels, and analyzed the relationship among abnormal angiogenesis, abnormal vascular structure, irregular blood flow, extensive permeability of tumor vessels, and the EPR effect. In this commentary, nanoparticles including liposomes, micelles, and polymers extravasate through the tumor vasculature, which are based on modulating tumor vessels, to increase the EPR effect, thereby increasing their therapeutic effect.

Pre- and Post-Transcriptional Regulation of cFLIP for Effective Cancer Therapy Using pH-Ultrasensitive Nanoparticles

Cellular FLIP (cFLIP) is a crucial player of apoptosis-regulated pathways that is frequently overexpressed in solid cancers. To inhibit c-FLIP, pre- and post-transcriptionally, a multifunctional nanoparticle (NP) was created to deliver cFLIP-specific small interfering RNA (siRNA) into cancer cells. Specifically, Vorinostat (Vor)-loaded mesoporous silica nanoparticles (MSN) were conjugated with polyethylenimine-biotin (PB), followed by electrostatically binding with cFLIP siRNA (Vor/siR@MSN-PB). To stabilize and prolong the circulation time of nanoparticles, a bialdehyde-modified poly(ethylene glycol) (PEG) was cross-linked onto the polyethylenimine (PEI) backbone via the formation of the imine linkage (Schiff base) (Vor/siR@MSN-PB-PEG). The Schiff base is highly stable at physiological pH 7.4 but labile under slightly acidic pH conditions. In the acidic tumor microenvironment (TME), the PEG outer layer could be rapidly cleaved, resulting in the switching of the nanoparticle surface charge to positive, which specifically enhances internalization of the NPs to the biotin-positive tumor cells. Our results demonstrated the successful preparation of Vor/siR@MSN-PB-PEG NPs, in which the siRNA was effectively protected in serum and regulated the expression of cFlip, post-transcriptionally. The presence of the PEG layer resulted in high tumor accumulation and high efficacy in tumor inhibition, which was a result of the efficient cFLIP suppression. Furthermore, in the low-dose regimen of Vorinostat-the pre-transcriptional cFLIP suppressor, treatment with Vor/siR@MSN-PB-PEG NPs was found to be safe with the treated mice, indicating a promising combination regimen for cancer therapy.

Aptamer-Functionalized Nanoparticles in Targeted Delivery and Cancer Therapy

Using nanoparticles to carry and delivery anticancer drugs holds much promise in cancer therapy, but nanoparticles per se are lacking specificity. Active targeting, that is, using specific ligands to functionalize nanoparticles, is attracting much attention in recent years. Aptamers, with their several favorable features like high specificity and affinity, small size, very low immunogenicity, relatively low cost for production, and easiness to store, are one of the best candidates for the specific ligands of nanoparticle functionalization. This review discusses the benefits and challenges of using aptamers to functionalize nanoparticles for active targeting and especially presents nearly all of the published works that address the topic of using aptamers to functionalize nanoparticles for targeted drug delivery and cancer therapy.

Biotin-decorated all-HPMA polymeric micelles for paclitaxel delivery

To avoid poly(ethylene glycol)-related issues of nanomedicines such as accelerated blood clearance, fully N-2-hydroxypropyl methacrylamide (HPMAm)-based polymeric micelles decorated with biotin for drug delivery were designed. To this end, a biotin-functionalized chain transfer agent (CTA), 4-cyano-4-[(dodecylsulfanylthiocarbonyl)-sulfanyl]pentanoic acid (biotin-CDTPA), was synthesized for reversible addition-fragmentation chain-transfer (RAFT) polymerization. Amphiphilic poly(N-2-hydroxypropyl methacrylamide)-block-poly(N-2-benzoyloxypropyl methacrylamide) (p(HPMAm)-b-p(HPMAm-Bz)) with molecular weights ranging from 8 to 24 kDa were synthesized using CDTPA or biotin-CDTPA as CTA and 2,2'-azobis(2-methylpropionitrile) as initiator. The copolymers self-assembled in aqueous media into micelles with sizes of 40-90 nm which positively correlated to the chain length of the hydrophobic block in the polymers, whereas the critical micelle concentrations decreased with increasing hydrophobic block length. The polymer with a molecular weight of 22.1 kDa was used to prepare paclitaxel-loaded micelles which had sizes between 61 and 70 nm, and a maximum loading capacity of around 10 wt%. A549 lung cancer cells overexpressing the biotin receptor, internalized the biotin-decorated micelles more efficiently than non-targeted micelles, while very low internalization of both types of micelles by HEK293 human embryonic kidney cells lacking the biotin receptor was observed. As a consequence, the paclitaxel-loaded micelles with biotin decoration exhibited stronger cytotoxicity in A549 cells than non-targeted micelles. Overall, a synthetic pathway to obtain actively targeted poly(ethylene glycol)-free micelles fully based on a poly(HPMAm) backbone was established. These polymeric micelles are promising systems for the delivery of hydrophobic anticancer drugs.

Enhancement of tumour penetration by nanomedicines through strategies based on transport processes and barriers

Nanomedicines for antitumour therapy have been widely studied in recent decades, but only a few have been used in clinical applications. One of the most important reasons is the poor tumour permeability of the nanomedicines. In this three-part review, intravascular, transvascular and extravascular transport were introduced one by one according to their roles in the overall process of nanomedicine transport into tumours. Transportation obstacles, such as elevated interstitial fluid pressure (IFP), abnormal blood vessels, dense tumour extracellular matrix (ECM) and binding site barriers (BSB), were each discussed in the context of the respective transport processes. Furthermore, homologous resolution strategies were summarized on the basis of each transportation obstacle, such as the normalization of blood vessels, regulation of the tumour microenvironment (TME) and application of transformable nanoparticles. At the end of this review, we propose holistic, concrete, and innovative views for better tumour penetration of nanomedicines.