Stimuli-Responsive Nanotheranostics

Enhancing drug penetration in solid tumors via nanomedicine: Evaluation models, strategies and perspectives

Effective tumor treatment depends on optimizing drug penetration and accumulation in tumor tissue while minimizing systemic toxicity. Nanomedicine has emerged as a key solution that addresses the rapid clearance of free drugs, but achieving deep drug penetration into solid tumors remains elusive. This review discusses various strategies to enhance drug penetration, including manipulation of the tumor microenvironment, exploitation of both external and internal stimuli, pioneering nanocarrier surface engineering, and development of innovative tactics for active tumor penetration. One outstanding strategy is organelle-affinitive transfer, which exploits the unique properties of specific tumor cell organelles and heralds a potentially transformative approach to active transcellular transfer for deep tumor penetration. Rigorous models are essential to evaluate the efficacy of these strategies. The patient-derived xenograft (PDX) model is gaining traction as a bridge between laboratory discovery and clinical application. However, the journey from bench to bedside for nanomedicines is fraught with challenges. Future efforts should prioritize deepening our understanding of nanoparticle-tumor interactions, re-evaluating the EPR effect, and exploring novel nanoparticle transport mechanisms.

Dual Tumor-Selective β-Carboline-Based Fluorescent Probe for High-Contrast/Rapid Diagnosis of Clinical Tumor Tissues

Given that precise/rapid intraoperative tumor margin identification is still challenging, novel fluorescent probes HY and HYM, based on acidic tumor microenvironment (TME) activation and organic anion transporting polypeptide (OATPs)-mediated selective uptake, were constructed and synthesized. Both of them possessed acidic pH-activatable and reversible fluorescence as well as large Stokes shift. Compared with HY, HYM had a higher (over 9-fold) enhancement in fluorescence with pH ranging from 7.6 to 4.0, and the fluorescence quantum yield of HYM (ΦF = 0.49) at pH = 4.0 was 8-fold stronger than that (ΦF = 0.06) at pH = 7.4. Mechanism research demonstrated that acidic TME-induced protonation of the pyridine N atom on β-carbolines accounted for the pH-sensitive fluorescence by influencing the intramolecular charge transfer (ICT) effect. Furthermore, HYM selectively lit up cancer cells and tumor tissues not only by "off-on" fluorescence but also by OATPs (overexpressed on cancer cells)-mediated cancer cellular internalization, offering dual tumor selectivity for precise visualization of tumor mass and intraoperative guidance upon in situ spraying. Most importantly, HYM enabled rapid and high-contrast (tumor-to-normal tissue ratios > 6) human tumor margin identification in clinical tumor tissues by simple spraying within 6 min, being promising for aiding in clinical surgical resection.

Logic gate controlled theranostic nanoagents for in situ microwave thermal therapeutic efficacy evaluation

In vivo monitoring of treatment response is of great significance for tumor therapy in clinical trials, but it remains a formidable challenge. Herein, we demonstrate a logic AND gate theranostic nanoagent that responds to the coexistence of endogenous and exogenous stimuli, namely HAuCl4@1-Tetradecanol@Gd-based metal-organic framework@SiO2 nanocomposites (APGS NCs). Upon microwave (MW) irradiation, HAuCl4 in the inner part of APGS NCs reacts with the tumor-associated glutathione (GSH). Subsequently, it transforms into an active luminescent form of Au@1-Tetradecanol@Gd-MOF@SiO2 nanocomposites (AuPGS NCs). The intensity of generated fluorescence is correlated with the tumor thermal-injury status. Thus, the generation of AuPGS NCs with high intensity fluorescence under the co-activation of MW and GSH can visualize the treatment effects during MW thermal therapy and instantly modulate the irradiation time and range for optimal outcomes. Hence, this logic gate controlled APGS NCs makes MW thermal therapy eliminate tumor cells completely. This research offers an effective strategy for the design and preparation of activatable theranostic nanoagents for precise tumor imaging and therapy.

Framework Nucleic Acid-Based Multifunctional Tumor Theranostic Nanosystem for miRNA Fluorescence Imaging and Chemo/Gene Therapy

Intelligent stimulus-responsive theranostic systems capable of specifically sensing low-abundance tumor-related biomarkers and efficiently killing tumors remain a pressing endeavor. Here, we report a multifunctional framework nucleic acid (FNA) nanosystem for simultaneous imaging of microRNA-21 (miR-21) and combined chemo/gene therapy. To achieve this, two FNA nanoarchitectures labeled with Cy5/BHQ2 signal tags were designed, each of which contained an AS1411 aptamer, two pairs of DNA/RNA hybrids, a pH-sensitive DNA catcher, and doxorubicin (DOX) intercalating between cytosine and guanine in the tetrahedral DNA nanostructure (TDN). In the acidic tumor microenvironment, the DNA catchers spontaneously triggered to form an i-motif and create an FNA dimer (dFNA) while releasing DOX molecules to exert a cytotoxic effect. In addition, the overexpressed miR-21 in tumor cells dismantled the DNA/RNA hybrids to produce vascular endothelial growth factor-associated siRNA via a toehold-mediated strand displacement reaction, thus enabling a potent RNA interfering. Also importantly, the liberated miR-21 could initiate cascade-reaction amplification to efficiently activate the Cy5 signal reporters, thereby realizing on-site fluorescence imaging of miR-21 in living cells. The exquisitely designed FNA-based nanosystem showed favorable biocompatibility and stability as well as acid-driven DOX release characteristics. Owing to the aptamer-guided targeting delivery, specific uptake of the FNA-based theranostic nanosystem by HepG2 cells was verified with confocal laser scanning microscopy and flow cytometry analyses, which therefore resulted in apoptosis of HepG2 cells while doing minimal damage to normal H9c2 and HL-7702 cells. Strikingly, both in vitro and in vivo experiments demonstrated the achievements of the FNA-enabled miR-21 imaging and synergistically enhanced chemo/gene therapy. This work thus represents a noteworthy advance on the FNA-based theranostic strategy that can effectively avoid the undesirable premature leakage of anticarcinogen and off-target of siRNA, and achieve on-demand reagents release for tumor diagnostics and treatment.

A, Gota V, Goda JS. Insight into lipid-based nanoplatform-mediated drug and gene delivery in neuro-oncology and their clinical prospects

Tumors of the Central nervous System (CNS) are a spectrum of neoplasms that range from benign lesions to highly malignant and aggressive lesions. Despite aggressive multimodal treatment approaches, the morbidity and mortality are high with dismal survival outcomes in these malignant tumors. Moreover, the non-specificity of conventional treatments substantiates the rationale for precise therapeutic strategies that selectively target infiltrating tumor cells within the brain, and minimize systemic and collateral damage. With the recent advancement of nanoplatforms for biomaterials applications, lipid-based nanoparticulate systems present an attractive and breakthrough impact on CNS tumor management. Lipid nanoparticles centered immunotherapeutic agents treating malignant CNS tumors could convene the clear need for precise treatment strategies. Immunotherapeutic agents can selectively induce specific immune responses by active or innate immune responses at the local site within the brain. In this review, we discuss the therapeutic applications of lipid-based nanoplatforms for CNS tumors with an emphasis on revolutionary approaches in brain targeting, imaging, and drug and gene delivery with immunotherapy. Lipid-based nanoparticle platforms represent one of the most promising colloidal carriers for chemotherapeutic, and immunotherapeutic drugs. Their current application in oncology especially in brain tumors has brought about a paradigm shift in cancer treatment by improving the antitumor activity of several agents that could be used to selectively target brain tumors. Subsequently, the lab-to-clinic transformation and challenges towards translational feasibility of lipid-based nanoplatforms for drug and gene/immunotherapy delivery in the context of CNS tumor management is addressed.

A Dendritic Polymer-Based Nanosystem Mediates Drug Penetration and Irreversible Endoplasmic Reticulum Stresses in Tumor via Neighboring Effect

Nanoparticles (NPs)-based cancer therapeutics are generally impeded by poor drug penetration into solid tumors due to their dense tumor extracellular matrix (ECM). Herein, pH/redox-responsive dendritic polymer-based NPs are developed to amplify the neighboring effect for improving drug penetration and driving cell apoptosis via combination therapy. Pyropheophorbide a (Ppa) is conjugated with PEGylated dendritic peptides via disulfide bonds and doxorubicin (DOX) encapsulated in the conjugate to construct dual-responsive NPs, PDPP@D. Delayed released DOX and Ppa from PDPP@D exert their combination therapeutic effect to induce cell apoptosis, and then they are liberated out of dying cells to amplify the neighboring effect, resulting in their diffusion through the dense ECM and penetration into solid tumors. Transcriptome studies reveal that PDPP@D leads to irreversible stress on the endoplasmic reticulum and inhibits cell protection through blocking the IRE1-dependent survival pathway and unleashing the DR5-mediated caspase activity to promote cell death. The strategy of amplifying the neighboring effect of NPs through combination therapy may offer great potential in enhancing drug penetration and eradicating solid tumors.

Noninvasive remote-controlled nanomedicine by using electric field stimulation for in vivo effective cancer therapy

Precision therapy has developed as an important strategy for cancer treatment. We have developed an external electric field (EF) controlled targeting drug delivery nanosystem (TDDS) for precision cancer therapy. The electric field responsive targeting drug delivery nanosystem (EFTDDS) is synthesized by functionalizing mesoporous silica with polynitrophenyl-methacrylamide-folate (PNMAFA). The functional molecules grafted in the mesopores effectively encapsulate the drugs in the EFTDDS and control the drug release by nitrylphenyl dipolar responding to electric field. The EFTDDS has achieved high electric field control as demonstrated by the promoted EF-responsive release and the low nonspecific leakage of the doxorubicin. Furthermore, when breast cancer xenograft models on nude mice were treated with EF-stimulated nanomedicine, the tumor-inhibition rate increases to 75%, which is 2.7 times as high as that without electric field stimulation. The EFTDDS is demonstrated biodegradable, biocompatible, and EF remotely controllable, represents excellent inhibiting effect on tumor in vivo, and might become a promising nanomedicine platform for electrodynamic therapy (EDT) in the potential clinical applications.