Synthesis of a targeted, dual pH and redox-responsive nanoscale coordination polymer theranostic against metastatic breast cancer in vitro and in vivo

Aptamer-mediated therapeutic strategies provide a potential approach for cancer

The treatment of tumors still faces considerable challenges. While conventional treatments such as surgery, chemotherapy, and radiation therapy provide some curative effects, their side effects and limitations highlight the importance of finding more precise treatment strategies. Aptamers have become an important target molecule in the field of drug delivery systems due to their good affinity and targeting, and they have gradually become an important link from basic research to clinical application. In this paper, we discussed the latest progress of aptamer-mediated nanodrugs, as well as aptamer-mediated photodynamic therapy, photothermal therapy, and immunotherapy strategies for tumor treatment, and explored the possibility of aptamer-mediated therapy for accurate tumor treatment. The purpose of this review is to provide novel insights for treating tumors with aptamer-mediated therapies by summarizing these innovative strategies, thereby ultimately enhancing the therapeutic efficacy for cancer patients.

Targeted co-delivery of FOXM1 aptamer and DOX by nucleolin aptamer-functionalized pH-responsive biocompatible nanodelivery system to enhance therapeutic efficacy against breast cancer: in vitro and in vivo

Targeted nanodelivery systems offer a promising approach to cancer treatment, including the most common cancer in women, breast cancer. In this study, a targeted, pH-responsive, and biocompatible nanodelivery system based on nucleolin aptamer-functionalized biogenic titanium dioxide nanoparticles (TNP) was developed for targeted co-delivery of FOXM1 aptamer and doxorubicin (DOX) to improve breast cancer therapy. The developed targeted nanodelivery system exhibited almost spherical morphology with 124.89 ± 12.97 nm in diameter and zeta potential value of - 23.78 ± 3.66 mV. FOXM1 aptamer and DOX were loaded into the nanodelivery system with an efficiency of 100% and 97%, respectively. Moreover, the targeted nanodelivery system demonstrated excellent stability in serum and a pH-responsive sustained drug release profile over a period of 240 h following Higuchi kinetic and Fickian diffusion mechanism. The in vitro cytotoxicity experiments demonstrated that the targeted nanodelivery system provided selective internalization and strong growth inhibition effects of about 45 and 51% against nucleolin-positive 4T1 and MCF-7 breast cancer cell lines. It is noteworthy that these phenomena were not observed in nucleolin-negative cells (CHO). The preclinical studies revealed that a single-dose intravenous injection of the targeted nanodelivery system into 4T1-bearing mice inhibited tumor growth by 1.7- and 1.4-fold more efficiently than the free drug and the non-targeted nanodelivery system, respectively. Our results suggested that the developed innovative targeted pH-responsive biocompatible nanodelivery system could serve as a prospectively potential platform to improve breast cancer treatment.

Zirconium-containing nanoscale coordination polymers for positron emission tomography and fluorescence-guided cargo delivery to triple-negative breast tumors

Nanoscale coordination polymer (NCP) is a class of hybrid materials formed by self-assembly of metal ions and organic ligands through coordination. The applications of NCP in biomedicine are quite extensive due to the diversity choice of metal ions and organic ligands. Here we designed Zr-P1 NCP based on Zr4+ selected as metal ion nodes and tetrakis(4-carboxyphenyl) ethylene as bridging ligands. Zr-P1 NCP was modified with functionalized pyrene derived polyethylene glycol (Py-PAA-PEG-Mal) on the surface and further conjugated with cRGD for active targeting of integrin αvβ3 overexpressed in triple-negative breast cancer. Doxorubicin was loaded on Zr-P1 NCP with encapsulation efficiency up to 22 % for the treatment of triple negative breast cancer. 89Zr-P1 NCP can be used for in vivo tumor imaging due to the fluorescence properties resulting from the enhanced aggregation-induced Emission (AIE) behavior of P1 ligands and its positron emission tomography (PET) capability. Cellular evaluation indicated that the functionalized Zr-P1@PEG-RGD presented a good function for tumor cell targeting imaging and doxorubicin could be targeted to triple negative breast cancer when it was loaded onto Zr-P1@PEG-RGD, which corroborated with the in vivo results. In summary, 89Zr-P1@PEG-RGD can serve as a biocompatible nanoplatform for fluorescence and PET image-guided cargo delivery. STATEMENT OF SIGNIFICANCE: Nanoscale coordination polymer (NCP) is a class of hybrid materials formed by self-assembly of metal ions and organic ligands through coordination. The diversity of available metals and ligand structures upon NCP synthesis plays an advantage in establishing multimodal imaging platforms. Here we designed 89Zr-P1@PEG-RGD NCP based on Zr4+ selected as metal ion nodes and tetrakis(4-carboxyphenyl) ethylene as bridging ligands. 89Zr-P1@PEG-RGD nanomaterials have positron emission tomography (PET) capability due to the incorporation of zirconium-89, which can be used for in vivo tumor imaging with high sensitivity. The chemotherapeutic drug DOX was loaded on Zr-P1 NCP for the treatment of triple-negative breast cancer, and dual modality imaging can provide visual guidance for drug delivery.

Engineered aptamers for molecular imaging

Molecular imaging, including quantification and molecular interaction studies, plays a crucial role in visualizing and analysing molecular events occurring within cells or organisms, thus facilitating the understanding of biological processes. Moreover, molecular imaging offers promising applications for early disease diagnosis and therapeutic evaluation. Aptamers are oligonucleotides that can recognize targets with a high affinity and specificity by folding themselves into various three-dimensional structures, thus serving as ideal molecular recognition elements in molecular imaging. This review summarizes the commonly employed aptamers in molecular imaging and outlines the prevalent design approaches for their applications. Furthermore, it highlights the successful application of aptamers to a wide range of targets and imaging modalities. Finally, the review concludes with a forward-looking perspective on future advancements in aptamer-based molecular imaging.

Synthesis and Characterization of Folic Acid-Functionalized DPLA-co-PEG Nanomicelles for the Targeted Delivery of Letrozole

An effective treatment for hormone-dependent breast cancer is chemotherapy using cytotoxic agents such as letrozole (LTZ). However, most anticancer drugs, including LTZ, are classified as class IV biopharmaceuticals, which are associated with low water solubility, poor bioavailability, and significant toxicity. As a result, developing a targeted delivery system for LTZ is critical for overcoming these challenges and limitations. Here, biodegradable LTZ-loaded nanocarriers were synthesized by solvent emulsification evaporation using nanomicelles prepared with dodecanol-polylactic acid-co-polyethylene glycol (DPLA-co-PEG). Furthermore, cancer cell-targeting folic acid (FA) was conjugated into the nanomicelles to achieve a more effective and safer cancer treatment. During our investigation, DPLA-co-PEG and DPLA-co-PEG-FA displayed a uniform and spherical morphology. The average diameters of DPLA-co-PEG and DPLA-co-PEG-FA nanomicelles were 86.5 and 241.3 nm, respectively. Our preliminary data suggest that both nanoformulations were cytocompatible, with ≥90% cell viability across all concentrations tested. In addition, the amphiphilic nature of the nanomicelles led to high drug loading and dispersion in water, resulting in the extended release of LTZ for up to 50 h. According to the Higuchi model, nanomicelles functionalized with FA have a greater potential for the controlled delivery of LTZ into target cells. This model was confirmed experimentally, as LTZ-containing DPLA-co-PEG-FA was significantly and specifically more cytotoxic (up to 90% cell death) toward MCF-7 cells, a hormone-dependent human breast cancer cell line, when compared to free LTZ and LTZ-containing DPLA-co-PEG. Furthermore, a half-maximal inhibitory concentration (IC50) of 87 ± 1 nM was achieved when MCF-7 cells were exposed to LTZ-containing DPLA-co-PEG-FA, whereas higher doses of 125 ± 2 and 100 ± 2 nM were required for free LTZ and LTZ-containing DPLA-co-PEG, respectively. Collectively, DPLA-co-PEG-FA represents a promising nanosized drug delivery system to target controllably the delivery of drugs such as chemotherapeutics.

Surface engineering of hollow gold nanoparticle with mesenchymal stem cell membrane and MUC-1 aptamer for targeted theranostic application against metastatic breast cancer

Mesenchymal stem cell membrane (MSCM)-coated biomimetic doxorubicin-loaded hollow gold nanoparticles were fabricated and decorated with MUC1 aptamer in order to provide smart theranostic platform. The prepared targeted nanoscale biomimetic platform was extensively characterized and evaluated in terms of selective delivery of DOX and CT-scan imaging. The fabricated system illustrated spherical morphology with 118 nm in diameter. Doxorubicin was loaded into the hollow gold nanoparticles through physical absorption technique with encapsulation efficiency and loading content of 77%±10 and 31%±4, respectively. The in vitro release profile demonstrated that the designed platform could respond to acidic environment, pH 5.5 and release 50% of the encapsulated doxorubicin during 48 h, while 14% of the encapsulated doxorubicin was released in physiological condition, pH 7.4 up to 48 h. The in vitro cytotoxicity experiments on 4T1 as MUC1 positive cell line illustrated that the targeted formulation could significantly increase mortality at 0.468 and 0.23 µg/ml of equivalent DOX concentration compared to non-targeted formulation while this cytotoxicity was not observed in CHO as MUC1 negative cell line. Furthermore, in vivo experiments showed high tumor accumulation of the targeted formulation even 24 h after intravenous injection which induced effective tumor growth suppression against 4T1 tumor bearing mice. On the other hand, existence of hollow gold in this platform provided CT scan imaging capability of the tumor tissue in 4T1 tumor bearing mice up to 24 h post-administration. The obtained results indicated that the designed paradigm are promising and safe theranostic system for fighting against metastatic breast cancer.

HPMA copolymer conjugated 5-aminolevulinic acid exhibits superior efficacy for photodynamic therapy with tumor-responsive and targeting properties

In this study, we developed a nanoformulation of 5-aminolevulinic acid (5-ALA) for tumor-targeted photodynamic therapy, in which 5-ALA was conjugated with a biocompatible polymer N-(2-hydroxypropyl)methacrylamide (HPMA) through the hydrazone bond, i.e., P-ALA. P-ALA behaves as the nano-sized molecule with an average size of 5.5 nm in aqueous solution. P-ALA shows a largely increased release rate in acidic pH than physiological pH, suggesting the rapid release profile in acidic tumor environment. P-ALA did not show apparent cytotoxicity up to 0.1 mg/ml, however, under light irradiation, remarkable cell death was induced with the IC₅₀ of 20-30 μg/ml. More importantly, we found significantly higher tumor accumulation of P-ALA than 5-ALA which benefit from its nano-size by taking advantage of the enhanced permeability and retention (EPR) effect. Consequently, P-ALA exhibited much improved in vivo antitumor efficacy without any apparent side effects. We thus anticipate the application of P-ALA as a nano-designed photosensitizer for anticancer photodynamic therapy.

Targeted poly(L-glutamic acid)-based hybrid peptosomes co-loaded with doxorubicin and USPIONs as a theranostic platform for metastatic breast cancer

Peptosomes, as a vesicular polypeptide-based system and a versatile carrier for co-delivery of hydrophilic and hydrophobic materials, provide great delivery opportunities due to the intrinsic biocompatibility and biodegradability of the polypeptides backbone. In the current study, a novel poly(L-glutamic acid)-block-polylactic acid di-block copolymer (PGA-PLA) was synthesized in two steps. Firstly, γ-benzyl L-glutamate-N-carboxy anhydride (BLG-NCA) and 3,6-dimethyl-1,4-dioxane-2,5-dione were polymerized using N-hexylamine and benzyl alcohol as initiators to produce poly(γ-benzyl L-glutamate (PBLG) and polylactic acid. Then, PBLG was deprotected to produce PGA. Secondly, PGA was conjugated to the benzyl-PLGA to fabricate PGA-PLA diblock copolymer. The synthesized diblock copolymer was used for the encapsulation of doxorubicin, as hydrophilic anticancer and ultra-small superparamagnetic iron oxide nanoparticles (USPIONs) as hydrophobic contrast agent within aqueous core and bilayer of vesicular peptosome, respectively via double emulsion method. The prepared peptosomes (Pep@USPIONs-DOX) controlled the release of DOX (<15 % of the encapsulated DOX release up to 240 h of incubation at the physiological conditions) while increasing the stability and solubility of the hydrophobic USPIONs. Then, AS1411 DNA aptamer was decorated on the surface of the PGA-PLA peptosomes (Apt-Pep@USPIONs-DOX). The prepared targeted and non-targeted platforms showed spherical morphology with hydrodynamic sizes of 265 ± 52 and 229 ± 44 nm respectively. In vitro cellular cytotoxicity and cellular uptake were studied in nucleolin positive (4T1) and nucleolin negative (CHO) cell lines. Cellular uptake of the targeted formulation was greater than that of non-targeted peptosome, while cellular internalization of these peptosomes was identical in CHO cells. Moreover, targeted peptosomes showed greater toxicity than non-targeted peptosome in 4T1 cell line. The prepared theranostic targeted peptosomes demonstrated improved capability in terms of survival rate, biodistribution, tumor suppression efficiency, and MR imaging in the 4T1 tumor-bearing mice.