Bisphosphonate-functionalized coordination polymer nanoparticles for the treatment of bone metastatic breast cancer

Luminescent Alendronic Acid-Conjugated Micellar Nanostructures for Potential Application in the Bone-Targeted Delivery of Cholecalciferol

Vitamin D, an essential micronutrient crucial for skeletal integrity and various non-skeletal physiological functions, exhibits limited bioavailability and stability in vivo. This study is focused on the development of polyethylene glycol (PEG)-grafted phospholipid micellar nanostructures co-encapsulating vitamin D3 and conjugated with alendronic acid, aimed at active bone targeting. Furthermore, these nanostructures are rendered optically traceable in the UV-visible region of the electromagnetic spectrum via the simultaneous encapsulation of vitamin D3 with carbon dots, a newly emerging class of fluorescents, biocompatible nanoparticles characterized by their resistance to photobleaching and environmental friendliness, which hold promise for future in vitro bioimaging studies. A systematic investigation is conducted to optimize experimental parameters for the preparation of micellar nanostructures with an average hydrodynamic diameter below 200 nm, ensuring colloidal stability in physiological media while preserving the optical luminescent properties of the encapsulated carbon dots. Comprehensive chemical-physical characterization of these micellar nanostructures is performed employing optical and morphological techniques. Furthermore, their binding affinity for the principal inorganic constituent of bone tissue is assessed through a binding assay with hydroxyapatite nanoparticles, indicating significant potential for active bone-targeting. These formulated nanostructures hold promise for novel therapeutic interventions to address skeletal-related complications in cancer affected patients in the future.

Nanoparticles for the Treatment of Bone Metastasis in Breast Cancer: Recent Advances and Challenges

Although the frequency of bone metastases from breast cancer has increased, effective treatment is lacking, prompting the development of nanomedicine, which involves the use of nanotechnology for disease diagnosis and treatment. Nanocarrier drug delivery systems offer several advantages over traditional drug delivery methods, such as higher reliability and biological activity, improved penetration and retention, and precise targeting and delivery. Various nanoparticles that can selectively target tumor cells without causing harm to healthy cells or organs have been synthesized. Recent advances in nanotechnology have enabled the diagnosis and prevention of metastatic diseases as well as the ability to deliver complex molecular "cargo" particles to metastatic regions. Nanoparticles can modulate systemic biodistribution and enable the targeted accumulation of therapeutic agents. Several delivery strategies are used to treat bone metastases, including untargeted delivery, bone-targeted delivery, and cancer cell-targeted delivery. Combining targeted agents with nanoparticles enhances the selective delivery of payloads to breast cancer bone metastatic lesions, providing multiple delivery advantages for treatment. In this review, we describe recent advances in nanoparticle development for treating breast cancer bone metastases.

Targeted Nanoparticles Based on Alendronate Polyethylene Glycol Conjugated Chitosan for the Delivery of siRNA and Curcumin for Bone Metastasized Breast Cancer Applications

Bone metastasized breast cancer reduces the quality of life and median survival. Targeted delivery of small interfering RNA (siRNA) and chemotherapeutic drugs using nanoparticles (NPs) is a promising strategy to overcome current limitations in treating these metastatic breast cancers. This research develops alendronate conjugated polyethylene glycol functionalized chitosan (ALD-PEG-CHI) NP for the delivery of cell death siRNA (CD-siRNA) and curcumin (CUR) and explores its targeting ability and in vitro cell cytotoxicity. Polyethylene glycol functionalized CHI (mPEG-CHI) NPs serve as control. The size of CD-siRNA loaded NPs is below 100 nm while CUR loaded NPs is below 200 nm, with near neutral zeta potential for all NPs. The CUR encapsulation efficiency (EE) is 70% and 88% for targeted and control NPs, respectively, while complete encapsulation of CD-siRNA is achieved in both NP systems. The bone targeting ability of CY5-dsDNA loaded ALD-PEG-CHI NPs using hydroxyapatite discs is fivefold compared to control indicating ALD presentation at the targeting NP surface. Delivery of CD-siRNA loaded NPs and CUR loaded NPs show synergistic and additive growth inhibition effects against MCF-7 cells by mPEG-CHI and ALD-PEG-CHI NPs, respectively. Overall, these in vitro results illustrate the potential of the targeted NPs as an effective therapeutic system toward bone metastasized breast cancer.

Dual-Targeting Biomimetic Semiconducting Polymer Nanocomposites for Amplified Theranostics of Bone Metastasis

Bone metastasis is a type of metastatic tumors that involves the spreads of malignant tumor cells into skeleton, and its diagnosis and treatment remain a big challenge due to the unique tumor microenvironment. We herein develop osteoclast and tumor cell dual-targeting biomimetic semiconducting polymer nanocomposites (SPFeNOC ) for amplified theranostics of bone metastasis. SPFeNOC contain semiconducting polymer and iron oxide (Fe3 O4 ) nanoparticles inside core and surface camouflaged hybrid membrane of cancer cells and osteoclasts. The hybrid membrane camouflage enables their targeting to both metastatic tumor cells and osteoclasts in bone metastasis through homologous targeting mechanism, thus achieving an enhanced nanoparticle accumulation in tumors. The semiconducting polymer mediates near-infrared (NIR) fluorescence imaging and sonodynamic therapy (SDT), and Fe3 O4 nanoparticles are used for magnetic resonance (MR) imaging and chemodynamic therapy (CDT). Because both cancer cells and osteoclasts are killed synchronously via the combinational action of SDT and CDT, the vicious cycle in bone metastasis is broken to realize high antitumor efficacy. Therefore, 4T1 breast cancer-based bone metastasis can be effectively detected and cured by using SPFeNOC as dual-targeting theranostic nanoagents. This study provides an unusual biomimetic nanoplatform that simultaneously targets osteoclasts and cancer cells for amplified theranostics of bone metastasis.

Design of Nanodrug Delivery Systems for Tumor Bone Metastasis

Tumor metastasis is a complex process that is controlled at the molecular level by numerous cytokines. Primary breast and prostate tumors most commonly metastasize to bone, and the development of increasingly accurate targeted nanocarrier systems has become a research focus for more effective anti-bone metastasis therapy. This review summarizes the molecular mechanisms of bone metastasis and the principles and methods for designing bone-targeted nanocarriers and then provides an in-depth review of bone-targeted nanocarriers for the treatment of bone metastasis in the context of chemotherapy, photothermal therapy, gene therapy, and combination therapy. Furthermore, this review also discusses the treatment of metastatic and primary bone tumors, providing directions for the design of nanodelivery systems and future research.

Structural Diversity in Antiosteolytic Bisphosphonates: Deciphering Structure-Activity Trends in Ultra Long Controlled Release Phenomena

Bisphosphonate (BP)-based treatments have been extensively prescribed for bone-related conditions, particularly for osteoporosis. Their low bioavailability creates the need for prescribed dosage increase to reach therapeutic levels but generates a plethora of undesirable side effects. A viable approach to alleviating these issues is to design and exploit controlled release strategies. Herein, the controlled release profiles of 15 structurally characterized BPs (actual drugs and structural analogs) were thoroughly studied from tablets containing three (cellulose, lactose, and silica) or two (cellulose, and silica) excipients in human stomach-simulated pH conditions. The BPs were of two types, alkyl-BPs and amino-BPs. Alkyl-BPs included four derivatives of etidronate (acid, disodium, tetra-sodium, and monopotassium forms), medronic acid, and three analogs of etidronate, in which the -CH3 group was replaced by the moieties -H, -CH2CH2CH3, and -CH2CH2CH2CH2CH3. Amino-BPs included the commercial drugs pamidronate, alendronate, neridronate, and ibandronate, as well as three analog compounds. Release curves were constructed based on data taken from 1H NMR peak integration and were expressed as "% BP release" vs time. The controlled release profiles (initial release rate, plateau value, etc.) were correlated with certain structural features (number of hydrogen and metal-oxygen bonds), showing that the molecular and crystal lattice features of each BP profoundly influence its release characteristics. It was concluded that for all BPs, in general, the initial rate became lower as the total number of lattice interactions increased. For the alkyl-BPs elongation of the alkyl side chain seems to decelerate the release. Amino-BPs, in general, show slower release than the alkyl-BPs. No adverse effects of alkyl- and amino-BP drugs on NIH3T3 cell viability were noted.

Impact of Nanomedicine in Women's Metastatic Breast Cancer

Metastatic breast cancer is responsible for 90% of mortalities among women suffering from various types of breast cancers. Traditional cancer treatments such as chemotherapy and radiation therapy can cause significant side effects and may not be effective in many cases. However, recent advances in nanomedicine have shown great promise in the treatment of metastatic breast cancer. For example, nanomedicine demonstrated robust capacity in detection of metastatic cancers at early stages (i.e., before the metastatic cells leave the initial tumor site), which gives clinicians a timely option to change their treatment process (for example, instead of endocrine therapy they may use chemotherapy). Here recent advances in nanomedicine technology in the identification and treatment of metastatic breast cancers are reviewed.

Metastatic Breast Cancer: Review of Emerging Nanotherapeutics

Metastases of breast cancer (BC) are often referred to as stage IV breast cancer due to their severity and high rate of mortality. The median survival time of patients with metastatic BC is reduced to 3 years. Currently, the treatment regimens for metastatic BC are similar to the primary cancer therapeutics and are limited to conventional chemotherapy, immunotherapy, radiotherapy, and surgery. However, metastatic BC shows organ-specific complex tumor cell heterogeneity, plasticity, and a distinct tumor microenvironment, leading to therapeutic failure. This issue can be successfully addressed by combining current cancer therapies with nanotechnology. The applications of nanotherapeutics for both primary and metastatic BC treatments are developing rapidly, and new ideas and technologies are being discovered. Several recent reviews covered the advancement of nanotherapeutics for primary BC, while also discussing certain aspects of treatments for metastatic BC. This review provides comprehensive details on the recent advancement and future prospects of nanotherapeutics designed for metastatic BC treatment, in the context of the pathological state of the disease. Furthermore, possible combinations of current treatment with nanotechnology are discussed, and their potential for future transitions in clinical settings is explored.

Research progress of bone metastases: From disease recognition to clinical practice

Bone metastases, as one of the common types of metastatic tumors, have a great impact on the survival period and quality of life of patients. Bone metastases are usually characterized by bone destruction. Skeletal related events caused by bone destruction often lead to pain, pathological fractures and even paralysis. In this review, we provide a detailed explanation of bone metastases from the epidemiology, clinical features, pathogenesis, and recently developed clinical treatment viewpoints. We concluded that the incidence of bone metastases is increasing gradually, with serious clinical symptoms, complex pathogenesis and diverse clinical treatment. Tumor cells, immune cells, osteoblasts/osteoclasts and other cells as well as cytokines and enzymes all play a key role in the pathogenesis of bone metastases. We believe that the future treatment of bone metastases will be diversified and comprehensive. Some advanced technologies, such as nanomedicine, could be used for treatment, but this depends on understanding how disease occurs. With the development of treatment, the survival time and quality of life of patients will be improved.

The treatment of hepatocellular carcinoma with SP94 modified asymmetrical bilayer lipid-encapsulated Cu(DDC)2 nanoparticles facilitating Cu accumulation in the tumor

BACKGROUND

Copper diethyldithiocarbamate (Cu(DDC)₂) has been demonstrated to possess excellent antitumor activity. However, the extremely poor water solubility of Cu(DDC)₂ bring difficulty for its formulation research. In this study, we aim to develop a novel nanocarrier for Cu(DDC)₂ delivery to overcome this obstacle and enhance antitumor activity.

METHODS

The SP94 modified asymmetrical bilayer lipid-encapsulated Cu(DDC)₂ nanoparticles (DCDP) was established by combining the method of inverse microemulsion aggregation and thin-film dispersion. In vitro cellular assays and in vivo tumor-xenograft experiments were conducted to evaluate the tumor chemotherapeutic effect of DCDP. And the vital role of copper ions played in DSF or DDC (DSF/DDC)-based cancer chemotherapy was also explored.

RESULTS

DCDP with an encapsulation efficiency (EE%) of 74.0% were successfully prepared. SP94 modification facilitated cellular intake for DCDP, and promoted apoptosis to repress tumor cell proliferation (IC₅₀, 200 nM). And DCDP effectively inhibited tumor growth with a high tumor inhibition rate of 74.84%. Furthermore, Cu(DDC)₂ was found to facilitate the copper ion accumulation in tumor tissues, which is beneficial to therapy with high potency.

CONCLUSION

DCDP exhibited high-efficient tumor chemotherapeutic efficacy and provided a novel strategy for investigating the anticancer mechanism of Cu(DDC)₂.

Research progress of bone-targeted drug delivery system on metastatic bone tumors

Bone metastases are common in malignant tumors and the effect of conventional treatment is limited. How to effectively inhibit tumor bone metastasis and deliver the drug to the bone has become an urgent issue to be solved. While bone targeting drug delivery systems have obvious advantages in the treatment of bone tumors. The research on bone-targeted anti-tumor therapy has made significant progress in recent years. We introduced the related tumor pathways of bone metastases. The tumor microenvironment plays an important role in metastatic bone tumors. We introduce a drug-loading systems based on different environment-responsive nanocomposites for anti-tumor and anti-metastatic research. According to the process of bone metastases and the structure of bone tissue, we summarized the information on bone-targeting molecules. Bisphosphate has become the first choice of bone-targeted drug delivery carrier because of its affinity with hydroxyapatite in bone. Therefore, we sought to summarize the bone-targeting molecule of bisphosphate to identify the modification effect on bone-targeting. And this paper discusses the relationship between bisphosphate bone targeting molecular structure and drug delivery carriers, to provide some new ideas for the research and development of bone-targeting drug delivery carriers. Targeted therapy will make a more outstanding contribution to the treatment of tumors.

A DNA damage nanoamplifier for the chemotherapy of triple-negative breast cancer via DNA damage induction and repair blocking

Due to a powerful DNA damage repair system and a lack of surface markers, there is currently no effective chemotherapy or tailored targeted therapies available for triple-negative breast cancer (TNBC) treatment. Herein, a tailored DNA damage nanoamplifier (Lipo@Nir/Pt(IV)_C18) was engineered to simultaneously induce DNA damage and inhibit DNA reparation for highly efficient TNBC treatment. A newly synthesized Pt(IV)_C18 prodrug, the DNA damaging inducer, and the hydrophobic poly(ADP-ribose) polymerases (PARPs) inhibitor niraparib, which is used as the DNA repair blocker, were concurrently encapsulated in highly biocompatible PEGylated liposomes to prepare Lipo@Nir/Pt(IV)_C18, for enhanced cancer therapy and future clinical translation. Lipo@Nir/Pt(IV)_C18 with an appropriate size and excellent stability, effectively accumulated at the tumor site. After internalization by tumor cells, niraparib, a highly-selective hydrophobic PARP1 inhibitor, could exacerbate the accumulation of platinum-induced DNA lesions to induce excessive genome damage for synergistic cell apoptosis, which was evidenced by the upregulated γ-H₂AX and cleaved-PARP levels. Importantly, Lipo@Nir/Pt(IV)_C18 exhibited remarkable antitumor efficacy on TNBC without BRCA mutants in vivo with little systemic toxicity. Inspired by the concept of "synthetic lethality", this study provides an inspirational and clinically transformable nanobased DNA damaging amplification strategy for the expansion of TNBC beneficiaries and highly efficient TNBC treatment via DNA damage induction and DNA repair blocking.

Blocking Cancer-Nerve Crosstalk for Treatment of Metastatic Bone Cancer Pain

The tumor microenvironment is a complex milieu where neurons constitute an important non-neoplastic cell type. From "cancer neuroscience," the crosstalk between tumors and neurons favors the rapid growth of both, making the cancer-nerve interaction a reciprocally beneficial process. Thus, cancer-nerve crosstalk may provide new targets for therapeutic intervention against cancer and cancer-related symptoms. We proposed a nerve-cancer crosstalk blocking strategy for metastatic bone cancer pain treatment, achieved by Mg/Al layered-double-hydroxide nanoshells (Mg/Al-LDH) with AZ-23 loaded inside and alendronate decorated outside. The pain-causing H⁺ is rapidly eliminated by the LDH, with neurogenesis inhibited by the antagonist AZ-23. As positive feedback, the decreased pain reverses the nerve-to-cancer Ca²⁺ crosstalk-related cell cycle, dramatically inhibiting tumor growth. All experiments confirm the improved pain threshold and enhanced tumor inhibition. The study may inspire multidisciplinary researchers to focus on cancer-nerve crosstalk for treating cancer and accompanied neuropathic diseases.

Bone-targeted nanoplatform enables efficient modulation of bone tumor microenvironment for prostate cancer bone metastasis treatment

As there is currently no effective therapy for patients with prostate cancer (PCa) bone metastasis, it was stringent to explore the relevant treatment strategies. Actually, the interaction between cancer cells and bone microenvironment plays important role in prostate cancer bone metastasis, especially the Sonic hedgehog protein (SHH) signaling in the bone microenvironment. The SHH promotes osteoblast maturation and osteoblast then secretes RANKL to induce osteoclastogenesis. Herein, this study develops bone-targeting calcium phosphate lipid hybrid nanoparticles (NPs) loaded with docetaxel (DTXL) and SHH siRNA for PCa bone metastasis treatment. For bone targeting purposes, the nanoplatform was modified with alendronate (ALN). (DTXL + siRNA)@NPs-ALN NPs effectively change the bone microenvironment by inhibiting the SHH paracrine and autocrine signaling, enhancing the anti-tumor effects of DTXL. Besides showing good in vitro cellular uptake, the NPs-ALN also inhibited tumor growth both in vitro and in vivo by inducing apoptosis, cell cycle arrest, and autophagy. This DDS comprised of (DTXL + siRNA)-loaded NPs provides an excellent strategy to treat PCa bone metastasis.

Metal nanoparticles as a promising technology in targeted cancer treatment

Traditional anticancer treatments have several limitations, but cancer is still one of the deadliest diseases. As a result, new anticancer drugs are required for the treatment of cancer. The use of metal nanoparticles (NPs) as alternative chemotherapeutic drugs is on the rise in cancer research. Metal NPs have the potential for use in a wide range of applications. Natural or surface-induced anticancer effects can be found in metals. The focus of this review is on the therapeutic potential of metal-based NPs. The potential of various types of metal NPs for tumor targeting will be discussed for cancer treatment. The in vivo application of metal NPs for solid tumors will be reviewed. Risk factors involved in the clinical application of metal NPs will also be summarized.

Breast Cancer Bone Metastasis: A Narrative Review of Emerging Targeted Drug Delivery Systems

Bone is one of the most common metastatic sites among breast cancer (BC) patients. Once bone metastasis is developed, patients' survival and quality of life will be significantly declined. At present, there are limited therapeutic options for BC patients with bone metastasis. Different nanotechnology-based delivery systems have been developed aiming to specifically deliver the therapeutic agents to the bone. The conjugation of targeting agents to nanoparticles can enhance the selective delivery of various payloads to the metastatic bone lesion. The current review highlights promising and emerging advanced nanotechnologies designed for targeted delivery of anticancer therapeutics, contrast agents, photodynamic and photothermal materials to the bone to achieve the goal of treatment, diagnosis, and prevention of BC bone metastasis. A better understanding of various properties of these new therapeutic approaches may open up new landscapes in medicine towards improving the quality of life and overall survival of BC patients who experience bone metastasis.

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.

A Review on Re-Packaging of Bisphosphonates Using Biomaterials

The need for bone repair and insight into new regeneration therapies as well as improvement of existing regeneration routes is constantly increasing as a direct consequence of the rise in the number of trauma victims, musculoskeletal disorders, and increased life expectancy. Bisphosphonates (BPs) have emerged as a class of drugs with proven efficacy against many bone disorders. The most recent ability of this class of drugs is being explored in its anti-cancer ability. However, despite the pharmacological success, there are certain shortcomings that have circumvented this class of the drug. The mediation of biomaterials in delivering bisphosphonates has greatly helped in overcoming some of these shortcomings. This article is focused on reviewing the benefits the bisphosphonates have provided upon getting delivered via the use of biomaterials. Furthermore, the role of bisphosphonates as a potent anticancer agent is also accounted. It is witnessed that employing engineering tools in combination with therapeutics has the potential to provide solutions to bone loss from degenerative, surgical, or traumatic processes, and also aid in accelerating the healing of large bone fractures and problematic non-union fractures. The role of nanotechnology in enhancing the efficacy of the bisphosphonates is also reviewed and innovative approaches are identified.

Laser/GSH-Activatable Oxaliplatin/Phthalocyanine-Based Coordination Polymer Nanoparticles Combining Chemophotodynamic Therapy to Improve Cancer Immunotherapy

There are two severe obstacles in cancer immunotherapy. The first is that the low response rate challenges the immune response owing to the immunosuppressive tumor microenvironment (ITM) and poor immunogenicity of the tumor. The second obstacle is that the dense and intricate pathophysiology barrier seriously restricts deep drug delivery in solid tumors. A laser/glutathione (GSH)-activatable nanosystem with tumor penetration for achieving highly efficient immunotherapy is reported. The core of the nanosystem was synthesized by coordinating zinc ions with GSH-activatable oxaliplatin (OXA) prodrugs and carboxylated phthalocyanine. Such an OXA/phthalocyanine-based coordination polymer nanoparticle (OPCPN) was wrapped by a phospholipid bilayer and NTKPEG. NTKPEG is a PEGylated indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor prodrug containing a thioketal (TK) linker, which was modified on the OPCPN (OPCPN@NTKPEG). Upon the laser irradiation tumor site, ROS production of the OPCPN@NTKPEG triggers cleavage of NTKPEG by degradation of TK for promoted tumor penetration and uptake. OXA, phthalocyanine, and IDO1 inhibitor were released by the intracellular high-level GSH. OXA inhibits cell growth and is combined with photodynamic therapy (PDT) to induce immunogenic cell death (ICD). The IDO1 inhibitor reversed the ITM by suppressing IDO1-mediated Trp degradation and exhaustion of cytotoxic T cells. Laser/GSH-activatable drug delivery was more conducive to enhancing ICD and reversing ITM in deep tumors. Chemo-PDT with OPCPN@NTKPEG significantly regressed tumor growth and reduced metastasis by improved cancer immunotherapy.

Engineered macrophages as near-infrared light activated drug vectors for chemo-photodynamic therapy of primary and bone metastatic breast cancer

Patients with primary and bone metastatic breast cancer have significantly reduced survival and life quality. Due to the poor drug delivery efficiency of anti-metastasis therapy and the limited response rate of immunotherapy for breast cancer, effective treatment remains a formidable challenge. In this work, engineered macrophages (Oxa(IV)@ZnPc@M) carrying nanomedicine containing oxaliplatin prodrug and photosensitizer are designed as near-infrared (NIR) light-activated drug vectors, aiming to achieve enhanced chemo/photo/immunotherapy of primary and bone metastatic tumors. Oxa(IV)@ZnPc@M exhibits an anti-tumor M1 phenotype polarization and can efficiently home to primary and bone metastatic tumors. Additionally, therapeutics inside Oxa(IV)@ZnPc@M undergo NIR triggered release, which can kill primary tumors via combined chemo-photodynamic therapy and induce immunogenic cell death simultaneously. Oxa(IV)@ZnPc@M combined with anti-PD-L1 can eliminate primary and bone metastatic tumors, activate tumor-specific antitumor immune response, and improve overall survival with limited systemic toxicity. Therefore, this all-in-one macrophage provides a treatment platform for effective therapy of primary and bone metastatic tumors.

Systemic metastasis-targeted nanotherapeutic reinforces tumor surgical resection and chemotherapy

Failure of conventional clinical therapies such as tumor resection and chemotherapy are mainly due to the ineffective control of tumor metastasis. Metastasis consists of three steps: (i) tumor cells extravasate from the primary sites into the circulation system via epithelial-mesenchymal transition (EMT), (ii) the circulating tumor cells (CTCs) form “micro-thrombi” with platelets to evade the immune surveillance in circulation, and (iii) the CTCs colonize in the pre-metastatic niche. Here, we design a systemic metastasis-targeted nanotherapeutic (H@CaPP) composed of an anti-inflammatory agent, piceatannol, and an anti-thrombotic agent, low molecular weight heparin, to hinder the multiple steps of tumor metastasis. H@CaPP is found efficiently impeded EMT, inhibited the formation of “micro-thrombi”, and prevented the development of pre-metastatic niche. When combined with surgical resection or chemotherapy, H@CaPP efficiently inhibits tumor metastasis and prolonged overall survival of tumor-bearing mice. Collectively, we provide a simple and effective systemic metastasis-targeted nanotherapeutic for combating tumor metastasis.

Failure of conventional clinical therapies such as tumor resection and chemotherapy are mainly due to the ineffective control of tumor metastasis. Here, the authors show that a systemic metastasis-targeted nanotherapeutic may offer a powerful adjunct therapy for suppressing tumor metastasis.

Bone targeting nano-aggregates prepared from self-assembled polyaspartamide graft copolymers for pH sensitive DOX delivery

Nanoparticles with bone targeting ability and pH-sensitivity were prepared with polyaspartamide (PASPAM) derivatives based on polysuccinimide (PSI) grafted with octadecylamine (C18), hydrazine (HYD) and polyethylene glycol (PEG, Mw: 5000). For the bone targeting, alendronate (ALN), which has bone affinity, was grafted to PEG and doxorubicin (DOX) was conjugated with linkers of acid sensitive hydrazone bonds, which can be cleaved most effectively in an intracellular acidic environment. At pH 5.0, ∼75% of the drug was released from ALN-PEG/C18/HYD-DOX-g-PASPAM due to the effective cleavage of HYD under the acidic condition. Also, ALN-PEG/C18/HYD-DOX-g-PASPAM particles were more effectively adsorbed on the surface of bone than PEG/C18/HYD-DOX-g-PASPAM. According to an in vivo antitumor activity test, the volume of tumor treated with ALN-PEG/C18/HYD-DOX-g-PASPAM decreased (1550 mm3) when compared with the PBS control sample (3850 mm3), proving that ALN-PEG/C18/HYD-DOX-g-PASPAM is an effective drug delivery system for the treatment of bone metastasis of breast cancer.

Reduction-responsive dehydroepiandrosterone prodrug nanoparticles loaded with camptothecin for cancer therapy by enhancing oxidation therapy and cell replication inhibition

The pentose phosphate pathway (PPP) plays a critical role by providing ribulose-5-phosphate (Ru5P) and NADPH for nucleotide synthesis and reduction energy, respectively. Accordingly, blocking the PPP process may be an effective strategy for enhancing oxidation therapy and inhibiting cell replication. Here, we designed a novel reduction-responsive PEGylated prodrug and constructed nanoparticles PsD@CPT to simultaneously deliver a PPP blocker, dehydroepiandrosterone (DHEA), and chemotherapeutic camptothecin (CPT) to integrate amplification of oxidation therapy and enhance cell replication inhibition. Following cellular uptake, DHEA and CPT were released from PsD@CPT in the presence of high glutathione (GSH) levels. As expected, DHEA-mediated reduction level decreases and CPT-induced oxidation level increases synergistically, breaking the redox balance to aggravate cancer oxidative stress. In addition, suppressing nucleotide synthesis by DHEA through the reduction of Ru5P and blocking DNA replication by CPT further motivates a synergistic inhibition effect on tumor cell proliferation. The results showed that PsD@CPT featuring multimodal treatment has satisfactory antitumor activity both in vitro and in vivo. This study provides a new tumor treatment strategy, which combines the amplification of oxidative stress and enhancement of inhibition of cell proliferation based on inhibition of the PPP process.

Alendronate/folic acid-decorated polymeric nanoparticles for hierarchically targetable chemotherapy against bone metastatic breast cancer

To considerably enhance treatment efficacy for bone metastatic breast cancer via dual bone/tumor-targeted chemotherapy, a nanoparticle-based delivery system comprising poly(lactic-co-glycolic acid) (PLGA) as the hydrophobic core coated with alendronate-modified d-α-tocopheryl polyethylene glycol succinate (ALN-TPGS) and folic acid-conjugated TPGS (FA-TPGS) was developed as a vehicle for paclitaxel (PTX) in this work. The ALN/FA-decorated nanoparticles not only showed superior ALN-mediated binding affinity for hydroxyapatite abundant in bone tissue but also promoted uptake of payloads by folate receptor-overexpressing cancer cells to significantly augment PTX cytotoxicity. Notably, through dual-targetable delivery to the bone matrix and folate receptor-overexpressing 4T1 tumors, the PTX-loaded nanoparticles substantially accumulated in bone metastases in vivo and inhibited 4T1 tumor growth and lung metastasis, leading to significant improvement of the survival rate of treated mice. Upon treatment with the ALN/FA-decorated PTX-loaded nanoparticles, the bone destruction and bone loss of the tumor-bearing mice were appreciably retarded, and the adverse effects on normal tissues were alleviated. These results demonstrate that the ALN/FA-decorated PTX-loaded delivery system developed in this study shows great promise for the effective treatment of bone metastatic breast cancer.

Alendronate-functionalized hypoxia-responsive polymeric micelles for targeted therapy of bone metastatic prostate cancer

Bone metastasis is one of the leading causes of cancer-related death and remains incurable in spite of great efforts. Bone-targeted nanoparticle-based drug carriers can overcome the difficulties in delivering therapeutic agents to metastatic bone and endowing them with a stimuli-responsive feature for controllable drug release can further maximize their therapeutic outcome. In light of hypoxic microenvironment of bone metastasis, we herein reported a bone-targeted and hypoxia-responsive polymeric micelle system for effective treatment of bone metastatic prostate cancer. The micelles were self-assembled from a polyethylene glycol and poly-l-lysine based copolymer using alendronate as a bone-targeted moiety and azobenzene as a hypoxia-responsive linker, showing a high affinity to metastatic bone and a high sensitivity in responding to hypoxia in vitro. In vivo studies further showed that after a selective accumulation in metastatic bone, the micelles could respond to hypoxic bone metastasis for rapid drug release to an effective therapeutic dosage. As a result, the micelles could suppress tumor growth in bone and inhibit bone destruction by inhibiting osteoclast activity and promoting osteoblast activity, achieving an enhanced therapeutic outcome with relieved bone pain and prolonged survival time. Bone-targeted and hypoxia-responsive nanocarriers therefore represent a promising advancement for treating bone metastasis. To our best knowledge, it might be the first example of the application of hypoxia-responsive nanocarriers in treating bone metastasis.

Review of a new bone tumor therapy strategy based on bifunctional biomaterials

Bone tumors, especially those in osteosarcoma, usually occur in adolescents. The standard clinical treatment includes chemotherapy, surgical therapy, and radiation therapy. Unfortunately, surgical resection often fails to completely remove the tumor, which is the main cause of postoperative recurrence and metastasis, resulting in a high mortality rate. Moreover, bone tumors often invade large areas of bone, which cannot repair itself, and causes a serious effect on the quality of life of patients. Thus, bone tumor therapy and bone regeneration are challenging in the clinic. Herein, this review presents the recent developments in bifunctional biomaterials to achieve a new strategy for bone tumor therapy. The selected bifunctional materials include 3D-printed scaffolds, nano/microparticle-containing scaffolds, hydrogels, and bone-targeting nanomaterials. Numerous related studies on bifunctional biomaterials combining tumor photothermal therapy with enhanced bone regeneration were reviewed. Finally, a perspective on the future development of biomaterials for tumor therapy and bone tissue engineering is discussed. This review will provide a useful reference for bone tumor-related disease and the field of complex diseases to combine tumor therapy and tissue engineering.

Bone-seeking nanoplatform co-delivering cisplatin and zoledronate for synergistic therapy of breast cancer bone metastasis and bone resorption

The "vicious cycle" established between tumor growth and osteolysis aggravates the process of breast cancer bone metastasis, leading to life-threatening skeletal-related events that severely reduce survival and quality of life. To effectively interrupt the "vicious cycle", innovative therapeutic strategies that not only reduce osteolysis but also relieve tumor burden are urgently needed. Herein, a bone-seeking moiety, alendronate (ALN), functionalized coordination polymer nanoparticles (DZ@ALN) co-delivering cisplatin prodrug (DSP) and antiresorptive agent zoledronate (ZOL) via Zn²⁺ crosslinking for combination therapy was reported. The versatile DZ@ALN with a diameter of about 40 nm can cross the fissure in the bone marrow sinus capillaries, and possesses an excellent bone-seeking ability both in vitro and in vivo. Additionally, DZ@ALN could synergistically inhibit the proliferation of cancer cells, suppress the formation of osteoclast-like cells and induce the apoptosis of osteoclasts in vitro. Importantly, it could preferentially accumulate in bone affected site, remarkably inhibit the proliferation of tumor cells, relieving bone pain, and significantly inhibit the activation of osteoclasts, protecting the bone from destruction in vivo, eventually leading to the breakdown of "vicious cycle" without inducing obvious systemic toxicity. This innovative nanoagent combines chemotherapy and osteolysis inhibition, exhibiting an inspiring strategy for effective treatment of bone metastasis.

Targeting nanoparticles for diagnosis and therapy of bone tumors: Opportunities and challenges

A variety of targeted nanoparticles were developed for the diagnosis and therapy of orthotopic and metastatic bone tumors during the past decade. This critical review will focus on principles and methods in the design of these bone-targeted nanoparticles. Ligands including bisphosphonates, aspartic acid-rich peptides and synthetic polymers were grafted on nanoparticles such as PLGA nanoparticles, liposomes, dendrimers and inorganic nanoparticles for bone targeting. Besides, other ligands such as monoclonal antibodies, peptides and aptamers targeting biomarkers on tumor/bone cells were identified for targeted diagnosis and therapy. Examples of targeted nanoparticles for the early detection of bone metastatic tumors and the ablation of cancer via chemotherapy, photothermal therapy, gene therapy and combination therapy will be intensively reviewed. The development of multifunctional nanoparticles to break down the "vicious" cycle between tumor cell proliferation and bone resorption, and the challenges and perspectives in this area will be discussed.

Polymerization and coordination synergistically constructed photothermal agents for macrophages-mediated tumor targeting diagnosis and therapy

Developing an ideal photothermal agent is one of the challenges for effective photothermal therapy (PTT). Herein, a green and simple yet versatile method is developed to construct a novel poly-(iron-dopamine coordination complexes) nanoparticles (P[Fe-DA]-NPs) based on polymerization and coordination synergistically by using Fe³⁺ ions and dopamine (DA) in aqueous solution, and simultaneously poly(vinylpyrrolidone) (PVP) is applied to improve dispersion stability. P[Fe-DA]-NPs can be laden into macrophages directly with no further purification required to target tumor tissue to perform cell-mediated strategy. P[Fe-DA]-laden macrophages as an ideal photothermal agent has the advantages of good biocompatibility, simple preparation process, high photothermal performance, and effective tumor targeting. Furthermore, the P[Fe-DA]-laden macrophages possess excellent photoacoustic imaging (PAI) capacity for guiding the precise PTT. The results show that the tumors are significantly suppressed after PTT with the help of the accurate PAI diagnosis. This cell-mediated strategy may be the most promising avenue for the future clinical cancer therapy.

Zoledronate and SPIO dual-targeting nanoparticles loaded with ICG for photothermal therapy of breast cancer tibial metastasis

Currently, nanoparticles (NPs) for cancer photothermal therapy (PTT) have limited in vivo clearance, lack targeting ability and have unsatisfactory therapeutic efficiency. Herein, we report a dual-targeting and photothermally triggered nanotherapeutic system based on superparamagnetic iron oxide (Fe3O4) and indocyanine green (ICG)-entrapped poly-lactide-co-glycolide modified by ZOL (PLGA-ZOL) NPs (ICG/Fe3O4@PLGA-ZOL) for PTT of breast cancer tibial metastasis, which occurs frequently in the clinic and causes challenging complications in breast cancer. In this system, both ICG and Fe3O4 can convert light into heat, while NPs with Fe3O4 and ZOL can be attracted to a specific location in bone under an external magnetic field. Specifically, the dual-targeting and double photothermal agents guaranteed high accumulation in the tibia and perfect PTT efficiency. Furthermore, the in vivo studies showed that ICG/Fe3O4@PLGA-ZOL NPs have extraordinary antitumor therapeutic effects and that these NPs can be accurately located in the medullary cavity of the tibia to solve problems with deep lesions, such as breast cancer tibial metastasis, showing great potential for cancer theranostics.

Design of Targeted Nanostructured Coordination Polymers (NCPs) for Cancer Therapy

Conventional cancer chemotherapy presents notable drug side effects due to non-selective action of the chemotherapeutics to normal cells. Nanoparticles decorated with receptor-specific ligands on the surface have shown an important role in improving site-selective binding, retention, and drug delivery to the cancer cells. This review summarizes the recent reported achievements using nanostructured coordination polymers (NCPs) with active targeting properties for cancer treatment in vitro and in vivo. Despite the controversy surrounding the effectivity of active targeting nanoparticles, several studies suggest that active targeting nanoparticles notably increase the selectivity and the cytotoxic effect in tumoral cells over the conventional anticancer drugs and non-targeted nanoparticle platform, which enhances drug efficacy and safety. In most cases, the nanocarriers have been endowed with remarkable capabilities such as stimuli-responsive properties, targeting abilities, or the possibility to be monitored by imaging techniques. Unfortunately, the lack of preclinical studies impedes the evaluation of these unique and promising findings for the translation of NCPs into clinical trials.

Bone Diseases: Current Approach and Future Perspectives in Drug Delivery Systems for Bone Targeted Therapeutics

Bone diseases include a wide group of skeletal-related disorders that cause mobility limitations and mortality. In some cases, e.g., in osteosarcoma (OS) and metastatic bone cancer, current treatments are not fully effective, mainly due to low patient compliance and to adverse side effects. To overcome these drawbacks, nanotechnology is currently under study as a potential strategy allowing specific drug release kinetics and enhancing bone regeneration. Polymers, ceramics, semiconductors, metals, and self-assembled molecular complexes are some of the most used nanoscale materials, although in most cases their surface properties need to be tuned by chemical or physical reactions. Among all, scaffolds, nanoparticles (NPs), cements, and hydrogels exhibit more advantages than drawbacks when compared to other nanosystems and are therefore the object of several studies. The aim of this review is to provide information about the current therapies of different bone diseases focusing the attention on new discoveries in the field of targeted delivery systems. The authors hope that this paper could help to pursue further directions about bone targeted nanosystems and their application for bone diseases and bone regeneration.

Antitumor activity of gemcitabine hydrochloride loaded lipid polymer hybrid nanoparticles (LPHNs): In vitro and in vivo

The present study demonstrated the application of gemcitabine hydrochloride (GEM) loaded lipid polymer hybrid nanoparticles (LPHNs) for the enhancement the chemotherapeutic response. GEM, which is an anti-tumor drug, is frequently utilized for the treatment of non-small cell lung cancer, breast cancer and pancreatic cancer. GEM loaded LPHNs were formed and examined for pharmacokinetic profile and in vivo anticancer activity. Modified double emulsion solvent evaporation method was employed in the preparation of the LPHNs. Cytotoxicities of the GEM loaded LPHNs formulation were evaluated on MCF-7 and MDA-MB-231 cells by MTT assays. Pharmacokinetics and in vivo anticancer efficacy studies were conducted following intraperitoneal administration in female Sprague-Dawley rats. In vivo pharmacokinetic studies in rats exhibited the advantage of the GEM loaded LPHNs over commercial product Gemko® and the GEM loaded LPHNs had longer circulation time. The half-life of GEM in LPHNs formulation was notable advanced (4.2 folds) comparing to commercial product of GEM (native). These findings indicated that GEM loaded LPHNs can be used for enhancing antitumor efficacy for breast cancer treatment.

Recent advances in bone-targeted therapy

The coordination between bone resorption and bone formation plays an essential role in keeping the mass and microstructure integrity of the bone in a steady state. However, this balance can be disturbed in many pathological conditions of the bone. Nowadays, the classical modalities for treating bone-related disorders are being challenged by severe obstacles owing to low tissue selectivity and considerable safety concerns. Moreover, as a highly mineralized tissue, the bone shows innate rigidity, low permeability, and reduced blood flow, features that further hinder the effective treatment of bone diseases. With the development of bone biology and precision medicine, one novel concept of bone-targeted therapy appears to be promising, with improved therapeutic efficacy and minimized systematic toxicity. Here we focus on the recent advances in bone-targeted treatment based on the unique biology of bone tissues. We summarize commonly used bone-targeting moieties, with an emphasis on bisphosphonates, tetracyclines, and biomimetic bone-targeting moieties. We also introduce potential bone-targeting strategies aimed at the bone matrix and major cell types in the bone. Based on these bone-targeting moieties and strategies, we discuss the potential applications of targeted therapy to treat bone diseases. We expect that this review will put together useful insights to help with the search for therapeutic efficacy in bone-related conditions.

A light-triggered self-reinforced nanoagent for targeted chemo-photodynamic therapy of breast cancer bone metastases via ER stress and mitochondria mediated apoptotic pathways

Current therapeutic strategies for the treatment of bone metastases are often limited by the lack of selectivity, severe systemic toxicity and suboptimal efficacy. Nanomedicine meditated chemo-photodynamic therapy provides a promising therapeutic opportunity for enhanced cancer therapy. Herein, we constructed an alendronate (ALN)-functionalized bone-seeking nanoagent (BTZ@ZnPc-ALN) to co-deliver the proteasome inhibitor bortezomib (BTZ) and the photosensitizer Zinc phthalocyanine (ZnPc) for synergistic chemo-photodynamic therapy of bone metastases. Results showed that BTZ@ZnPc-ALN possessed favorable bone affinity both in vitro and in vivo and could release drug in a pH-responsive manner. Under irradiation, BTZ@ZnPc-ALN could generate reactive oxygen species (ROS) to cause mitochondrial damage, and increase the cytosolic Ca²⁺ levels and the expression of GRP78 protein to induce excessive endoplasmic reticulum (ER) stress, thereby synergistically inhibiting cell proliferation. More importantly, BTZ@ZnPc-ALN could prolong blood circulation time and preferentially navigate to the bone affected site. As a result, tumor growth was significantly inhibited by bone targeted chemo-photodynamic therapy, with tumor volume cut down by 85% compared with PBS group and bone remained undamaged. Besides, the systemic toxicity of BTZ was significantly reduced. Therefore, the versatile nanoagent is expected to be a promising nanoplatform to concern multiple intracellular stress for remarkable synergistic chemo-photodynamic therapy of bone metastases.

Recent progress in nanotechnology-based novel drug delivery systems in designing of cisplatin for cancer therapy: an overview

Cisplatin cis-(diammine)dichloridoplatinum(II) (CDDP) is the first platinum-based complex approved by the food and drug administration (FDA) of the United States (US). Cisplatin is the first line chemotherapeutic agent used alone or combined with radiations or other anti-cancer agents for a broad range of cancers such as lung, head and neck. Aroplatin™, Lipoplatin™ and SPI-077 are PEGylated liposome-based nano-formulations that are still under clinical trials. They have many limitations, for example, poor aqueous solubility, drug resistance and toxicities, which can be overcome by encapsulating the cisplatin in Nemours nanocarriers. The extensive literature from different electronic databases covers the different nano-delivery systems that are developed for cisplatin. This review critically emphasizes on the recent advancement, development, innovations and updated literature reported for different carrier systems for CDDP.

Enhanced cancer therapy through synergetic photodynamic/immune checkpoint blockade mediated by a liposomal conjugate comprised of porphyrin and IDO inhibitor

Cancer metastases is still a hurdle for good prognosis and live quality of breast cancer patients. Treatment strategies that can inhibit metastatic cancer while treating primary cancer are needed to improve the therapeutic effect of breast cancer. Methods: In this study, a dual functional drug conjugate comprised of protoporphyrin IX and NLG919, a potent indoleamine-2,3-dioxygenase (IDO) inhibitor, is designed to combine photodynamic therapy and immune checkpoint blockade to achieve both primary tumor and distant metastases inhibition. Liposomal delivery is applied to improve the biocompatibility and tumor accumulation of the drug conjugate (PpIX-NLG@Lipo). A series of in vitro and in vivo experiments were carried out to examine the PDT effect and IDO inhibition activity of PpIX-NLG@Lipo, and subsequently evaluate its anti-tumor capability in the bilateral 4T1 tumor-bearing mice. Results: The in vitro and in vivo experiments demonstrated that PpIX-NLG@Lipo possess strong ability of ROS generation to damage cancer cells directly through PDT. Meanwhile, PpIX-NLG@ Lipo can induce immunogenic cell death to elicit the host immune system. Furthermore, PpIX-NLG@Lipo interferes the activity of IDO, which can amplify PDT-induced immune responses, leading to an increasing amount of CD8+ T lymphocytes infiltrated into tumor site, finally achieve both primary and distant tumor inhibition. Conclusion: This work presents a novel conjugate approach to synergize photodynamic therapy and IDO blockade for enhanced cancer therapy through simultaneously inhibiting both primary and distant metastatic tumor.

Biomaterial-assisted local and systemic delivery of bioactive agents for bone repair

Although bone tissues possess an intrinsic capacity for repair, there are cases where bone healing is either impaired or insufficient, such as fracture non-union, osteoporosis, osteomyelitis, and cancers. In these cases, treatments like surgical interventions are used, either alone or in combination with bioactive agents, to promote tissue repair and manage associated clinical complications. Improving the efficacy of bioactive agents often requires carriers, with biomaterials being a pivotal player. In this review, we discuss the role of biomaterials in realizing the local and systemic delivery of biomolecules to the bone tissue. The versatility of biomaterials enables design of carriers with the desired loading efficiency, release profile, and on-demand delivery. Besides local administration, systemic administration of drugs is necessary to combat diseases like osteoporosis, warranting bone-targeting drug delivery systems. Thus, chemical moieties with the affinity towards bone extracellular matrix components like apatite minerals have been widely utilized to create bone-targeting carriers with better biodistribution, which cannot be achieved by the drugs alone. Bone-targeting carriers combined with the desired drugs or bioactive agents have been extensively investigated to enhance bone healing while minimizing off-target effects. Herein, these advancements in the field have been systematically reviewed. STATEMENT OF SIGNIFICANCE: Drug delivery is imperative when surgical interventions are not sufficient to address various bone diseases/defects. Biomaterial-assisted delivery systems have been designed to provide drugs with the desired loading efficiency, sustained release, and on-demand delivery to enhance bone healing. By surveying recent advances in the field, this review outlines the design of biomaterials as carriers for the local and systemic delivery of bioactive agents to the bone tissue. Particularly, biomaterials that bear chemical moieties with affinity to bone are attractive, as they can present the desired bioactive agents to the bone tissue efficiently and thus enhance the drug efficacy for bone repair.

Development of Zoledronic Acid-Based Nanoassemblies for Bone-Targeted Anticancer Therapy

Bone metastasis occurs in the majority of cancer patients, which hampers quality of life and significantly decreases survival. Aggressive chemotherapy is a traditional treatment regimen that induces severe systemic toxicities. Therefore, bone-directed therapies are highly warranted. We report a novel nanoparticle formulation that is composed of poly(vinylpyrrolidone) and tannic acid core nanoparticles (PVT NPs) that forms self-assembly with zoledronic acid (ZA@PVT NPs). The construction of ZA@PVT NPs was confirmed by particle size, zeta potential, transmission electron microscopy, and spectral analyses. An optimized bone-targeted ZA@PVT NPs formulation showed greater binding and internalization in in vitro with metastasis prostate and breast cancer cells. ZA@PVT NPs were able to deliver ZA more efficiently to tumor cells, which inhibited proliferation of human prostate and breast cancer cells. In addition, ZA@PVT NPs were capable of targeting mouse bones and prostate tumor microarray tissues (ex vivo) while sparing all other vital organs. More importantly, ZA@PVT NPs induce chemo sensitization to docetaxel treatment in cancer cells. Overall, the study results confirm that ZA-based, bone-targeted NPs have great potential for the treatment of bone metastasis in the near future.

Recent advances in functional nanostructured materials for bone-related diseases

Bone-related diseases seriously threaten people's health and research studies have been dedicated towards searching for new and effective treatment methods. Nanotechnologies have opened up a new field in recent decades and nanostructured materials, which exist in a variety of forms, are considered to be promising materials in this field. This article reviews the most recent progress in the development of nanostructured materials for bone-related diseases, including osteoporosis, osteoarthritis, bone metastasis, osteomyelitis, myeloma, and bone defects. We highlight the advantages and functions of nanostructured materials, including sustained release, bone targeting, scaffolding in bone tissue engineering, etc., in bone-related diseases. We also include the remaining challenges of these emerging materials.

Bortezomib-catechol conjugated prodrug micelles: combining bone targeting and aryl boronate-based pH-responsive drug release for cancer bone-metastasis therapy

The treatment of metastatic tumors is highly desirable in clinics, which has also increased the interest in the design of nanoscale drug delivery systems. Bone metastasis is one of the most common pathways in the metastasis of breast cancer, and it is also an important cause for tumor recurrence and death. The aryl boronate group, as an acid-labile linker, has been introduced into nano-assemblies in recent years. Especially, as a proteasome inhibitor anticancer drug with a boric acid group, bortezomib can facilitate the formation of pH-sensitive aryl boric acid ester linkage with the catecholic group. In this study, bortezomib-loaded micelles with bone targeting properties were constructed for the treatment of breast cancer bone metastasis. The mixed micelles employed alendronate (ALN) as the bone-targeting ligand and encapsulated bortezomib-catechol conjugates as the cargo. In vitro and in vivo studies showed that compared with free drugs or control micelles, these prodrug micelles (ALN-NP) exhibited many favorable properties such as reduced systemic toxicity and improved therapeutic effects. Therefore, ALN-NP is promising as a nanovehicle for bone-targeting delivery of chemotherapeutic drugs. Furthermore, this study offers a novel strategy combining bone targeting and aryl boronate-based pH-responsive drug release for anti-metastasis therapy.

Bone-targeting poly(ethylene sodium phosphate)

Poly(ethylene sodium phosphate) (PEP·Na) showed excellent cytocompatibility and in vivo bone affinity. Moreover, PEP·Na did not interact with thrombin, which is a coagulation-related protein. Because immobilization of therapeutic agents and imaging probes on PEP·Na is easily performed, PEP·Na is a promising polymer for bone-targeted therapies.

Phthalocyanine-based coordination polymer nanoparticles for enhanced photodynamic therapy

In the photodynamic therapy (PDT) of cancer, zinc phthalocyanine (ZnPc) as a photosensitizer possesses superior photosensitive properties. However, the therapeutic effect of ZnPc in PDT is limited due to its aggregation, low solubility and poor selectivity. In this study, charge-reversal phthalocyanine-based coordination polymer nanoparticles (PCPN) are developed for improving the curative effect of ZnPc. Tetra(4-carboxyphenoxy)-phthalocyaninatozinc(ii) (TPZnPc) is coordinated with the zinc ion to form the core of PCPN, which is coated with a lipid bilayer by self-assembly (PCPNs@Lip). TPZnPc molecules in the core of PCPN are in the monomeric state and can generate cytotoxic singlet oxygen (¹O₂) efficiently, which solves the solubility and aggregation problems of ZnPc. Meanwhile, 1,2-dicarboxylic-cyclohexane anhydride modified lysyl-cholesterol (DLC) is functionalized on the surface of PCPN (PCPNs@Lip/DLC), endowing PCPN with a charge-reversal ability which could be triggered by a mildly acidic tumor microenvironment. PCPNs@Lip/DLC is proved to enhance tumor cellular uptake and generate more intracellular ¹O₂ after irradiation. As confirmed by in vitro and in vivo studies, PCPNs@Lip/DLC remarkably increases the PDT effect. All these results demonstrate that PCPNs@Lip/DLC is a promising nanoplatform for the application of ZnPc in effective PDT.