Acid-degradable Dextran as an Image Guided siRNA Carrier for COX-2 Downregulation

Polysaccharide-Based Stimulus-Responsive Nanomedicines for Combination Cancer Immunotherapy

Cancer immunotherapy is a promising antitumor approach, whereas nontherapeutic side effects, tumor microenvironment (TME) intricacy, and low tumor immunogenicity limit its therapeutic efficacy. In recent years, combination immunotherapy with other therapies has been proven to considerably increase antitumor efficacy. However, achieving codelivery of the drugs to the tumor site remains a major challenge. Stimulus-responsive nanodelivery systems show controlled drug delivery and precise drug release. Polysaccharides, a family of potential biomaterials, are widely used in the development of stimulus-responsive nanomedicines due to their unique physicochemical properties, biocompatibility, and modifiability. Here, the antitumor activity of polysaccharides and several combined immunotherapy strategies (e.g., immunotherapy combined with chemotherapy, photodynamic therapy, or photothermal therapy) are summarized. More importantly, the recent progress of polysaccharide-based stimulus-responsive nanomedicines for combination cancer immunotherapy is discussed, with the focus on construction of nanomedicine, targeted delivery, drug release, and enhanced antitumor effects. Finally, the limitations and application prospects of this new field are discussed.

Stratifying non-small cell lung cancer patients using an inverse of the treatment decision rules: validation using electronic health records with application to an administrative database

BACKGROUND

To validate a stratification method using an inverse of treatment decision rules that can classify non-small cell lung cancer (NSCLC) patients in real-world treatment records.

METHODS

(1) To validate the index classifier against the TNM 7th edition, we analyzed electronic health records of NSCLC patients diagnosed from 2011 to 2015 in a tertiary referral hospital in Seoul, Korea. Predictive accuracy, stage-specific sensitivity, specificity, positive predictive value, negative predictive value, F1 score, and c-statistic were measured. (2) To apply the index classifier in an administrative database, we analyzed NSCLC patients in Korean National Health Insurance Database, 2002-2013. Differential survival rates among the classes were examined with the log-rank test, and class-specific survival rates were compared with the reference survival rates.

RESULTS

(1) In the validation study (N = 1375), the overall accuracy was 93.8% (95% CI: 92.5-95.0%). Stage-specific c-statistic was the highest for stage I (0.97, 95% CI: 0.96-0.98) and the lowest for stage III (0.82, 95% CI: 0.77-0.87). (2) In the application study (N = 71,593), the index classifier showed a tendency for differentiating survival probabilities among classes. Compared to the reference TNM survival rates, the index classification under-estimated the survival probability for stages IA, IIIB, and IV, and over-estimated it for stages IIA and IIB.

CONCLUSION

The inverse of the treatment decision rules has a potential to supplement a routinely collected database with information encoded in the treatment decision rules to classify NSCLC patients. It requires further validation and replication in multiple clinical settings.

PSMA-specific degradable dextran for multiplexed immunotargeted siRNA therapeutics against prostate cancer

Small interfering RNA (siRNA) is ideal for gene silencing through a sequence-specific RNA interference process. The redundancy and complexity of molecular pathways in cancer create a need for multiplexed targeting that can be achieved with multiplexed siRNA delivery. Here, we delivered multiplexed siRNA with a PSMA-targeted biocompatible dextran nanocarrier to downregulate CD46 and PD-L1 in PSMA expressing prostate cancer cells. The selected gene targets, PD-L1 and CD46, play important roles in the escape of cancer cells from immune surveillance. PSMA, abundantly expressed by prostate cancer cells, allowed the prostate cancer-specific delivery of the nanocarrier. The nanocarrier was modified with acid cleavable acetal bonds for a rapid release of siRNA. Cell imaging and flow cytometry studies confirmed the PSMA-specific delivery of CD46 and PD-L1 siRNA to high PSMA expressing PC-3 PIP cells. Immunoblot, qRT-PCR and flow cytometry methods confirmed the downregulation of CD46 and PD-L1 following treatment with multiplexed siRNA.

Design of therapeutic biomaterials to control inflammation

Inflammation plays an important role in the response to danger signals arising from damage to our body and in restoring homeostasis. Dysregulated inflammatory responses occur in many diseases, including cancer, sepsis and autoimmunity. The efficacy of anti-inflammatory drugs, developed for the treatment of dysregulated inflammation, can be potentiated using biomaterials, by improving the bioavailability of drugs and by reducing side effects. In this Review, we first outline key elements and stages of the inflammatory environment and then discuss the design of biomaterials for different anti-inflammatory therapeutic strategies. Biomaterials can be engineered to scavenge danger signals, such as reactive oxygen and nitrogen species and cell-free DNA, in the early stages of inflammation. Materials can also be designed to prevent adhesive interactions of leukocytes and endothelial cells that initiate inflammatory responses. Furthermore, nanoscale platforms can deliver anti-inflammatory agents to inflammation sites. We conclude by discussing the challenges and opportunities for biomaterial innovations in addressing inflammation.

Non-viral nanoparticles for RNA interference: Principles of design and practical guidelines

Ribonucleic acid interference (RNAi) is an innovative treatment strategy for a myriad of indications. Non-viral synthetic nanoparticles (NPs) have drawn extensive attention as vectors for RNAi due to their potential advantages, including improved safety, high delivery efficiency and economic feasibility. However, the complex natural process of RNAi and the susceptible nature of oligonucleotides render the NPs subject to particular design principles and requirements for practical fabrication. Here, we summarize the requirements and obstacles for fabricating non-viral nano-vectors for efficient RNAi. To address the delivery challenges, we discuss practical guidelines for materials selection and NP synthesis in order to maximize RNA encapsulation efficiency and protection against degradation, and to facilitate the cytosolic release of oligonucleotides. The current status of clinical translation of RNAi-based therapies and further perspectives for reducing the potential side effects are also reviewed.

PD-L1 siRNA Theranostics With a Dextran Nanoparticle Highlights the Importance of Nanoparticle Delivery for Effective Tumor PD-L1 Downregulation

Purpose

The inhibition of immune checkpoints such as programmed cell death ligand-1 (PD-L1/CD274) with antibodies is providing novel opportunities to expose cancer cells to the immune system. Antibody based checkpoint blockade can, however, result in serious autoimmune complications because normal tissues also express immune checkpoints. As sequence-specific gene-silencing agents, the availability of siRNA has significantly expanded the specificity and range of “druggable” targets making them promising agents for precision medicine in cancer. Here, we have demonstrated the ability of a novel biodegradable dextran based theranostic nanoparticle (NP) to deliver siRNA downregulating PD-L1 in tumors. Optical imaging highlighted the importance of NP delivery and accumulation in tumors to achieve effective downregulation with siRNA NPs, and demonstrated low delivery and accumulation in several PD-L1 expressing normal tissues.

Methods

The dextran scaffold was functionalized with small molecules containing amine groups through acetal bonds. The NP was decorated with a Cy5.5 NIR probe allowing visualization of NP delivery, accumulation, and biodistribution. MDA-MB-231 triple negative human breast cancer cells were inoculated orthotopically or subcutaneously to achieve differences in vascular delivery in the tumors. Molecular characterization of PD-L1 mRNA and protein expression in cancer cells and tumors was performed with qRT-PCR and immunoblot analysis.

Results

The PD-L1 siRNA dextran NPs effectively downregulated PD-L1 in MDA-MB-231 cells. We identified a significant correlation between NP delivery and accumulation, and the extent of PD-L1 downregulation, with in vivo imaging. The size of the NP of ~ 20 nm allowed delivery through leaky tumor vasculature but not through the vasculature of high PD-L1 expressing normal tissue such as the spleen and lungs.

Conclusions

Here we have demonstrated, for the first time, the feasibility of downregulating PD-L1 in tumors using siRNA delivered with a biodegradable dextran polymer that was decorated with an imaging reporter. Our data demonstrate the importance of tumor NP delivery and accumulation in achieving effective downregulation, highlighting the importance of imaging in siRNA NP delivery. Effective delivery of these siRNA carrying NPs in the tumor but not in normal tissues may mitigate some of the side-effects of immune checkpoint inhibitors by sparing PD-L1 inhibition in these tissues.

Engineering of SPECT/Photoacoustic Imaging/Antioxidative Stress Triple-Function Nanoprobe for Advanced Mesenchymal Stem Cell Therapy of Cerebral Ischemia

The precise transplantation, long-term tracking, and maintenance of stem cells with maximizing therapeutic effect are significant challenges in stem cell-based therapy for stroke treatment. In this study, a unique core-shell labeling nanoagent was prepared by encapsulating a cobalt protoporphyrin IX (CoPP)-loaded mesoporous silica nanoparticle (CPMSN) into a ¹²⁵I-conjugated/spermine-modified dextran polymer (¹²⁵I-SD) by microfluidics for mesenchymal stem cell (MSC) tracking and activity maintenance. The CPMSN core not only exhibits excellent photoacoustic (PA) imaging performance induced by the intermolecular aggregation of CoPP within the mesopores but also protects the MSCs against oxidative stress by sustained release of CoPP. Meanwhile, the addition of a ¹²⁵I-SD shell can increase the uptake efficiency in MSCs without inducing cell variability and enable the single-photon-emission computed tomography (SPECT) nuclear imaging. In vivo results indicated that CPMSN@¹²⁵I-SD labeling could allow for an optimal combination of instant imaging of MSCs, with PA to guide intracerebral injection, followed by multiple time point SPECT imaging to consecutively track the cell homing. Importantly, the sustained release of CoPP from CPMSN@¹²⁵I-SD significantly increased the survival of MSCs after injection into an ischemic mouse brain and promoted neurobehavioral recovery in ischemic mice. Thus, CPMSN@¹²⁵I-SD represents a robust theranostic probe for both MSC tracking and maintaining their therapeutic effect in the treatment of brain ischemia.

Mirror siRNAs loading for dual delivery of doxorubicin and autophagy regulation siRNA for multidrug reversing chemotherapy

The multidrug resistance (MDR) which widely observed in multiple cancer types is responsible for the poor chemotherapy benefits of doxorubicin (Dox). Here in our study, Dox was firstly loaded into a scramble siRNA and then condensed by polyethyleneimine (PEI) 25k together with anti-autophagy siRNA, the obtained PEI/Si-D containing mirror RNAs was further coated with hyaluronic acid (HA) to shield the surface charge of PEI and offer tumor-homing property that finally developed a platform for effective cancer chemotherapy (HP/Si-D). Our results revealed that the obtained HP/Si-D was showed high stability and biocompatibility with promising transfection profile. As a result, the anti-autophagy siRNA downregulated autophagy level of target cells, which further decreased ATP supply to enhance drug retention and cell cycle arrest. These results contributed significantly to reverse the MDR of A549/Dox (Dox resistance A549 cell line) cells with promising in vitro and in vivo results, which suggested the potential of effective MDR cancer therapy using synergistic anti-autophagy and chemotherapy.

Cellular Delivery of Bioorthogonal Pretargeting Therapeutics in PSMA-Positive Prostate Cancer

Prostate cancer is primarily fatal after it becomes metastatic and castration-resistant despite novel combined hormonal and chemotherapeutic regimens. Hence, new therapeutic concepts and drug delivery strategies are urgently needed for the eradication of this devastating disease. Here we report the highly specific, in situ click chemistry driven pretargeted delivery of cytotoxic drug carriers to PSMA(+) prostate cancer cells. Anti-PSMA 5D3 mAb and its F(ab')₂ fragments were functionalized with trans-cyclooctene (TCO), labeled with a fluorophore, and used as pretargeting components. Human serum albumin (ALB) was loaded with the DM1 antitubulin agent, functionalized with PEGylated tetrazine (PEG₄-Tz), labeled with a fluorophore, and used as the drug delivery component. The internalization kinetics of components and the therapeutic efficacy of the pretargeted click therapy were studied in PSMA(+) PC3-PIP and PSMA(-) PC3-Flu control cells. The F(ab')₂ fragments were internalized faster than 5D3 mAb in PSMA(+) PC3-PIP cells. In the two-component pretargeted imaging study, both components were colocalized in a perinuclear location of the cytoplasm of PC3-PIP cells. Better colocalization was achieved when 5D3 mAb was used as the pretargeting component. Consecutively, the in vitro cell viability study shows a significantly higher therapeutic effect of click therapy in PC3-PIP cells when 5D3 mAb was used for pretargeting, compared to its F(ab')₂ derivative. 5D3 mAb has a longer lifetime on the cell surface, when compared to its F(ab')₂ analogue, enabling efficient cross-linking with the drug delivery component and increased efficacy. Pretargeting and drug delivery components were cross-linked via multiple bioorthogonal click chemistry reactions on the surface of PSMA(+) PC cells forming nanoclusters, which undergo fast cellular internalization and intracellular transport to perinuclear locations.

Theranostic small interfering RNA nanoparticles in cancer precision nanomedicine

Due to their ability to effectively downregulate the expression of target genes, small interfering RNA (siRNA) have emerged as promising candidates for precision medicine in cancer. Although some siRNA-based treatments have advanced to clinical trials, challenges such as poor stability during circulation, and less than optimal pharmacokinetics and biodistribution of siRNA in vivo present barriers to the systemic delivery of siRNA. In recent years, theranostic nanomedicine integrating siRNA delivery has attracted significant attention for precision medicine. Theranostic nanomedicine takes advantage of the high capacity of nanoplatforms to ferry cargo with imaging and therapeutic capabilities. These theranostic nanoplatforms have the potential to play a major role in gene specific treatments. Here we have reviewed recent advances in the use of theranostic nanoplatforms to deliver siRNA, and discussed the opportunities as well as challenges associated with this exciting technology. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Detection of tyrosine kinase inhibitors-induced COX-2 expression in bladder cancer by fluorocoxib A

Among challenges of targeted therapies is the activation of alternative pro-survival signaling pathways in cancer cells, resulting in an acquired drug resistance. Cyclooxygenase-2 (COX-2) is overexpressed in bladder cancer cells, making it an attractive molecular target for the detection and treatment of cancer. Fluorocoxib A is an optical imaging agent that selectively targets COX-2. In this study, we evaluated the ability of fluorocoxib A to monitor the responses of bladder cancer to targeted therapies in vivo. The effects of several tyrosine kinase inhibitors (TKIs: axitinib, AB1010, toceranib, imatinib, erlotinib, gefitinib, imatinib, sorafenib, vandetanib, SP600125, UO126, and AZD 5438) on COX-2 expression were validated in ten human and canine bladder cancer cell lines (J82, RT4, T24, UM-UC-3, 5637, SW780, TCCSUP, K9TCC#1Lillie, K9TCC#2Dakota, K9TCC#5Lilly) in vitro. The effects of TKIs on bladder cancer in vivo were evaluated using the COX-2-expressing K9TCC#5Lilly xenograft mouse model and detected by fluorocoxib A. The increased COX-2 expression was detected by all tested TKIs in at least one of the tested COX-2-expressing bladder cancer cell lines (5637, SW780, TCCSUP, K9TCC#1Lillie, K9TCC#2Dakota, and K9TCC#5Lilly) in vitro. In addition, fluorocoxib A uptake correlated with the AB1010- and imatinib-induced COX-2 expression in the K9TCC#5Lilly xenografts in vivo. In conclusion, these results indicate that fluorocoxib A could be used for the monitoring the early responses to targeted therapies in COX-2-expressing bladder cancer.

Polymeric nanoparticles as carrier for targeted and controlled delivery of anticancer agents

In recent decades, many novel methods by using nanoparticles (NPs) have been investigated for diagnosis, drug delivery and treatment of cancer. Accordingly, the potential of NPs as carriers is very significant for the delivery of anticancer drugs, because cancer treatment with NPs has led to the improvement of some of the drug delivery limitations such as low blood circulation time and bioavailability, lack of water solubility, drug adverse effect. In addition, the NPs protect drugs against enzymatic degradation and can lead to the targeted and/or controlled release of the drug. The present review focuses on the potential of NPs that can help the targeted and/or controlled delivery of anticancer agents for cancer therapy.

Carbohydrate-based nanomaterials for biomedical applications

Carbohydrates are abundant biomolecules, with a strong tendency to form supramolecular networks. A host of carbohydrate-based nanomaterials have been exploited for biomedical applications. These structures are based on simple mono- or disaccharides, as well as on complex, polymeric systems. Chemical modifications serve to tune the shapes and properties of these materials. In particular, carbohydrate-based nanoparticles and nanogels were used for drug delivery, imaging, and tissue engineering applications. Due to the reversible nature of the assembly, often based on a combination of hydrogen bonding and hydrophobic interactions, carbohydrate-based materials are valuable substrates for the creations of responsive systems. Herein, we review the current research on carbohydrate-based nanomaterials, with a particular focus on carbohydrate assembly. We will discuss how these systems are formed and how their properties are tuned. Particular emphasis will be placed on the use of carbohydrates for biomedical applications. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Structure-function relationships of nonviral gene vectors: Lessons from antimicrobial polymers

In recent years, substantial advances have been achieved in the design and synthesis of nonviral gene vectors. However, lack of effective and biocompatible vectors still remains a major challenge that hinders their application in clinical settings. In the past decade, there has been a rapid expansion of cationic antimicrobial polymers, due to their potent, rapid, and broad-spectrum biocidal activity against resistant microbes, and biocompatible features. Given that antimicrobial polymers share common features with nonviral gene vectors in various aspects, such as membrane affinity, functional groups, physicochemical characteristics, and unique macromolecular architectures, these polymers may provide us with inspirations to overcome challenges in the design of novel vectors toward more safe and efficient gene delivery in clinic. Building off these observations, we provide here an overview of the structure-function relationships of polymers for both antimicrobial applications and gene delivery by elaborating some key structural parameters, including functional groups, charge density, hydrophobic/hydrophilic balance, MW, and macromolecular architectures. By borrowing a leaf from antimicrobial agents, great advancement in the development of newer nonviral gene vectors with high transfection efficiency and biocompatibility will be more promising. STATEMENT OF SIGNIFICANCE: The development of gene delivery is still in the preclinical stage for the lack of effective and biocompatible vectors. Given that antimicrobial polymers share common features with gene vectors in various aspects, such as membrane affinity, functional groups, physicochemical characteristics, and unique macromolecular architectures, these polymers may provide us with inspirations to overcome challenges in the design of novel vectors toward more safe and efficient gene delivery in clinic. In this review, we systematically summarized the structure-function relationships of antimicrobial polymers and gene vectors, with which the design of more advanced nonviral gene vectors is anticipated to be further boosted in the future.

Low molecular weight PEI-based fluorinated polymers for efficient gene delivery

Fluorinated biomaterials have been reported to have promising features as non-viral gene carriers. In this study, a series of fluorinated polymeric gene carriers were synthesized via Michael addition from low molecular weight polyethyleneimine (PEI) and fluorobenzoic acids (FBAs)-based linking compounds with different numbers of fluorine atoms. The structure-activity relationship (SAR) of these materials was systematically investigated. SAR studies showed that fluorine could screen the positive charge of these polymers. However, this shielding effect of fluorine would endow fluorinated polymers with good balance between DNA condensation and release. In vitro transfection results suggested that these fluorinated polymers could mediate efficient gene delivery. Flow cytometry and confocal microscopy studies demonstrated that more efficient cell uptake could be achieved by fluorinated materials with more fluorine atoms. Cytotoxicity assays showed that these fluorinated materials exhibited very low cytotoxicity even at high mass ratios. This study demonstrates that FBA-based fluorinated biopolymers have the potential for practical application.

Cyclooxygenase-2 in cancer: A review

Cyclooxygenase-2 (COX-2) is frequently expressed in many types of cancers exerting a pleiotropic and multifaceted role in genesis or promotion of carcinogenesis and cancer cell resistance to chemo- and radiotherapy. COX-2 is released by cancer-associated fibroblasts (CAFs), macrophage type 2 (M2) cells, and cancer cells to the tumor microenvironment (TME). COX-2 induces cancer stem cell (CSC)-like activity, and promotes apoptotic resistance, proliferation, angiogenesis, inflammation, invasion, and metastasis of cancer cells. COX-2 mediated hypoxia within the TME along with its positive interactions with YAP1 and antiapoptotic mediators are all in favor of cancer cell resistance to chemotherapeutic drugs. COX-2 exerts most of the functions through its metabolite prostaglandin E2. In some and limited situations, COX-2 may act as an antitumor enzyme. Multiple signals are contributed to the functions of COX-2 on cancer cells or its regulation. Members of mitogen-activated protein kinase (MAPK) family, epidermal growth factor receptor (EGFR), and nuclear factor-κβ are main upstream modulators for COX-2 in cancer cells. COX-2 also has interactions with a number of hormones within the body. Inhibition of COX-2 provides a high possibility to exert therapeutic outcomes in cancer. Administration of COX-2 inhibitors in a preoperative setting could reduce the risk of metastasis in cancer patients. COX-2 inhibition also sensitizes cancer cells to treatments like radio- and chemotherapy. Chemotherapeutic agents adversely induce COX-2 activity. Therefore, choosing an appropriate chemotherapy drugs along with adjustment of the type and does for COX-2 inhibitors based on the type of cancer would be an effective adjuvant strategy for targeting cancer.

A nanomedicine approach enables co-delivery of cyclosporin A and gefitinib to potentiate the therapeutic efficacy in drug-resistant lung cancer

Drug resistance, accounting for therapeutic failure in the clinic, remains a major challenge to effectively manage cancer. Cyclosporin A (CsA) can reverse multidrug resistance (MDR), especially resistance to epidermal growth factor receptor tyrosine kinase inhibitors. However, the application of both drugs in cancer therapies is hampered by their poor aqueous solubility and low bioavailability due to oral administration. CsA augments the potency of gefitinib (Gef) in both Gef-sensitive and Gef-resistant cell lines. Here, we show that the simultaneous encapsulation of CsA and Gef within polyethylene glycol-block-poly(_{D, L}-lactic acid) (PEG-PLA) produced a stable and systemically injectable nanomedicine, which exhibited a sub-50-nm diameter and spherical structures. Impressively, the co-delivery of therapeutics via single nanoparticles (NPs) outperformed the oral administration of the free drug combination at suppressing tumor growth. Furthermore, in vivo results indicated that CsA formulated in NPs sensitized Gef-resistant cells and Gef-resistant tumors to Gef treatment by inactivating the STAT3/Bcl-2 signaling pathway. Collectively, our nanomedicine approach not only provides an alternative administration route for the drugs of choice but also effectively reverses MDR, facilitating the development of effective therapeutic modalities for cancer.

Injection of nanoparticles containing the anticancer drug gefitinib and the immunosuppressant cyclosporin A reverses drug-resistant cancer growth in mice. The development of multidrug resistance is the main reason why many forms of chemotherapy fail. Cyclosporin A, a drug used to prevent immune rejection after organ transplantation, has previously been shown to enhance the potency of gefitinib. Hangxiang Wang and colleagues at Zhejiang University, Hangzhou, China, have successfully combined cyclosporin A and gefitinib, two poorly water-soluble and slowly absorbed drugs, into stable injectable nanoparticles that delay the growth of gefitinib resistant human lung cancer cells as well as the growth of drug resistant tumors in mice. Importantly, this novel co-formulation was more effective than oral co-administration of the two drugs. Further investigation into this drug delivery route could yield much needed alternative treatments for patients with multidrug-resistant cancers.

Theranostics and metabolotheranostics for precision medicine in oncology

Most diseases, especially cancer, would significantly benefit from precision medicine where treatment is shaped for the individual. The concept of theragnostics or theranostics emerged around 2002 to describe the incorporation of diagnostic assays into the selection of therapy for this purpose. Increasingly, theranostics has been used for strategies that combine noninvasive imaging-based diagnostics with therapy. Within the past decade theranostic imaging has transformed into a rapidly expanding field that is located at the interface of diagnosis and therapy. A critical need in cancer treatment is to minimize damage to normal tissue. Molecular imaging can be applied to identify targets specific to cancer with imaging, design agents against these targets to visualize their delivery, and monitor response to treatment, with the overall purpose of minimizing collateral damage. Genomic and proteomic profiling can provide an extensive 'fingerprint' of each tumor. With this cancer fingerprint, theranostic agents can be designed to personalize treatment for precision medicine of cancer, and minimize damage to normal tissue. Here, for the first time, we have introduced the term 'metabolotheranostics' to describe strategies where disease-based alterations in metabolic pathways detected by MRS are specifically targeted with image-guided delivery platforms to achieve disease-specific therapy. The versatility of MRI and MRS in molecular and functional imaging makes these technologies especially important in theranostic MRI and 'metabolotheranostics'. Our purpose here is to provide insights into the capabilities and applications of this exciting new field in cancer treatment with a focus on MRI and MRS.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

Fabrication of Charge-Conversion Nanoparticles for Cancer Imaging by Flash Nanoprecipitation

Traditional charge-conversion nanoparticles (NPs) need the breakage of acid-labile groups on the surface, which impedes the rapid response to the acidic microenvironment. Here, we developed novel rodlike charge-conversion NPs with amphiphilic dextran- b-poly(lactic- co-glycolic acid), poly(2-(dimethylamino) ethylmethylacrylate)- b-poly(ε-caprolactone), and an aggregation-induced emission-active probe through flash nanoprecipitation (FNP). These NPs exhibit reversible negative-to-positive charge transition at a slightly acidic pH relying on the rapid protonation/deprotonation of polymers. The size and the critical charge-conversion pH can be further tuned by varying the flow rate and polymer ratio. Consequently, the charge conversion endows NPs with resistance to protein adsorption at physiological pH and enhanced internalization to cancer cells under acidic conditions. Ex vivo imaging on harvest organs shows that charge-conversion NPs were predominantly distributed in tumors after intravenous administration to mice due to the robust response of NPs to the acidic microenvironment in tumor tissue, whereas control NPs or free probes were broadly accumulated in tumor, liver, kidney, and lung. These results suggest the great potential of the current FNP strategy in the facile and generic fabrication of charge-conversion NPs for tumor-targeting delivery of drugs or fluorescent probes.