MMP2-Targeting and Redox-Responsive PEGylated Chlorin e6 Nanoparticles for Cancer Near-Infrared Imaging and Photodynamic Therapy

Stimuli-responsive hydrogel based on natural polymers for breast cancer

Aims: Breast cancer is the most common malignancy among women in both high- and low-resource settings. Conventional breast cancer therapies were inefficient and had low patient compliance. Stimuli-responsive hydrogels possessing similar physicochemical features as soft tissue facilitate diagnostic and therapeutic approaches for breast cancer subtypes. Scope: Polysaccharides and polypeptides are major natural polymers with unique biocompatibility, biodegradability, and feasible modification approaches utilized frequently for hydrogel fabrication. Alternating the natural polymer-based hydrogel properties in response to external stimuli such as pH, temperature, light, ultrasonic, enzyme, glucose, magnetic, redox, and electric have provided great potential for the evolution of novel drug delivery systems (DDSs) and various advanced technologies in medical applications. Stimuli-responsive hydrogels are triggered by specific cancer tissue features, promote target delivery techniques, and modify release therapeutic agents at localized sites. This narrative review presented innovation in preparing and characterizing the most common stimuli-responsive natural polymer-based hydrogels for diagnostic and therapeutic applications in the breast cancer area. Conclusion: Stimuli-responsive hydrogels display bioinspiration products as DDSs for breast cancer subtypes, protect the shape of breast tissue, provide modified drug release, enhance therapeutic efficacy, and minimize chemotherapy agents' side effects. The potential benefits of smart natural polymer-based hydrogels make them an exciting area of practice for breast cancer diagnosis and treatment.

Enzyme-Responsive Double-Locked Photodynamic Molecular Beacon for Targeted Photodynamic Anticancer Therapy

An advanced photodynamic molecular beacon (PMB) was designed and synthesized, in which a distyryl boron dipyrromethene (DSBDP)-based photosensitizer and a Black Hole Quencher 3 moiety were connected via two peptide segments containing the sequences PLGVR and GFLG, respectively, of a cyclic peptide. These two short peptide sequences are well-known substrates of matrix metalloproteinase-2 (MMP-2) and cathepsin B, respectively, both of which are overexpressed in a wide range of cancer cells either extracellularly (for MMP-2) or intracellularly (for cathepsin B). Owing to the efficient Förster resonance energy transfer between the two components, this PMB was fully quenched in the native form. Only upon interaction with both MMP-2 and cathepsin B, either in a buffer solution or in cancer cells, both of the segments were cleaved specifically, and the two components could be completely separated, thereby restoring the photodynamic activities of the DSBDP moiety. This PMB could also be activated in tumors, and it effectively suppressed the tumor growth in A549 tumor-bearing nude mice upon laser irradiation without causing notable side effects. In particular, it did not cause skin photosensitivity, which is a very common side effect of photodynamic therapy (PDT) using conventional "always-on" photosensitizers. The overall results showed that this "double-locked" PMB functioned as a biological AND logic gate that could only be unlocked by the coexistence of two tumor-associated enzymes, which could greatly enhance the tumor specificity in PDT.

Hepatocyte-targeting and tumor microenvironment-responsive liposomes for enhanced anti-hepatocarcinoma efficacy

To increase the antitumor drug concentration in the liver tumor site and improve the therapeutic effects, a functionalized liposome (PPP-LIP) with tumor targetability and enhanced internalization after matrix metalloproteinase-2 (MMP2)-triggered cell-penetrating peptide (TATp) exposure was modified with myrcludex B (a synthetic HBV preS-derived lipopeptide endowed with compelling liver tropism) for liver tumor-specific delivery. After intravenous administration, PPP-LIP was mediated by myrcludex B to reach the hepatocyte surface. The MMP2-overexpressing tumor microenvironment deprotected PEG, exposing it to TATp, facilitating tumor penetration and subsequent efficient destruction of tumor cells. In live imaging of small animals and cellular uptake, PPP-LIP was taken up much more than typical unmodified liposomes in the ICR mouse liver and liver tumor cells. Hydroxycamptothecin (HCPT)-loaded PPP-LIP showed a better antitumor effect than commercially available HCPT injections among MTT, three-dimensional (3 D) tumor ball, and tumor-bearing nude mouse experiments. Our findings indicated that PPP-LIP nanocarriers could be a promising tumor-targeted medication delivery strategy for treating liver cancers with elevated MMP2 expression.

Pegylation – in search of balance and enhanced bioavailability

In the process of finding better therapeutics, thousands of new molecules are synthesised every day. Many of these can be poorly soluble in water, leading to a potentially promising drug being rejected during testing due to its poor solubility. Polyethylene glycol (PEG) has become known as an excellent modification to remedy this and was initially used to increase circulation time and reduce the immunogenicity of therapeutic proteins. Thus significantly increasing their safety and range of use. Another group of compounds in which significant benefits of pegylation have been seen are photosensitisers. Used in photodynamic therapy, they are often characterised by very high hydrophobicity. Pegylation of their structure significantly increases their affinity for cancer cells and facilitates their penetration through cell membranes. Classical small-molecule drugs can benefit from temporary combinations hydrolysed in the body or very short PEG chains. This approach allows a significant increase in the bioavailability of the drug while avoiding the disadvantages of small molecule pegylation. However, the most common motive for pegylation recently is the creation of drug carriers. Liposomes and nanoparticles make it possible to exploit the advantages of PEG to stabilise their structure and increase circulation time while not modifying the structure of the active compound. Unfortunately, PEGs also have their drawbacks. The first is their high molecular weight range, especially for longer chains, which poses difficulties in purification. Another is the emergence of antibodies directed against PEG. Nevertheless, pegylation is still an up-and-coming method for modifying pharmaceutically active molecules.

Core-Coordinated Elliptic Polymer Nanoparticles Loading Copper(II) and Chlorambucil for Cooperative Chemodynamic/Chemotherapy

Chemodynamic therapy (CDT) reflects an innovative cancer treatment modality; however, to enhance its relatively low therapeutic efficiency, rational combination with extra therapeutic modes is highly appreciated. Here, core-coordinated amphiphilic, elliptic polymer nanoparticles (Cu/CBL-POEGEA NPs) are constructed via the self-assembly of a glutathione (GSH)-responsive polymer-drug conjugate, bearing side-chain acylthiourea (ATU) motifs which behave as ligands capable of coordinating Cu(II), such a design is featured by combined chemo (CT)/CDT with dual GSH depletion collectively triggered by the Cu(II) reduction reaction and disulfide bond breakage. To do so, an amphiphilic random copolymer poly[oligo(ethylene glycol)ethyl acrylate-co-thiourea] [P(OEGEA-co-ATU)] is synthesized, followed by conjugation of chlorambucil (CBL) to ATU motifs linked via a disulfide bond, thus yielding the targeted P[OEGEA-co-(ATU-g-CBL)]. In such a system, hydrophilic POEGEA serves as the biocompatible section and ATU motifs coordinate Cu(II), resulting in core-coordinated elliptic Cu/CBL-POEGEA NPs. Benefitting from the GSH-induced reduction reaction, Cu(II) is converted into Cu(I) and subsequently react with endogenous H₂O₂ to create ^•OH, realizing GSH-depletion-promoted CDT. Additionally, the disulfide bond endows GSH-responsive CBL release and provokes further GSH decline, finally realizing combined CDT/CT toward enhancing antitumor outcomes, and in vitro as well as in vivo studies indeed reveal remarkable efficacy. Such a system can provide valuable advantages to create novel nanomedicines toward cascade antitumor therapy.

Efficient Delivery of P3H4 siRNA and Chlorin e6 by cRGDfK-Installed Polyarginine Nanoparticles for Tumor-Targeting Therapy of Bladder Cancer

Purpose: Prolyl 3-hydroxylase family member 4 (P3H4) is a potent prognostic oncogene in bladder cancer (BC), and the inhibition of P3H4 suppresses BC tumor growth. This study aimed to evaluate the efficiency of P3H4 inhibition for BC tumor therapy via tumor-targeting nanoparticles. Methods and results: A linear polyarginine peptide (R9) was synthesized, azide-modified, and then assembled with cyclic pentapeptide cRGDfK. Chlorin e6 (ce6)-conjugated CH3-R9-RGD nanoparticles were prepared for the delivery of siP3H4 into T24 cells in vitro and BC tumors in vivo. Dynamic light scattering analysis identified that the optimum CH3-R9-RGD@siP3H4 molar ratio was 30/1. CH3-R9-RGD@ce6/siP3H4 nanocomposites decreased P3H4 expression and cell proliferation and promoted reactive oxygen species production, apoptosis, and calreticulin exposure in T24 cells in vitro. In vivo experiments showed that CH3-R9-RGD@ce6/siP3H4 nanocomposites caused pathological changes, suppressed BC tumor growth, promoted caspase 3 expression, and enhanced calreticulin exposure in tumor cells. Conclusions: The tumor-targeting CH3-R9-RGD nanocomposites encapsulating siP3H4 and ce6 might be an alternative therapeutic strategy or intravesical instillation chemotherapy for BC.

CeO2-Decorated Metal-Organic Framework for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) is quickly developing as a hopeful cancer treatment. However, hypoxic tumors, poor targeting, and photosensitizers (PS) aggregation limited the efficiency of PDT. Here, we report a hyaluronic acid (HA)-modified CeO₂-nanoparticle-decorated metal-organic framework (PCN-224@CeO₂-HA) to enhance PDT and achieve targeted treatment. CeO₂ catalyzes H₂O₂ to produce O₂ to solve hypoxia problems. HA could target the CD44 receptor, which is highly expressed on the tumor cell membranes. The growth of tumor cells 4T1 and MCF-7 was controlled distinctly after being incubated with PCN-224@CeO₂-HA under laser irradiation, while the survival ability of normal cell LO2 was nearly unchanged. Importantly, PCN-224@CeO₂-HA could be effectively aggregated within the tumor area after 12 h of injection, and the tumor growth was remarkably inhibited under laser irradiation. PCN-224@CeO₂-HA presented good biocompatibility and an excellent antitumor effect, providing a new strategy to produce O₂ in situ for enhanced PDT.

Novel Short PEG Chain-Substituted Porphyrins: Synthesis, Photochemistry, and In Vitro Photodynamic Activity against Cancer Cells

This work presents the synthesis and characterization of metal-free, zinc (II), and cobalt (II) porphyrins substituted with short PEG chains. The synthesized compounds were characterized by UV-Vis, ¹H and ¹³C NMR spectroscopy, and MALDI-TOF mass spectrometry. The origin of the absorption bands for tested compounds in the UV-Vis range was determined using a computational model based on the electron density functional theory (DFT) and its time-dependent variant (TD-DFT). The photosensitizing activity was evaluated by measuring the ability to generate singlet oxygen (ΦΔ), which reached values up to 0.54. The photodynamic activity was tested using bladder (5637), prostate (LNCaP), and melanoma (A375) cancer cell lines. In vitro experiments clearly showed the structure-activity relationship regarding types of substituents, their positions in the phenyl ring, and the variety of central metal ions on the porphyrin core. Notably, the metal-free derivative 3 and its zinc derivative 6 exerted strong cytotoxic activity toward 5637 cells, with IC₅₀ values of 8 and 15 nM, respectively. None of the tested compounds induced a cytotoxic effect without irradiation. In conclusion, these results highlight the potential value of the tested compounds for PDT application.

Size-Controllable DNA Origami-Stacked Gold Nanoparticles for Deep Tumor-Penetrating Therapy

With the rapid development of nanotechnology, researchers have designed a variety of intelligent nanodelivery systems to enhance tumor targeting of anticancer drugs. However, increased tumor accumulation does not indicate deeper penetration in the tumor tissue, without which the tumor cells in the core area cannot be sufficiently killed. Herein, we develop a size-controllable nanoparticle system for deep-penetrating cancer therapy, which will be programmably disassembled with the decrease of the pH from the normal tissue to the tumor microenvironment and to the intracellular area. The integrated nanoparticle is composed of a gold nanoparticle (GNP, ∼30 nm) and a tetrahedral DNA nanostructure (TDN, ∼25 nm) loaded with doxorubicin (DOX). Initially, the nanoparticles maintain a larger size (∼100 nm) to accumulate in the tumor through the enhanced permeability and retention effect. At a pH of about 6.5 at the tumor microenvironment, with the linkage of DNA sequences converting into a triplex structure, the TDNs detach from the GNP and penetrate deeply into the tumor interstitium and then are internalized into the cells. Finally, in acidic lysosomes with pH 5.0, the TDNs release DOX by forming an i-motif structure. This nanosmart delivery system thus shows effective deep penetration into the tumor core with good antitumor efficacy and satisfactory biocompatibility and provides new insights into the development of intelligent nanosystems for anti-cancer treatment.

Novel active stealth micelles based on β2M achieved effective antitumor therapy

Micelles have been extensively investigated as drug delivery systems for loading of antitumor drugs with the advantages of good dispersibility, controllable size distribution, and high loading capacity. However, phagocytic clearance by the mononuclear phagocyte system remains a major impediment that inhibits blood circulation and thus tumor accumulation of micelles. Inspired by the antiphagocytic properties of β₂-microglobulin (β₂M), here we developed a β₂M-derived peptide for the surface functionalization of micelles. A β₂M-derived sequence was integrated with a matrix metalloproteinase-2 (MMP-2) cleavable sequence and then modified on the surface of poly(ethylene glycol)-b-poly(caprolactone) (PEG-PCL) micelles, endowing the micelles with both antiphagocytic and MMP-2-responsive properties. Compared to pristine PEG-PCL micelles, micelles modified with the dual-functional peptide exhibited higher inhibition of phagocytosis by macrophages in the absence of MMP-2, and enhanced internalization by tumor-associated macrophages in the presence of MMP-2, leading to enhanced tumor accumulation of the loaded photosensitizer, thus enabling antitumor therapy. These results demonstrated that antiphagocytic peptides derived from endogenous proteins are promising for functionalization of micelles in smart drug delivery.

Nano-ultrasonic Contrast Agent for Chemoimmunotherapy of Breast Cancer by Immune Metabolism Reprogramming and Tumor Autophagy

The functional status of innate immune cells is a considerable determinant of effective antitumor immune response. However, the triple-negative breast cancer tumor microenvironment with high lactic acid metabolism and high antioxidant levels limits immune cell survival, differentiation, and function. Here, we determine that the tumor microenvironment-responsive nano-ultrasonic contrast agent Pt(IV)/CQ/PFH NPs-^DPPA-1 boosts the ratio of mature dendritic cells (mDCs) and proinflammatory macrophages by reprogramming the metabolism of immature DCs (iDCs) and tumor-associated macrophages (TAMs). Specifically, platinum(IV) in cancer cells or iDCs was reduced to cisplatin, which can increase the intracellular content of ROS and therefore enhance the ratio of mDCs and apoptotic tumor cells. Meanwhile, chloroquine (CQ) released from nanoparticles (NPs) minimizes protective autophagy caused by cisplatin in tumor cells and reprograms the metabolism of TAMs to enhance the proportion of proinflammatory macrophages, achieving a superior synergistic effect of chemoimmunotherapy combined with Pt(IV) and anti-PD-L1 peptide (^DPPA-1). Furthermore, perfluorohexane (PFH) in NPs realizes monitoring treatment corresponding to ultrasound. Collectively, the nano-ultrasonic contrast agent supports a candidate for monitoring treatment and augmenting antitumor chemoimmunotherapy by suppressing tumor cell autophagy and reprogramming immunocyte metabolism.

Self-Assembled Nanoparticles for Tumor-Triggered Targeting Dual-Mode NIRF/MR Imaging and Photodynamic Therapy Applications

In this study, the self-assembling strategy was used to synthesize a therapeutic and diagnostic nanosystem for tumor-triggered targeting dual-mode near-infrared fluorescence (NIRF)/magnetic resonance (MR) imaging and photodynamic therapy applications. This theranostic nanosystem was synthesized based on the self-assembling of the short peptide (PLGVRGRGDC) and the gadolinium chelator (diethylenetriamine pentaacetic acid) functionalized amphiphilic DSPE-PEG₂₀₀₀, followed by loading with the insoluble photosensitizer therapeutic agent chlorin e6 (Ce6). The formed theranostic nanosystem can accumulate in the matrix metalloproteinase 2 (MMP2) rich tumor sites guided by the enhanced permeability and retention effect and MMP2-substrate peptide (PLGVR) targeting. After PLGVR was hydrolyzed in the tumor microenvironment by MMP2, the nanosystem was actively taken up by tumor cells via Arg-Gly-Asp (RGD) peptide-mediated internalization. With the coexistence of gadolinium and Ce6, the formed nanosystem can be used for both NIRF/MR dual-mode imaging and photodynamic therapy. These tumor-triggered targeting self-assembled nanoparticles with low cytotoxicity and high endocytosis efficiency can efficiently induce A549 cancer cell apoptosis under laser irradiation. Meanwhile, they possessed enhanced tumor-targeted NIRF/MR imaging ability and efficiently inhibited tumor growth with minimal side effects in mice bearing A549 lung cancer. Therefore, these self-assembled theranostic nanoparticles may have great potential for cancer clinical diagnosis and therapy.

Biodegradable Materials with Disulfide-Bridged-Framework Confine Photosensitizers for Enhanced Photo-Immunotherapy

Purpose

Photodynamic therapy (PDT) with spatiotemporal controlled and noninvasive advantages has obtained growing attention in cancer treatment. Nevertheless, PDT still suffers from self-aggregation-induced photosensitizer quenching and reactive oxygen species (ROS) scavenging in cancer cells with abundant glutathione (GSH) pools, leading to insufficient performance.

Methods

In this study, we develop a versatile nanocarrier (SSNs) with a disulfide-bond-bridged silica framework for enhanced photo-immunotherapy. Such SSNs spatially confine photosensitizers Ce6 in the matrix to prevent self-aggregation. Under the high GSH level of cancer cells, the disulfide-bond-bridged framework was degradable and triggered the exposure of photosensitizers to oxygen, accelerating the ROS generation during PDT. In addition, GSH depletion via the break of the disulfide-bond increased the ROS level, together resulting in efficient tumor killing outcomes with a considerable immunogenic cell death effect in vitro. Importantly, the SSNs@Ce6 accumulated in the tumor site and exhibited enhanced PDT efficacy with low systemic toxicity in vivo.

Results

The GEN-loaded nanoplatform (Ag-MONs@GEN) showed glutathione-responsive matrix degradation, resulting in the simultaneous controlled release of GEN and silver ions. Ag-MONs@GEN exhibited excellent anti-bacterial activities than Ag-MONs and GEN alone, especially enhancing synergetic effects against four antibiotic-resistant bacteria including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis. Moreover, Ag-MONs@GEN showed good biocompatibility on L929 and HUVECS.

Conclusion

Notably, SSNs@Ce6-mediated PDT completely eradicated 4T1 tumors when combined with the PD-1 checkpoint blockade. Overall, the confinement of photosensitizers in a biodegradable disulfide-bridged-framework provides a promising strategy to unleash the potential of photosensitizers in PDT, especially in combined cancer photo-immunotherapy.

Oxidative Damage Induced by Phototoxic Pheophorbide a 17-Diethylene Glycol Ester Encapsulated in PLGA Nanoparticles

Pheophorbide a 17-diethylene glycol ester (XL-8), is a promising high-active derivative of known photosensitizer chlorin e6 used in photodynamic therapy. However, high lipophilicity and poor tumor accumulation limit XL-8 therapeutic application. We developed a novel XL-8 loaded with poly(D,L-lactide-co-glycolide) nanoparticles using the single emulsion-solvent evaporation method. The nanoparticles possessed high XL-8 loading content (4.6%) and encapsulation efficiency (87.7%) and a small size (182 ± 19 nm), and negative surface charge (-22.2 ± 3.8 mV) contributed to a specific intracellular accumulation. Sustained biphasic XL-8 release from nanoparticles enhanced the photosensitizer photostability upon irradiation that could potentially reduce the quantity of the drug applied. Additionally, the encapsulation of XL-8 in the polymer matrix preserved phototoxic activity of the payload. The nanoparticles displayed enhanced cellular internalization. Flow cytometry and confocal laser-scanning microscopy studies revealed rapid XL-8 loaded nanoparticles distribution throughout the cell and initiation of DNA damage, glutathione depletion, and lipid peroxidation via reactive oxygen species formation. The novel nanoformulated XL-8 simultaneously revealed a significant phototoxicity accompanied with enhanced photostability, in contrast with traditional photosensitizers, and demonstrated a great potential for further in vivo studies.

Smart Nanotherapeutics and Lung Cancer

Lung cancer is a significant health problem worldwide. Unfortunately, current therapeutic strategies lack a sufficient level of specificity and can harm adjacent healthy cells. Consequently, to address the clinical need, novel approaches to improve treatment efficiency with minimal side effects are required. Nanotechnology can substantially contribute to the generation of differentiated products and improve patient outcomes. Evidence from previous research suggests that nanotechnology-based drug delivery systems could provide a promising platform for the targeted delivery of traditional chemotherapeutic drugs and novel small molecule therapeutic agents to treat lung cancer cells more effectively. This has also been found to improve the therapeutic index and reduce the required drug dose. Nanodrug delivery systems also provide precise control over drug release, resulting in reduced toxic side effects, controlled biodistribution, and accelerated effects or responses. This review highlights the most advanced and novel nanotechnology-based strategies, including targeted nanodrug delivery systems, stimuli-responsive nanoparticles, and bio-nanocarriers, which have recently been employed in preclinical and clinical investigations to overcome the current challenges in lung cancer treatments.

Recent Advances in Photosensitizers as Multifunctional Theranostic Agents for Imaging-Guided Photodynamic Therapy of Cancer

In recent years tremendous effort has been invested in the field of cancer diagnosis and treatment with an overall goal of improving cancer management, therapeutic outcome, patient survival, and quality of life. Photodynamic Therapy (PDT), which works on the principle of light-induced activation of photosensitizers (PS) leading to Reactive Oxygen Species (ROS) mediated cancer cell killing has received increased attention as a promising alternative to overcome several limitations of conventional cancer therapies. Compared to conventional therapies, PDT offers the advantages of selectivity, minimal invasiveness, localized treatment, and spatio-temporal control which minimizes the overall therapeutic side effects and can be repeated as needed without interfering with other treatments and inducing treatment resistance. Overall PDT efficacy requires proper planning of various parameters like localization and concentration of PS at the tumor site, light dose, oxygen concentration and heterogeneity of the tumor microenvironment, which can be achieved with advanced imaging techniques. Consequently, there has been tremendous interest in the rationale design of PS formulations to exploit their theranostic potential to unleash the imperative contribution of medical imaging in the context of successful PDT outcomes. Further, recent advances in PS formulations as activatable phototheranostic agents have shown promising potential for finely controlled imaging-guided PDT due to their propensity to specifically turning on diagnostic signals simultaneously with photodynamic effects in response to the tumor-specific stimuli. In this review, we have summarized the recent progress in the development of PS-based multifunctional theranostic agents for biomedical applications in multimodal imaging combined with PDT. We also present the role of different imaging modalities; magnetic resonance, optical, nuclear, acoustic, and photoacoustic in improving the pre-and post-PDT effects. We anticipate that the information presented in this review will encourage future development and design of PSs for improved image-guided PDT for cancer treatment.

Self-Assembled Porphyrinoids: One-Component Nanostructured Photomedicines

Photodynamic therapy (PDT) is becoming a promising way to treat various kinds of cancers, with few side effects. Porphyrinoids are the most relevant photosensitizers (PS) in PDT, because they present high extinction coefficients, biocompatibility, and excellent photochemical behavior. To maximize therapeutic effects, polymer-PS conjugates, and PS-loaded nanoparticles have been developed, with insights in improving tumor delivery. However, some drawbacks such as non-biodegradability, multistep fabrication, and low reagent loadings limit their clinical application. A novel strategy, noted by some authors as the "one-for-all" approach, is emerging to circumvent the use of additional delivery agents. This approach relies on the self-assembly of amphiphilic PS to fabricate nanostructures with improved transport properties. In this review we focus on different rational designs of porphyrinoid PS to achieve some of the following attributes in nanoassembly: i) selective uptake, through the incorporation of recognizable biological vectors; ii) responsiveness to stimuli; iii) combination of imaging and therapeutic functions; and iv) multimodal therapy, including photothermal or chemotherapy abilities.

Recent progress in sono-photodynamic cancer therapy: From developed new sensitizers to nanotechnology-based efficacy-enhancing strategies

Many sensitizers have not only photodynamic effects, but also sonodynamic effects. Therefore, the combination of sonodynamic therapy (SDT) and photodynamic therapy (PDT) using sensitizers for sono-photodynamic therapy (SPDT) provides alternative opportunities for clinical cancer therapy. Although significant advances have been made in synthesizing new sensitizers for SPDT, few of them are successfully applied in clinical settings. The anti-tumor effects of the sensitizers are restricted by the lack of tumor-targeting specificity, incapability in deep intratumoral delivery, and the deteriorating tumor microenvironment. The application of nanotechnology-based drug delivery systems (NDDSs) can solve the above shortcomings, thereby improving the SPDT efficacy. This review summarizes various sensitizers as sono/photosensitizers that can be further used in SPDT, and describes different strategies for enhancing tumor treatment by NDDSs, such as overcoming biological barriers, improving tumor-targeted delivery and intratumoral delivery, providing stimuli-responsive controlled-release characteristics, stimulating anti-tumor immunity, increasing oxygen supply, employing different therapeutic modalities, and combining diagnosis and treatment. The challenges and prospects for further development of intelligent sensitizers and translational NDDSs for SPDT are also discussed.

Immune/Hypoxic Tumor Microenvironment Regulation-Enhanced Photodynamic Treatment Realized by pH-Responsive Phase Transition-Targeting Nanobubbles

Due to a special pathological type of triple-negative breast cancer (TNBC) and the lack of expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her 2), targeted therapies are not effective. The lack of effective treatment drugs and insensitivity to the current single-treatment methods are the biggest problems that we face with the TNBC treatment. Therefore, new strategies to achieve selective treatment and further visual efficacy evaluation will be powerful tools against TNBC. Herein, a novel tumor-targeted nanosized ultrasound contrast nanobubble loaded with chlorin e6 (Ce6), metformin (MET), and perfluorohexane (PFH) and covalently connected to the anti-PD-L1 peptide (^DPPA-1) in the outer shell was fabricated. When accumulated in acidic tumor tissues, poly(ethylene glycol) (PEG) ligands detach, and ^DPPA-1 is exposed for programmed death-ligand 1 (PD-L1) targeting and blocking. The released metformin can relieve hypoxia by inhibiting mitochondrial complex I in the tumor microenvironment (TME) and enhance the therapeutic efficacy of Ce6 while synergizing with ^DPPA-1 by reducing PD-L1 expression. More significantly, photodynamic therapy (PDT) using multifunctional tumor-targeted nanosized ultrasound contrast agents (PD-L1-targeted pH-sensitive chlorin e6 (Ce6) and metformin (MET) drug-loaded phase transitional nanoparticles (Ce6/MET NPs-^DPPA-1)) combined with PD-L1 checkpoint blocking can not only reduce tumor-mediated immunosuppression but also produce strong antitumor immunity. This finding provides a new idea for constructing multifunctional TNBC therapeutic nanoagents.

Redox-responsive hyaluronic acid-based nanoparticles for targeted photodynamic therapy/chemotherapy against breast cancer

Specific cellular uptake and sufficient drug release in tumor tissues are important for effective cancer therapy. Hyaluronic acid (HA), a skeleton material, could specifically bind to cluster determinant 44 (CD44) receptors highly expressed on the surface of tumor cells to realize active targeting. Cystamine (cys) is sensitive highly reductive environment inside tumor cells and was used as a connecting arm to connect docosahexaenoic acid (DHA) and chlorin e6 (Ce6) to the HA skeleton to obtain redox-sensitive polymer HA-cys-DHA/Ce6 (CHD). Nanoparticles were fabricated and loaded with chemotherapeutic drug docetaxel (DTX) by physical encapsulation. The prepared nanoparticles had significantly increased uptake by MCF-7 cells that overexpressed CD44 receptors, and DTX was effectively released at high reducing condition. Compared with mono-photodynamic therapy (PDT) or mono-chemotherapy, the prepared nanoparticles exhibited superior anti-tumor effect by inhibiting microtubule depolymerization, blocking cell cycle and generating reactive oxygen species (ROS). In vivo anti-tumor experiments proved that DTX/CHD nanoparticles had the best antitumor response versus DTX and CHD nanoparticles under near-infrared (NIR) irradiation. These studies revealed that redox-responsive DTX-loaded CHD nanoparticles held great potential for the treatment of breast cancer.

Chlorin e6 and polydopamine modified gold nanoflowers for combined photothermal and photodynamic therapy

Combinational photo-based approaches with enhanced efficacy for cancer therapy have garnered increasing attention in recent years. In this work, a multifunctional system for synergistic photothermal and photodynamic cancer therapy was successfully prepared. The system consists of gold nanoflowers (AuNFs) conjugated with Chlorin e6 (Ce6), and then coated with a polydopamine (PDA) layer. AuNFs with diameters around 80 nm and a broad absorbance in the visible-near infrared (Vis-NIR) range of 500 to 800 nm, were successfully synthesized by a two-step process at 0 °C, using HAuCl4, ascorbic acid (AA), and hydroxylamine hydrochloride (NH2OH·HCl) as the reactants. Glutathione (GSH) molecules chemically anchored to the gold surfaces were used to provide addressable sites for Ce6 conjugated to GSH-AuNFs through an amidation reaction. A PDA layer was then wrapped outside the Ce6-GSH-AuNFs via self-polymerization of dopamine, which provided additional chemical modification and functionalization. Finally, the multifunctional PDA-Ce6-GSH-AuNFs were obtained. The content of Ce6 incorporated into the AuNFs was 14.0 wt%, and the singlet oxygen yield of PDA-Ce6-GSH-AuNFs was approximately 91.0% of that of free Ce6. PDA-Ce6-GSH-AuNFs showed better photothermal conversion efficiency (η = 23.6%), lower cytotoxicity, and faster cell internalization. Both in vitro and in vivo investigation of the combined treatment with a near-infrared (NIR) laser (660 nm for photodynamic therapy, and 808 nm for photothermal therapy) demonstrated that PDA-Ce6-GSH-AuNFs had excellent phototoxicity and synergistic effects of killing cancer cells. Hence, PDA-Ce6-GSH-AuNFs are a dual phototherapeutic agent that exhibits photodynamic and photothermal therapeutic effects and has potential application in enhanced cancer therapy.

Polymer-Drug Conjugates as Nanotheranostic Agents

Since the last decade, the polymer-drug conjugate (PDC) approach has emerged as one of the most promising drug-delivery technologies owing to several benefits like circumventing premature drug release, offering controlled and targeted drug delivery, improving the stability, safety, and kinetics of conjugated drugs, and so forth. In recent years, PDC technology has advanced with the objective to further enhance the treatment outcomes by integrating nanotechnology and multifunctional characteristics into these systems. One such development is the ability of PDCs to act as theranostic agents, permitting simultaneous diagnosis and treatment options. Theranostic nanocarriers offer the opportunity to track the distribution of PDCs within the body and help to localize the diseased site. This characteristic is of particular interest, especially among those therapeutic approaches where external stimuli are supposed to be applied for abrupt drug release at the target site for localized delivery to avoid systemic side effects (e.g., Visudyne®). Thus, with the help of this review article, we are presenting the most recent updates in the domain of PDCs as nanotheranostic agents. Different methodologies utilized to design PDCs along with imaging characteristics and their applicability in a wide range of diseases, have been summarized in this article.

Ultra-small gold nanoparticles self-assembled by gadolinium ions for enhanced photothermal/photodynamic liver cancer therapy

Gold nanomaterials are widely used in biomedical research as drug delivery systems, imaging agents and therapeutic materials owing to their unique physicochemical properties and high biocompatibility. In this study, we prepared ultra-small gold nanoparticles (AuNPs) and induced them with gadolinium ions to form a spherical self-assembly. The nanoparticles were coupled with matrix metalloproteinase-2 (MMP-2) and loaded with the photosensitive drug IR820 for photothermal/photodynamic combination therapy of liver cancer. The formed nanoprobes were metabolised in vivo via degradation under dual-mode real-time imaging because of their acid response degradation characteristics. In addition, the nanoprobe showed excellent tumour-targeting ability due to the presence of surface-modified MMP-2. In vivo treatment experiments revealed that the nanoprobes achieved enhanced photodynamic/photothermal combination therapy under laser irradiation and significantly inhibited tumour growth. Therefore, the nanoprobes have great potential for anti-tumour therapy guided by dual-mode real-time imaging of liver cancer.

Synergistic Effects of Acoustics-based Therapy and Immunotherapy in Cancer Treatment

Cancer is an intractable disease and has ability to escape immunological recognition. Cancer immunotherapy to enhance the autogenous immune response to cancer tissue is reported to be the most promising method for cancer treatment. After the release of damage-associated molecular patterns, dendritic cells come mature and then recruit activated T cells to induce immune response. To trigger the release of cancer associated antigens, cancer acoustics-based therapy has various prominent advantages and has been reported in various research. In this review, we classified the acoustics-based therapy into sonopyrolysis-, sonoporation-, and sonoluminescence-based therapy. Then, detailed mechanisms of these therapies are discussed to show the status of cancer immunotherapy induced by acoustics-based therapy in quo. Finally, we express some future prospects in this research field and make some predictions of its development direction

Chondroitin sulfate-based nanoparticles for enhanced chemo-photodynamic therapy overcoming multidrug resistance and lung metastasis of breast cancer

As a major therapeutic approach for cancer treatment, the effectiveness of chemotherapy is challenged by multidrug resistance (MDR). Herein, we fabricated novel redox-responsive, chondroitin sulfate-based nanoparticles that could simultaneously deliver quercetin (chemosensitizer), chlorin e6 (photosensitizer) and paclitaxel (chemotherapeutic agent) to exert enhanced chemo-photodynamic therapy for overcoming MDR and lung metastasis of breast cancer. In vitro cell study showed that nanoparticles down-regulated the expression of P-glycolprotein (P-gp) on MCF-7/ADR cells and thereby improved the anticancer efficacy of PTX against MCF-7/ADR cells. Moreover, NIR laser irradiation could induce nanoparticles to generate cellular reactive oxygen species (ROS), leading to mitochondrial membrane potential loss, and meanwhile facilitating lysosomal escape of drugs. Importantly, the novel nanoplatform exhibited effective in vivo MDR inhibition and anti-metastasis efficacy through enhanced chemo-photodynamic therapy. Thus, the study suggested that the multifunctional nanoplatform had good application prospect for effective breast cancer therapy.

Dual activatable self-assembled nanotheranostics for bioimaging and photodynamic therapy

Multifunctional nanosystems that can transport therapeutic and diagnostic agents into tumor sites and activate their respective functions via tumor-microenvironment recognition are highly desirable for clinical applications. We fabricated pH and redox dual-activatable self-assembled nanotheranostics (named as DA-SNs) via coordination-driven self-assembly of chlorin e6 (Ce6) disulfide-linked pH sensitive polymer ligand, poly (isobutylene-alt-maleic anhydride-graft-methoxy-poly (ethyleneglycol)-graft-imidazole-graft-Cystamine-Ce6) [PIMA-mPEG-API-SS-Ce6], and gadolinium ions (Gd³⁺). DA-SNs exhibited uniform particle size of ~48 nm, excellent stability, and inherent biosafety. Negatively charged DA-SNs could prolong blood circulation time (t_1/2 = 2.91 h) and improve tumor accumulation. Moreover, DA-SNs could undergo surface charge switch from negative charge to positive one in a slightly acidic tumor extracellular environment (pH 6.8), thus enhancing cellular uptake. After entering tumor cells, fluorescence, photodynamic therapeutic activity, and T₁MR contrast from DA-SNs could be activated within this intracellular environment with lowered pH and high level of GSH. Importantly, human tumors implanted in mice could be successfully visualized via distinct pH and redox dual-sensitive T₁MR contrast and fluorescence imaging, indicating that DA-SNs could serve as a dual-modal MR/fluorescence imaging probe for tumor-targeting diagnosis. In addition, DA-SNs exhibited superior photodynamic therapeutic efficiency with negligible side effects. Therefore, this DA-SN shows great promise for synergistic photodynamic therapy and diagnostic imaging.

Surface-Charge-Switchable Nanoclusters for Magnetic Resonance Imaging-Guided and Glutathione Depletion-Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) is an effective noninvasive therapeutic method that employs photosensitizers (PSs) converting oxygen to highly cytotoxic singlet oxygen (¹O₂) under light irradiation. The conventional PDT efficacy is, however, compromised by the nonspecific delivery of PSs to tumor tissue, the hypoxic tumor microenvironment, and the reduction of generated ¹O₂ by the intracellular antioxidant glutathione (GSH). Herein, an intelligent multifunctional synergistic nanoplatform (CMGCC) for T₁-weighted magnetic resonance (MR) imaging-guided enhanced PDT is presented, which consists of nanoparticles composed of catalase (CAT) and manganese dioxide (MnO₂) that are integrated within chlorin-e6-modified glycol chitosan (GC) polymeric micelles. In this system, (1) GC polymers with pH-sensitive surface charge switchability from neutral to positive could improve the PS accumulation within the tumor region, (2) CAT could effectively reoxygenate the hypoxic tumor via catalyzing endogenous hydrogen peroxide to O₂, and (3) MnO₂ could consume the intracellular GSH while simultaneously producing Mn²⁺ as a contrast agent for T₁-weighted MR imaging. The CMGCC particles possess uniform size distribution, well-defined structure, favorable enzyme activity, and superior ¹O₂ generation ability. Both in vitro and in vivo experiments demonstrate that the CMGCC exhibit significantly enhanced PDT efficacy toward HeLa cells and subcutaneous HeLa tumors. Our study thereby demonstrates this to be a promising synergistic theranostic nanoplatform with highly efficient PDT performance for cancer therapy.

Hybrid cell membrane-coated nanoparticles: A multifunctional biomimetic platform for cancer diagnosis and therapy

Biomimetic nanotechnology through camouflaging synthetic nanoparticles (NPs) with natural cell membranes, which bestows with immune evasion and superior targeting capacity, has been extensively used in drug delivery systems (DDS) over the last decades. These biomimetic NPs not only retain the physicochemical features of the synthetic vehicles but also inherit the cell membranes' intrinsic functionalities. Combined with these benefits, optimized nano-biomimetic DDS allow maximum delivery efficacy. Compared to erythrocyte/cancer single cell membrane, the hybrid cell membrane expressing CD47 membrane protein and self-recognition molecules, from erythrocytes and cancer cells, provides remarkable features to the synthetic vehicles, such as immune evasion, long-term circulation, and homotypic targeting. In this review, we describe the preparation strategies, the camouflaging mechanism, and the antitumor applications of hybrid cell membrane-camouflaged NPs. Moreover, we discuss further modification of the hybrid cell membrane and the surface properties of fusion cellular membranes. Finally, we summarize the primary challenges and opportunities associated with these NPs. STATEMENT OF SIGNIFICANCE: Camouflaging synthetic nanoparticles with hybrid cell membrane has been extensively highlighted in recent years. The resultant biomimetic nanoparticles not only reserve the physicochemical properties of the synthetic nanoparticles but also inherit the biological functions of source cells. Compared with single cell membrane, hybrid cell membrane can endow synthetic nanoparticles with multiple biofunctions derived from the original source cells. To provide a timely review of this rapidly developing subject of research, this paper summarized recent progress on the hybrid cell membrane-camouflaged nanoparticles as drug delivery systems for cancer diagnosis and treatment. In this review, we focused primarily on five different types of hybrid cell membrane-camouflaged nanoparticles with the preparation strategies, the camouflaging mechanism, and the antitumor applications. Moreover, further modification of the hybrid cell membrane was also discussed for isolating effectively circulating tumor cells.

Human iPS Cells Loaded with MnO2-Based Nanoprobes for Photodynamic and Simultaneous Enhanced Immunotherapy Against Cancer

HIGHLIGHTS

MnO₂@Ce6 nanoprobes-loaded-iPS cells (iPS-MnO₂@Ce6) were developed for enhanced photodynamic and immunotherapy against cancer. Under the guidance of multi-mode real-time imaging, iPS-MnO₂@Ce6 achieved an enhanced photodynamic therapeutic effect and stimulated a strong anti-tumor immune response in the tumor-bearing mouse.

ABSTRACT

How to trigger strong anti-tumor immune responses has become a focus for tumor therapy. Here, we report the human-induced pluripotent stem cells (iPSs) to deliver MnO₂@Ce6 nanoprobes into tumors for simultaneous photodynamic therapy (PDT) and enhanced immunotherapy. Ce6 photosensitizer was attached on manganese dioxide (MnO₂) nanoparticles, and resultant MnO₂@Ce6 nanoprobes were delivered into mitomycin-treated iPSs to form iPS-MnO₂@Ce6 nanoprobes. The iPS-MnO₂@Ce6 actively targeted in vivo tumors, the acidic microenvironment triggered interaction between MnO₂ and H₂O₂, released large quantities of oxygen, alleviated hypoxia in tumor. Upon PDT, singlet oxygen formed, broken iPSs released tumor-shared antigens, which evoked an intensive innate and adaptive immune response against the tumor, improving dendritic cells matured, effector T cells, and natural killer cells were activated. Meanwhile, regulatory T cells were reduced, and then the immune response induced by iPS-MnO₂@Ce6 was markedly stronger than the immune reaction induced by MnO₂@Ce6 (P < 0.05). The iPS-MnO₂@Ce6 markedly inhibited tumor growth and metastasis and reduced mortality in mice models with tumor. Human iPSs loaded with MnO₂-based nanoprobes are a promising strategy for simultaneous PDT and enhanced immunotherapy against tumor and own clinical translational prospect. [Image: see text]

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (10.1007/s40820-020-00452-y) contains supplementary material, which is available to authorized users.

Redox dual-stimuli responsive drug delivery systems for improving tumor-targeting ability and reducing adverse side effects

Cancer is a big challenge that has plagued the human beings for ages and one of the most effective treatments is chemotherapy. However, the low tumor-targeting ability limits the wide clinical application of chemotherapy. The microenvironment plays a critical role in many aspects of tumor genesis. It generates the tumor vasculature and it is highly implicated in the progression to metastasis. To maintain a suitable environment for tumor progression, there are special microenvironment in tumor cell, such as low pH, high level of glutathione (GSH) and reactive oxygen species (ROS), and more special enzymes, which is different to normal cell. Microenvironment-targeted therapy strategy could create new opportunities for therapeutic targeting. Compared to other targeting strategies, microenvironment-targeted therapy strategy will control the drug release into tumor cells more accurately. Redox responsive drug delivery systems (DDSs) are developed based on the high level of GSH in tumor cells. However, there are also GSH in normal cell though its level is lower. In order to control the release of drugs more accurately and reduce side effects, other drug release stimuli have been introduced to redox responsive DDSs. Under the synergistic reaction of two stimuli, redox dual-stimuli responsive DDSs will control the release of drugs more accurately and quickly and even increase the accumulation. This review summarizes strategies of redox dual-stimuli responsive DDSs such as pH, light, enzyme, ROS, and magnetic guide to delivery chemotherapeutic agents more accurately, aiming at providing new ideas for further promoting the drug release, enhancing tumor-targeting and improving anticancer effects. To better illustrate the redox dual-stimuli responsive DDS, preparations of carriers are also briefly described in the review.

Coupling Chlorin e6 to the surface of Nanoscale Gas Vesicles strongly enhance their intracellular delivery and photodynamic killing of cancer cells

Protein-based nanobubbles such as halophilic archaeabacterial gas vesicles (GVs) represent a new class of stable, homogeneous nanoparticles with acoustic properties that allow them to be visualized by ultrasound (US) waves. To design GVs as theranostic agents, we modified them to respond to light, with a view to locally generate reactive oxygen species that can kill cancer cells. Specifically, up to 60,000 photoreactive chlorin e6 (Ce6) molecules were chemically attached to lysine ε-amino groups present on the surface of each purified Halobacterium sp. NRC-1 GV. The resulting fluorescent NRC-1 Ce6-GVs have dimensions comparable to that of native GVs and were efficiently taken up by human breast [MCF-7] and human hypopharyngeal [FaDu-GFP] cancer cells as monitored by confocal microscopy and flow cytometry. When exposed to light, internalized Ce6-GVs were 200-fold more effective on a molar basis than free Ce6 at killing cells. These results demonstrate the potential of Ce6-GVs as novel and promising nanomaterials for image-guided photodynamic therapy.

Activatable Phototheranostic Materials for Imaging-Guided Cancer Therapy

Cancer theranostics, which combines diagnostic and therapeutic effects into one entity, holds promise in precision medicine. Conventional theranostic agents possess always-on imaging signals and cytotoxic effects and thus often encounter poor selectivity or specificity in cancer treatment. To tackle this issue, activatable phototheranostic materials (PMs) have been developed to simultaneously and specifically turn on their diagnostic signals (fluorescence/self-luminescence/photoacoustic signals) and photothermal/photodynamic effects in response to cancer hallmarks. This Review summarizes the recent progress in the design, synthesis and proof-of-concept applications of activatable PMs. The molecular engineering strategy to increase tumor accumulation and enhance treatment efficacy are highlighted. Current challenges and future perspectives in this emerging field are also discussed.

Nanoparticle-based drug delivery systems for controllable photodynamic cancer therapy

Compared with the traditional treatment, photodynamic therapy (PDT) in the treatment of malignant tumors has the advantages of less damage to normal tissues, quick therapeutic effect, and ability to repeat treatments to the same site. However, most of the traditional photosensitizers (PSs) have severe skin photosensitization, poor tumor targeting, and low therapeutic effect in hypoxic tumor environment, which limit the application of PDT. Nanoparticle-based drug delivery systems can improve the targeting of PSs and release drugs with controllable photoactivity at predetermined locations, so as to achieve desired therapeutic effects with minimal side-effects. The present review summarizes the current nanoparticle platforms for PDT, and offers the description of different strategies including tumor-targeted delivery, controlled-release of PSs and the triggered photoactivity to achieve controllable PDT by nanoparticle-based drug delivery systems. The challenges and prospects for further development of intelligent PSs for PDT are also discussed.

Anti-LDLR modified TPZ@Ce6-PEG complexes for tumor hypoxia-targeting chemo-/radio-/photodynamic/photothermal therapy

Hypoxia, a state of low oxygen tension in solid tumors, is not only closely correlated with resistance to both radiotherapy and chemotherapy, but also associated with poor prognosis of tumors and regional lymph node status. Herein, based on the analysis of cell samples from tumor patients, low-density lipoprotein receptor (LDLR) was found to be overexpressed on the surface of hypoxic tumor cell membranes, and confirmed to be an effective hypoxia marker through specific binding with anti-LDLR antibody in solid tumors. In addition, using the special therapeutic microenvironment of hypoxia, tirapazamine (TPZ, which can be used as both a hypoxia-activated chemotherapy prodrug and radiotherapy sensitizer) was integrated with PEGylated photosensitizer chlorin e6 (Ce6-PEG) by self-assembly, and anti-LDLR was then modified on the surface to form tumor hypoxia-targeting multifunctional nanoparticles (CPTA). CPTA possesses a multimodal antitumor effect via a simultaneous photothermal therapy (PTT)/photodynamic therapy (PDT) effect generated by Ce6, and chemotherapy/radiotherapy actions sensitized by TPZ. It is noteworthy that tumor oxygen was consumed in the process of PDT and the hypoxia was subsequently exacerbated, which can greatly increase the TPZ-sensitized chemotherapy and lead to a synergistic antitumor effect. Both in vitro and in vivo experiments demonstrated that CPTA possesses an excellent therapeutic effect through PTT, PDT, and TPZ sensitized radiotherapy and chemotherapy. This hypoxic tumor targeting synergetic therapeutic strategy has great potential for future clinical transformation.

Polyphotosensitizer nanogels for GSH-responsive histone deacetylase inhibitors delivery and enhanced cancer photodynamic therapy

Photodynamic therapy (PDT) is one of the non-invasive and selective treatment methodologies for cancer. However, many highly efficient photosensitizers (PSs) are usually low physiological solubility, limited bioavailability and tending aggregation, impeding the effectiveness of PDT, as well as cancer resistance of PDT further reduce its therapeutic effect. Though some smart delivery systems have been developed, the problem of photosensitizer leakage/release has not been completely solved. Herein, we developed a smart therapeutic nanoplatform based on polyphotosensitizer nanogel as novel nanophotosensitizers and drug carriers. Moreover, by loading of histone deacetylase inhibitors (SAHA), it allows for enhanced synergistic therapy strategy of prostate cancer via inhibiting HIF-1α and VEGF pathways of cancer cells involved in PDT resistance. Our study presents the well-designed nanoplatform of nanogel-Ce6, which could serve as a photodynamic agent without Ce6 molecules release in the responsive environment, offering the potential to encapsulate diverse functional components for smart drug release and imaging-guided combination therapy in vitro and in vivo.

Prospective of nanoscale metal organic frameworks [NMOFs] for cancer therapy

Nano metal organic frameworks (NMOFs) belong to the group of nanoporous materials. Over the decades, the conducted researches explored the area for the potential applications of NMOFs in areas like biomedical, chemical engineering and materials science. Recently, NMOFs have been explored for their potential use in cancer diagnosis and therapeutics. The excellent physico-chemical features of NMOFs also make them a potential candiadate to facilitate drug design, delivery and storage against cancer cells. In this review, we have explored the characterstic features, synthesis methods, NMOFs based drug delivery, diagnosis and imaging in various cancer types. In addition to this, we have also pondered on the stability and toxicological concerns of NMOFs. Despite, a significant research has been done for the potential use of NMOFs in cancer diagonostic and therapeutics, more information regarding the stability, in-vivo clearance, toxicology, and pharmacokinetics is still needed to ehnace the use of NMOFs in cancer diagonostic and therapeutics.

Nanocarriers in photodynamic therapy-in vitro and in vivo studies

Photodynamic therapy (PDT) is a minimally invasive technique which has proven to be successful in the treatment of several types of tumors. This relatively simple method exploits three inseparable elements: phototoxic compound (photosensitizer [PS]), light source, and oxygen. Upon irradiation by light with specified wavelength, PS generates reactive oxygen species, which starts the cascade of reactions leading to cell death. The positive therapeutic outcome of PDT may be limited due to several aspects, including low water solubility of PSs, hampering their effective administration and blood circulation, as well as low tumor specificity, inefficient cellular uptake and activation energies requiring prolonged illumination times. One of the promising approaches to overcome these obstacles involves the use of carrier systems modulating pharmacokinetics and pharmacodynamics of the PSs. In the present review, we summarized current in vitro and in vivo studies regarding the use of nanoparticles as potential delivery devices for PSs to enhance their cellular uptake and cytotoxic properties, and thus-the therapeutic outcome of PDT. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Multifunctional Theranostic Liposomes Loaded with a Hypoxia-Activated Prodrug for Cascade-Activated Tumor Selective Combination Therapy

Photodynamic therapy (PDT) is becoming a promising therapeutic regimen but is limited by the hypoxic microenvironment in solid tumors and the undesirable post-treatment phototoxicity side effects on normal tissues. To overcome these restrictions and enhance the antitumor therapeutic effect, near-infrared (NIR) light-activated, cancer cell-specific, hypoxia prodrug-loaded chlorin e6 liposomes were developed for tumor selective combination therapy guided by multimodal imaging. The photothermal agent indocyanine green (ICG) and hypoxia-activated prodrug tirapazamine (TPZ) were coencapsulated into the liposomes, followed by modification with cRGD and conjugation with Gd^III to form ICG/TPZ@Ce6-Gd^III theranostic liposomes (ITC-Gd^III TLs). In the ITC-Gd^III TLs, both the fluorescence and photodynamic effect of Ce6 were quenched by ICG via fluorescence resonance energy transfer. The ITC-Gd^III TLs can effectively reach the tumor site through the enhanced permeability and retention effect as well as the cRGD-mediated active targeting ability. The fluorescence and photodynamic effect of Ce6 can be activated by the photothermal effect of ICG under NIR light. Upon subsequent irradiation with a 660 nm laser, the released Ce6 could kill cancer cells by generating cytotoxic singlet oxygen. Furthermore, the PDT process would induce hypoxia, which in turn activated the antitumor activity of the codelivered hypoxia-activated prodrug TPZ for a combination antitumor effect. The TLs could be utilized for multimodal imaging (fluorescence/photoacoustic/magnetic resonance imaging)-guided cascade-activated tumor inhibition with optimized therapeutic efficiency and minimized side effects, holding great potential for constructing intelligent nanotheranostics.

Matrix metalloproteinase-2-targeted superparamagnetic Fe3O4-PEG-G5-MMP2@Ce6 nanoprobes for dual-mode imaging and photodynamic therapy

This work explored the application of matrix metalloproteinase 2-targeted superparamagnetic nanoprobes for magnetic resonance imaging (MRI), near infrared (NIR) fluorescence imaging and photodynamic therapy of tumors. PEG, PAMAM (G5) and matrix metalloproteinase 2 (MMP2) were attached to the surface of carboxylated Fe3O4 nanoparticles (NPs) using a chemical coupling method and then finally loaded with the photosensitizer chlorin e6 (Ce6). In vitro and in vivo experiments demonstrated that the Fe3O4-PEG-G5-MMP2@Ce6 nanoprobes exhibited excellent stability, precise tumor targeting and biocompatibility. Furthermore, the fluorescence properties of Fe3O4-PEG-G5-MMP2@Ce6 nanoprobes were analogous to Ce6 and could be employed for fluorescence imaging. Meanwhile, the Fe3O4-PEG-G5-MMP2@Ce6 nanoprobes have also been shown to be effective as contrast agents for T2-weighted MRI. The target molecule MMP2 enhanced the tumor targeting ability of Fe3O4-PEG-G5-MMP2@Ce6 nanoprobes. Additionally, the Fe3O4-PEG-G5-MMP2@Ce6 nanoprobes significantly inhibited tumor growth compared with PBS and free Ce6. This work will inspire greater enthusiasm for the construction of multifunctional magnetic nanoplatforms for biomedical applications.

Size-Tunable Targeting-Triggered Nanophotosensitizers Based on Self-Assembly of a Phthalocyanine-Biotin Conjugate for Photodynamic Therapy

Self-assembled phototheranostic nanomaterials used for photodynamic therapy (PDT) have attracted increasing attention owing to their several advantages. Herein, we developed a novel strategy for size-tunable self-assembled nanophotosensitizers for PDT through a simple method. A series of switchable self-assembled nanophotosensitizers (NanoPc90, NanoPc40, NanoPc20, and NanoPc10) of different particle sizes were readily prepared based on an amphiphilic silicon(IV) phthalocyanine (SiPc)-biotin conjugate by regulating the amount of the Cremophor EL surfactant used. The photoactivities, including fluorescence and reactive oxygen species (ROS), of the self-assemblies could be regulated by the particle size. The self-assemblies could be specifically disassembled by tumor-overexpressing biotin receptors, leading to the recovery of quenched photoactivities. Demonstrated by the competitive assay, the self-assemblies were able to enter HepG2 cells through a biotin-receptor-mediated pathway, followed by biotin-receptor-triggered fluorescence recovery at the cellular level. Moreover, the particle size could also affect the in vitro and in vivo PDT effects and tumor targeting. The photocytotoxicity of NanoPc20 against HepG2 cells was more potent compared to that of NanoPc90 because of its strong intracellular fluorescence, higher intracellular ROS generation, and different subcellular localization. In addition, NanoPc20 showed higher in vivo tumor targeting and photodynamic therapeutic efficacy than NanoPc90. This work would provide a valuable reference for the development of self-assembled nanophotosensitizers for cancer diagnosis and therapy.

Porphyrinoid-based photosensitizers for diagnostic and therapeutic applications: An update

Porphyrin-based molecules are actively studied as dual function theranostics: fluorescence-based imaging for diagnostics and fluorescence-guided therapeutic treatment of cancers. The intrinsic fluorescent and photodynamic properties of the bimodal molecules allows for these theranostic approaches. Several porphyrinoids bearing both hydrophilic and/or hydrophobic units at their periphery have been developed for the aforementioned applications, but better tumor selectivity and high efficacy to destroy tumor cells is always a key setback for their use. Another issue related to their effective clinical use is that, most of these chromophores form aggregates under physiological conditions. Nanomaterials that are known to possess incredible properties that cannot be achieved from their bulk systems can serve as carriers for these chromophores. Porphyrinoids, when conjugated with nanomaterials, can be enabled to perform as multifunctional nanomedicine devices. The integrated properties of these porphyrinoid-nanomaterial conjugated systems make them useful for selective drug delivery, theranostic capabilities, and multimodal bioimaging. This review highlights the use of porphyrins, chlorins, bacteriochlorins, phthalocyanines and naphthalocyanines as well as their multifunctional nanodevices in various biomedical theranostic platforms.

Construction of a Polypyrrole-Based Multifunctional Nanocomposite for Dual-Modal Imaging and Enhanced Synergistic Phototherapy against Cancer Cells

Design and construction of multifunctional theranostic nanoplatforms are still desired for cancer-effective treatment. Herein, a kind of polypyrrole (PPy)-based multifunctional nanocomposite was designed and successfully constructed for dual-model imaging and enhanced synergistic phototherapy against cancer cells. Through graphene oxide (GO) sheet coating, PPy nanoparticles (NPs) were effectively combined with polyethylene glycol chains, Au NPs, and IR820 molecules. The obtained PGPAI NPs showed promising ability for photoacoustic/computed tomography imaging. Under near-infrared light irradiation, the PPy core and IR820 molecule effectively generated heat and reactive oxygen species (ROS), respectively. Furthermore, the loaded Au NPs owning catalase-like activity produced oxygen by decomposing H₂O₂ (up-regulated in tumor region), enhancing the oxygen-dependent photodynamic therapy efficacy. The formed PGPAI NPs were also proved to own desirable photothermal conversion efficiency, photothermal stability, colloidal stability, cytocompatibility, and cellular internalization behaviors. Furthermore, cell assay demonstrated that PGPAI NPs displayed enhanced synergistic phototherapy efficacy against cancer cells. These developed multifunctional nanoplatforms are promising for effective cancer theranostic applications.