Phthalocyanine-based photoacoustic contrast agents for imaging and theranostics

"Alkyl-Substituted Phenoxy" Spacer Strategy: Antiaggregated and Highly Soluble Zinc Phthalocyanines for Color Films

A series of zinc phthalocyanine derivatives (ZnPcs) were designed by introducing different volumes of steric hindrance groups (chlorine atom, n-propyloxy, isopropyloxy, n-butoxy, isobutoxy, tert-butoxy, 2,4-di-tert-butylphenoxy, 2,4-di-tert-pentylphenoxy) on the peripheral and nonperipheral positions of phthalocyanine. Density functional theory (DFT) calculations presented that the substitution of sterically hindered 2,4-di-tert-butylphenoxy or 2,4-di-tert-pentylphenoxy on the peripheral positions effectively reduced the aggregation of ZnPcs, improving the solubility of ZnPcs, and the simultaneous substitution on the peripheral and nonperipheral positions could achieve ZnPcs with different colors. From the calculation results, six low-aggregation ZnPcs were synthesized for the first time. The solubilities of the synthesized ZnPcs are above 6.0/100 g. Furthermore, their color films displayed excellent transmittance because of the introduction of sterically hindered 2,4-di-tert-butoxyphenoxy or 2,4-di-tert-pentylphenoxy moieties. Also, the color films exhibit great photo and thermal stability (ΔE < 3).

Glycolysis-non-canonical glutamine dual-metabolism regulation nanodrug enhanced the phototherapy effect for pancreatic ductal adenocarcinoma treatment

Clinical pancreatic ductal adenocarcinoma (PDAC) treatment is severely limited by lack of effective KRAS suppression strategies. To address this dilemma, a reactive oxygen species (ROS)-responsive and PDAC-targeted nanodrug named Z/B-PLS was constructed to confront KRAS through dual-blockade of its downstream PI3K/AKT/mTOR and RAF/MEK/ERK for enhanced PDAC treatment. Specifically, photosensitizer zinc phthalocyanine (ZnPc) and PI3K/mTOR inhibitor BEZ235 (BEZ) were co-loaded into PLS which was constructed by click chemistry conjugating MEK inhibitor selumetinib (SEL) to low molecular weight heparin with ROS-responsive oxalate bond. The BEZ and SEL blocked PI3K/AKT/mTOR and RAF/MEK/ERK respectively to remodel glycolysis and non-canonical glutamine metabolism. ZnPc mediated photodynamic therapy (PDT) could enhance drug release through ROS generation, further facilitating KRAS downstream dual-blockade to create treatment-promoting drug delivery-therapeutic positive feedback. Benefiting from this broad metabolic modulation cascade, the metabolic symbiosis between normoxic and hypoxic tumor cells was also cut off simultaneously and effective tumor vascular normalization effects could be achieved. As a result, PDT was dramatically promoted through glycolysis-non-canonical glutamine dual-metabolism regulation, achieving complete elimination of tumors in vivo. Above all, this study achieved effective multidimensional metabolic modulation based on integrated smart nanodrug delivery, helping overcome the therapeutic challenges posed by KRAS mutations of PDAC.

Cancer cell membrane-coated nanoparticles: a promising anti-tumor bionic platform

Nanoparticle (NP) drug delivery systems have shown promise in tumor therapy. However, limitations such as susceptibility to immune clearance and poor targeting in a complex intercellular environment still exist. Recently, cancer cell membrane-encapsulated nanoparticles (CCM-NPs) constructed using biomimetic nanotechnology have been developed to overcome these problems. Proteins on the membrane surface of cancer cells can provide a wide range of activities for CCM-NPs, including immune escape and homologous cell recognition properties. Meanwhile, the surface of the cancer cell membrane exhibits obvious antigen enrichment, so that CCM-NPs can transmit tumor-specific antigen, activate a downstream immune response, and produce an effective anti-tumor effect. In this review, we first provided an overview of the functions of cancer cell membranes and summarized the preparation techniques and characterization methods of CCM-NPs. Then, we focused on the application of CCM-NPs in tumor therapy. In addition, we summarized the functional modifications of cancer cell membranes and compiled the patent applications related to CCM-NPs in recent years. Finally, we proposed the future challenges and directions of this technology in order to provide guidance for researchers in this field.

Hybrid ultrasound and photoacoustic contrast agent designs combining metal phthalocyanines and PBCA microbubbles

Photoacoustic (PA) imaging is an emerging diagnostic technology that combines the penetration depth of ultrasound (US) imaging and the contrast resolution of optical imaging. Although PA imaging can visualize several endogenous chromophores to obtain clinically-relevant information, multiple applications require the administration of external contrast agents. Metal phthalocyanines have strong PA properties and chemical stability, but their extreme hydrophobicity requires their encapsulation in delivery systems for biomedical applications. Hence, we developed hybrid US/PA contrast agents by encapsulating metal phthalocyanines in poly(butyl cyanoacrylate) microbubbles (PBCA MB), which display acoustic response and ability to efficiently load hydrophobic drugs. Six different metal chromophores were loaded in PBCA MB, showing greater encapsulation efficiency with higher chromophore hydrophobicity. Notably, while the US response of the MB was unaffected by the loading of the chromophores, the PA characteristics varied greatly. Among the different formulations, MB loaded with zinc and cobalt naphthalocyanines showed the strongest PA contrast, as a result of high encapsulation efficiencies and tunable optical properties. The strong US and PA contrast signals of the formulations were preserved in biological environment, as demonstrated by in vitro imaging in serum and whole blood, and ex vivo imaging in deceased mice. Taken together, these findings highlight the advantages of combining highly hydrophobic PA contrast agents and polymeric MB for the development of contrast agents for hybrid US/PA imaging, where different types of information (structural, functional, or potentially molecular) can be acquired by combining both imaging modalities.

A reductively convertible nickel phthalocyanine precursor as a biological thiol-responsive turn-on photoacoustic contrast agent

A nickel phthalocyanine precursor bearing poly(ethylene glycol) as a turn-on contrast agent for photoacoustic imaging was prepared. The water-soluble polymeric chains were smoothly eliminated through thiol-mediated reductive aromatization in cancer cells, enabling the detection of endogenous biological thiols in vitro and in vivo.

Innovative Design Strategies Advance Biomedical Applications of Phthalocyanines

Owing to their long absorption wavelengths, high molar absorptivity, and tunable photosensitivity, phthalocyanines have been widely used in photodynamic therapy (PDT). However, phthalocyanines still face the drawbacks of poor targeting, "always-on" photosensitizing properties, and unsatisfactory therapeutic efficiency, which limit their wide applications in biomedical fields. Thus, new design strategies such as modification of targeting molecules, formation of nanoparticles, and activating photosensitizers are developed to improve the above defects. Notably, recent studies have shown that novel phthalocyanines are not only used in fluorescence imaging and PDT, but also in photoacoustic imaging, photothermal imaging, sonodynamic therapy, and photothermal therapy. This review focuses on recent design strategies, applications in biomedicine, and clinical development of phthalocyanines, providing ideas and references for the design and application of phthalocyanine, so as to promote their future transformation into clinical applications.

A Photosensitizer-Loaded Polydopamine Nanomedicine Agent for Synergistic Photodynamic and Photothermal Therapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) have emerged as promising non-invasive approaches to cancer treatment. However, the development of multifunctional nanomedicines is necessary to enhance these approaches' effectiveness and safety. In this study, we investigated a polydopamine-based nanoparticle (PDA-ZnPc+ Nps) loaded with the efficient photosensitizer ZnPc(4TAP)12+ (ZnPc+) through in vitro and in vivo experiments to achieve synergistic PDT and PTT. Our results demonstrated that PDA-ZnPc+ Nps exhibited remarkable efficacy due to its ability to generate reactive oxygen species (ROS), induce photothermal effects, and promote apoptosis in cancer cells. Moreover, in both MCF-7 cells and MCF-7 tumor-bearing mice, the combined PDT/PTT treatment with PDA-ZnPc+ Nps led to synergistic effects. Subcellular localization analysis revealed a high accumulation of ZnPc+ in the cytoplasm of cancer cells, resulting in cellular disruption and vacuolation following synergistic PDT/PTT. Furthermore, PDA-ZnPc+ Nps exhibited significant antitumor effects without causing evident systemic damage in vivo, enabling the use of lower doses of photosensitizer and ensuring safer treatment. Our study not only highlights the potential of PDA-ZnPc+ Nps as a dual-functional anticancer agent combining PDA and PTT but also offers a strategy for mitigating the side effects associated with clinical photosensitizers, particularly dark toxicity.

Red blood cell membrane nanoparticles for tumor phototherapy

Non-invasive phototherapy includes photodynamic therapy (PDT) and photothermal therapy (PTT), and has garnered special interest in anti-tumor therapy. However, traditional photosensitizers or photothermal agents are faced with major challenges, including easy recognition by immune system, rapid clearance from blood circulation, and low accumulation in target sites. Combining the characteristics of natural cell membrane with the characteristics of photosensitizer or photothermal agent is an important technology to achieve the ideal therapeutic effect of cancer. Red cell membrane (RBMs) coated can disguise phototherapy agents as endogenous substances, thus constructing a new nano bionic therapeutic platform, resisting blood clearance and prolonging circulation time. At present, a variety of phototherapy agents based on Nano-RBMs have been isolated or designed. In this review, firstly, the basic principles of Nano-RBMs and phototherapy are expounded respectively. Then, the latest progress of Nano-RBMs for PDT, PTT and PDT/PTT applications in recent five years has been introduced respectively. Finally, the problems and challenges of Nano-RBMs in the field of phototherapy are put forward.

Ce doped polyaniline nanoparticles for absorption and photoacoustic imaging response to GSH in vitro and in vivo

Glutathione (GSH) is an important biological thiol in cells, which is involved in many physiological processes in the organism and regulates pathological processes of cells. Rapid and accurate monitoring of GSH in vitro and in vivo is quite needed in investigating important biochemical events. In this contribution, innovative cerium (Ce) doped polyaniline (Ce–Fe@PANI NPs) were prepared via Fe(III) induced oxidization polymerization method. Upon addition of GSH, the absorption of Ce–Fe@PANI NPs red shifted from the visible to the NIR region, confirming the excellent absorption response to GSH. Moreover, Ce–Fe@PANI NPs exhibited excellent photoacoustic (PA) imaging enhancement in tube and shifted the PA intensity peak from 680 nm to 820 nm upon addition of GSH. In vitro and in vivo experiment verified that Ce–Fe@PANI NPs can monitor GSH in deep tissues via PA imaging technology. Collectively, this research provides Ce–Fe@PANI NPs would serve as a powerful nanoplatform to realize PA imaging detection of GSH in vitro and in vivo.

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Ce doped polyaniline nanoparticles (Ce–Fe@PANI NPs) with NIR absorption were prepared.

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Ce–Fe@PANI NPs demonstrated absorption response to GSH.

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Ce–Fe@PANI NPs had excellent PA enhancement and shifted the PA intensity peak from 680 nm to 820 nm upon addition of GSH.

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Ce–Fe@PANI NPs can monitor GSH in deep tissues via PA imaging technology in vivo.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: "always-on" and "turn-on," based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

[3 + 1] Mixed Cyclization: A Synthetic Route to Prepare Low-Symmetry Phthalocyanines

A novel synthetic strategy for low-symmetry phthalocyanines has been developed, which involves the base-promoted cyclization of a preconnected trisphthalonitrile and a free phthalonitrile in the presence of a metal template. By using this [3 + 1] mixed cyclization approach, a series of zinc(II) phthalocyanine derivatives have been synthesized in up to 12% yields, including a very rare ABCD-type phthalocyanine and an amphiphilic ABAC-type analogue that can self-assemble in aqueous media, forming stable spherical nanoparticles.

Graphene quantum dots-porphyrins/phthalocyanines multifunctional hybrid systems: from interfacial dialogue to applications

Engineered well-ordered hybrid nanomaterials are at a symbolically pivotal point, just ahead of a long-anticipated human race transformation. Incorporating newer carbon nanomaterials like graphene quantum dots (GQDs) with tetrapyrrolic porphyrins...