Glycopolymer Decorated pH-Dependent Ratiometric Fluorescent Probe Based on Förster Resonance Energy Transfer for the Detection of Cancer Cells

Development of fluorescent imaging probes is an important topic of research for the early diagnosis of cancer. Based on the difference between the cellular environment of tumor cells and normal cells, several "smart" fluorescent probes have been developed. In this work, a glycopolymer functionalized Förster resonance energy transfer (FRET) based fluorescent sensor is developed, which can monitor the pH change in cellular system. One-pot sequential reversible addition-fragmentation chain transfer (RAFT)polymerization technique is employed to synthesize fluorescent active triblock glycopolymer that can undergo FRET change on the variation of pH. A FRET pair, fluorescein o-acrylate (FA) and 7-amino-4-methylcoumarin (AMC) is linked via a pH-responsive polymer poly [2-(diisopropylamino)ethyl methacrylate] (PDPAEMA), which can undergo reversible swelling/deswelling under acidic/neutral condition. The presence of glycopolymer segment provides stability, water solubility, and specificity toward cancer cells. The cellular FRET experiments on cancer cells (MDA MB 231) and normal cells (3T3 fibroblast cells) demonstrate that the material is capable of distinguishing cells as a function of pH change.

New horizons in the identification of circulating tumor cells (CTCs): An emerging paradigm shift in cytosensors

Circulating tumor cells (CTCs) are cancer cells that are shed from a primary tumor into the bloodstream and function as seeds for cancer metastasis at distant locations. Enrichment and identification methods of CTCs in the blood of patients plays an important role in diagnostic assessments and personalized treatments of cancer. However, the current traditional identification methods not only impact the viability of cells, but also cannot determine the type of cancer cells when the disease is unknown. Hence, new methods to identify CTCs are urgently needed. In this context, many advanced and safe technologies have emerged to distinguish between cancer cells and blood cells, and to distinguish specific types of cancer cells. In this review, at first we have briefly discussed recent advances in technologies related to the enrichment of CTCs, which lay a good foundation for the identification of CTCs. Next, we have summarized state-of-the-art technologies to confirm whether a given cell is indeed a tumor cell and determine the type of tumor cell. Finally, the challenges for application and potential directions of the current identification methods in clinical analysis of CTCs have been discussed.

High-Contrast Fluorescence Diagnosis of Cancer Cells/Tissues Based on β-Lapachone-Triggered ROS Amplification Specific in Cancer Cells

Discrimination of cancer cells/tissues from normal ones is of critical importance for early diagnosis and treatment of cancers. Herein, we present a new strategy for high-contrast fluorescence diagnosis of cancer cells/tissues based on β-Lapachone (β-Lap, an anticancer agent) triggered ROS (reactive oxygen species) amplification specific in cancer cells/tissues. With the strategy, a wide range of cancer cells/tissues, including surgical tissue specimens harvested from patients, were distinguished from normal ones by using a combination of β-Lap and a Si-rhodamine-based NIR fluorescent ROS probe PSiR3 developed in this work with average tumor-to-normal (T/N) ratios up to 15 in cell level and 24 in tissue level, far exceeding the clinically acceptable threshold of 2.0. What's more, the strategy allowed the fluorescence discrimination of tumor tissues from inflammatory ones based on whether a marked fluorescence enhancement could be induced when treated with PSiR3 and β-Lap/PSiR3 combination, respectively.

Solvent assisted size effect on AuNPs and significant inhibition on K562 cells

Herein, the synthesis and characterization of ideal size (∼10 and 40 nm, in diameter) AuNPs (gold nanoparticles) were reported. Two different organic solvents such as DMF (dimethyl formamide) and NMPL (N-methyl-2-pyrrolidone) were used to synthesize AuNPs along with agents reducing agents such as NaBH4 (sodium borohydrate) and Na3C6H5O7 (sodium citrate). The combination of [(HAuCl4)-(DMF)-(NaBH4)] gives AuNPs with an avg. size of 10.2 nm. Similarly, the combination of [(HAuCl4)-(NMPL)-(Na3C6H5O7)] gives AuNPs with an avg. size of 40.4 nm. The morphology of these nanoscale AuNPs has been characterized through TEM and HRTEM imaging followed by SAED for lattice parameters such as d-spacing value (2.6 Å/0.26 nm) of crystalline metal (Au) nanoparticles. Further, these unique and ideal nanoscale AuNPs were used to evaluate the potential working efficacy by using in vitro cell based studies on K562 (leukaemia) blood cancer cells. From the MTT assay results around 88% cell inhibition was measured for ∼10 nm sized AuNPs. The treated cells were stained with different fluorescent dyes such as FITC, DAPI, Rho-6G and their ruptured morphology has been reported in the respective sections. These types of ideal sized metal (Au) nanoparticles are recommended for various theranostics such as to cure breast, colon, lung and liver cancers.

Dual-channel fluorescence diagnosis of cancer cells/tissues assisted by OATP transporters and cysteine/glutathione

A 2-(diphenylphosphino)phenol-functionalized pyronin dye has successfully been developed for dual-channel fluorescence diagnosis of cancer cells/tissues assisted by OATP transporters and Cys/GSH.

Although fluorescence imaging diagnosis of the differences between cancer cells and normal cells by targeting ligand-based fluorescent probes is useful for recommending personalized therapy to patients, using the differences to diagnose a wide range of cancers is often not possible due to the genetic or phenotypic heterogeneity of cancer cells. In this work a 2-(diphenylphosphino)phenol-functionalized pyronin POP was presented as a dual-channel fluorescence agent for diagnosing a wide range of cancer cell types. The agent could efficiently penetrate cancer cell, rather than normal cell, membranes by active transport of the organic-anion transporting polypeptide (OATP) transporters overexpressed in many types of cancer cell, and is then activated by intracellular cysteine (Cys) and glutathione (GSH) to produce green-emission aminopyronin NP and red-emission thiopyronin SP, thereby enabling its use in dual-channel fluorescence diagnosis of a wide range of cancer cells with excellent contrast. Crucially, POP also displays the ability of dual-channel fluorescence diagnosis of cancer tissues from tumour xenograft models of mice and harvested surgical specimens of patients, thus holding great potential for clinical applications.

Activatable Water-Soluble Probes Enhance Tumor Imaging by Responding to Dysregulated pH and Exhibiting High Tumor-to-Liver Fluorescence Emission Contrast

Dysregulated pH has been recognized as a universal tumor microenvironment signature that can delineate tumors from normal tissues. Existing fluorescent probes that activate in response to pH are hindered by either fast clearance (in the case of small molecules) or high liver background emission (in the case of large particles). There remains a need to design water-soluble, long circulating, pH-responsive nanoprobes with high tumor-to-liver contrast. Herein, we report a modular chemical strategy to create acidic pH-sensitive and water-soluble fluorescent probes for high in vivo tumor detection and minimal liver activation. A combination of a modified Knoevenagel reaction and PEGylation yielded a series of NIR BODIPY fluorophores with tunable pKas, high quantum yield, and optimal orbital energies to enable photoinduced electron transfer (PeT) activation in response to pH. After intravenous administration, Probe 5c localized to tumors and provided excellent tumor-to-liver contrast (apparent T/L = 3) because it minimally activates in the liver. This phenomenon was further confirmed by direct ex vivo imaging experiments on harvested organs. Because no targeting ligands were required, we believe that this report introduces a versatile strategy to directly synthesize soluble probes with broad potential utility including fluorescence-based image-guided surgery, cancer diagnosis, and theranostic nanomedicine.

Hydrophobic study of increasing alkyl chain length of platinum surfactant complexes: synthesis, characterization, micellization, thermodynamics, thermogravimetrics and surface morphology

This paper contains details on the synthesis, characterization, physicochemical properties and surface morphology of five supramolecular metallosurfactants (SMMSs).

Preparation of pH-responsive mesoporous hydroxyapatite nanoparticles for intracellular controlled release of an anticancer drug

A well-defined core–shell nano-carrier (PAA–MHAPNs) was successfully synthesized based on a graft-onto method by using mesoporous hydroxyapatite nanoparticles (MHAPNs) as the core and polyacrylic acid (PAA) as the shell.

A carbohydrate-grafted nanovesicle with activatable optical and acoustic contrasts for dual modality high performance tumor imaging

Activatable molecular systems enabling precise tumor localization are valuable for complete tumor resection. Herein, we report sialic acid-capped polymeric nanovesicles encapsulating the near infrared profluorophore (pNIR@P@SA) for lysosome activation based dual modality tumor imaging. The probe features surface-anchored sialic acid for tumor targeting and a core of near infrared profluorophore (pNIR) which undergoes lysosomal acidity triggered isomerization to give optical and optoacoustic signals upon cell internalization. Imaging studies reveal high-efficiency uptake and signal activation of pNIR@P@SA in subcutaneous tumors and millimeter-sized liver tumor foci in mice. The high tumor-to-healthy organ signal contrasts and discernment of tiny liver tumors from normal liver tissues validate the potential of pNIR@P@SA for high performance optical and optoacoustic imaging guided tumor resection.

A ratiometric lysosomal pH probe based on the naphthalimide–rhodamine system

The ratiometric pH probe RNL was constructed by integrating the naphthalimide moiety as an FRET donor into the rhodamine moiety as an FRET acceptor. The probe with a pK_a of 4.82 could detect pH in the range of 4.50–5.50, selectively stain lysosome and detect lysosomal pH changes.

A sialic acid-targeted near-infrared theranostic for signal activation based intraoperative tumor ablation

Agents enabling tumor staging are valuable for cancer surgery. Herein, a targetable sialic acid-armed near-infrared profluorophore (SA-pNIR) is reported for fluorescence guided tumor detection. SA-pNIR consists of a sialic acid entity effective for in vivo tumor targeting and a profluorophore which undergoes lysosomal acidity-triggered fluorogenic isomerization. SA-pNIR displays a number of advantageous biomedical properties in mice, e.g. high tumor-to-normal tissue signal contrast, long-term retention in tumors and low systemic toxicity. In addition, SA-pNIR effectively converts NIR light into cytotoxic heat in cells, suggesting tumor-activatable photothermal therapy. With high performance tumor illumination and lysosome-activatable photothermal properties, SA-pNIR is a promising agent for detection and photothermal ablation of surgically exposed tumors.

A rhodamine B-based lysosomal pH probe

A novel rhodamine B-based lysosomal pH probe RML was developed. RML responded to acidic pH with short response time, high selectivity and high sensitivity and could detect lysosomal pH change in living cells.

A fluorescently labelled sialic acid for high performance intraoperative tumor detection

Surgical resection is widely used for tumor treatment, necessitating approaches for the precise locating of elusive tumor foci. We report the high performance detection of tumors in mice with fluorescein-isothiocyanate (FITC) labelled sialic acid (FITC-SA), a fluorescent monosaccharide with low cytoxicity. Analysis of mice intravenously injected with FITC-SA revealed high target-to-background fluorescence ratios in subcutaneous tumors and liver tumor implants with 0.2-5 mm diameters, which are significantly below the clinical threshold of minimal residual cancer (∼1 cm clearance). Extracellular FITC-SA is quickly cleared from circulation whereas the intracellular FITC-SA could be metabolically incorporated into glycoproteins via a cellular sialylation pathway. Compared with FITC-SA-laden nanoparticles, free FITC-SA is preferentially and quickly taken up by tumors in mice and displays high tumor-to-background signal contrast, suggesting the potential for fluorescence directed surgical ablation of tumors.

Rhodamine based pH-sensitive “intelligent” polymers as lysosome targeting probes and their imaging applications in vivo

Two rhodamine-based polymers were prepared via free radical polymerization and could serve as lysosome targeting probes with good pH sensitivity. Fluorescence imaging of nude mice displayed a chance for visualization of cancerous tissue in vivo by sensing its acidic microenvironments.

A photothermal cell viability-reporting theranostic nanoprobe for intraoperative optical ablation and tracking of tumors

A photothermal acid-responsive nanoprobe was developed for intraoperative detection and photothermal killing of tumors, and tracking of therapeutic effects.

Study of single and double chain surfactant–cobalt(iii) complexes and their hydrophobicity, micelle formation, interaction with serum albumins and antibacterial activities

Single and double chain surfactant–cobalt(iii) complexes show respectively, electrostatic and hydrophobic interactions with serum albumins.

pH-responsive near-infrared nanoprobe imaging metastases by sensing acidic microenvironment

A pH responsive near-infrared fluorescence nanoprobe was developed and visualized pulmonary metastases in a mouse model with a volume as small as 0.5 mm³ by sensing the acidic tumor microenvironment.

Rhodamine-based lysosome-targeted fluorescence probes: high pH sensitivity and their imaging application in living cells

Two rhodamine-based pH probes were synthesized via the click reaction. Cell imaging experiments demonstrated RhPA was a good lysosome targeting probe in living cells with low cytotoxicity and excellent photostability.