Temoporfin-Conjugated PEGylated Poly(N,N-dimethylacrylamide)-Coated Upconversion Colloid for NIR-Induced Photodynamic Therapy of Pancreatic Cancer.

Photodynamic therapy (PDT) has the potential to cure pancreatic cancer with minimal side effects. Visible wavelengths are primarily used to activate hydrophobic photosensitizers, but in clinical practice, these wavelengths do not sufficiently penetrate deeper localized tumor cells. In this work, NaYF4:Yb3+,Er3+,Fe2+ upconversion nanoparticles (UCNPs) were coated with polymer and labeled with meta-tetra(hydroxyphenyl)chlorin (mTHPC; temoporfin) to enable near-infrared light (NIR)-triggered PDT of pancreatic cancer. The coating consisted of alendronate-terminated poly[N,N-dimethylacrylamide-co-2-aminoethylacrylamide]-graft-poly(ethylene glycol) [P(DMA-AEM)-PEG-Ale] to ensure the chemical and colloidal stability of the particles in aqueous physiological fluids, thereby also improving the therapeutic efficacy. The designed particles were well tolerated by the human pancreatic adenocarcinoma cell lines CAPAN-2, PANC-1, and PA-TU-8902. After intratumoral injection of mTHPC-conjugated polymer-coated UCNPs and subsequent exposure to 980 nm NIR light, excellent PDT efficacy was achieved in tumor-bearing mice.

Homopurine guanine-rich sequences in complex with N-methyl mesoporphyrin IX form parallel G-quadruplex dimers and display a unique symmetry tetrad.

DNA can fold into G-quadruplexes (GQs), non-canonical secondary structures formed by π-π stacking of G-tetrads. GQs are important in many biological processes, which makes them promising therapeutic targets. We identified a 42-nucleotide long, purine-only G-rich sequence from human genome, which contains eight G-stretches connected by A and AAAA loops. We divided this sequence into five unique segments, four guanine stretches each, named GA1-5. In order to investigate the role of adenines in GQ structure formation, we performed biophysical and X-ray crystallographic studies of GA1-5 and their complexes with a highly selective GQ ligand, N-methyl mesoporphyrin IX (NMM). Our data indicate that all variants form parallel GQs whose stability depends on the number of flexible AAAA loops. GA1-3 bind NMM with 1:1 stoichiometry. The Ka for GA1 and GA3 is modest, ∼0.3 µM -1, and that for GA2 is significantly higher, ∼1.2 µM -1. NMM stabilizes GA1-3 by 14.6, 13.1, and 7.0 °C, respectively, at 2 equivalents. We determined X-ray crystal structures of GA1-NMM (1.98 Å resolution) and GA3-NMM (2.01 Å). The structures confirm the parallel topology of GQs with all adenines forming loops and display NMM binding at the 3' G-tetrad. Both complexes dimerize through the 5' interface. We observe two novel structural features: 1) a 'symmetry tetrad' at the dimer interface, which is formed by two guanines from each GQ monomer and 2) a NMM dimer in GA1-NMM. Our structural work confirms great flexibility of adenines as structural elements in GQ formation and contributes greatly to our understanding of the structural diversity of GQs and their modes of interaction with small molecule ligands.

An anticancer gold(III)-activated porphyrin scaffold that covalently modifies protein cysteine thiols.

Cysteine thiols of many cancer-associated proteins are attractive targets of anticancer agents. Herein, we unequivocally demonstrate a distinct thiol-targeting property of gold(III) mesoporphyrin IX dimethyl ester (AuMesoIX) and its anticancer activities. While the binding of cysteine thiols with metal complexes usually occurs via M-S bond formation, AuMesoIX is unique in that the meso-carbon atom of the porphyrin ring is activated by the gold(III) ion to undergo nucleophilic aromatic substitution with thiols. AuMesoIX was shown to modify reactive cysteine residues and inhibit the activities of anticancer protein targets including thioredoxin, peroxiredoxin, and deubiquitinases. Treatment of cancer cells with AuMesoIX resulted in the formation of gold-bound sulfur-rich protein aggregates, oxidative stress-mediated cytotoxicity, and accumulation of ubiquitinated proteins. Importantly, AuMesoIX exhibited effective antitumor activity in mice. Our study has uncovered a gold(III)-induced ligand scaffold reactivity for thiol targeting that can be exploited for anticancer applications.

Photodynamic therapy synergizes with PD-L1 checkpoint blockade for immunotherapy of CRC by multifunctional nanoparticles.

Checkpoint inhibitors, such as anti-PD-1/PD-L1 antibodies, have been shown to be extraordinarily effective, but their durable response rate remains low, especially in colorectal cancer (CRC). Recent studies have shown that photodynamic therapy (PDT) could effectively enhance PD-L1 blockade therapeutic effects, although the reason is still unclear. Here, we report the use of multifunctional nanoparticles (NPs) loaded with photosensitized mTHPC (mTHPC@VeC/T-RGD NPs)-mediated PDT treatment to potentiate the anti-tumor efficacy of PD-L1 blockade for CRC treatment and investigate the underlying mechanisms of PDT enhancing PD-L1 blockade therapeutic effect in this combination therapy. In this study, the mTHPC@VeC/T-RGD NPs under the 660-nm near infrared (NIR) laser could kill tumor cells by inducing apoptosis and/or necrosis and stimulating systemic immune response, which could be further promoted by the PD-L1 blockade to inhibit primary and distant tumor growth, as well as building long-term host immunological memory to prevent tumor recurrence. Furthermore, we detected that mTHPC@VeC/T-RGD NP-mediated PDT sensitizes tumors to PD-L1 blockade therapy mainly because PDT-mediated hypoxia could induce the hypoxia-inducible factor 1α (HIF-1α) signaling pathway that upregulates PD-L1 expression in CRC. Taken together, our work demonstrates that mTHPC@VeC/T-RGD NP-mediated PDT is a promising strategy that may potentiate the response rate of anti-PD-L1 checkpoint blockade immunotherapies in CRC.

FRET-Based In-Cell Detection of Highly Selective Supramolecular Complexes of meso-Tetraarylporphyrin with Peptide/BODIPY-Modified Per-O-Methyl-ß-Cyclodextrins.

Artificial supramolecular systems capable of self-assembly and that precisely function in biological media are in high demand. Herein, we demonstrate a highly specific host-guest-pair system that functions in living cells. A per-O-methyl-ß-cyclodextrin derivative (R8-B-CDMe ) bearing both an octaarginine peptide chain and a BODIPY dye was synthesized as a fluorescent intracellular delivery tool. R8-B-CDMe was efficiently taken up by HeLa cells through both endocytosis and direct transmembrane pathways. R8-B-CDMe formed a 2 : 1 inclusion complex with tetrakis(4-sulfonatophenyl)porphyrin (TPPS) as a guest molecule in water, from which fluorescence resonance energy transfer (FRET) from R8-B-CDMe to TPPS was observed. The FRET phenomenon was clearly detected in living cells using confocal microscopy techniques, which revealed that the formed supramolecular R8-B-CDMe /TPPS complex was maintained within the cells. The R8-B-CDMe cytotoxicity assay revealed that the addition of TPPS counteracts the strong cytotoxicity (IC50 =16 µM) of the CD cavity due to complexation within the cells. A series of experiments demonstrated the bio-orthogonality of the supramolecular per-O-methyl-ß-CD/tetraarylporphyrin host-guest pair in living cells.

Binding of a Soluble meso-Tetraarylporphyrin to Human Galectin-7 Induces Oligomerization and Modulates Its Pro-Apoptotic Activity.

The selective targeting of protein-protein interactions remains a significant determinant for the proper modulation and regulation of cell apoptosis. Prototypic galectins such as human galectin-7 (GAL-7) are characterized by their ability to form homodimers that control the molecular fate of a cell by mediating subtle yet critical glycan-dependent interactions between pro- and anti-apoptotic molecular partners. Altering the structural architecture of GAL-7 can therefore result in resistance to apoptosis in various human cancer cells, further illustrating its importance in cell survival. In this study, we used a combination of biophysical and cellular assays to illustrate that binding of a water-soluble meso-tetraarylporphyrin molecule to GAL-7 induces protein oligomerization and modulation of GAL-7-induced apoptosis in human Jurkat T cells. Our results suggest that the integrity of the GAL-7 homodimer architecture is essential for its molecular function, in addition to providing an interesting porphyrin binding modulator for controlling apoptosis in mammalian cells.

One Terminal Guanosine Flip of Intramolecular Parallel G-Quadruplex: Catalytic Enhancement of G-Quadruplex/Hemin DNAzymes.

Numerous studies have shown compelling evidence that incorporation of an inversion of polarity site (IPS) in G-rich sequences can affect the topological and structural characteristics of G-quadruplexes (G4s). Herein, the influence of IPS on the formation of a previously studied intramolecular parallel G4 of d(G3 TG3 TG3 TG3 ) (TTT) and its stacked higher-order structures is explored. Insertion of 3'-3' or 5'-5' IPS did not change the parallel folding pattern of TTT. However, both the species and position of the IPS in TTT have a significant impact on the G4 stability and end-stacking through the alteration of G4-G4 interfaces properties. The data demonstrate that one base flip in each terminal G-tetrad can stabilize parallel G4s and facilitate intermolecular packing of monomeric G4s. Such modifications can also enhance the fluorescence and enzymatic performances by promoting interactions between parallel G4s with N-methyl mesoporphyrin IX (NMM) and hemin, respectively.

Optical properties of photodynamic therapy drugs in different environments: the paradigmatic case of temoporfin.

Computational tools have been used to study the photophysical and photochemical features of photosensitizers in photodynamic therapy (PDT) - a minimally invasive, less aggressive alternative for cancer treatment. PDT is mainly based on the activation of molecular oxygen through the action of a photoexcited sensitizer (photosensitizer). Temoporfin, widely known as mTHPC, is a second-generation photosensitizer, which produces the cytotoxic singlet oxygen when irradiated with visible light and hence destroys tumor cells. However, the bioavailability of the mostly hydrophobic photosensitizer, and hence its incorporation into cells, is fundamental to achieve the desired effect on malignant tissues via PDT. In this study, we focus on the optical properties of the temoporfin chromophore in different environments -in vacuo, in solution, encapsulated in drug delivery agents, namely cyclodextrin, and interacting with a lipid bilayer.

Surface plasmon resonance study of the interaction of N-methyl mesoporphyrin IX with G-quadruplex DNA.

Surface plasmon resonance (SPR) was used to investigate the interaction between N-methyl mesoporphyrin IX (NMM) and different G-quadruplex (G4) topologies. The study was associated with circular dichroism analysis (CD) to assess the topology of the G4s when they interacted with NMM. We demonstrate the high selectivity of NMM for the parallel G4 structure with a dissociation constant at least ten times lower than those of other G4 topologies. We also confirm the ability of NMM to shift the G4 conformation from both the hybrid and antiparallel topologies toward the parallel structure.

N-Methylmesoporphyrin IX Exhibits G-Quadruplex-Specific Photocleavage Activity.

N-Methylmesoporphyrin IX (NMM) has long been known as a G-quadruplex DNA (G4) ligand. However, there has been little investigation into its G-quadruplex photocleavage activity. Herein, we demonstrate that NMM is a highly selective photocleavage agent for G4 structures but not duplex DNA. Analysis of the cleavage products by PAGE demonstrates that G4 photocleavage by NMM occurs at sites similar to those cleaved by TMPyP4, a nonselective DNA photocleavage agent. Although NMM is shown here to generate singlet oxygen in the presence of both duplex and G4, the lack of increased photocleavage in D2 O indicated that singlet oxygen is not involved in the photocleavage of G4 by NMM.

A fluorescence method for homogeneous detection of influenza A DNA sequence based on guanine-quadruplex-N-methylmesoporphyrin IX complex and assistance-DNA inhibition.

In his study, we report a fluorescence method for homogeneous detection of influenza A (H1N1) DNA sequence based on G-quadruplex-NMM complex and assistance-DNA (A-DNA) inhibition. The quadruplex-based functional DNA (QBF-DNA), composed of a complementary probe to the target H1N1 DNA sequence and G-rich fragment, was designed as the signal DNA. The A-DNA consisted of two parts, one part was complementary to target H1N1 DNA and the other part was complementary to the signal DNA. In the absence of target H1N1 DNA, the G-rich fragment of QBF-DNA can form G-quadruplex-NMM complex, which outputted a fluorescent signal. With the presence of target H1N1 DNA, QBF-DNA, and A-DNA can simultaneously hybridize with target H1N1 DNA to form double-helix structure. In this case, the A-DNA partially hybridized with the QBF-DNA, which inhibited the formation of G-quadruplex-NMM complex, leading to the decrease of fluorescent signal. Under the optimum conditions, the fluorescence intensity was inversely proportional to the concentration of target H1N1 DNA over the range from 25 to 700 pmol/L with a detection limit of 8 pmol/L. In addition, the method is target specific and practicability, and would become a new diagnostic assay for H1N1 DNA sequence and other infectious diseases.

Hybrid Lipid Polymer Nanoparticles for Combined Chemo- and Photodynamic Therapy.

Retinoblastoma is a malignant tumor of the retina in infants. Conventional therapies are associated to severe side effects and some of them induce secondary tumors. Photodynamic therapy (PDT) thus appears as a promising alternative as it is nonmutagenic and generates minimal side effects. The effectiveness of PDT requires the accumulation of a photosensitizer (PS) in the tumor. However, most porphyrins are hydrophobic and aggregate in aqueous medium. Their incorporation into a nanocarrier may improve their delivery to the cell cytoplasm. In this work, we designed biodegradable liponanoparticles (LNPs) consisting of a poly(d,l)-lactide (PDLLA) nanoparticle coated with a phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-3-trimethylammonium-propane) bilayer. An anticancer drug, beta-lapachone (ß-Lap) and a PS, m-THPC, were co-encapsulated for combined chemo- and PDT because it has been suggested that they may have a synergistic effect based on the activation of ß-Lap by PDT-induced over-expression of the enzyme NQO1. Using dynamic light scattering measurements, cryogenic transmission electron microscopy, and fluorescence confocal microscopy, we selected the appropriate conditions for the encapsulation of the compounds. LNPs were internalized in retinoblastoma cells within few hours. No obvious synergistic effect related to the activation of ß-Lap by PDT was observed. Conversely, the LNPs were cytotoxic at lower doses of the two encapsulated compounds as compared to the single therapies. Analysis of the combinatorial treatment showed that PDT and chemotherapy had an additive effect on the viability of retinoblastoma cells.

A cascade toehold-mediated strand displacement strategy for label-free and sensitive non-enzymatic recycling amplification detection of the HIV-1 gene.

In this work, a label-free fluorescence biosensor for simple detection of the HIV-1 gene was proposed by using toehold-mediated strand displacement reactions (TMSDRs) combined with a non-enzymatic target recycling amplification strategy. In this system, two TMSDRs were used. In the presence of the HIV-1 gene, an autocatalytic DNA machine can be activated. This leads to the generation of numerous free G-rich sequences, which can associate with a fluorescent dye N-methylmesoporphyrin IX (NMM) to yield an amplified fluorescence signal for the target detection. This sensing platform showed a high sensitivity towards the HIV-1 gene with a detection limit as low as 1.9 pM without any labelling, immobilization, or washing steps. The designed sensing system also exhibits an excellent selectivity for the HIV-1 gene compared with other interference DNA sequences. Furthermore, the presented biosensor is robust and has been successfully applied for the detection of the HIV-1 gene in a real biological sample with satisfactory results, suggesting that this method is promising for simple and early clinical diagnosis of HIV infection. Thanks to its simplicity, cost-effectiveness and ultrasensitivity, our proposed sensing strategy provides a universal platform for the detection of other genes by substituting the target-recognition element.

An ultrasensitive and simple fluorescence biosensor for detection of the Kras wild type by using the three-way DNA junction-driven catalyzed hairpin assembly strategy.

In this work, a label-free fluorescence biosensor was proposed for simple detection of the Kras wild type by using the three way DNA junction-driven catalyzed hairpin assembly strategy. In this system, a three-way DNA junction probe (JP) and two hairpin probes (H1 and H2) were designed. In the presence of the Kras wild type, an autocatalytic DNA machine can be activated. This leads to the generation of numerous free G-rich sequences, which can associate with a fluorescent dye N-methylmesoporphyrin IX (NMM) to yield an amplified fluorescence signal for the target detection. This sensing platform showed a high sensitivity towards the Kras wild type with a detection limit as low as 2.7 fM without any labelling, immobilization, or washing steps. The designed sensing system also exhibits an excellent selectivity for the Kras wild type compared with other interference DNA sequences. Furthermore, the presented biosensor is robust and has been successfully applied for the detection of the Kras wild type in a real biological sample with satisfactory results, suggesting that this method is promising for simple and early clinical diagnosis of genetic diseases. Thanks to its simplicity, cost-effectiveness, and ultrasensitivity, our proposed sensing strategy provides a universal platform for the detection of other genetic diseases by substituting the target-recognition element.

Primer remodeling amplification-activated multisite-catalytic hairpin assembly enabling the concurrent formation of Y-shaped DNA nanotorches for the fluorescence assay of ochratoxin A.

DNA can be configured into unique high-order structures due to its significantly high programmability, such as a three-way junction-based structure (denoted Y-shaped DNA), for further applications. Herein, we report a label-free fluorescent signal-on biosensor based on the target-driven primer remodeling rolling circle amplification (RCA)-activated multisite-catalytic hairpin assembly (CHA) enabling the concurrent formation of Y-shaped DNA nanotorches (Y-DNTs) for ultrasensitive detection of ochratoxin A (OTA). Two kinds of masterfully-designed probes, termed Complex I and II, were pre-prepared by the combination of a circular template (CT) with an OTA aptamer (S1), a substrate probe (S2) and hairpin probe 1 (HP1), respectively. Target OTA specifically binds to Complex I, resulting in the release of the remnant element in S2 and successive remodeling into a mature primer for RCA by phi29 DNA polymerase, thus a usable primer-CT complex is produced, which actuates primary RCA. Then, numerous Complex II probes can anneal with the first-generation RCA product (RP) with multiple sites to activate the CHA process. With the participation of endonuclease IV (Endo IV) and phi29, HP1 as a pre-primer containing a tetrahydrofuran abasic site mimic (AP site) in Complex II is converted into a mature primer to initiate additional rounds of RCA. So, countless Y-DNTs are formed concurrently containing a G-quadruplex structure that enables the N-methylmesoporphyrin IX (NMM) to be embedded, generating remarkably strong fluorescence signals. The biosensor was demonstrated to enable rapid and accurate highly efficient and selective detection of OTA with an improved detection limit of as low as 0.0002 ng mL-1 and a widened dynamic range of over 4 orders of magnitude. Meanwhile, this method was proven to be capable of being used to analyze actual samples. Therefore, this proposed strategy may be established as a useful and practical platform for the ultrasensitive detection of mycotoxins in food safety testing.

A simple enzyme-assisted cascade amplification strategy for ultrasensitive and label-free detection of DNA.

A simple fluorescence biosensor is developed based on the enzyme-assisted cascade amplification strategy. The amplification system consists of a hairpin-structure DNA (H-DNA) and exonuclease III. The target DNA can hybridize with the H-DNA and initiate exonuclease III-assisted target recycling amplification to generate abundant G-rich DNA (G-DNA). One region of G-DNA is designed to possess the same sequence as target DNA. Thus, the G-DNA can also hybridize with H-DNA and initiate the digestion of H-DNA. The cascade strategy in this amplification system causes the concentration of G-DNA to grow exponentially. The fluorescence intensity of N-methylmesoporphyrin IX (NMM) is highly enhanced due to the formation of G-quadruplex configuration. Under optimal conditions, the cascade system could achieve an admirable sensitivity with a detection limit of 52 fM for HIV DNA, and guarantees a satisfactory specificity. Moreover, the cascade system could be implemented for other target DNA detections by substituting the recognition region of the H-DNA. In this way, a detection limit of 65 fM for HBV DNA could be achieved by the cascade system. The target DNA analysis in a real serum sample further indicates that this biosensor has potential for future application in clinical diagnosis. Graphical abstract A simple and label-free cascade amplification strategy is developed by exploiting hairpin DNA and EXO III for sensitive DNA detection.

Intensive Distribution of G2-Quaduplexes in the Pseudorabies Virus Genome and Their Sensitivity to Cations and G-Quadruplex Ligands.

Guanine-rich sequences in the genomes of herpesviruses can fold into G-quadruplexes. Compared with the widely-studied G3-quadruplexes, the dynamic G2-quadruplexes are more sensitive to the cell microenvironment, but they attract less attention. Pseudorabies virus (PRV) is the model species for the study of the latency and reactivation of herpesvirus in the nervous system. A total of 1722 G2-PQSs and 205 G3-PQSs without overlap were identified in the PRV genome. Twelve G2-PQSs from the CDS region exhibited high conservation in the genomes of the Varicellovirus genus. Eleven G2-PQSs were 100% conserved in the repeated region of the annotated PRV genomes. There were 212 non-redundant G2-PQSs in the 3' UTR and 19 non-redundant G2-PQSs in the 5' UTR, which would mediate gene expression in the post-transcription and translation processes. The majority of examined G2-PQSs formed parallel structures and exhibited different sensitivities to cations and small molecules in vitro. Two G2-PQSs, respectively, from 3' UTR of UL5 (encoding helicase motif) and UL9 (encoding sequence-specific ori-binding protein) exhibited diverse regulatory activities with/without specific ligands in vivo. The G-quadruplex ligand, NMM, exhibited a potential for reducing the virulence of the PRV Ea strain. The systematic analysis of the distribution of G2-PQSs in the PRV genomes could guide further studies of the G-quadruplexes' functions in the life cycle of herpesviruses.

Label-free and enzyme-free sensitive fluorescent method for detection of viable Escherichia coli O157:H7.

We have developed a label-free, enzyme-free, modification-free and DNA extraction-free fluorescent aptasensing (LEFA) method for detection of E. coli O157:H7 based on G-quadruplex formation using two ingeniously designed hairpin probes (GHP1 and GHP2). In the presence of E. coli O157:H7, it released the single stranded initiation sequence (IS) resulting in the toehold strand displacement between GHP1 and GHP2, which in turn led to the cyclic reuse of the production of DNA assemblies with numerous G-quadruplex structures and initiation sequences. Then these G-quadruplex structures can be recognized quickly by N-methyl mesoporphyrin IX (NMM) resulting in significantly enhanced fluorescence. The LEFA method was successfully implemented for detecting E. coli O157:H7 with a detection limit of 66 CFU/mL in pure culture, 10 CFU/mL and 1 CFU/mL after pre-incubation of the milk and tap water for 4 and 8 h, respectively. Moreover, the strategy could distinguish viable E. coli O157:H7 from dead E. coli O157:H7 and other species of pathogen cells. Furthermore, the whole process of the strategy is accomplished within 100 min. The results indicated that the approach may be used to effectively control potential microbial hazards in human health, food safety, and animal husbandry.

Use of Light-Degradable Aliphatic Polycarbonate Nanoparticles As Drug Carrier for Photosensitizer.

Aliphatic poly(carbonate)s (APCs) with rapid and controlled degradation upon specific stimulation have great advantages for a variety of biomedical and pharmaceutical applications. In the present work, we reported a new poly(trimethylene carbonate) (PTMC)-based copolymer containing multiple 4,5-dimethoxy-2-nitrobenzyl photo cleavable groups as pendent chains. The six-membered light-responsive cyclic carbonate monomer (LrM) was first prepared from 2-(hydroxymethyl)-2-methylpropane-1,3-diol and 4,5-dimethoxy-2-nitrobenzyl alcohol and then copolymerized with trimethylene carbonate (TMC) by 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) catalyzed ring-opening polymerization (ROP) to afford the light-responsive polycarbonate (LrPC). The light-triggered decomposition of LrM and LrPC was studied by NMR, UV/vis spectroscopy, and size exclusion chromatography (SEC), as well as ESI-ToF mass spectrometry. Stable monodisperse nanoparticles with hydrodynamic diameter of 100 nm could be formulated from 25% LrPC and 75% poly(lactide- co-glycolide) (PLGA) and applied for the encapsulation of temoporfin. Upon irradiation with UV light these particles displayed a significant decrease of the particle countrate and increased the release rate of temoporfin in comparison to standard PLGA nanoparticles. This work demonstrated that a combination of encapsulation of photosensitizer and light degradation using light-responsive polymers is suitable to enhance photodynamic therapy (PDT).

Effects of meta-tetrahydroxyphenylchlorin photodynamic therapy on isogenic colorectal cancer SW480 and SW620 cells with different metastatic potentials.

The aim of this study is to investigate the antitumor effects and possible mechanisms of meta-tetrahydroxyphenylchlorin-mediated photodynamic therapy (m-THPC-PDT) on human primary (SW480) and metastatic (SW620) colon cancer cell lines. SW480 and SW620 cells were incubated with various concentrations of m-THPC, followed by photodynamic irradiation. Subcellular localization of m-THPC in cells was observed with confocal laser scanning microscopy (CLSM). Photocytotoxicity of m-THPC in the two cells was investigated by using MTT assay. The flow cytometry was employed to detect the cell apoptosis. The migration and long-term recovery ability were determined by scratch test and colony formation assay respectively. CLSM showed that m-THPC was mainly distributed within the endoplasmic reticulum (ER) and lysosome of SW480 cells and within the lysosome and mitochondria of SW620 cells. m-THPC-PDT induced a dose-dependent and light energy-dependent cytotoxicity in SW480 and SW620 cells. Apoptosis rate was approximately 65 and 25% in SW480 and SW620 respectively when the concentration of m-THPC increased to 11.76 µM. However, the rate of necrotic cells had no significant changes in two cell lines. The colony formation and migration ability of the two cell lines were decreased with m-THPC-PDT treatment in a dose-dependent manner. PDT with m-THPC not only could effectively inhibit cell proliferation and decrease migration ability and colony formation ability, but also could effectively kill SW480 and SW620 cells in a dose-dependent manner in vitro. These results suggest that m-THPC is a promising sensitizer that warrants further development and extensive studies towards clinical use of colorectal cancer.