Chitosan-based hydrogel incorporated with polydopamine and protoporphyrin for photothermal-oxidation sterilization of bacteria-infected wound therapy.

Phototherapy has emerged as a potential treatment strategy for bacteria-infected wounds, but the inadequate bacteria-capturing ability and excessive damage to normal tissues from single phototherapy are huge limitations. To solve the issues, herein we report the design of chitosan-based hydrogel with bacteria capturing and combined photothermal/photodynamic sterilization functions. Such hydrogel is prepared by mixing chitosan (CS) as matrix, protoporphyrin (PpIX) as photosensitizer and polydopamine (PDA) as photothermal agent and then chemically cross-linking CS with glutaraldehyde. The resulting CS-PpIX-PDA hydrogel possesses a porous architecture (average pore porosity = 60.9 %), excellent swelling capabilities (swelling ratio = 1855 %) and rheological property (G' > G″). The hydrogel can effectively produce reactive oxygen species (ROS) under 660 nm light irradiation due to the photodynamic effect of PpIX. Owing to the presence of PDA, the hydrogel displays a photoabsorption range between 600 and 1500 nm and can generate maximal temperature of 60 °C within 10 min under 808 nm laser illumination (0.6 W/cm2) through photothermal effect. Besides, under synergetic illumination of 808/660 nm laser, CS-PpIX-PDA hydrogel can induce the death of 99.9999 % of E. coli and 99.99999 % of S. aureus. Importantly, when coated on the wound site, the hydrogel exhibits a remarkable bacteria-trapping ability due to its porous structure and the presence of amino groups on chitosan. Under the excitation of 660/808 nm, the combined photothermal and photodynamic effects can effectively eradicate bacteria. Simultaneously, the hydrogel also demonstrates anti-inflammatory properties and upregulates Heat Shock Protein 90 (HSP90) expression, thereby promoting collagen deposition and facilitating wound healing. Therefore, the study may provide some new insights into the development of multifunctional hydrogel for photothermal-oxidation sterilization of bacteria-infected wound therapy.

Protoporphyrin IX-Dependent Antiviral Effects of 5-Aminolevulinic Acid against Feline Coronavirus Type II.

5-Aminolevulinic acid (5-ALA), a non-proteinogenic amino acid, is an intermediate in the biosynthesis of heme and exerts antiviral effects against feline coronavirus (FCoV); however, the underlying mechanisms remain unclear. In the biosynthesis of heme, 5-ALA is condensed and converted to protoporphyrin IX (PpIX), which is then transformed into heme by the insertion of ferrous iron. Previous research has suggested that the metabolites generated during heme biosynthesis contribute to the antiviral effects of 5-ALA. Therefore, the present study investigated the in vitro mechanisms responsible for the antiviral effects of 5-ALA. The results obtained revealed that 5-ALA and PpIX both effectively reduced the viral titer in the supernatant of FCoV-infected fcwf-4 cells. Moreover, PpIX exerted virucidal effects against FCoV. We also confirmed that 5-ALA increased PpIX levels in cells. While hemin induced heme oxygenase-1 gene expression, it did not reduce the viral titer in the supernatant. Sodium ferrous citrate decreased PpIX levels and suppressed the antiviral effects of 5-ALA. Collectively, these results suggest that the antiviral effects of 5-ALA against FCoV are dependent on PpIX.

Iron Metabolism in Aminolevulinic Acid-Photodynamic Therapy with Iron Chelators from the Thiosemicarbazone Group.

Iron plays a crucial role in various metabolic processes. However, the impact of 5-aminolevulinic acid (ALA) in combination with iron chelators on iron metabolism and the efficacy of ALA-photodynamic therapy (PDT) remain inadequately understood. This study aimed to examine the effect of thiosemicarbazone derivatives during ALA treatment on specific genes related to iron metabolism, with a particular emphasis on mitochondrial iron metabolism genes. In our study, we observed differences depending on the cell line studied. For the HCT116 and MCF-7 cell lines, in most cases, the decrease in the expression of selected targets correlated with the increase in protoporphyrin IX (PPIX) concentration and the observed photodynamic effect, aligning with existing literature data. The Hs683 cell line showed a different gene expression pattern, previously not described in the literature. In this study, we collected an extensive analysis of the gene variation occurring after the application of novel thiosemicarbazone derivatives and presented versatile and effective compounds with great potential for use in ALA-PDT.

Combined use of 5-ALA-induced protoporphyrin IX and chlorin e6 for fluorescence diagnostics and photodynamic therapy of skin tumors.

Different types of photosensitizers (PSs) have different dynamics and intensities of accumulation, depending on the type of tumor or different areas within the same tumor. This determines the effectiveness of fluorescence diagnostics and photodynamic therapy (PDT). This paper studies the processes of 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) and chlorin e6 (Ce6) accumulation in the central and border zones of a tumor after combined administration of two PSs into the patient's body. Fluorescence diagnostic methods have shown that sublingual administration of 5-ALA leads to the more intense accumulation of PpIX in a tumor compared to oral administration. Differences have been identified in the dynamics of 5-ALA-induced PpIX and Ce6 accumulation in the central and border zones of the tumor, as well as normal tissues. Ce6 accumulates mainly in the central zone of the tumor while PpIX accumulates in the border zone of the tumor. All patients with combined PDT experienced complete therapeutic pathomorphosis and relapse-free observation.

Designed Nanodrugs for Ultrasonic Removal of Toxic Polyglutamine Aggregates from Neuron Cells.

Clearing of toxic polyglutamine aggregates from neuronal cells is crucial for ameliorating Huntington's disease. However, such clearance is challenging, requiring the targeting of affected neuron cells in the brain, followed by the removal of polyglutamine from cells. Here we report a designed nanodrug that can be used for the ultrasound-based removal of toxic polyglutamine aggregates from neuron cells. The nanodrug is composed of a sonosensitizer molecule, chlorin e6- or protoporphyrin IX-loaded polymer micelle of 20-30 nm in size that rapidly delivers the sonosensitizer into the cell nucleus. Ultrasound exposure of these cells generates singlet oxygen in the nucleus/perinuclear region that induces strong autophagic flux and clears toxic polyglutamine aggregates from cells. It has been demonstrated that the nanodrug and ultrasound treatment can enhance the cell survival against polyglutamine aggregates by 4 times. This result suggests that the nanodrug can be designed for focused ultrasound-based wireless treatment of various neurodegenerative diseases.

CRISPR/Cas9-Mediated fech Knockout Zebrafish: Unraveling the Pathogenesis of Erythropoietic Protoporphyria and Facilitating Drug Screening.

Erythropoietic protoporphyria (EPP1) results in painful photosensitivity and severe liver damage in humans due to the accumulation of fluorescent protoporphyrin IX (PPIX). While zebrafish (Danio rerio) models for porphyria exist, the utility of ferrochelatase (fech) knockout zebrafish, which exhibit EPP, for therapeutic screening and biological studies remains unexplored. This study investigated the use of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated fech-knockout zebrafish larvae as a model of EPP1 for drug screening. CRISPR/Cas9 was employed to generate fech-knockout zebrafish larvae exhibiting morphological defects without lethality prior to 9 days post-fertilization (dpf). To assess the suitability of this model for drug screening, ursodeoxycholic acid (UDCA), a common treatment for cholestatic liver disease, was employed. This treatment significantly reduced PPIX fluorescence and enhanced bile-secretion-related gene expression (abcb11a and abcc2), indicating the release of PPIX. Acridine orange staining and quantitative reverse transcription polymerase chain reaction analysis of the bax/bcl2 ratio revealed apoptosis in fech-/- larvae, and this was reduced by UDCA treatment, indicating suppression of the intrinsic apoptosis pathway. Neutral red and Sudan black staining revealed increased macrophage and neutrophil production, potentially in response to PPIX-induced cell damage. UDCA treatment effectively reduced macrophage and neutrophil production, suggesting its potential to alleviate cell damage and liver injury in EPP1. In conclusion, CRISPR/Cas9-mediated fech-/- zebrafish larvae represent a promising model for screening drugs against EPP1.

Evaluation of the potential use of protoporphyrins as biomarkers of anemic disease in human urine from inflammatory bowel disease patients.

Protoporphyrins are organic compounds with cyclic structure that are synthesised by a wide variety of organisms. In humans, these compounds are detected in blood and urine, with significantly higher levels in blood. Their potential as biomarkers of anemia and other diseases is currently being investigated, as their levels change according to the biochemical processes associated with the disease. The most widely used biomarker of anemia is serum ferritin, but it is unreliable in patients with inflammatory bowel disease (IBD) because its levels can be altered by acute inflammation and/or infections. There is therefore a need to look for new markers to help diagnose anemia in IBD patients. This work develops and validates a method for the determination of three protoporphyrins in human urine: protoporphyrin IX (PPIX), protoporphyrin IX complex with Zn (ZnPPIX) and protoporphyrin IX complex with Fe (II) (FePPIX), the latter also known as heme. The aim is to evaluate their potential as biomarkers of anemic disease in patients diagnosed with IBD. The proposed analytical method is based on high performance liquid chromatography (HPLC) with dual detection based on photodiode array (PDA) and fluorescence (FD). Quantification of the analytes at very low concentrations is possible due to the efficient preconcentration provided by dispersive liquid-liquid microextraction (DLLME) and the sensitivity of the detection systems. The method was validated by evaluating linearity (25-1000 ng mL-1), matrix effect, sensitivity (limits of quantification were between 5 and 11 ng mL-1), selectivity, accuracy, carry-over, dilution integrity, stability and precision (< 12.1 %). Finally, statistical analyses applied to the sample quantification results showed these three markers, together with five clinical markers, were significantly different between anemic and non-anemic IBD patients.

Label-Free and Universal CRISPR/Cas12a-Based Detection Platform for Nucleic Acid Biomarkers.

CRISPR/Cas12a has been widely used in molecular diagnostics due to its excellent trans-cleavage activity. However, conventional reporters, such as F/Q-labeled single-stranded DNA (ssDNA) reporters, enzyme-labeled reporters, and spherical nucleic acid reporters, require complex modification or labeling processes. In this study, we have developed a rapid, universal, and label-free CRISPR/Cas12a-based biomarker detection platform via designing a G-quadruplex (G4) containing a hairpin structure as the reporter. The hairpin loop design of hairpin G4 improves the cleavage efficiency of Cas12a and the signal strength of the G4 binding ligand. Meanwhile, the incorporation of a G4 binding dye (protoporphyrin IX) eliminates the need for complex modifications. The CRISPR-hairpin G4 detection platform is capable of detecting ssDNA, double-stranded DNA, genetic RNAs, and miRNAs. Moreover, this platform achieves label-free detection in clinical samples, demonstrating its practical applicability and efficiency.

Dual-Locked Probe with Activatable Sonoafterglow Luminescence for Precise Imaging of MET-Induced Liver Injury.

Metformin (MET) is currently the first-line treatment for type 2 diabetes mellitus (T2DM). However, overdose and long-term use of MET may induce a serious liver injury. What's worse, diagnosis of MET-induced liver injury remains challenging in clinic. Although several probes have been reported for imaging MET-induced liver injury utilizing upregulated hepatic H2S as a biomarker, they are still at risk of nonspecific activation in complex physiological environments and rely on light excitation with limited imaging depth. Herein, we rationally designed and developed a dual-locked probe, DPA-H2S, for precise imaging of MET-induced liver injury by H2S-activated sonoafterglow luminescence. DPA-H2S is a small molecule consisting of a sonosensitizer protoporphyrin IX (PpIX) and an afterglow substrate that is dual-locked with a H2S-responsive 2,4-dinitrobenzene group and a 1O2-responsive electron-rich double bond. When employing DPA-H2S for imaging of MET-induced liver injury in vivo, since the PpIX moiety can produce 1O2 in situ at the liver site under focused ultrasound (US) irradiation, the two locks of DPA-H2S can be specifically activated by the highly upregulated H2S at the liver injury sites and the in situ generated 1O2, respectively. Thus, the sonoafterglow signal of DPA-H2S is significantly turned on, enabling precise imaging of the MET-induced liver injury. In vitro results showed that, through H2S-activated sonoafterglow luminescence, DPA-H2S was capable of imaging H2S with good sensitivity and high selectivity and realized deep tissue imaging (∼20 mm, signal-to-background ratio (SBR) = 3.4). Furthermore, we successfully applied DPA-H2S for precise in vivo imaging of MET-induced liver injury. We anticipate that our dual-locked probe, DPA-H2S, may serve as a promising tool in assisting the diagnosis of MET-induced liver injury in clinics and informing the clinical utilization of MET in the near future.

The Role of Heme Oxygenase 1 in Rheumatoid Arthritis and IL-1 Induced Inflammatory Cell Model.

OBJECTIVE: Rheumatoid arthritis (RA) is a common chronic autoimmune inflammatory disease. The pathogenesis of RA is complex, and RA lacks effective therapeutic drugs. Heme oxygenase 1 (HO-1) is found to be reduced in RA. However, the role of HO-1 in RA and related mechanisms have not been elucidated. METHODS: RA rat model was established. The expression of HO-1 was upregulated by hemin. The increase weight rate, the degree of toe swelling, and the arthritis index were analyzed to evaluate the therapeutic effect of HO-1 on RA. In vitro RAW264.7 inflammatory cell model was established using 5 ng/mL IL-1. SnPP or hemin were used to inhibit or upregulate HO-1 expression. Tetrazolium salt colorimetric assay (MTT) was selected to test cell proliferation. ELISA was used to determine the concentrations of cellular inflammatory factors IL-1 and IL-6. Reactive oxygen species (ROS) activity was assessed. Western blot was performed to analyze NF-[Formula: see text]B and MMP-3 expressions. RESULTS: The expression of HO-1 was decreased in RA rats, and hemin increased HO-1 level in arthritic rats, which elevated the increase weight rate and decreased toe swelling degree and arthritis index (P<0.05). Hemin significantly upregulated HO-1 expression, inhibited inflammatory cell proliferation, decreased IL-1 and IL-6 expressions, declined ROS level, restrained NF-[Formula: see text]B expression, and enhanced MMP-3 expression in Raw264.7 cells induced by LPS (P<0.05). SnPP obviously inhibited the expression of HO-1, promoted cell proliferation, elevated IL-1 and IL-6 secretions, increased ROS level, promoted NF-[Formula: see text]B expression, and decreased MMP-3 level compared with LPS group (P<0.05). CONCLUSION: Upregulation of HO-1 can improve arthritis symptoms by reducing ROS expression, inhibiting NF-[Formula: see text]B signaling pathway, elevating MMP-3 expression, attenuating inflammatory factor secretion, and suppressing inflammatory cell proliferation.

Generation of singlet oxygen inside living cells: correlation between phosphorescence decay lifetime, localization and outcome of photodynamic action.

Photodynamic therapy (PDT) is a promising alternative treatment for localized lesions and infections, utilizing reactive oxygen species (ROS) generated by photosensitizers (PS) upon light activation. Singlet oxygen (1O2) is a key ROS responsible for photodynamic damage. However, the effectiveness of PS in biological systems may not correlate with the efficiency of singlet oxygen generation in homogeneous solutions. This study investigated singlet oxygen generation and its decay in various cellular microenvironments using liposome and ARPE-19 cell models. Rose Bengal (RB), methylene blue (MB), and protoporphyrin IX (PpIX) were employed as selected PS. Lifetimes of singlet oxygen generated by the selected photosensitizers in different cellular compartments varied, indicating different quenching rates with singlet oxygen. RB, located near cell membranes, exhibited the highest phototoxicity and lipid/protein peroxidation, followed by PpIX, while MB showed minimal cytotoxicity in similar conditions. Singlet oxygen decay lifetimes provide insights into PS localization and potential phototoxicity, highlighting the importance of the lipid microenvironment in PDT efficacy, providing useful screening method prior to in vivo applications.

The effect of fluence rate and wavelength on the formation of protoporphyrin IX photoproducts.

Photodynamic diagnosis and therapy (PDD and PDT) are emerging techniques for diagnosing and treating tumors and malignant diseases. Photoproducts of protoporphyrin IX (PpIX) used in PDD and PDT may be used in the diagnosis and treatment, making a detailed analysis of the photoproduct formation under various treatment and diagnosis conditions important.Spectroscopic and mass spectrometric analysis of photoproduct formation from PpIX dissolved in dimethyl sulfoxide were performed under commonly used irradiation conditions for PDD and PDT, i.e., wavelengths of 405 and 635 nm and fluence rates of 10 and 100 mW/cm2. Irradiation resulted in the formation of hydroxyaldehyde photoproduct (photoprotoporphyrin; Ppp) and formyl photoproduct (product II; Pp II) existing in different quantities with the irradiation wavelength and fluence rate. Ppp was dominant under 635 nm irradiation of PpIX, with a fluorescence peak at 673 nm and a protonated monoisotopic peak at m/z 595.3. PpIX irradiation with 405 nm yielded more Pp II, with a fluorescence peak at 654 nm. A higher photoproduct formation was observed at a low fluence rate for irradiation with 635 nm, while irradiation with 405 nm indicated a higher photoproduct formation at a higher fluence rate.The photoproduct formation with the irradiation conditions can be exploited for dosimetry estimation and may be used as an additional photosensitizer to improve the diagnostics and treatment efficacies of PDD and PDT. Differences in environmental conditions of the present study from that of a biological environment may result in a variation in the photoproduct formation rate and may limit their clinical utilization in PDD and PDT. Thus, further investigation of photoproduct formation rates in more complex biological environments, including in vivo, is necessary. However, the results obtained in this study will serve as a basis for understanding reaction processes in such biological environments.

Chimeric peptide-engineered immunostimulant for endoplasmic reticulum targeted photodynamic immunotherapy against metastatic tumor.

The combination of therapy-induced immunogenic cell death (ICD) and immune checkpoint blockade can provide a mutually reinforced strategy to reverse the poor immunogenicity and immune escape behavior of tumors. In this work, a chimeric peptide-engineered immunostimulant (ER-PPB) is fabricated for endoplasmic reticulum (ER)-targeted photodynamic immunotherapy against metastatic tumors. Among which, the amphiphilic chimeric peptide (ER-PP) is composed of ER-targeting peptide FFKDEL, hydrophilic PEG8 linker and photosensitizer protoporphyrin IX (PpIX), which could be assembled with a PD-1/PD-L1 blocker (BMS-1) to prepare ER-PPB. After passively targeting at tumor tissues, ER-PPB will selectively accumulate in the ER. Next, the localized PDT of ER-PPB will produce a lot of ROS to destroy the primary tumor cells, while increasing the ER stress to initiate a robust ICD cascade. Moreover, the concomitant delivery of BMS-1 can impede the immune escape of tumor cells through PD-1/PD-L1 blockade, thus synergistically activating the immune system to combat metastatic tumors. In vitro and in vivo results demonstrate the robust immune activation and metastatic tumor inhibition characteristics of ER-PPB, which may offer a promising strategy for spatiotemporally controlled metastatic tumor therapy.

In Vitro Effect of Epigallocatechin Gallate on Heme Synthesis Pathway and Protoporphyrin IX Production.

Photodynamic therapy (PDT) treats nonmelanoma skin cancer. PDT kills cells through reactive oxygen species (ROS), generated by interaction among cellular O2, photosensitizer and specific light. Protoporphyrin IX (PpIX) is a photosensitizer produced from methyl aminolevulinate (MAL) by heme group synthesis (HGS) pathway. In PDT-resistant cells, PDT efficacy has been improved by addition of epigallocatechin gallate (EGCG). Therefore, the aim of this work is to evaluate the effect of EGCG properties over MAL-TFD and PpIX production on A-431 cell line. EGCG's role over cell proliferation (flow cytometry and wound healing assay) and clonogenic capability (clonogenic assay) was evaluated in A-431 cell line, while the effect of EGCG over MAL-PDT was determined by cell viability assay (MTT), PpIX and ROS detection (flow cytometry), intracellular iron quantification and gene expression of HGS enzymes (RT-qPCR). Low concentrations of EGCG (<50 µM) did not have an antiproliferative effect over A-431 cells; however, EGCG inhibited clonogenic cell capability. Furthermore, EGCG (<50 µM) improved MAL-PDT cytotoxicity, increasing PpIX and ROS levels, exerting a positive influence on PpIX synthesis, decreasing intracellular iron concentration and modifying HGS enzyme gene expression such as PGB (upregulated) and FECH (downregulated). EGCG inhibits clonogenic capability and modulates PpIX synthesis, enhancing PDT efficacy in resistant cells.

Inhibition of Heme Oxygenase 1 Suppresses Growth, Migration, and Invasion, and Regulates Tumor-Infiltrating CD8+ T Cells and in Uveal Melanoma.

Purpose: Metastatic uveal melanoma (UM) treatment is difficult, and effective treatments are urgently needed. We aimed to explore the role of heme oxygenase 1 (HO-1) in UM and provide new therapeutic strategies for UM. Methods: Bioinformatics was used to analyze the relationship between HMOX1 and immunity in UM and other tumors. Cell Counting Kit-8, Western blot, immunofluorescence staining, wound healing, and Transwell assays were used. A subcutaneous transplanted UM tumor model was used in mice to verify the therapeutic effect. Results: In UM, the expression level of HMOX1 was strongly correlated with the immune score and the infiltration level of various immune cells. ZnPP can inhibit the growth of UM cells, promote cell apoptosis, and block the cell cycle at G0/G1 phase in vitro. HO-1 knockout can effectively inhibit the proliferation of UM cells. ZnPP effectively inhibited the growth of UM and promoted the infiltration of CD8+ T cells in a subcutaneous tumor transplantation model. Conclusions: These results indicate that targeting HO-1 in UM has the potential for independent targeted immunotherapy or adjuvant immunotherapy.

Antimicrobial photodynamic therapy against Escherichia coli by exploiting endogenously produced Protoporphyrin IX- In vitro study.

Due to antimicrobial drug resistance, there is a growing interest in the development of light based alternative antibacterial therapies. This research work is focused on the inactivation of Escherichia coli (E. coli) by exploiting the absorption bands 405, 505, 542, 580 and 631 nm of its indigenously produced Protoporphyrin IX (PpIX) excited by three LEDs with broad emission bands at 418, 522 and 630 nm and two laser diodes with narrow emission bands at 405 and 635 nm. Fluorescence spectroscopy and plate count method have been employed for studying the inactivation rate of E. coli strain in autoclaved water suspension. It has been found that LEDs at 418, 522 and 630 nm produced pronounced antimicrobial photodynamic effect on E. coli strain comparing laser diodes at 405 and 635 nm, which might be attributed to the overlapping of broad emission bands of LEDs with the absorption bands of PpIX than narrow emission bands of laser diodes. Particular effect of LED at 522 nm has been noticed because its broad emission band overlaps three absorption bands 505, 542 and 580 nm of PpIX. The gold standard plate count method strongly correlates with Fluorescence spectroscopy, making it an innovative tool to administer bacterial inactivation. The experimental results suggested the development of a light source that entirely overlap absorption bands of PpIx to produce a pronounced antimicrobial photodynamic effect, which might become an effective modality for in vivo disinfection of antibiotic resistant microbes in wounds and lesions.

All-in-One Nanohybrids Combining Sonodynamic Photodynamic and Photothermal Therapies.

A wide variety of methods are being developed to ultimately defeat cancer; while some of these strategies have shown highly positive results, there are serious obstacles to overcome to completely eradicate this disease. So, it is crucial to construct multifunctional nanostructures possessing intelligent capabilities that can be utilized to treat cancer. A possible strategy for producing these multifunctional nanostructures is to combine various cancer treatment techniques. Based on this point of view, we successfully synthesized multifunctional HCuS@Cu2S@Au-P(NIPAM-co-AAm)-PpIX nanohybrids. The peculiarities of these thermosensitive polymer-modified and protoporphyrin IX (PpIX)-loaded hollow nanohybrids are that they combine photodynamic therapy (PDT), sonodynamic therapy (SDT), and photothermal therapy (PTT) with an intelligent design. As an all-in-one nanohybrids, HCuS@Cu2S@Au-P(NIPAM-co-AAm)-PpIX nanohybrids were employed in the SDT-PDT-PTT combination therapy, which proved to have a synergistic therapeutic effect for in vitro tumor treatments against breast tumors.

Pressure-enhanced sensing of tissue oxygenation via endogenous porphyrin: Implications for dynamic visualization of cancer in surgery.

Fluorescence guidance is routinely used in surgery to enhance perfusion contrast in multiple types of diseases. Pressure-enhanced sensing of tissue oxygenation (PRESTO) via fluorescence is a technique extensively analyzed here, that uses an FDA-approved human precursor molecule, 5-aminolevulinic acid (ALA), to stimulate a unique delayed fluorescence signal that is representative of tissue hypoxia. The ALA precontrast agent is metabolized in most tissues into a red fluorescent molecule, protoporphyrin IX (PpIX), which has both prompt fluorescence, indicative of the concentration, and a delayed fluorescence, that is amplified in low tissue oxygen situations. Applied pressure from palpation induces transient capillary stasis and a resulting transient PRESTO contrast, dominant when there is near hypoxia. This study examined the kinetics and behavior of this effect in both normal and tumor tissues, with a prolonged high PRESTO contrast (contrast to background of 7.3) across 5 tumor models, due to sluggish capillaries and inhibited vasodynamics. This tissue function imaging approach is a fundamentally unique tool for real-time palpation-induced tissue response in vivo, relevant for chronic hypoxia, such as vascular diseases or oncologic surgery.

Fluorometric Methods to Measure Bioavailable and Total Heme.

Heme b (iron protoporphyrin IX) is an essential but potentially cytotoxic cofactor, signaling molecule, and nutritional source of iron. Its importance in cell biology and metabolism is underscored by the fact that numerous diseases, including various cancers, neurodegenerative disorders, infectious diseases, anemias, and porphyrias, are associated with the dysregulation of heme synthesis, degradation, trafficking, and/or transport. Consequently, methods to measure, image, and quantify heme in cells are required to better understand the physiology and pathophysiology of heme. Herein, we describe fluorescence-based protocols to probe heme bioavailability and trafficking dynamics using genetically encoded fluorescent heme sensors in combination with various modalities, such as confocal microscopy, flow cytometry, and microplate readers. Additionally, we describe a protocol for measuring total heme and its precursor protoporphyrin IX using a fluorometric assay that exploits porphyrin fluorescence. Together, the methods described enable the monitoring of total and bioavailable heme to study heme homeostatic mechanisms in virtually any cell type and organism.

Direct Spectroscopic Ferrochelatase Assay.

Ferrochelatases (E.C. 4.99.1.1) catalyze the insertion of ferrous iron into either protoporphyrin IX to make protoheme IX or coproporphyrin III to make coproheme III. Ferrochelatase activity in extracts or purified protein can be measured via several assays. Here, we describe a rapid real-time direct spectroscopic ferrochelatase assay for both protoporphyrin and coproporphyrin ferrochelatases.