Molecular-level effects on cell membrane models to explain the phototoxicity of gold shell-isolated nanoparticles to cancer cells

Regulation of CTLs/Tregs via Highly Stable and Ultrasound-Responsive Cerasomal Nano-Modulators for Enhanced Colorectal Cancer Immunotherapy

Immunotherapy is showing good potential for colorectal cancer therapy, however, low responsive rates and severe immune-related drug side effects still hamper its therapeutic effectiveness. Herein, a highly stable cerasomal nano-modulator (DMC@P-Cs) with ultrasound (US)-controlled drug delivery capability for selective sonodynamic-immunotherapy is fabricated. DMC@P-Cs' lipid bilayer is self-assembled from cerasome-forming lipid (CFL), pyrophaeophorbid conjugated lipid (PL), and phospholipids containing unsaturated chemical bonds (DOPC), resulting in US-responsive lipid shell. Demethylcantharidin (DMC) as an immunotherapy adjuvant is loaded in the hydrophilic core of DMC@P-Cs. With US irradiation, reactive oxygen species (ROS) can be effectively generated from DMC@P-Cs, which can not only kill tumor cells for inducing immunogenic cell death (ICD), but also oxidize unsaturated phospholipids-DOPC to change the permeability of the lipid bilayers and facilitate controlled release of DMC, thus resulting in down-regulation of regulatory T cells (Tregs) and amplification of anti-tumor immune responses. After intravenous injection, DMC@P-Cs can efficiently accumulate at the tumor site, and local US treatment resulted in 94.73% tumor inhibition rate. In addition, there is no detectable systemic toxicity. Therefore, this study provides a highly stable and US-controllable smart delivery system to achieve synergistical sonodynamic-immunotherapy for enhanced colorectal cancer therapy.

Enhancing Phototoxicity in Human Colorectal Tumor Cells Through Nanoarchitectonics for Synergistic Photothermal and Photodynamic Therapies

Phototherapies are promising for noninvasive treatment of aggressive tumors, especially when combining heat induction and oxidative processes. Herein, we show enhanced phototoxicity of gold shell-isolated nanorods conjugated with toluidine blue-O (AuSHINRs@TBO) against human colorectal tumor cells (Caco-2) with synergic effects of photothermal (PTT) and photodynamic therapies (PDT). Mitochondrial metabolic activity tests (MTT) performed on Caco-2 cell cultures indicated a photothermal effect from AuSHINRs owing to enhanced light absorption from the localized surface plasmon resonance (LSPR). The phototoxicity against Caco-2 cells was further increased with AuSHINRs@TBO where oxidative processes, such as hydroperoxidation, were also present, leading to a cell viability reduction from 85.5 to 39.0%. The molecular-level mechanisms responsible for these effects were investigated on bioinspired tumor membranes using Langmuir monolayers of Caco-2 lipid extract. Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) revealed that the AuSHINRs@TBO incorporation is due to attractive electrostatic interactions with negatively charged groups of the Caco-2 lipid extract, resulting in the expansion of surface pressure isotherms. Upon irradiation, Caco-2 lipid extract monolayers containing AuSHINRs@TBO (1:1 v/v) exhibited ca. 1.0% increase in surface area. This is attributed to the generation of reactive oxygen species (ROS) and their interaction with Caco-2 lipid extract monolayers, leading to hydroperoxide formation. The oxidative effects are facilitated by AuSHINRs@TBO penetration into the polar groups of the extract, allowing oxidative reactions with carbon chain unsaturations. These mechanisms are consistent with findings from confocal fluorescence microscopy, where the Caco-2 plasma membrane was the primary site of the cell death induction process.

Photochemical outcomes triggered by gold shell-isolated nanorods on bioinspired nanoarchitectonics for bacterial membranes

Boosted by the indiscriminate use of antibiotics, multidrug-resistance (MDR) demands new strategies to combat bacterial infections, such as photothermal therapy (PTT) based on plasmonic nanostructures. PTT efficiency relies on photoinduced damage caused to the bacterial machinery, for which nanostructure incorporation into the cell envelope is key. Herein, we shall unveil the binding and photochemical mechanisms of gold shell-isolated nanorods (AuSHINRs) on bioinspired bacterial membranes assembled as Langmuir and Langmuir-Schaefer (LS) monolayers of DOPE, Lysyl-PG, DOPG and CL. AuSHINRs incorporation expanded the isotherms, with stronger effect on the anionic DOPG and CL. Indeed, FTIR of LS films revealed more modifications for DOPG and CL owing to stronger attractive electrostatic interactions between anionic phosphates and the positively charged AuSHINRs, while electrostatic repulsions with the cationic ethanolamine (DOPE) and lysyl (Lysyl-PG) polar groups might have weakened their interactions with AuSHINRs. No statistical difference was observed in the surface area of irradiated DOPE and Lysyl-PG monolayers on AuSHINRs, which is evidence of the restricted nanostructures insertion. In contrast, irradiated DOPG monolayer on AuSHINRs decreased 4.0 % in surface area, while irradiated CL monolayer increased 3.7 %. Such results agree with oxidative reactions prompted by ROS generated by AuSHINRs photoactivation. The deepest AuSHINRs insertion into DOPG may have favored chain cleavage while hydroperoxidation is the mostly like outcome in CL, where AuSHINRs are surrounding the polar groups. Furthermore, preliminary experiments on Escherichia coli culture demonstrated that the electrostatic interactions with AuSHINRs do not inhibit bacterial growth, but the photoinduced effects are highly toxic, resulting in microbial inactivation.

Unveiling the mechanisms underlying photothermal efficiency of gold shell-isolated nanoparticles (AuSHINs) on ductal mammary carcinoma cells (BT-474)

Gold nanoparticles are valuable photothermal agents owing to their efficient photothermal conversion, photobleaching resistance, and potential surface functionalization. Herein, we combined bioinspired membranes with in vitro assays to elicit the molecular mechanisms of gold shell-isolated nanoparticles (AuSHINs) on ductal mammary carcinoma cells (BT-474). Langmuir and Langmuir-Schaefer (LS) films were handled to build biomembranes from BT-474 lipid extract. AuSHINs incorporation led to surface pressure-area (π-A) isotherms expansion, increasing membrane flexibility. Fourier-transform infrared spectroscopy (FTIR) of LS multilayers revealed electrostatic AuSHINs interaction with head portions of BT-474 lipid extract, causing lipid chain disorganization. Limited AuSHINs insertion into monolayer contributed to hydroperoxidation of the unsaturated lipids upon irradiation, consistently with the surface area increments of ca. 2.0%. In fact, membrane disruption of irradiated BT-474 cells containing AuSHINs was confirmed by confocal microscopy and LDH leakage, with greater damage at 2.2 × 1013 AuSHINs/mL. Furthermore, the decrease in nuclei dimensions indicates cell death through photoinduced damage.

Immunoassay platform with surface-enhanced resonance Raman scattering for detecting trace levels of SARS-CoV-2 spike protein

The early diagnosis of Coronavirus disease (COVID-19) requires either an accurate detection of genetic material or a sensitive detection of viral proteins. In this work, we designed an immunoassay platform for detecting trace levels of SARS-CoV-2 spike (S) protein. It is based on surface-enhanced resonance Raman scattering (SERRS) of methylene blue (MB) adsorbed onto spherical gold nanoparticles (AuNPs) and coated with a 6 nm silica shell. The latter shell in the SERRS nanoprobe prevented aggregation and permitted functionalization with SARS-CoV-2 antibodies. Specificity of the immunoassay was achieved by combining this functionalization with antibody immobilization on the cover slides that served as the platform support. Different concentrations of SARS-CoV-2 antigen could be distinguished and the lack of influence of interferents was confirmed by treating SERRS data with the multidimensional projection technique Sammon's mapping. With SERRS using a laser line at 633 nm, the lowest concentration of spike protein detected was 10 pg/mL, achieving a limit of detection (LOD) of 0.046 ng/mL (0.60 pM). This value is comparable to the lowest concentrations in the plasma of COVID-19 patients at the onset of symptoms, thus indicating that the SERRS immunoassay platform may be employed for early diagnosis.

The efficiency of photothermal action of gold shell-isolated nanoparticles against tumor cells depends on membrane interactions

Photoinduced hyperthermia with nanomaterials has been proven effective in photothermal therapy (PTT) of tumor tissues, but a precise control in PTT requires determination of the molecular-level mechanisms. In this paper, we determined the mechanisms responsible for the action of photoexcited gold shell-isolated nanoparticles (AuSHINs) in reducing the viability of MCF7 (glandular breast cancer) and especially A549 (lung adenocarcinoma) cells in vitro experiments, while the photoinduced damage to healthy cells was much smaller. The photoinduced effects were more significant than using other nanomaterials, and could be explained by the different effects from incorporating AuSHINs on Langmuir monolayers from lipid extracts of tumoral (MCF7 and A549) and healthy cells. The incorporation of AuSHINs caused similar expansion of the Langmuir monolayers, but Fourier-transform infrared spectroscopy (FTIR) data of Langmuir-Schaefer films (LS) indicated distinct levels of penetration into the monolayers. AuSHINs penetrated deeper into the A549 extract monolayers, affecting the vibrational modes of polar groups and carbon chains, while in MCF7 monolayers penetration was limited to the surroundings of the polar groups. Even smaller insertion was observed for monolayers of the healthy cell extract. The photochemical reactions were modulated by AuSHINs penetration, since upon irradiation the surface area of A549 monolayer decreased owing to lipid chain cleavage by oxidative reactions. For MCF7 monolayers, hydroperoxidation under illumination led to a ca. 5% increase in surface area. The monolayers of healthy cell lipid extract were barely affected by irradiation, consistent with the lowest degree of AuSHINs insertion. In summary, efficient photothermal therapy may be devised by producing AuSHINs capable of penetrating the chain region of tumor cell membranes.

Plasma membrane permeabilization to explain erythrosine B phototoxicity on in vitro breast cancer cell models

Lipid oxidation is ubiquitous in cell life under oxygen and essential for photodynamic therapy (PDT) of carcinomas. However, the mechanisms underlying lipid oxidation in rather complex systems such as plasma membranes remain elusive. Herein, Langmuir monolayers were assembled with the lipid extract of glandular breast cancer (MCF7) cells and used to probe the molecular interactions allowing adsorption of the photosensitizer (PS) erythrosine B and subsequent photooxidation outcomes. Surface pressure (π) versus area (cm²/mL) isotherms of MCF7 lipid extract shifted to larger areas upon erythrosine incorporation, driven by secondary interactions that affected the orientation of the carbonyl groups and lipid chain organization. Light-irradiation increased the surface area of the MCF7 lipid extract monolayer containing erythrosine owing to the lipid hydroperoxidation, which may further undergo decomposition, resulting in the chain cleavage of phospholipids and membrane permeabilization. Incorporation of erythrosine by MCF7 cells induced slight toxic effects on in vitro assays, differently of the severe phototoxicity caused by light-irradiation, which significantly decreased cell viability by more than 75% at 2.5 × 10^-6 mol/L of erythrosine incubated for 3 and 24 h, reaching nearly 90% at 48 h of incubation. The origin of the phototoxic effects is in the rupture of the plasma membrane shown by the frontal (FSC) and side (SSC) light scattering of flow cytometry. Consistent with hydroperoxide decomposition, membrane permeabilization was also confirmed by cleaved lipids detected in mass spectrometry and subsidizes the necrotic pathway of cell death.

Study of the interactions of gold nanoparticles functionalized with aminolevulinic acid in membrane models

Gold nanoparticles have been intensively studied in cancer therapy to improve drug release, increasing therapeutic action and reducing adverse effects. The interaction between gold nanoparticles and cell membranes can give information about the cell internalization. In this study, gold nanoparticles with aminolevulinic acid (5-ALA) were synthesized using the photoreduction method (5-ALA: AuNPs). The prodrug 5-ALA is responsible for protoporphyrin IX synthesis inside the cell and allows the use of therapies as photodynamic and sonodynamic therapies. The cytotoxicity test was performed on a breast cancer tumor line (MCF-7), and high Content Screening assay was applied to evaluate the entry of nanoparticles into cells. DPPS Langmuir monolayers were assembled at the air/water interface and employed as a simplified membrane model for half of a tumorigenic cell membrane. We assessed the molecular interactions between 5-ALA: AuNPs and phospholipids using tensiometry (π-A isotherms) and vibrational spectroscopy (PM-IRRAS) experiments. We found that the functionalized gold nanoparticles strongly interact with DPPS polar head groups (especially phosphate and carbonyl), changing the phospholipid hydration and leading to a general decrease in the monolayer conformational order. This work then probes that specific interaction between 5-ALA: AuNPs and the negatively charged phospholipid can be assessed using Langmuir monolayers as simplified biomembrane models.

Chemical and morphological effects of the contraceptive hormone 17 α-ethynylestradiol on fluid lipid membranes

The lack of studies involving the effects in human health associated with the chronic ingestion of pollutants lead to the path of investigating the action of these compounds in cell membrane models. We demonstrated the interaction (causes and consequences) of the hormone 17 α-ethinylestradiol (EE2) with lipid monolayers (prepared as Langmuir films) and bilayers prepared as small unilamellar vesicles (SUVs) and giant unilamellar vesicles (GUVs). Both fluidity and majority chemical composition of real plasma cell membrane were guaranteed using the phospholipid 1-palmitoil-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC). Surface pressure-mean molecular area (π-A) isotherms and PM-IRRAS measurements highlighted the strong interaction of EE2 with POPC monolayers, leading the hormone to remain at the air/water interface and promoting its penetration into the phospholipid hydrophobic chains. In the case of bilayers, the entrance of the hormone inside the SUV is likely facilitated by their high curvature. In GUVs, EE2 was responsible for changes in the spherical shape, forming structures like buds and lipid protrusions. The set of results indicates the strong effects of EE2 on fluid membranes, which is an important feature to predict its damage in human cells.

Chain Cleavage of Bioinspired Bacterial Membranes Photoinduced by Eosin Decyl Ester

Photodynamic therapy (PDT) is promising for bacterial inactivation since cellular internalization of photosensitizers (PS) is not crucial for the treatment effectiveness. Photoinduced damage in the lipid envelope may already induce microbial inactivation, which requires PS capable of easily penetrating into the membrane. Herein, we report on the insertion of the PS eosin decyl ester (EosDec) into Langmuir films of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG), and cardiolipin (CLP) used as mimetic systems of bacterial membranes. Surface pressure isotherms and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) indicated that the hydrophobic nature of EosDec favored deeper penetration in all the phospholipid monolayers. The incorporation of EosDec led to monolayer expansion, especially in the anionic DOPG and CLP owing to repulsive electrostatic interactions, and induced disorder in the lipid chains. Light irradiation of DOPE, DOPG, and CLP monolayers containing EosDec increased the rate of material loss to the subphase, which is attributed to cleavage of lipid chains triggered by contact-dependent reactions between excited states of EosDec and lipid unsaturations. The latter is key for membrane permeabilization and efficiency in microbial inactivation.