Development of immunoliposomes containing cytotoxic gold payloads against HER2-positive breast cancers.

Overexpression of the human epidermal growth factor receptor 2 (HER2) is found in 20-30% of breast cancer tumors (HER2-positive breast cancers) and is associated with more aggressive onset of disease, higher recurrence rate and increased mortality. Monoclonal antibodies (mAb) like trastuzumab and pertuzumab in combination with chemotherapeutics, and trastuzumab-based antibody drug conjugates (ADCs) are used in the clinic to treat these cancers. An alternative targeted strategy (not yet in clinical use) is the encapsulation of chemotherapeutic drugs in immunoliposomes. Such systems may not only facilitate targeted delivery to the tumor and improve intracellular penetration, but also override some of the resistance developed by tumors in response to cytotoxic loads. As a supplement to classical chemotherapeutics (based on organic compounds and conventional platinum-based derivatives), gold compounds are emerging as potential anticancer agents due to their high cytotoxicity and capacity for immunogenic cell death. Here, we describe the development of immunoliposomes functionalized with trastuzumab and pertuzumab; containing simple gold(i) neutral compounds ([AuCl(PR3)] (PR3 = PPh3 (1), PEt3 (2))) generated by the thin-film method to afford Lipo-1-Lipo-2. Trastuzumab and pertuzumab were engrafted onto these liposomes to generate gold-based immunoliposomes (Immunolipo-Tras-1, Immunolipo-Tras-2, Immunolipo-Per-1, Immunolipo-Per-2). We have characterized all liposomal formulations and demonstrated that the immunoliposomes (190 nm) are stable, have high binding affinity for HER2, and display selective cytotoxicity towards HER2-positive breast cancer cell lines. Trastuzumab-based immunoliposomes of a smaller size (100 nm) - encapsulating [AuCl(PEt3)] (2) - have been generated by an extrusion homogenization method. These optimized immunoliposomes (Opt-Immunolipo-Tras-2) have a trastuzumab engraftment efficiency, encapsulation efficiency for 2, and affinity for HER-2 similar to the immunoliposomes obtained by sonication (Immunolipo-Tras-2). While the amount of Au encapsulated is slightly lower, they display almost identical cytotoxicity and selectivity profiles. Moreover, the fluorescently-labeled phosphane drug [AuCl(PPh2-BODIPY)] (3) was encapsulated in both larger (Immunolipo-Tras-3) and smaller (Opt-Immunolipo-Tras-3) immunoliposomes and used to visualize the intracellular localization of the payload. Fluorescent imaging studies found that Opt-Immunolipo-Tras-3 accumulates in the cells more than 3 and that the unencapsulated payload accumulates primarily in lysosomes, while targeted liposomal 3 localizes in mitochondria and ER, hinting at different possibilities for modes of action.

Correction to "Shifting the Antibody-Drug Conjugate Paradigm: A Trastuzumab-Gold-Based Conjugate Demonstrates High Efficacy against Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Mouse Model".

[This corrects the article DOI: 10.1021/acsptsci.3c00270.].

Shifting the Antibody-Drug Conjugate Paradigm: A Trastuzumab-Gold-Based Conjugate Demonstrates High Efficacy against Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Mouse Model.

Antibody-drug conjugates (ADCs) combine the selectivity of monoclonal antibodies (mAbs) with the efficacy of chemotherapeutics to target cancers without toxicity to normal tissue. Clinically, most chemotherapeutic ADCs are based on complex organic molecules, while the conjugation of metallodrugs to mAbs has been overlooked, despite the resurgent interest in metal-based drugs as cancer chemotherapeutics. In 2019, we described the first gold ADCs containing gold-triphenylphosphane fragments as a proof of concept. The ADCs (based on the antibody trastuzumab) were selective and highly active against HER2-positive breast cancer cells. In this study, we developed site-specific ADCs (Thio-1b and Thio-2b) using the cysteine-engineered trastuzumab derivative THIOMAB antibody technology with gold(I)-containing phosphanes and a maleimide-based linker amenable to bioconjugation (1b and 2b). In addition, we developed lysine-directed ADCs with gold payloads based on phosphanes and N-heterocyclic carbenes featuring an activated ester moiety (2c and 5c) with trastuzumab (Tras-2c and Tras-5c) and another anti-HER2 antibody, pertuzumab (Per-2c and Per-5c). Both sets of ADCs demonstrated significant anticancer potency in vitro assays. Based on these results, one ADC (Tras-2c), containing the [Au(PEt3)] fragment present in FDA-approved auranofin, was selected for an in vivo antitumor efficacy study. Immunocompromised mice xenografted with the HER2-positive human cancer cell line SKBR-3 exhibited almost complete tumor reduction and low toxicity with intravenous administration of Tras-2c. With this highly selective targeting system, we demonstrated that a subnanomolar cytotoxicity profile in cells is not required for an impressive antitumor effect in a mouse xenograft model.

5-Nitrofuryl-Containing Thiosemicarbazone Gold(I) Compounds: Synthesis, Stability Studies, and Anticancer Activity.

Invited for this month's cover are the collaborating groups of Esteban Rodríguez-Arce from the University of Chile and María Contel from The City University of New York Brooklyn College. The cover picture shows "Supergold" a very powerful gender neutral warrior with superpowers who fights against cancer! The warrior's golden armor and sword represent the pharmacological power of the gold atom. Engraved on the shield, the gold-thiosemicarbazone molecules are the warrior's coat of arms. Supergold selectively destroys different cancer cells. More information can be found in the Research Article by Esteban Rodríguez-Arce, María Contel, and co-workers.

Platinum(IV)-Gold(I) Agents with Promising Anticancer Activity: Selected Studies in 2D and 3D Triple-Negative Breast Cancer Models.

New heterometallic binuclear and trinuclear platinum(IV)-gold(I) compounds of the type [Pt(L)n Cl2 (OH){(OOC-4-C6 H4 -PPh2 )AuCl}x ] (L=NH3 , n=2; x=1, 2; L=diaminocyclohexane, DACH, n=1; x=2) are described. These compounds are cytotoxic and selective against a small panel of renal, bladder, ovarian, and breast cancer cell lines. We selected a trinuclear PtAu2 compound containing the PtIV core based on oxaliplatin, to further investigate its cell-death pathway, cell and organelle uptake and anticancer effects against the triple-negative breast cancer (TNBC) MDA-MB-231 cell line. This compound induces apoptosis and accumulates mainly in the nucleus and mitochondria. It also exerts remarkable antimigratory and antiangiogenic properties, and has a potent cytotoxic effect against TNBC 3D spheroids. Trinuclear compounds do not seem to display relevant interactions with calf thymus (CT) DNA and plasmid (pBR322) even in the presence of reducing agents, but inhibit pro-angiogenic enzyme thioredoxin reductase (TrxR) in TNBC cells.

5-Nitrofuryl-Containing Thiosemicarbazone Gold(I) Compounds: Synthesis, Stability Studies, and Anticancer Activity.

This work describes the synthesis of four gold(I) [AuClL] compounds containing chloro and biologically active protonated thiosemicarbazones based on 5-nitrofuryl (L=HSTC). The stability of the compounds in dichloromethane, DMSO, and DMSO/culture media solutions was investigated by spectroscopy, cyclic voltammetry, and conductimetry, indicating the formation overtime of cationic monometallic [Au(HTSC)(DMSO)]± or [Au(HTSC)2 ]± , and/or dimeric species. Neutral [{Au(TSC)}2 ] species were obtained from one of the compounds in dichlomethane/n-hexane solution and characterized by X-ray crystallography revealing a Au-Au bond, and deprotonated thiosemicarbazone (TSC). The cytotoxicity of the gold compounds and thiosemicarbazone ligands was evaluated against selected cancer cell lines and compared to that of Auranofin. Studies of the most stable, cytotoxic, and selective compound on a renal cancer cell line (Caki-1) demonstrated its relevant antimigratory and anti-angiogenic properties, and preferential accumulation in the cell nuclei. Its mode of action seems to involve interaction with DNA, and subsequent cell death via apoptosis.

N-Acetylation of Biodegradable Supramolecular Peptide Nanofilaments Selectively Enhances Their Proteolytic Stability for Targeted Delivery of Gold-Based Anticancer Agents.

Peptide materials are promising for various biomedical applications; however, a significant concern is their lack of stability and rapid degradation in vivo due to non-specific proteolysis. For materials specifically designed to respond to disease-specific proteases, it would be desirable to retain high susceptibility to target proteases while minimizing the impact of non-specific proteolysis. We describe N-terminal acetylation as a simple synthetic modification of amphiphilic self-assembling peptides that contain an MMP-9-cleavable segment and form soluble, nanoscale filaments. We found that the N-terminus capping of these peptides did not significantly impact their self-assembly behavior, critical aggregation concentration, or ability to encapsulate hydrophobic payloads. By contrast, their proteolytic stability in human plasma (especially for anionic peptide sequences) was considerably increased while susceptibility to hydrolysis by MMP-9 was retained when compared to non-acetylated peptides, especially during the first 12 h. We note, however, that due to the longer time scale required for in vitro studies (72 h), non-specific proteolysis of both anionic acetylated peptides leads to similar activity in vitro despite differing MMP-9 kinetics during the early stages. Overall, the enhanced stability against non-specific proteases, combined with the ability of these nanofilaments to enhance the effectiveness of gold-based drugs toward cancerous cells compared to healthy cells, brings these acetylated peptide filaments a step closer toward clinical translation.

Encapsulation of Gold-Based Anticancer Agents in Protease-Degradable Peptide Nanofilaments Enhances Their Potency.

We investigated the use of amphiphilic, protease-cleavable peptides as encapsulation moieties for hydrophobic metallodrugs, in order to enhance their bioavailability and consequent activity. Two hydrophobic, gold-containing anticancer agents varying in aromatic ligand distribution (Au(I)-N-heterocyclic carbene compounds 1 and 2) were investigated. These were encapsulated into amphiphilic decapeptides that form soluble filamentous structures with hydrophobic cores, varying supramolecular packing arrangements and surface charge. Peptide sequence strongly dictates the supramolecular packing within the aromatic core, which in turn dictates drug loading. Anionic peptide filaments can effectively load 1, and to a lesser extent 2, while their cationic counterparts could not, collectively demonstrating that loading efficiency is dictated by both aromatic and electrostatic (mis)matching between drug and peptide. Peptide nanofilaments were nontoxic to cancerous and noncancerous cells. By contrast, those loaded with 1 and 2 displayed enhanced cytotoxicity in comparison to 1 and 2 alone, when exposed to Caki-1 and MDA-MB-231 cancerous cell lines, while no cytotoxicity was observed in noncancerous lung fibroblasts, IMR-90. We propose that the enhanced in vitro activity results from the enhanced proteolytic activity in the vicinity of the cancer cells, thereby breaking the filaments into drug-bound peptide fragments that are taken up by these cells, resulting in enhanced cytotoxicity toward cancer cells.

Promising heterometallic compounds as anticancer agents: Recent studies in vivo.

Over the past decade, interest on multitarget anticancer drugs -including heterometallic compounds-has increased considerably. Heterometallic species display improved efficacy and physicochemical properties compared to the individual metallic fragments for a variety of metal pair combinations. By 2018, several compounds had emerged as promising candidates against cisplatin resistant cancers. Here, we summarize research contributions to this topic over the past four years (July 2018-July 2022). In particular, we highlight five articles reporting on the in vivo activity and preliminary mechanisms of action for five groups of compounds. From this selection, we further feature two families of compounds based on Pt(IV)-Gd(III) and Ti(IV)-Au(I) metal combinations, given their potential for clinical translation.

Self-Complementary Zwitterionic Peptides Direct Nanoparticle Assembly and Enable Enzymatic Selection of Endocytic Pathways.

Supramolecular self-assembly in biological systems holds promise to convert and amplify disease-specific signals to physical or mechanical signals that can direct cell fate. However, it remains challenging to design physiologically stable self-assembling systems that demonstrate tunable and predictable behavior. Here, the use of zwitterionic tetrapeptide modalities to direct nanoparticle assembly under physiological conditions is reported. The self-assembly of gold nanoparticles can be activated by enzymatic unveiling of surface-bound zwitterionic tetrapeptides through matrix metalloprotease-9 (MMP-9), which is overexpressed by cancer cells. This robust nanoparticle assembly is achieved by multivalent, self-complementary interactions of the zwitterionic tetrapeptides. In cancer cells that overexpress MMP-9, the nanoparticle assembly process occurs near the cell membrane and causes size-induced selection of cellular uptake mechanism, resulting in diminished cell growth. The enzyme responsiveness, and therefore, indirectly, the uptake route of the system can be programmed by customizing the peptide sequence: a simple inversion of the two amino acids at the cleavage site completely inactivates the enzyme responsiveness, self-assembly, and consequently changes the endocytic pathway. This robust self-complementary, zwitterionic peptide design demonstrates the use of enzyme-activated electrostatic side-chain patterns as powerful and customizable peptide modalities to program nanoparticle self-assembly and alter cellular response in biological context.

Intracellular Localization Studies of the Luminescent Analogue of an Anticancer Ruthenium Iminophosphorane with High Efficacy in a Triple-Negative Breast Cancer Mouse Model.

The potential of ruthenium(II) compounds as an alternative to platinum-based clinical anticancer agents has been unveiled after extensive research for over 2 decades. As opposed to cisplatin, ruthenium(II) compounds have distinct mechanisms of action that do not rely solely on interactions with DNA. In a previous report from our group, we described the synthesis, characterization, and biological evaluation of a cationic, water-soluble, organometallic ruthenium(II) iminophosphorane (IM) complex of p-cymene, ([(η6-p-cymene)Ru{(Ph3P═N-CO-2N-C5H4)-κ-N,O}Cl]Cl (1 or Ru-IM), that was found to be highly cytotoxic against a panel of cell lines resistant to cisplatin, including triple-negative breast cancer (TNBC) MDA-MB-231, through canonical or caspase-dependent apoptosis. Studies on a MDA-MB-231 xenograft mice model (after 28 days of treatment) afforded an excellent tumor reduction of 56%, with almost negligible systemic toxicity, and a favored ruthenium tumor accumulation compared to other organs. 1 is known to only interact weakly with DNA, but its intracellular distribution and ultimate targets remain unknown. To gain insight on potential mechanisms for this highly efficacious ruthenium compound, we have developed two luminescent analogues containing the BOPIPY fluorophore (or a modification) in the IM scaffold with the general structure of [(η6-p-cymene)Ru{(BODIPY-Ph2P═N-CO-2-NC5H4)-κ-N,O}Cl]Cl {BODIPY-Ph2P = 8-[(4-diphenylphosphino)phenyl]-4,4-dimethyl-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (3a) and 4,4-difluoro-8-[4-[[2-[4-(diphenylphosphino)benzamido]ethyl]carbamoyl]phenyl]-1,3,5,7-tetramethyl,2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (3b)}. We report on the synthesis, characterization, lipophilicity, stability, luminescence properties, and cell viability studies in the TNBC cell line MDA-MB-231, nonmalignant breast cells (MCF10a), and lung fibroblasts (IMR-90) of the new compounds. The ruthenium derivative 3b was studied by fluorescence confocal microscopy. These studies point to a preferential accumulation of the compound in the endoplasmic reticulum, mitochondria, and lysosomes. Inductively coupled plasma optical emission spectrometry (ICP-OES) analysis also confirms a greater ruthenium accumulation in the cytoplasmic fraction, including endoplasmic reticulum and lysosomes, and a smaller percentage of accumulation in mitochondria and the nucleus. ICP-OES analysis of the parent compound 1 indicates that it accumulates preferentially in the mitochondria and cytoplasm. Subsequent experiments in 1-treated MDA-MB-231 cells demonstrate significant reactive oxygen species generation.

Investigation of the Effects and Mechanisms of Anticancer Action of a Ru(II)-Arene Iminophosphorane Compound in Triple Negative Breast Cancer Cells.

Triple negative breast cancer (TNBC) is one of the breast cancers with poorer prognosis and survival rates. TNBC has a disproportionally high incidence and mortality in women of African descent. We report on the evaluation of Ru-IM (1), a water-soluble organometallic ruthenium compound, in TNBC cell lines derived from patients of European (MDA-MB-231) and African (HCC-1806) ancestry (including IC50 values, cellular and organelle uptake, cell death pathways, cell cycle, effects on migration, invasion, and angiogenesis, a preliminary proteomic analysis, and an NCI 60 cell-line panel screen). 1 was previously found highly efficacious in MDA-MB-231 cells and xenografts, with little systemic toxicity and preferential accumulation in the tumor. We observe a similar profile for this compound in the two cell lines studied, which includes high cytotoxicity, apoptotic behavior and potential antimetastatic and antiangiogenic properties. Cytokine M-CSF, involved in the PI3/AKT pathway, shows protein expression inhibition with exposure to 1. We also demonstrate a p53 independent mechanism of action.

Exploring the Potential of Metallodrugs as Chemotherapeutics for Triple Negative Breast Cancer.

This review focuses on studies of coordination and organometallic compounds as potential chemotherapeutics against triple negative breast cancer (TNBC) which has one of the poorest prognoses and worst survival rates from all breast cancer types. At present, chemotherapy is still the standard of care for TNBC since only one type of targeted therapy has been recently developed. References for metal-based compounds studied in TNBC cell lines will be listed, and those of metal-specific reviews, but a detailed overview will also be provided on compounds studied in vivo (mostly in mice models) and those compounds for which some preliminary mechanistic data was obtained (in TNBC cell lines and tumors) and/or for which bioactive ligands have been used. The main goal of this review is to highlight the most promising metal-based compounds with potential as chemotherapeutic agents in TNBC.

Auranofin-Based Analogues Are Effective Against Clear Cell Renal Carcinoma In Vivo and Display No Significant Systemic Toxicity.

Effective pharmacological treatments for patients with advanced clear cell renal carcinoma (ccRCC) are limited. Bimetallic titanium-gold containing compounds exhibit significant cytotoxicity against ccRCC in vitro and in vivo and inhibit invasion and angiogenisis in vitro and markers driving these phenomena. However, in vivo preclinical evaluations of such compounds have not examined their pharmacokinetics, pathology, and hematology. Here we use NOD.CB17-Prkdc SCID/J mice bearing xenograft ccRCC Caki-1 tumors to evaluate the in vivo efficacies of two titanium-gold compounds Titanocref and Titanofin (based on auranofin analogue scaffolds) accompanied by pharmacokinetic and pathology studies. A therapeutic trial was performed over 21 days at 5 mg/kg/72h of Titanocref and 10 mg/kg/72h of Titanofin tracking changes in tumor size. We observed a significant reduction of 51% and 60%, respectively (p < 0.01) in tumor size in the Titanocref- and Titanofin-treated mice compared to the starting size, while the vehicle-treated mice exhibited a tumor size increase of 138% (p < 0.01). Importantly, no signs of pathological complication as a result of treatment were found. In addition, Titanocref and Titanofin treatment reduced angiogenesis by 38% and 54%, respectively. Microarray and qRT-PCR analysis of ccRCC Caki-1 cells treated with Titanocref revealed that the compound alters apoptosis, JNK MAP kinase, and ROS pathways within 3 h of treatment. We further show activation of apoptosis by Titanocref and Titanofin in vivo by caspase 3 assay. Titanocref is active against additional kidney cancer cells. Titanocref and Titanofin are therefore promising candidates for further evaluation toward clinical application in the treatment of ccRCC.

SEC hyphenated to a multielement-specific detector unravels the degradation pathway of a bimetallic anticancer complex in human plasma.

The bimetallic metal complex Titanocref exhibits relevant anticancer activity, but it is unknown if it is stable to reach target tissues intact. To gain insight, a pharmacologically relevant dose was added to human blood plasma and the mixture was incubated at 37 °C. The obtained mixture was analyzed 5 and 60 min later by size-exclusion chromatography hyphenated to an inductively coupled plasma atomic emission spectrometer (SEC-ICP-AES). We simultaneously detected several titanium (Ti), gold (Au) and sulfur (S)-peaks, which corresponded to a Ti degradation product that eluted partially, and a Au degradation product that eluted entirely bound to plasma proteins (both time points). Although ~70% of the intact Titanocref was retained on the column after 60 min, our results allowed us to establish - for the first time - its likely degradation pathway in human plasma at near physiological conditions. These results suggest that ~70% of Titanocref remain in plasma after 60 min, which supports results from a recent in vivo study in which mice were treated with Titanocref and revealed Ti:Au molar ratios in tumors and organs close to 1:1. Thus, our stability studies suggest that the intact drug is able to reach target tissue. Overall, our results exemplify that SEC-ICP-AES enables the execution of intermediate in vitro studies with human plasma in the context of advancing bimetallic metal-based drugs to more costly clinical studies.

Metal-based antibody drug conjugates. Potential and challenges in their application as targeted therapies in cancer.

Antibody drug conjugates have emerged as a very attractive type of targeted therapy in cancer. They combine the antigen-targeting specificity of monoclonal antibodies (mAbs) with the cytotoxic potency of chemotherapeutics. This review focuses on antibody drug conjugates based on metal-containing cytotoxic payloads. We will also describe antibody drug conjugates (ADCs) in which a metal-based component (mostly metallic nanoparticles) exerts a relevant function in the ADC (for photodynamic or photothermal therapy, as air-plasma-enhancer or chemo-sensitizer, as carrier of other cytotoxic payloads or as an integral part of the linker structure). Challenges and opportunities to increase the translational potential of these ADCs will be discussed.

Preclinical evaluation of an unconventional ruthenium-gold-based chemotherapeutic: RANCE-1, in clear cell renal cell carcinoma.

BACKGROUND: There are few effective treatments for patients with advanced clear cell renal cell carcinoma (CCRCC). Recent findings indicate that ruthenium-gold containing compounds exhibit significant antitumor efficacy against CCRCC in vitro affecting cell viability as well as angiogenesis and markers driving those 2 phenomena. However, no in vivo preclinical evaluation of this class of compounds has been reported. METHODS: Following the dose-finding pharmacokinetic determination, NOD.CB17-Prkdc SCID/J mice bearing xenograft CCRCC Caki-1 tumors were treated in an intervention trial for 21 days at 10 mg/kg/72h of RANCE-1. At the end of the trial, tumor samples were analyzed for histopathological and changes in protein expression levels were assessed. RESULTS: After 21 days of treatment there was no significant change in tumor size in the RANCE-1-treated mice as compared to the starting size (+3.87%) (P = 0.082) while the vehicle treated mice exhibited a significant tumor size increase (+138%) (P < 0.01). There were no signs of pathological complications as a result of treatment. Significant reduction in the expression of VEGF, PDGF, FGF, EGFR, and HGRF, all key to the proliferation of tumor cells and stromal cells serving protumorigenic purposes was observed. CONCLUSIONS: The tumor growth inhibition displayed and favorable pathology profile of RANCE-1 makes it a promising candidate for further evaluation toward clinical use for the treatment of advanced CCRCC.

Preparation of Titanocene-Gold Compounds Based on Highly Active Gold(I)-N-Heterocyclic Carbene Anticancer Agents: Preliminary in†vitro Studies in Renal and Prostate Cancer Cell Lines.

Heterometallic titanocene-based compounds containing gold(I)-phosphane fragments have been extremely successful against renal cancer in vitro and in vivo. The exchange of phosphane by N-heterocyclic carbene ligands to improve or modulate their pharmacological profile afforded bimetallic complexes effective against prostate cancer, but less effective against renal cancer in vitro. Herein we report the synthesis of new bimetallic Ti-Au compounds by the incorporation of two previously reported highly active gold(I)-N-heterocyclic carbene fragments derived from 4,5-diarylimidazoles. The two new compounds [(η5 -C5 H5 )2 TiMe(µ-mba)Au(NHC)] (where NHC=1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene, NHC-Bn 2 a; or 1,3-diethyl-4,5-diphenylimidazol-2-ylidene, NHC-Et 2 b) with the dual linker (-OC(O)-p-C6 H4 -S-) containing both a carboxylate and a thiolate group were evaluated in vitro against renal and prostate cancer cell lines. The compounds were found to be more cytotoxic than previously described Ti-Au compounds containing non-optimized gold(I)-N-heterocyclic fragments. We present studies to evaluate their effects on cell death pathways, migration, inhibition of thioredoxin reductase (TrxR) and vascular endothelial growth factor (VEGF) in the PC3 prostate cancer cell line. The results show that the incorporation of a second metallic fragment such as titanocene into biologically active gold(I) compounds improves their pharmacological profile.

Trastuzumab gold-conjugates: synthetic approach and in vitro evaluation of anticancer activities in breast cancer cell lines.

We describe the preparation of gold(i)-compounds that are amenable to efficient bioconjugation with monoclonal antibodies via activated ester or maleimide linkers. New Trastuzumab-gold conjugates were synthesized and fully characterized. These bioconjugates are significantly more cytotoxic (sub-micromolar range) to HER2-positive breast cancer cells than the gold complexes and Trastuzumab.

Customizing Morphology, Size, and Response Kinetics of Matrix Metalloproteinase-Responsive Nanostructures by Systematic Peptide Design.

Overexpression and activation of matrix metalloproteinase-9 (MMP-9) is associated with multiple diseases and can serve as a stimulus to activate nanomaterials for sensing and controlled release. In order to achieve autonomous therapeutics with improved space-time targeting capabilities, several features need to be considered beyond the introduction of an enzyme-cleavable linker into a nanostructure. We introduce guiding principles for a customizable platform using supramolecular peptide nanostructures with three modular components to achieve tunable kinetics and morphology changes upon MMP-9 exposure. This approach enables (1) fine-tuning of kinetics through introduction of ordered/disordered structures, (2) a 12-fold variation in hydrolysis rates achieved by electrostatic (mis)matching of particle and enzyme charge, and (3) selection of enzymatic reaction products that are either cell-killing nanofibers or disintegrate. These guiding principles, which can be rationalized and involve exchange of just a few amino acids, enable systematic customization of enzyme-responsive peptide nanostructures for general use in performance optimization of enzyme-responsive materials.