Heparan sulfate proteoglycan-mediated entry pathway for charged tri-platinum compounds: differential cellular accumulation mechanisms for platinum

A Comparison of Di- and Trinuclear Platinum Complexes Interacting with Glycosaminoglycans for Targeted Chemotherapy

Heparan sulfate proteoglycans (HSPGs) and their associated proteins aid in tumor progression through modulation of biological events such as cell invasion, angiogenesis, metastasis, and immunological responses. Metalloshielding of the anionic heparan sulfate (HS) chains by cationic polynuclear platinum complexes (PPCs) prevents the HS from interacting with HS-associated proteins and thus diminishes the critical functions of HSPG. Studies herein exploring the PPC-HS interactions demonstrated that a series of PPCs varying in charge, nuclearity, distance between Pt centers, and hydrogen-bonding ability influence HS affinity. We report that the polyamine-linked complexes have high HS affinity and display excellent in vivo activity against breast cancer metastases and those arising in the bone and liver compared to carboplatin. Overall, the PPC-HS niche offers an attractive approach for targeting HSPG-expressing tumor cells.

Probing Disaccharide Binding to Triplatin as Models for Tumor Cell Heparan Sulfate (GAG) Interactions

In this study, we have used [1H, 15N] NMR spectroscopy to investigate the interactions of the trinuclear platinum anticancer drug triplatin (1) (1,0,1/t,t,t or BBR3464) with site-specific sulfated and carboxylated disaccharides. Specifically, the disaccharides GlcNS(6S)-GlcA (I) and GlcNS(6S)-IdoA(2S) (II) are useful models of longer-chain glycosaminoglycans (GAGs) such as heparan sulfate (HS). For both the reactions of 15N-1 with I and II, equilibrium conditions were achieved more slowly (65 h) compared to the reaction with the monosaccharide GlcNS(6S) (9 h). The data suggest both carboxylate and sulfate binding of disaccharide I to the Pt with the sulfato species accounting for <1% of the total species at equilibrium. The rate constant for sulfate displacement of the aqua ligand (kL2) is 4 times higher than the analogous rate constant for carboxylate displacement (kL1). There are marked differences in the equilibrium concentrations of the chlorido, aqua, and carboxy-bound species for reactions with the two disaccharides, notably a significantly higher concentration of carboxylate-bound species for II, where sulfate-bound species were barely detectable. The trend mirrors that reported for the corresponding dinuclear platinum complex 1,1/t,t, where the rate constant for sulfate displacement of the aqua ligand was 3 times higher than that for acetate. Also similar to what we observed for the reactions of 1,1/t,t with the simple anions, aquation of the sulfato group is rapid, and the rate constant k-L2 is 3 orders of magnitude higher than that for displacement of the carboxylate (k-L1). Molecular dynamics calculations suggest that extra hydrogen-bonding interactions with the more sulfated disaccharide II may prevent or diminish sulfate binding of the triplatin moiety. The overall results suggest that Pt-O donor interactions should be considered in any full description of platinum complex cellular chemistry.

Glycosaminoglycan-directed cobalt complexes

The biological activity of the 6+ Co containing Werner's Complex has been described and mechanistic considerations suggest that the highly anionic glycosaminoglycans (heparan sulfate, HS, GAGs) are implicated in this activity [Paiva et al. 2021]. To examine in detail the molecular basis of Werner's Complex biological properties we have examined a selection of simple mononuclear Co3+ compounds for their interactions with HS and Fondaparinux (FPX). FPX is a highly sulfated synthetic pentasaccharide used as a model HS substrate [Mangrum et al. 2014, Peterson et al. 2017]. The Co complexes were chosen to be formally substitution-inert and/or have the potential for covalent binding to the biomolecule. Using both indirect competitive inhibition assays and direct mass spectrometric assays, formally substitution-inert complexes bound to FPX with protection from multiple sulfate loss in the gas phase through metalloshielding. Covalent binding of Co-Cl complexes as in [CoCl(NH3)5]2+ and cis-[CoCl2(en)2]+ was confirmed by mass spectrometry. Interestingly, the former complex was shown to be an effective inhibitor of bacterial heparinase enzyme activity and to inhibit heparanase-dependent cellular invasion through the extracellular matrix (ECM). Pursuing the theme of metalloglycomics, we have observed the hitherto unappreciated biological activity of the simple [CoCl(NH3)5]2+ compound, a staple of most inorganic chemistry lab curricula.

Exploitation of sulfated glycosaminoglycan status for precision medicine of Triplatin in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer lacking targetable biomarkers. TNBC is known to be most aggressive, and when metastatic is often drug resistant and uncurable. Biomarkers predicting response to therapy improve treatment decisions and allow personalized approaches for TNBC patients. This study explores sulfated glycosaminoglycan (sGAG) levels as a predictor of TNBC response to platinum therapy. sGAG levels were quantified in three distinct TNBC tumor models including cell line-derived, patient-derived xenograft (PDX) tumors, and isogenic models deficient in sGAG biosynthesis. The in vivo antitumor efficacy of Triplatin, a sGAG-directed platinum agent, was compared in these models to the clinical platinum agent, carboplatin. We determined that >40% of TNBC PDX tissue microarray samples have high levels of sGAGs. The in vivo accumulation of Triplatin in tumors as well as antitumor efficacy of Triplatin positively correlated with sGAG levels on tumor cells, whereas carboplatin followed the opposite trend. In carboplatin-resistant tumor models expressing high levels of sGAGs, Triplatin decreased primary tumor growth, reduced lung metastases, and inhibited metastatic growth in lungs, liver, and ovaries. sGAG levels served as a predictor of Triplatin sensitivity in TNBC. Triplatin may be particularly beneficial in treating patients with chemotherapy-resistant tumors who have evidence of residual disease after standard neoadjuvant chemotherapy. More effective neoadjuvant and adjuvant treatment will likely improve clinical outcome of TNBC.

On the Biology of Werner's Complex

Werner's Complex, as a cationic coordination complex (CCC), has hitherto unappreciated biological properties derived from its binding affinity to highly anionic biomolecules such as glycosaminoglycans (GAGs) and nucleic acids. Competitive inhibitor and spectroscopic assays confirm the high affinity to GAGs heparin, heparan sulfate (HS), and its pentasaccharide mimetic Fondaparinux (FPX). Functional consequences of this affinity include inhibition of FPX cleavage by bacterial heparinase and mammalian heparanase enzymes with inhibition of cellular invasion and migration. Werner's Complex is a very efficient condensing agent for DNA and tRNA. In proof-of-principle for translational implications, it is demonstrated to display antiviral activity against human cytomegalovirus (HCMV) at micromolar concentrations with promising selectivity. Exploitation of non-covalent hydrogen-bonding and electrostatic interactions has motivated the unprecedented discovery of these properties, opening new avenues of research for this iconic compound.

Antitumor substitution-inert polynuclear platinum complexes stabilize G-quadruplex DNA and suppress G-quadruplex-mediated gene expression

Anticancer substitution-inert polynuclear platinum(ii) complexes (SI-PPCs) effectively stabilize DNA G-quadruplexes (G4) and terminate DNA polymerization on templates containing G4-forming sequences.

Metal ions and the extracellular matrix in tumor migration

In this review, we explore the roles of divalent metal ions in structure and function within the extracellular matrix (ECM), specifically, their interaction with glycosaminoglycans (GAGs) during tumor progression. Metals and GAGs have been individually associated with physiological and pathological processes, however, their combined activities in regulating cell behavior and ECM remodeling have not been fully explored to date. During tumor progression, divalent metals and GAGs participate in central processes, such as cell migration and angiogenesis, either by modulating cell surface molecules, as well as soluble signaling factors. In addition, studies on metals and polysaccharides interactions have been of great value, as they provide structural information that can be correlated with function. Finally, we believe that understanding how metals are regulated in physiological and pathological conditions is paramount for the development of new treatment strategies, as well as diagnostic and exploratory tools.

Influence of geometric isomerism on the binding of platinum anticancer agents with phospholipids

Reported herein is a detailed NMR and DFT study of the interaction of the 15N-labelled dinuclear platinum anticancer compound [{cis-PtCl(NH3)2}2{μ-H2N(CH2)6NH2}]2+ (15N-1, 1,1/c,c) with 1,2-dihexanoyl-sn-glycero-3-phosphate (DHPA), as a comparison with an earlier study of the interaction of the same water-soluble phospholipid fragment with the geometric trans isomer (1,1/t,t). The reaction of 15N-1 with the sodium salt of DHPA was studied at 298 K, pH ∼ 5.6, by [1H,15N] HSQC 2D NMR spectroscopy. The NMR data, supported by DFT models, provide evidence that the monofunctional DHPA adduct of 15N-1 exists in two conformational forms, with different orientation of the (CH2)6 linker; one has an interaction between the unbound {PtN3Cl} moiety and the coordinated DHPA molecule. Similarly, two bifunctional adduct conformers are identified, in which one has an interaction between the phosphate groups of the two bound DHPA molecules. When compared to the previously reported reactions of 1,1/t,t with DHPA, equilibrium conditions of the 1,1/c,c reaction are reached more slowly (120 h), similar to the reaction with phosphate. The rate constant for the first step of DHPA binding (kL) is slightly lower (1.6 fold) for the cis-compared to the trans-isomer, whereas the rate constant for the reverse reaction is 4-fold lower, resulting in a much greater proportion of DHPA bound species at equilibrium.

Substitution-Inert Polynuclear Platinum Complexes with Dangling Amines: Condensation/Aggregation of Nucleic Acids and Inhibition of DNA-Related Enzymatic Activities

The substitution-inert polynuclear platinum complexes (SI-PPCs) are now recognized as a distinct subclass of platinum anticancer drugs with high DNA binding affinity. Here, we investigate the effects of SI-PPCs containing dangling amine groups in place of NH₃ as ligands to increase the length of the molecule and therefore overall charge and its distribution. The results obtained with the aid of biophysical techniques, such as total intensity light scattering, gel electrophoresis, and atomic force microscopy, show that addition of dangling amine groups considerably augments the ability of SI-PPCs to condense/aggregate nucleic acids. Moreover, this enhanced capability of SI-PPCs correlates with their heightened efficiency to inhibit DNA-related enzymatic activities, such as those connected with DNA transcription, catalysis of DNA relaxation by DNA topoisomerase I, and DNA synthesis catalyzed by Taq DNA polymerase. Thus, the addition of the dangling amine groups resulting in structures of SI-PPCs, which differ so markedly from the derivatives of cisplatin used in the clinic, appears to contribute to the overall biological activity of these molecules.

Substitution-Inert Polynuclear Platinum Complexes Act as Potent Inducers of Condensation/Aggregation of Short Single- and Double-Stranded DNA and RNA Oligonucleotides

Compounds condensing DNA and RNA molecules can essentially affect important biological processes including DNA replication and transcription. Here, this work shows with the aid of total intensity light scattering, gel electrophoresis, and atomic force microscopy (AFM) that the substitution-inert polynuclear platinum complexes (SI-PPCs), particularly [{trans-Pt(NH₃ )₂ (NH₂ (CH₂ )₆ - NH₃ ⁺ )}₂ -μ-{trans-Pt(NH₃ )₂ (NH₂ (CH₂ )₆ NH₂ )₂ }]⁸⁺ (Triplatin NC), exhibit an unprecedented high potency to condense/aggregate fragments of DNA and RNA as short as 20 base pairs. SI-PPCs condensates are distinctive from those generated by the naturally occurring polyamines (commonly used DNA compacting/condensing agents). Collectively, the results further confirm that SI-PPCs are very efficient inducers of condensation of DNA and RNA, including their short fragments that might have potential in gene therapy, biotechnology, and bionanotechnology. Moreover, the data confirm the structural advantages of the phosphate clamp, with a well-defined rigid DNA recognition motif in initiating condensation and aggregation phenomena on oligonucleotides.

Glycans as Ligands in Bioinorganic Chemistry. Probing the Interaction of a Trinuclear Platinum Anticancer Complex with Defined Monosaccharide Fragments of Heparan Sulfate

We report herein a detailed NMR study of the aquation and subsequent covalent binding of the trinuclear clinical agent [{ trans-PtCl(¹⁵NH₃)₂}₂{μ- trans-Pt(¹⁵NH₃)₂(¹⁵NH₂(CH₂)₆¹⁵NH₂)₂}]⁴⁺ (1, 1,0,1/ t, t, t or Triplatin) with three d-glucosamine residues containing varied O-sulfate and N-sulfate or N-acetyl substitutions, which represent monosaccharide fragments present within the repeating disaccharide sequences of cell surface heparan sulfate (HS). The monosaccharides GlcNS(6S), GlcNS, and GlcNAc(6S) were synthesized in good yield from a common 4,6-diol α-methyl glucopyranoside intermediate. The reactions of ¹⁵N-1 with sodium sulfate, GlcNS(6S), GlcNS, and GlcNAc(6S) were followed by 2D [¹H,¹⁵N] heteronuclear single quantum coherence (HSQC) NMR spectroscopy using conditions (298 K, pH ≈5.4) similar to those previously used for other anionic systems, allowing for a direct comparison. The equilibrium constants (p K₁) for the aquation of 1 in the presence of GlcNS(6S) and GlcNS were slightly higher compared to that of the aquation in a sulfate solution, while a comparable p K₁ value was observed in the presence of GlcNAc(6S). A comparison of the rate constants for sulfate displacement of the aqua ligand showed preferential binding to 2- N-sulfate compared to 6- O-sulfate but a more rapid liberation. For disulfated GlcNS(6S), equilibrium conditions were achieved rapidly (9 h) and strongly favored the dichloro form, with <2% sulfato species observed. The value of k_L1 was up to 15-fold lower than that for binding to sulfate, whereas the rate constant for the reverse ligation ( k_-L1) was comparable. Equilibrium conditions were achieved much more slowly (∼ 100 h) for the reactions of 1 with GlcNS and GlcNAc(6S), attributed to covalent binding also to the N-donor of the sulfamate (GlcNS) group and the O-donor of the N-acetyl [GlcNAc(6S)] group. The rate constants ( k_L2) were 20-40-fold lower than that for binding to the 2- N- or 6- O-sulfate, but the binding was less reversible, so that their equilibrium concentrations (5-8%) were comparable to the 2- N- or 6- O-sulfate-bound species. The results emphasize the relevance of glycans in bioinorganic chemistry and underpin a fundamental molecular description of the HS-Pt interactions that alter the profile of platinum agents from cytotoxic to metastatic in a systematic manner.

Comparison of Metal-Ammine Compounds Binding to DNA and Heparin. Glycans as Ligands in Bioinorganic Chemistry

We present spectroscopic and biophysical approaches to examine the affinity of metal-ammine coordination complexes for heparin as a model for heparan sulfate (HS). Similar to nucleic acids, the highly anionic nature of heparin means it is associated in vivo with physiologically relevant cations, and this work extends their bioinorganic chemistry to substitution-inert metal-ammine compounds (M). Both indirect and direct assays were developed. M compounds are competitive inhibitors of methylene blue (MB)-heparin binding, and the change in the absorbance of the dye in the presence or absence of heparin can be used as an indirect reporter of M-heparin affinity. A second indirect assay uses the change in fluorescence of TAMRA-R₉, a nonaarginine linked to a fluorescent TAMRA moiety, as a reporter for M-heparin binding. Direct assays are surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). The K_d values for TriplatinNC-heparin varied to some extent depending on the technique from 33.1 ± 2 nM (ITC) to 66.4 ± 1.3 nM (MB absorbance assay) and 340 ± 30 nM (SPR). The differences are explained by the nature of the technique and the use of heparin of differing molecular weight. Indirect probes using the displacement of ethidium bromide from DNA or, separately, fluorescently labeled oligonucleotide (DNA-Fl) can measure the relative affinities of heparin and DNA for M compounds. These assays showed essentially equivalent affinity of TriplatinNC for heparin and DNA. The generality of these methods was confirmed with a series of mononuclear cobalt, ruthenium, and platinum compounds with significantly lower affinity because of their smaller overall positive charge but in the order [Co(NH₃)₆]³⁺ > [Ru(NH₃)₆]³⁺ > [Pt(NH₃)₄]²⁺. The results on heparin can be extrapolated to glycosoaminoglycans such as HS, emphasizing the relevance of glycan interactions in understanding the biological properties of coordination compounds and the utility of the metalloglycomics concept for extending bioinorganic chemistry to this class of important biomolecules.

A Novel Pseudo-Protein-Based Biodegradable Nanomicellar Platform for the Delivery of Anticancer Drugs

Amino acid-based poly(ester amide)s are a new family of biodegradable polymers that exhibit "pseudo-protein" characteristics and the structural varieties of poly(ester amide)s make them hold great potential in multiple biomedical applications. In this study, a lysine-phenylalanine-based pseudo-protein is developed as the self-assembled nanomicellar carrier for efficient delivery of doxorubicin. The lysine moieties from the pseudo-protein provide available sites for further functionalization, and methylcoumarin is introduced for easy and photocontrollable crosslinking, to effectively improve the micellar stability in serum containing environment and against dilution. However, photocrosslinks do not bring in any barrier for the intracellular release of doxoubicin. Doxorubicin release is significantly accelerated by proteolytic enzyme, due to the biodegradability of pseudo-protein micelles. In addition, pseudo-protein delivery system exhibits unique interactions with HCT116 human colon cancer cells. Doxorubicin loaded in pseudo-protein micelles colocalizes with mitochondria and endolysosomes, while free doxorubicin is distributed only in the nuclei. Doxorubicin-loaded pseudo-protein micelles stimulate increased level of intracellular reactive oxygen species and mitochondrial damage. Free doxorubicin induces conditional apoptosis in HCT116 cells between 0.5× 10^-6 and 2 × 10^-6 m, while DOX loaded in pseudo-protein micelles induces apoptosis over a higher/broader concentration range (2 × 10^-6 -10 × 10^-6 m).

Modular sub-monomeric cell-penetrating guanidine-rich peptoids – synthesis, assembly and biological evaluation

Development of a guanidinium-rich transporters toolset to study GAG-mediated cell permeation.

Antiangiogenic platinum through glycan targeting

Heparan sulfate is identified as a ligand receptor for polynuclear platinum anti-cancer agents through sulfate cluster binding. We present a new biological role for platinum and coordination compounds and a new target for metal-based drugs while presenting a new chemotype for heparanase and growth factor inhibition through modulation (metalloshielding) of their interactions. Masking of extracellular (ECM)-resident heparan sulfate (HS) through metalloshielding results in very effective inhibition of physiologically critical HS functions including enzyme (heparanase, HPSE) and protein growth factor recognition. The interaction of the highly cationic polynuclear platinum complexes (PPCs) with the highly sulfated pentasaccharide Fondaparinux (FPX, in this case as a model HS-like substrate) results in inhibition of its cleavage by the HS-related enzyme heparanase. Binding of the fibroblast growth factor FGF-2 to HS is also inhibited with consequences for downstream signalling events as measured by a reduction in accumulation of phospho-S6 ribosomal protein in human colon tumor HCT-116 cells. The end-point of inhibition of HPSE activity and growth factor growth factor signaling is the prevention of cell invasion and angiogenesis. Finally these events culminate in inhibition of HCT-116 cell invasion at sub-cytotoxic concentrations and the process of angiogenesis. A competition assay shows that Fondaparinux can sequester the 8+ TriplatinNC from bound DNA, emphasising the strength of PPC-HS interactions. Altering the profile of platinum agents from cytotoxic to anti-metastatic has profound implications for future directions in the development of platinum-based chemotherapeutics.

A Photoactivatable Platinum(IV) Anticancer Complex Conjugated to the RNA Ligand Guanidinoneomycin

A photoactivatable platinum(IV) complex, trans,trans,trans-[Pt(N3 )2 (OH)(succ)(py)2 ] (succ=succinylate, py=pyridine), has been conjugated to guanidinoneomycin to study the effect of this guanidinum-rich compound on the photoactivation, intracellular accumulation and phototoxicity of the pro-drug. Surprisingly, trifluoroacetic acid treatment causes the replacement of an azido ligand and the axial hydroxide ligand by trifluoroacetate, as shown by NMR spectroscopy, MS and X-ray crystallography. Photoactivation of the platinum-guanidinoneomycin conjugate in the presence of 5'-guanosine monophosphate (5'-GMP) led to the formation of trans-[Pt(N3 )(py)2 (5'-GMP)](+) , as does the parent platinum(IV) complex. Binding of the platinum(II) photoproduct {PtN3 (py)2 }(+) to guanine nucleobases in a short single-stranded oligonucleotide was also observed. Finally, cellular uptake studies showed that guanidinoneomycin conjugation improved the intracellular accumulation of the platinum(IV) pro-drug in two cancer cell lines, particularly in SK-MEL-28 cells. Notably, the higher phototoxicity of the conjugate in SK-MEL-28 cells than in DU-145 cells suggests a degree of selectivity towards the malignant melanoma cell line.

Multi-platinum anti-cancer agents. Substitution-inert compounds for tumor selectivity and new targets

Substitution-inert polynuclear platinum complexes are inherently dual-function anti-cancer agents combining extra and intra-cellular effects in one structural chemotype.

Agrin and perlecan mediate tumorigenic processes in oral squamous cell carcinoma

Oral squamous cell carcinoma is the most common type of cancer in the oral cavity, representing more than 90% of all oral cancers. The characterization of altered molecules in oral cancer is essential to understand molecular mechanisms underlying tumor progression as well as to contribute to cancer biomarker and therapeutic target discovery. Proteoglycans are key molecular effectors of cell surface and pericellular microenvironments, performing multiple functions in cancer. Two of the major basement membrane proteoglycans, agrin and perlecan, were investigated in this study regarding their role in oral cancer. Using real time quantitative PCR (qRT-PCR), we showed that agrin and perlecan are highly expressed in oral squamous cell carcinoma. Interestingly, cell lines originated from distinct sites showed different expression of agrin and perlecan. Enzymatically targeting chondroitin sulfate modification by chondroitinase, oral squamous carcinoma cell line had a reduced ability to adhere to extracellular matrix proteins and increased sensibility to cisplatin. Additionally, knockdown of agrin and perlecan promoted a decrease on cell migration and adhesion, and on resistance of cells to cisplatin. Our study showed, for the first time, a negative regulation on oral cancer-associated events by either targeting chondroitin sulfate content or agrin and perlecan levels.

Nucleolar targeting by platinum: p53-independent apoptosis follows rRNA inhibition, cell-cycle arrest, and DNA compaction

TriplatinNC is a highly positively charged, substitution-inert derivative of the phase II clinical anticancer drug, BBR3464. Such substitution-inert complexes form a distinct subset of polynuclear platinum complexes (PPCs) interacting with DNA and other biomolecules through noncovalent interactions. Rapid cellular entry is facilitated via interaction with cell surface glycosoaminoglycans and is a mechanism unique to PPCs. Nanoscale secondary ion mass spectrometry (nanoSIMS) showed rapid distribution within cytoplasmic and nucleolar compartments, but not the nucleus. In this article, the downstream effects of nucleolar localization are described. In human colon carcinoma cells, HCT116, the production rate of 47S rRNA precursor transcripts was dramatically reduced as an early event after drug treatment. Transcriptional inhibition of rRNA was followed by a robust G₁ arrest, and activation of apoptotic proteins caspase-8, -9, and -3 and PARP-1 in a p53-independent manner. Using cell synchronization and flow cytometry, it was determined that cells treated while in G₁ arrest immediately, but cells treated in S or G₂ successfully complete mitosis. Twenty-four hours after treatment, the majority of cells finally arrest in G₁, but nearly one-third contained highly compacted DNA; a distinct biological feature that cannot be associated with mitosis, senescence, or apoptosis. This unique effect mirrored the efficient condensation of tRNA and DNA in cell-free systems. The combination of DNA compaction and apoptosis by TriplatinNC treatment conferred striking activity in platinum-resistant and/or p53 mutant or null cell lines. Taken together, our results support that the biological activity of TriplatinNC reflects reduced metabolic deactivation (substitution-inert compound not reactive to sulfur nucleophiles), high cellular accumulation, and novel consequences of high-affinity noncovalent DNA binding, producing a new profile and a further shift in the structure–activity paradigms for antitumor complexes.

Substitution-inert trinuclear platinum complexes efficiently condense/aggregate nucleic acids and inhibit enzymatic activity

The trinuclear platinum complexes (TriplatinNC-A [{Pt(NH3 )3 }2 -μ-{trans-Pt(NH3 )2 (NH2 (CH2 )6 NH2 )2 }](6+) , and TriplatinNC [{trans-Pt(NH3 )2 (NH2 (CH2 )6 NH3 (+) )}2 -μ-{trans-Pt(NH3 )2 (NH2 (CH2 )6 NH2 )2 }](8+) ) are biologically active agents that bind to DNA through noncovalent (hydrogen bonding, electrostatic) interactions. Herein, we show that TriplatinNC condenses DNA with a much higher potency than conventional DNA condensing agents. Both complexes induce aggregation of small transfer RNA molecules, and TriplatinNC in particular completely inhibits DNA transcription at lower concentrations than naturally occurring spermine. Topoisomerase I-mediated relaxation of supercoiled DNA was inhibited by TriplatinNC-A and TriplatinNC at concentrations which were 60 times and 250 times lower than that of spermine. The mechanisms for the biological activity of TriplatinNC-A and TriplatinNC may be associated with their ability to condense/aggregate nucleic acids with consequent inhibitory effects on crucial enzymatic activities.

A new approach to glycan targeting: enzyme inhibition by oligosaccharide metalloshielding

Metalloglycomics - the effects of defined coordination compounds on oligosaccharides and their structure and function - opens new areas for bioinorganic chemistry and expands its systematic study to the third major class of biomolecules after DNA/RNA and proteins.

Dinuclear platinum complexes containing planar aromatic ligands to enhance stacking interactions with proteins

In an approach to design drugs with higher affinity for π-π stacking and electrostatic interactions with targeted biomolecules, complexes of the type [{cis-Pt(A)2 (L)}2 -μ-{trans-1,4-dach}](NO3 )4 ((A)2 =(NH3 )2 or ethylenediamine (en), L=quinoline (quin) or benzothiazole (bztz), dach=trans-1,4-diaminocyclohexane) were synthesized. The quinoline complex, [{cis-Pt(en)(quin)}2 -μ-(dach)](NO3 )4 (9) was synthesized from the precursor K[PtCl3 (quin)] (1), while the benzothiazole complexes, [{cis-Pt(A)2 (bztz)}2 -μ-(dach)](NO3 )4 ((A)2 =(NH3 )2 (10) and (A)2 =en (11)) were synthesized from the precursors cis-[Pt(A)2 Cl(bztz)] ((A)2 =(NH3 )2 (7) and (A)2 =en (8)). Their interactions with N-acetyltryptophan and a model pentapeptide (N-Ac-WLDSW-OH), modeled on the pentapeptide recognition sequence (FSDLW) of p53-mdm2 interaction, were examined by fluorescence spectroscopy. The dinuclear complexes were found to be significantly stronger at quenching the fluorescence of tryptophan than their mononuclear Pt-based analogues indicating stronger binding. Molecular modeling suggests a "sandwich" mode of binding, and the flexibility of the dinuclear motif can allow the design of more selective and stronger-binding complexes. Based on these results a further prototype, [{Pt(en)(9-EtGua)}2 μ-H2 N(CH2 )6 NH2 ](4+) , incorporating the purine 9-ethylguanine (9-EtG) as a stacking moiety, was prepared which showed good cytotoxicity in A2780 and OsACL tumor cell lines.

NanoSIMS multi-element imaging reveals internalisation and nucleolar targeting for a highly-charged polynuclear platinum compound

Simultaneous multi-element imaging using NanoSIMS (nano-scale secondary ion mass spectrometry), exploiting the novel combination of (195)Pt and (15)N in platinum-am(m)ine antitumour drugs, provides information on the internalisation and subcellular localisation of both metal and ligands, and allows identification of ligand exchange.

Multinuclear ruthenium(ii) complexes as anticancer agents

The dinuclear ruthenium complex with X = H is four-times more cytotoxic than cisplatin against breast cancer cell lines; however, when X = NO₂ the ruthenium complex is less active than cisplatin.

Polymeric nanoparticles with sequential and multiple FRET cascade mechanisms for multicolor and multiplexed imaging

The ability to map multiple biomarkers at the same time has far-reaching biomedical and diagnostic applications. Here, a series of biocompatible poly(D,L-lactic-co-glycolic acid) and polyethylene glycol particles for multicolor and multiplexed imaging are reported. More than 30 particle formulations that exhibit distinct emission signatures (ranging from the visible to NIR wavelength region) are designed and synthesized. These particles are encapsulated with combinations of carbocyanine-based fluorophores DiO, Dil, DiD, and DiR, and are characterized as <100 nm in size and brighter than commercial quantum dots. A particle formulation is identified that simultaneously emits fluorescence at three different wavelengths upon a single excitation at 485 nm via sequential and multiple FRET cascade events for multicolor imaging. Three other particles that display maximum fluorescence intensities at 570, 672, or 777 nm for multiplexed imaging are also identified. These particles are individually conjugated with specific (Herceptin or IgG2A11 antibody) or nonspecific (heptaarginine) ligands for targeting and, thus, could be applied to differentiate different cancer cells from a cell mixture according to the expressions of cell-surface human epidermal growth factor receptor 2 and the receptor for advanced glycation endproducts. Using an animal model subcutaneously implanted with the particles, it is further demonstrated that the developed platform could be useful for in vivo multiplexed imaging.

Platinum and Palladium Polyamine Complexes as Anticancer Agents: The Structural Factor

Since the introduction of cisplatin to oncology in 1978, Pt(II) and Pd(II) compounds have been intensively studied with a view to develop the improved anticancer agents. Polynuclear polyamine complexes, in particular, have attracted special attention, since they were found to yield DNA adducts not available to conventional drugs (through long-distance intra- and interstrand cross-links) and to often circumvent acquired cisplatin resistance. Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly regulated by their structural characteristics, which renders this series of compounds worth investigating and their synthesis being carefully tailored in order to develop third-generation drugs coupling an increased spectrum of activity to a lower toxicity. The present paper addresses the latest developments in the design of novel antitumor agents based on platinum and palladium, particularly polynuclear chelates with variable length aliphatic polyamines as bridging ligands, highlighting the close relationship between their structural preferences and cytotoxic ability. In particular, studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate the structure-activity relationships (SARs) ruling anticancer activity.