Encapsulating antibiotics such as rifampicin in biodegradable nanoparticles provides several advantages compared to free drug administration, including reduced dosing due to localized targeting and sustained release. Consequently, these characteristics reduce systemic drug toxicity. However, new nanoformulations need to be tested in complex biological systems to fully characterize their potential for improved drug therapy. Tuberculosis, caused by infection with the bacterium Mycobacterium tuberculosis, requires lengthy and expensive treatment, and incomplete therapy contributes to an increasing incidence of drug resistance. Recent evidence suggests that standard therapy may be improved by combining antibiotics with bacterial efflux pump inhibitors, such as thioridazine. However, this drug is difficult to use clinically due to its toxicity. Here, we encapsulated thioridazine in poly(lactic-co-glycolic) acid nanoparticles and tested them alone and in combination with rifampicin nanoparticles, or free rifampicin in macrophages and in a zebrafish model of tuberculosis. Whereas free thioridazine was highly toxic in both cells and zebrafish embryos, after encapsulation in nanoparticles no toxicity was detected. When combined with rifampicin nanoparticles, the nanoparticles loaded with thioridazine gave a modest increase in killing of both Mycobacterium bovis BCG and M. tuberculosis in macrophages. In the zebrafish, the thioridazine nanoparticles showed a significant therapeutic effect in combination with rifampicin by enhancing embryo survival and reducing mycobacterial infection. Our results show that the zebrafish embryo is a highly sensitive indicator of drug toxicity and that thioridazine nanoparticle therapy can improve the antibacterial effect of rifampicin in vivo.

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Human galectin-3 (hGal-3) is a mammalian lectin involved in regulation of RNA splicing, apoptosis, cell differentiation, and proliferation. Multimerized extracellular hGal-3 is thought to crosslink cells by binding to glycoproteins and glycosylated cancer antigens on the cell surface or extracellular matrix. Fluorescence spectroscopy and circular dichroism were used to study the interaction of hGal-3 with two anticancer agents: bohemine and Zn porphyrin (ZnTPPS(4)). The dissociation constant (k(D)) for binding of bohemine with hGal-3 was k(D) 0.23+/-0.05 microM. The hyperbolic titration curve indicated the presence of a single bohemine binding site. The binding of ZnTPPS(4) to hGal-3 (with and without lactose) is of high affinity having k(D)=0.18-0.20 microM and is not inhibited by lactose, indicating that ZnTPPS(4) and carbohydrate bind different sites. Circular dichroism spectra of the hGal-3 complexes suggested that the binding of the hydrophobic compounds changed the hGal-3 secondary structure. In summary, we show that two compounds with anticancer activity, bohemine and ZnTPPS(4), have high affinity for hGal-3 at a site that is distinct from its carbohydrate site. Since hGal-3 binds to several carbohydrate cancer antigens, the results suggest that it may have utility in the targeted delivery of drugs for cancer.

The present work shows a novel binding activity of the tumor specific lectin--recombinant human galectin-1 (hGal-1)--to three porphyrin compounds: (1) Zn-porphyrin (ZnTPPS); (2) Mn-porphyrin and (3) Au-porphyrin. These compounds are widely applied in the photodynamic therapy of cancer (PDT). Our data indicate that hGal-1, similar to some plant lectins, a bacterial lectin from Pseudomonas aeruginosa and an animal lectin from Helix pomatia, possesses dual functions binding to both carbohydrate and non-carbohydrate ligands. The interaction of ZnTPPS with hGal-1 was studied by the specific fluorescence emission of the porphyrin. The protein binding properties to Mn/Au-porphyrins and adenine were measured by intrinsic protein fluorescence quenching. The values determined for the apparent dissociation constants (K(D)) of 0.6-1.5 microM are similar to the K(D) for complexes of concanavalin A and porphyrin, and are indicative of the high affinity of hGal-1 for these porphyrins. In addition, the analysis of the hyperbolic binding curves obtained suggests the presence of one hGal-1 binding site for porphyrins or adenine. Additionally, we found that hGal-1 interacts with the fluorescent probe 2-(p-toluidinyl)naphthalene sulfonic acid (TNS), that was used to identify the hydrophobic regions within hGal-1. Homodimeric hGal-1 has more than one class of binding site for TNS as revealed by the sigmoidal shape of the fluorescence titration curve. hGal-1 can be characterized as a porphyrin-binding protein based on its interactions with the Zn/Mn- and Au-porphyrins, and this indicates that hGal-1 may have potential as a delivery molecule to target systems (e.g., tumor cells) with possible application in photodynamic therapy.

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Many anticancer drugs cannot recognize selectively tumor tissues, and cause destruction to normal ones. Although it is very toxic, cisplatin is still one of the most applied chemotherapeutics used for treatment of sarcomas, carcinomas, etc. It causes severe side effects as a result of the lack of selectivity of the drug to tumor tissue and acquired or intrinsic resistance occurs. Wheat germ agglutinin (WGA) is a lectin that specifically recognizes transformed cells: prostate cancer cells, pancreatic cells etc., and is uptaken into the tumor cells for which it appears to be a suitable target for anticancer agents. A fluorescence spectroscopy method was used to study the interaction of WGA with four metal-based anticancer drugs: cisplatin, Pt porphyrin and two gold porphyrins. The affinity constant (k(D)) for binding of cisplatin with WGA was k(D) = 6.67 ± 2.5 μM. The hyperbolic curve indicated the presence of a single cisplatin binding site. The affinity of Au and Pt porphyrin to WGA (k(D) = 0.08-0.49 μM) is almost two orders of magnitude higher than that for cisplatin. We found that Pt porphyrin could displace fluorescent dye ANS showing an increase in the fluorescence intensity with a concomitant blue shift of the emission maximum suggesting that the compounds accommodate the same binding site. Current research characterizes the metalloanticancer binding capacity of WGA. Our results indicate that four metal-based anticancer agents have high affinity for WGA. Since WGA recognizes transformed cells, the obtained data show that this protein might have putative usage as a drug delivery molecule in cancer.