Folate binding protein: therapeutic natural nanotechnology for folic acid, methotrexate, and leucovorin

Anti-tumor Effect of Folate-Binding Protein: In Vitro and In Vivo Studies

Folate receptor (FR) overexpression in a wide range of solid tumors provides an opportunity to develop novel, targeted cancer therapeutics. In this study, we investigated whether prebinding the chemotherapeutic methotrexate (MTX) to folate-binding protein (FBP), the soluble form of FR, would enable the protein to serve as a targeted therapeutic vector, enhancing uptake into tumor cells and improving therapeutic efficacy. In an in vivo study, using an FR-overexpressing KB xenograft model in SCID mice, modest improvement in inhibiting tumor growth was observed for the MTX/FBP mixtures as compared to saline control and free MTX. Surprisingly, FBP alone inhibited tumor growth compared to saline control, free MTX, and FBP/MTX. In order to better understand this effect, we investigated the cytotoxicity of micromolar concentrations of FBP in vitro using the KB, HeLa, and A549 cancer cell lines. Our results revealed concentration-dependent apoptosis (24 h; 10-50 μM) in all three cell lines accompanied by a time- and concentration-dependent reduction (6, 12, and 24 h; 10-50 μM) in metabolic activity and compromised cell plasma membrane integrity. This study demonstrates an apoptosis pathway for cytotoxicity of FBP, an endogenous serum protein, in cancer cell lines with widely varying levels of FR expression. Furthermore, in vivo tumor growth suppression for xenograft KB tumors in SCID mice was observed. These studies suggest novel strategies for the elimination of cancer cells employing endogenous, serum transport proteins.

Molecular dynamics simulation study of doxorubicin adsorption on functionalized carbon nanotubes with folic acid and tryptophan

In this work, molecular dynamics (MD) simulation is used to study the adsorption of the anticancer drug, doxorubicin (DOX), on the wall or surface of pristine and functionalized carbon nanotubes (FCNTs) in an aqueous solution. Initially, the CNTs were functionalized by tryptophan (Trp) and folic acid (FA), and then the DOX molecules were added to the system. The simulation results showed that the drug molecules can intensely interact with the FCNTs at physiological pH. Furthermore, it was found that as a result of functionalization, the solubility of FCNTs in an aqueous solution increases significantly. The effect of pH variation on drug release from both pristine and FCNTs was also investigated. The obtained results indicated that in acidic environments due to protonation of functional groups (Trp) and as a result of repulsive interaction between the DOX molecule and functional groups, the release of DOX molecules from FCNT’s surface is facilitated. The drug release is also strongly dependent on the pH and protonated state of DOX and FCNT.

Unraveling the Effect of Breast Cancer Patients' Plasma on the Targeting Ability of Folic Acid-Modified Chitosan Nanoparticles

The formation of protein corona (PC) around nanoparticles (NPs) has been reported inside biological conditions. This effect can alter delivery capacity toward the targeted tissues. Here, we synthesized folic acid-modified chitosan NPs (FA-CS NPs) using different concentrations of folic acid (5, 10, and 20%). FA-CS NPs were exposed to plasmas of breast cancer patients and healthy donors to evaluate the possibility of PC formation. We also monitored uptake efficiency in in vitro conditions after incubation with human breast cancer cell line MDA-MB-231 and monocyte/macrophage-like Raw264.7 cells. Data showed that the formation of PC around FA-CS NPs can change physicochemical properties coincided with the rise in NP size and negative surface charge. SDS-PAGE electrophoresis revealed differences in the type and content rate of plasma proteins attached to NP surface in a personalized manner. Based on MTT data, the formation of PC around NPs did not exert cytotoxic effects on MDA-MB-231 cells while this phenomenon reduced uptake rate. Fluorescence imaging and flow cytometry analyses revealed reduced cellular internalization rate in NPs exposed to patients' plasma compared to the control group. In contrast to breast MDA-MB-231 cells, Raw264.7 cells efficiently adsorbed the bare and PC-coated NPs from both sources, indicating the involvement of ligand-receptor-dependent and independent cellular engulfment. These data showed that the PC formed on the FA-CS NPs is entirely different in breast cancer patients and healthy counterparts. PC derived from patients' plasma almost abolishes the targeting efficiency of FA-CS NPs even in different mechanisms, while this behavior was not shown in the control group. Surprisingly, Raw264.7 cells strongly adsorbed the PC-coated NPs, especially when these particles were in the presence of patients' sera. It is strongly suggested that the formation of PC around can affect delivering capacity of FA-CS NPs to cancer cells. It seems that the PC-coated FA-CS NPs can be used as an efficient delivery strategy for the transfer of specific biomolecules in immune system disorders.

Characterization of soluble folate receptors (folate binding proteins) in humans. Biological roles and clinical potentials in infection and malignancy

This review surveys soluble Folate Receptors (FOLRs) in humans. FOLR1 and FOLR2 are equipped with cellular glycosylphosphatidylinositol (GPI) anchors. FOLR1 is secreted from epithelia with or without a micelle-encapsulated GPI-anchor into milk and other body fluids/secretions, e.g. semen where its interaction with spermatozoa indicates a role in male fertility. FOLR1 and FOLR2 serve as serum biomarkers of various diseases. FOLR3 possesses no GPI-anchor and originates from secretory granules of neutrophil granulocytes; its concentration in serum correlates to the FOLR3 content in leukocytes and rises with increased leukocyte counts (infection, malignancy and pregnancy). FOLR3 exerts anti-microbial and anti-tumor effects by depriving bacteria and tumor cells of natural folates. Megalin receptors mediate reabsorption of ultrafiltered folate-bound FOLR into cells of proximal kidney tubules and of folate-bound FOLR uptake in growing embryos. Megalin receptors overexpressed in malignant tumors could be suitable therapeutic targets for folate-conjugated cytotoxic agents utilizing soluble FOLRs as vectors.

Application of rare earth-doped nanoparticles in biological imaging and tumor treatment

Rare earth-doped nanoparticles have been widely used in disease diagnosis, drug delivery, tumor therapy, and bioimaging. Among various bioimaging methods, the fluorescence imaging technology based on the rare earth-doped nanoparticles can visually display the cell activity and lesion evolution in living animals, which is a powerful tool in biological technology and has being widely applied in medical and biological fields. Especially in the band of near infrared (700–1700 nm), the emissions show the characteristics of deep penetration due to low absorption, low photon scattering, and low autofluorescence interference. Furthermore, the rare earth-doped nanoparticles can be endowed with the water solubility, biocompatibility, drug-loading ability, and the targeting ability for different tumors by surface functionalization. This confirms its potential in the cancer diagnosis and treatment. In this review, we summarized the recent progress in the application of rare earth-doped nanoparticles in the field of bioimaging and tumor treatment. The luminescent mechanism, properties, and structure design were also discussed.

Distributions: The Importance of the Chemist's Molecular View for Biological Materials

Characterization of materials with biological applications and assessment of physiological effects of therapeutic interventions are critical for translating research to the clinic and preventing adverse reactions. Analytical techniques typically used to characterize targeted nanomaterials and tissues rely on bulk measurement. Therefore, the resulting data represent an average structure of the sample, masking stochastic (randomly generated) distributions that are commonly present. In this Perspective, we examine almost 20 years of work our group has done in different fields to characterize and control distributions. We discuss the analytical techniques and statistical methods we use and illustrate how we leverage them in tandem with other bulk techniques. We also discuss the challenges and time investment associated with taking such a detailed view of distributions as well as the risks of not fully appreciating the extent of heterogeneity present in many systems. Through three case studies showcasing our research on conjugated polymers for drug delivery, collagen in bone, and endogenous protein nanoparticles, we discuss how identification and characterization of distributions, i.e., a molecular view of the system, was critical for understanding the observed biological effects. In all three cases, data would have been misinterpreted and insights missed if we had only relied upon spatially averaged data. Finally, we discuss how new techniques are starting to bridge the gap between bulk and molecular level analysis, bringing more opportunity and capacity to the research community to address the challenges of distributions and their roles in biology, chemistry, and the translation of science and engineering to societal challenges.

Targeted dual-mode imaging and phototherapy of tumors using ICG-loaded multifunctional MWCNTs as a versatile platform

ICG-loaded MWCNTs can be synthesized and used as a theranostic platform for targeted dual-mode imaging and phototherapy of tumors.

Conjugation Dependent Interaction of Folic Acid with Folate Binding Protein

Serum proteins play a critical role in the transport, uptake, and efficacy of targeted drug therapies, and here we investigate the interactions between folic acid-polymer conjugates and serum folate binding protein (FBP), the soluble form of the cellular membrane-bound folate receptor. We demonstrate that both choice of polymer and method of ligand conjugation affect the interactions between folic acid-polymer conjugates and serum FBP, resulting in changes in the folic acid-induced protein aggregation process. We have previously demonstrated that individual FBP molecules self-aggregate into nanoparticles at physiological concentrations. When poly(amidoamine) dendrimer-folic acid conjugates bound to FBP, the distribution of nanoparticles was preserved. However, the dendritic conjugates produced larger nanoparticles than those formed in the presence of physiologically normal human levels of folic acid, and the conjugation method affected particle size distribution. In contrast, poly(ethylene glycol)-folic acid conjugates demonstrated substantially reduced binding to FBP, did not cause folic acid-induced aggregation, and fully disrupted FBP self-aggregation. On the basis of these results, we discuss the potential implications for biodistribution, trafficking, and therapeutic efficacy of targeted nanoscale therapeutics, especially considering the widespread clinical use of poly(ethylene glycol) conjugates. We highlight the importance of considering specific serum protein interactions in the rational design of similar nanocarrier systems. Our results suggest that prebinding therapeutic nanocarriers to serum FBP may allow folate-specific metabolic pathways to be exploited for delivery while also affording benefits of utilizing an endogenous protein as a vector.