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Folic-acid-based radioconjugates have been developed for nuclear imaging of folate receptor (FR)-positive tumors; however, high renal uptake was unfavorable in view of a therapeutic application. Previously, it was shown that pre-injection of pemetrexed (PMX) increased the tumor-to-kidney ratio of radiofolates several-fold. In this study, PMX was combined with the currently best performing radiofolate ([177Lu]cm13), which is outfitted with an albumin-binding entity. Biodistribution studies were carried out in mice bearing KB or IGROV-1 tumor xenografts, both FR-positive tumor types. SPECT/CT was performed with control mice injected with [177Lu]folate only and with mice that received PMX in addition. Control mice showed high uptake of radioactivity in KB and IGROV-1 tumor xenografts, but retention in the kidneys was also high, resulting in tumor-to-kidney ratios of ~0.85 (4 h p.i.) and ~0.60 (24 h p.i.) or ~1.17 (4 h p.i.) and ~1.11 (24 h p.i.) respectively. Pre-injection of PMX improved the tumor-to-kidney ratio to values of ~1.13 (4 h p.i.) and ~0.92 (24 h p.i.) or ~1.79 (4 h p.i.) and ~1.59 (24 h p.i.), respectively, due to reduced uptake in the kidneys. It was found that a second injection of PMX—3 h or 7 h after administration of the radiofolate—improved the tumor-to-kidney ratio further to ~1.03 and ~0.99 or ~1.78 and ~1.62 at 24 h p.i. in KB and IGROV-1 tumor-bearing mice, respectively. SPECT/CT scans readily visualized the tumor xenografts, whereas accumulation of radioactivity in the kidneys was reduced in mice that received PMX. In this study, it was shown that PMX had a positive impact in terms of reducing the kidney uptake of albumin-binding radiofolates; hence, the administration of PMX resulted in ~1.3–1.7-fold higher tumor-to-kidney ratios. This is, however, a rather moderate effect in comparison to the previously shown effect of PMX on conventional radiofolates (without albumin binder), which led to 5–6-fold increased tumor-to-kidney ratios. An explanation for this result may be the different pharmacokinetic profiles of PMX and long-circulating radiofolates, respectively. Despite the promising potential of this concept, it is believed that a clinical translation would be challenging, particularly when PMX had to be injected more than once.

There is a large body of evidence to suggest that improving periconceptional folate status reduces the risk of neonatal neural tube defects. Thus increased folate intake is now recommended before and during the early stages of pregnancy, through folic acid supplements or fortified foods. Furthermore, there is growing evidence that folic acid may have a role in the prevention of other diseases, including dementia and certain types of cancer. Folic acid is a synthetic form of the vitamin, which is only found in fortified foods, supplements and pharmaceuticals. It lacks coenzyme activity and must be reduced to the metabolically active tetrahydrofolate form within the cell. L-5-methyl-tetrahydrofolate (L-5-methyl-THF) is the predominant form of dietary folate and the only species normally found in the circulation, and hence it is the folate that is normally transported into peripheral tissues to be used for cellular metabolism. L-5-methyl-THF is also available commercially as a crystalline form of the calcium salt (Metafolin®), which has the stability required for use as a supplement. Studies comparing L-5-methyl-THF and folic acid have found that the two compounds have comparable physiological activity, bioavailability and absorption at equimolar doses. Bioavailability studies have provided strong evidence that L-5-methyl-THF is at least as effective as folic acid in improving folate status, as measured by blood concentrations of folate and by functional indicators of folate status, such as plasma homocysteine. Intake of L-5-methyl-THF may have advantages over intake of folic acid. First, the potential for masking the haematological symptoms of vitamin B 12 deficiency may be reduced with L-5-methyl-THF. Second, L-5-methyl-THF may be associated with a reduced interaction with drugs that inhibit dihydrofolate reductase.

The radiolanthanide (161)Tb (T 1/2 = 6.90 days, Eβ(-) av = 154 keV) was recently proposed as a potential alternative to (177)Lu (T 1/2 = 6.71 days, Eβ(-) av = 134 keV) due to similar physical decay characteristics but additional conversion and Auger electrons that may enhance the therapeutic efficacy. The goal of this study was to compare (161)Tb and (177)Lu in vitro and in vivo using a tumour-targeted DOTA-folate conjugate (cm09). (161)Tb-cm09 and (177)Lu-cm09 were tested in vitro on folate receptor (FR)-positive KB and IGROV-1 cancer cells using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay. In vivo (161)Tb-cm09 and (177)Lu-cm09 (10 MBq, 0.5 nmol) were investigated in two different tumour mouse models with regard to the biodistribution, the possibility for single photon emission computed tomography (SPECT) imaging and the antitumour efficacy. Potentially undesired side effects were monitored over 6 months by determination of plasma parameters and examination of kidney function with quantitative SPECT using (99m)Tc-dimercaptosuccinic acid (DMSA). To obtain half-maximal inhibition of tumour cell viability a 4.5-fold (KB) and 1.7-fold (IGROV-1) lower radioactivity concentration was required for (161)Tb-cm09 (IC50 ~0.014 MBq/ml and ~2.53 MBq/ml) compared to (177)Lu-cm09 (IC50 ~0.063 MBq/ml and ~4.52 MBq/ml). SPECT imaging visualized tumours of mice with both radioconjugates. However, in therapy studies (161)Tb-cm09 reduced tumour growth more efficiently than (177)Lu-cm09. These findings were in line with the higher absorbed tumour dose for (161)Tb-cm09 (3.3 Gy/MBq) compared to (177)Lu-cm09 (2.4 Gy/MBq). None of the monitored parameters indicated signs of impaired kidney function over the whole time period of investigation after injection of the radiofolates. Compared to (177)Lu-cm09 we demonstrated equal imaging features for (161)Tb-cm09 but an increased therapeutic efficacy for (161)Tb-cm09 in both tumour cell lines in vitro and in vivo. Further preclinical studies using other tumour-targeting radioconjugates are clearly necessary to draw final conclusions about the future clinical perspectives of (161)Tb.

Conventional cancer treatment methods suffer from many limitations such as non-specificity and low efficacy in discrimination between healthy and cancer cells. Recent developments in nanotechnology have introduced novel and smart therapeutic nanomaterials that basically take advantage of various targeting approaches. Targeted nanomaterials selectively bind to the cancer cells and affect them with minor effects on healthy cells. Folic acid (folate) is an essential molecule in DNA synthesis pathway which is highly needed for cancer cell duplication. Some certain cancer cells overexpress folate receptors higher than normal cells, and this fact is the basis of folate targeting strategy. There are many publications reporting various folate conjugated nanomaterials among which folate-conjugated gold nanoparticles hold great promises in targeted cancer therapy. Gold nanoparticles have been identified as promising candidates for new cancer therapy modalities because of biocompatibility, easy synthesis and functionalization, chemo-physical stability, and optical tunable characteristics. In the last decade, there has been a significant explosion in gold nanoparticles research, with a rapid increase in publications related to the area of biomedicine. Although there are many reports published on “gold nanoparticles” and “folate targeting,” there are a few reports on “folate-conjugated gold nanoparticles” in biomedical literature. This paper intends to review and illustrate the recent advances in biomedicine which have been designed on the basis of folate-conjugated gold nanoparticles.

Non-invasive imaging of arthritis activity in rheumatoid arthritis (RA) patients using macrophage PET holds promise for early diagnosis and therapeutic response monitoring. Previously obtained results with macrophage tracer ( R )-[ 11 C]PK11195 were encouraging, but the imaging signal could be further improved by reduction of background uptake. Recently, the novel macrophage tracer [ 18 F]fluoro-PEG-folate was developed. This tracer showed excellent targeting of the folate receptor β on activated macrophages in synovial tissue in a preclinical arthritic rat model. We performed three substudies to investigate the biodistribution, potential for imaging arthritis and kinetic properties of [18F]fluoro-PEG-folate in RA patients. Firstly, biodistribution demonstrated fast clearance of [ 18 F]fluoro-PEG-folate from heart and blood vessels and no dose limiting uptake in organs. Secondly, [ 18 F]fluoro-PEG-folate showed uptake in arthritic joints with significantly lower background and hence significantly higher target-to-background ratios as compared to reference macrophage tracer ( R )-[ 11 C]PK11195. Lastly, dynamic scanning demonstrated fast tracer uptake in affected joints, reaching a plateau after 1 minute, co-existing with a rapid blood clearance. In conclusion, this first in man study demonstrates the potential of [ 18 F]fluoro-PEG-folate to image arthritis activity in RA with favourable imaging characteristics of rapid clearance and low background uptake, that allow for detection of inflammatory activity in the whole body.

A novel folate receptor-targeted β-cyclodextrin (β-CD) drug delivery vehicle was constructed to improve the bioavailability, biosafety, and drug loading capacity of curcumin. Controlled release and targeted delivery was achieved by modifying the nanoparticles with folic acid (FA). Folate-conjugated β-CD-polycaprolactone block copolymers were synthesized and characterized. Curcumin-loaded nanoparticles (FA-Cur-NPs) were structured by self-assembly. The physicochemical properties, stability, release behavior and tumor-targeting ability of the fabricated nanoparticles were studied. The average particle size and drug loading of FA-Cur-NPs was 151.8 nm and 20.27%, respectively. Moreover, the FA-Cur-NPs exhibited good stability in vitro for 72 h. The drug release profiles showed that curcumin from FA-Cur-NPs was released significantly faster in a pH 6.4 phosphate buffered solution (PBS) than in pH 7.4, indicating that curcumin can be enriched around the tumor site compared with normal cells. Additionally, the internalization of FA-Cur-NPs was aided by FA receptor-mediated endocytosis, and its cytotoxicity was proportional to the cellular uptake efficiency. Furthermore, in vivo studies confirmed that FA-Cur-NPs exhibited marked accumulation in the tumor site and excellent antitumor activity. These findings suggest that FA-Cur-NPs are a promising approach for improving cancer therapy through active targeting and controllable release.

Liver cancer is associated significantly with morbidity and mortality. The combination of low-intensity ultrasound with nanomedicine delivery systems holds promise as an alternative for the treatment for liver cancer. This study focuses on the utilization of folic acid (FA) modified nanoparticles, which are loaded with fluorescent dye DiR and liquid fluorocarbon (PFP). These nanoparticles have the potential to enhance liver cancer targeting under ultrasound stimulation and future applications in vivo. The pharmacokinetics and tissue distribution of folic acid-modified Crebanine polyethylene glycol-polylactic acid copolymer nanoparticles (FA-Cre@PEG-PLGA NPs) were investigated. The pharmacokinetic parameters, liver targeting, and in vivo distribution were assessed. Additionally, the inhibitory impacts of FA-Cre@PEG-PLGA NPs in combination with ultrasonic irradiation on the proliferation and acute toxicity of H22 cells of mouse hepatoma were investigated in vitro. The tumor targeting and anti-tumor efficacy of FA-Cre@PEG-PLGA NPs were assessed utilizing a small animal in vivo imaging system and an in situ hepatocellular carcinoma transplantation model, respectively. The pharmacokinetic studies and tissue distribution tests demonstrated that FA-Cre@PEG-PLGA NPs conspicuously prolonged the half-life and retention time of the drug in rats, and the liver targeting effect was pronounced. Additionally, the in vivo acute toxicity test indicated that FA-Cre@PEG-PLGA NPs had minimal adverse reactions and could fulfill the aim of attenuating the drug. The outcomes of the animal experiments further substantiated that FA-Cre@PEG-PLGA NPs had a longer retention time at the tumor site, a superior anti-tumor effect, and less damage to liver and kidney tissue. The integration of FA-Cre@PEG-PLGA NPs with ultrasound irradiation demonstrated exceptional safety and potent anti-tumor efficacy in vivo, presenting a promising therapeutic strategy for the treatment of liver cancer through the combination of ultrasound technology with a nanomedicine delivery system.

Folate is an essential vitamin involved in one-carbon metabolism. It can be acquired from many food sources or in synthetic form. A wide range of processing methods have been studied to improve the bioaccessibility and bioavailability of folate in foods, yet this is often accompanied by a decrease in stability. Encapsulation technology has emerged as an effective solution for protecting folate from degradation and liberation while also improving its bioavailability. Folate deficiency is a prevalent phenomenon worldwide, particularly in underprivileged countries, leading to various health problems, such as neural tube defects. Thus, folate was fortified through both exogenous addition and biofortification. Gene editing technology, especially CRISPR-Cas9, has great promise in this field when compared to transgenic engineering, because transgenic engineering may pose safety concerns and environmental risks. While ongoing research has identified additional potential effects of folate, the dosage and duration remain important factors to consider for optimal health outcomes. The mechanisms of how folate promotes the production of neurotransmitters associated with the gut microbiota–brain axis and reduces depression are not well understood. In addition to folate alone, there may be synergistic effects of combined supplementation of folate and other nutrients or medications, but this is not yet fully clarified and requires further examination. This review summarizes the food sources, enrichment, bioaccessibility, and bioavailability of folate. Furthermore, the health benefits of folate, including neural tube protection, cardiovascular protection, neuroprotection, anti-cancer, immune response augmentation, and gut homeostasis maintenance, with their potential bioactivity mechanisms, are discussed.

Objective. To prepare folic acid-chitosan conjugated nanoparticles (FA-CS NPs) and evaluate their targeting specificity on tumor cells. Methods. Chitosan (CS) NPs were prepared by ionic cross linking method, and folic acid (FA) was conjugated with CS NPs by electrostatic interaction. The properties of NPs were investigated, and doxorubicin hydrochloride (Dox) as a model drug was encapsulated for investigating drug release pattern in vitro. The cytotoxicity and cellular uptake of FA-CS NPs were also investigated. Results. The results reveal that the obtained FA-CS NPs were monodisperse nanoparticles with suitable average size and positive surface charge. Dox was easily loaded into FA-CS NPs, and the release pattern showed a long and biphasic drug release. Noticeable phagocytosis effect was observed in the presence of rhodamine B-labeled FA-CSNPs when incubating with the folate receptor-positive SMMC-7221 cells. Conclusion. Compared with the unmodified CS NPs, FA-CS NPs showed much higher cell uptaking ability due to the known folate-receptor mediated endocytosis. FA-CS NPs provide a potential way to enhance the using efficiency of antitumor drug by folate receptor mediated targeting delivery.

Doxorubicin (DOX), an anthracycline anticancer antibiotic, is used for treating various types of cancers. However, its use is associated with toxicity to normal cells and development of resistance due to overexpression of drug efflux pumps. Poloxamer 407 (P407) and vitamin E TPGS (D-α-tocopheryl polyethylene glycol succinate, TPGS) are widely used polymers as drug delivery carriers and excipients for enhancing the drug retention times and stability. TPGS reduces multidrug resistance, induces apoptosis, and shows selective anticancer activity against tumor cells. Keeping in view the problems, we designed a mixed micelle system encapsulating DOX comprising TPGS for its selective anticancer activity and P407 conjugated with folic acid (FA) for folate-mediated receptor targeting to cancer cells. FA-functionalized P407 was prepared by carbodiimide crosslinker chemistry. P407-TPGS/FA-P407-TPGS-mixed micelles were prepared by thin-film hydration method. Cytotoxicity of blank micelles, DOX, and DOX-loaded micelles was determined by alamarBlue(®) assay. The size of micelles was less than 200 nm with encapsulation efficiency of 85% and 73% for P407-TPGS and FA-P407-TPGS micelles, respectively. Intracellular trafficking study using nile red-loaded micelles indicated improved drug uptake and perinuclear drug localization. The micelles show minimal toxicity to normal human cell line WRL-68, enhanced cellular uptake of DOX, reduced drug efflux, increased DOX-DNA binding in SKOV3 and DOX-resistant SKOV3 human ovarian carcinoma cell lines, and enhanced in vitro cytotoxicity as compared to free DOX. FA-P407-TPGS-DOX micelles show potential as a targeted nano-drug delivery system for DOX due to their multiple synergistic factors of selective anticancer activity, inhibition of multidrug resistance, and folate-mediated selective uptake.