Evaluation of acute toxicity and in vitro antitumor activity of a novel doxorubicin-loaded folate-coated pH-sensitive liposome.

Doxorubicin (DOX) loaded liposomes have been used and studied in the last decades due to the significant decrease in DOX induced cardiac and systemic toxicity relative to administration of free drug. Therefore, new strategies are sought to improve DOX delivery and antitumor activity, while avoiding side effects. Recently, folate-coated pH-sensitive liposomes (SpHL-Fol) have been studied as a tool to enhance cellular uptake and antitumor activity of paclitaxel and DOX in breast cancer cells expressing folate receptor (FR+). However, the elucidation of folate functionalization relevance in DOX-loaded SpHL (SpHL-DOX-Fol) in different cell types (MDA-MB-231, MCF-7, and A549), as well as, the complete safety evaluation, is necessary. To achieve these objectives, SpHL-DOX-Fol was prepared and characterized as previously described. Antitumor activity and acute toxicity were evaluated in vivo through direct comparison of free DOX verses SpHL-DOX, a well-known formulation to reduce DOX cardiotoxicity. The obtained data are crucial to support future translational research. Liposomes showed long-term stability, suitable for biological use. Cellular uptake, cytotoxicity, and percentage of migration inhibition were significantly higher for MDA-MB-231 (FR+) treated with SpHL-DOX-Fol. In addition, SpHL-DOX-Fol demonstrated a decrease in the systemic toxic effects of DOX, mainly in renal and cardiac parameters evaluation, even using a higher dose (20 mg/kg). Collectively these data build the foundation of support demonstrating that SpHL-DOX-Fol could be considered a promising drug delivery strategy for the treatment of FR+ breast tumors.

Irinotecan-Loaded Polymeric Micelles as a Promising Alternative to Enhance Antitumor Efficacy in Colorectal Cancer Therapy.

Colorectal cancer has been considered a worldwide public health problem since current treatments are often ineffective. Irinotecan is a frontline chemotherapeutic agent that has dose-limiting side effects that compromise its therapeutic potential. Therefore, it is necessary to develop a novel, targeted drug delivery system with high therapeutic efficacy and an improved safety profile. Here, micellar formulations composed of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-mPEG2k) containing irinotecan were proposed as a strategy for colorectal cancer therapy. Firstly, the irinotecan-loaded micelles were prepared using the solvent evaporation method. Then, micelles were characterized in terms of size, polydispersity, zeta potential, entrapment efficiency, and release kinetics. Cytotoxicity and in vivo antitumor activity were evaluated. The micelles showed size around 13 nm, zeta potential near neutral (-0.5 mV), and encapsulation efficiency around 68.5% (irinotecan 3 mg/mL) with a sustained drug release within the first 8 h. The micelles were evaluated in a CT26 tumor animal model showing inhibition of tumor growth (89%) higher than free drug (68.7%). Body weight variation, hemolytic activity, hematological, and biochemical data showed that, at the dose of 7.5 mg/kg, the irinotecan-loaded micelles have low toxicity. In summary, our findings provide evidence that DSPE-mPEG2k micelles could be considered potential carriers for future irinotecan delivery and their possible therapeutic application against colorectal cancer.

Recent advances in point of care testing for COVID-19 detection.

The World Health Organizations declaration of the COVID-19 pandemic was a milestone for the scientific community. The high transmission rate and the huge number of deaths, along with the lack of knowledge about the virus and the evolution of the disease, stimulated a relentless search for diagnostic tests, treatments, and vaccines. The main challenges were the differential diagnosis of COVID-19 and the development of specific, rapid, and sensitive tests that could reach all people. RT-PCR remains the gold standard for diagnosing COVID-19. However, new methods, such as other molecular techniques and immunoassays emerged. Also, the need for accessible tests with quick results boosted the development of point of care tests (POCT) that are fast, and automated, with high precision and accuracy. This assay reduces the dependence on laboratory conditions and mass testing of the population, dispersing the pressure regarding screening and detection. This review summarizes the advances in the diagnostic field since the pandemic started, emphasizing various laboratory techniques for detecting COVID-19. We reviewed the main existing diagnostic methods, as well as POCT under development, starting with RT-PCR detection, but also exploring other nucleic acid techniques, such as digital PCR, loop-mediated isothermal amplification-based assay (RT-LAMP), clustered regularly interspaced short palindromic repeats (CRISPR), and next-generation sequencing (NGS), and immunoassay tests, and nanoparticle-based biosensors, developed as portable instruments for the rapid standard diagnosis of COVID-19.

PEGylated versus Non-PEGylated pH-Sensitive Liposomes: New Insights from a Comparative Antitumor Activity Study.

PEGylated liposomes are largely studied as long-circulating drug delivery systems. Nevertheless, the addition of PEG can result in reduced interactions between liposomes and cells, hindering liposomal internalization into target cells. The presence of PEG on the surface of pH-sensitive liposomes is not advantageous in terms of biodistribution and tumor uptake, raising the question of whether the indiscriminate use of PEG benefits the formulation. In this study, two doxorubicin-loaded pH-sensitive liposomal formulations, PEGylated (Lip2000-DOX) or non-PEGylated (Lip-DOX), were prepared and characterized. Overall, the PEGylated and non-PEGylated liposomes showed no differences in size or morphology in Cryo-TEM image analysis. Specifically, DLS analysis showed a mean diameter of 140 nm, PDI lower than 0.2, and zeta potential close to neutrality. Both formulations showed an EP higher than 90%. With respect to drug delivery, Lip-DOX had better cellular uptake than Lip2000-DOX, suggesting that the presence of PEG reduced the amount of intracellular DOX accumulation. The antitumor activities of free-DOX and both liposomal formulations were evaluated in 4T1 breast tumor-bearing BALB/c mice. The results showed that Lip-DOX was more effective in controlling tumor growth than other groups, inhibiting tumor growth by 60.4%. Histological lung analysis confirmed that none of the animals in the Lip-DOX group had metastatic foci. These results support that pH-sensitive liposomes have interesting antitumor properties and may produce important outcomes without PEG.

pH-sensitive doxorubicin-tocopherol succinate prodrug encapsulated in docosahexaenoic acid-based nanostructured lipid carriers: An effective strategy to improve pharmacokinetics and reduce toxic effects.

Side effects often limit the use of doxorubicin (DOX) in cancer treatment. We have recently developed a nanostructured lipid carrier (NLC) formulation for synergistic chemotherapy, encapsulating DOX and the anticancer adjuvants docosahexaenoic acid (DHA) and α-tocopherol succinate (TS). Hydrophobic ion-pairing with TS allowed a high DOX entrapment in the nanocarrier. In this work, we investigated the pharmacokinetics of this formulation after intravenous administration in mice. The first data obtained led us to propose synthesizing covalent DOX-TS conjugates to increase DOX retention in the NLC. We successfully conjugated DOX to TS via an amide or hydrazone bond. In vitro studies in 4T1 tumor cells indicated low cytotoxicity of the amide derivative, while the hydrazone conjugate was effective in killing cancer cells. We encapsulated the hydrazone derivative in a DHA-based nanocarrier (DOX-hyd-TS/NLC), which had reduced particle size and high drug encapsulation efficiency. The pH-sensitive hydrazone bond allowed controlled DOX release from the NLC, with increased drug release at acidic conditions. In vivo studies revealed that DOX-hyd-TS/NLC had a better pharmacokinetic profile than free DOX and attenuated the short-term cardiotoxic effects caused by DOX, such as QT prolongation and impaired left ventricular systolic function. Moreover, this formulation showed excellent therapeutic performance by reducing tumor growth in 4T1 tumor-bearing mice and decreasing DOX-induced toxicity to the heart and liver, demonstrated by hematologic, biochemical, and histologic analyses. These results indicate that DOX-hyd-TS/NLC may be a promising nanocarrier for breast cancer treatment.

pH-responsive and folate-coated liposomes encapsulating irinotecan as an alternative to improve efficacy of colorectal cancer treatment.

Irinotecan (IRN) is a semisynthetic derivative of camptothecin that acts as a topoisomerase I inhibitor. IRN is used worldwide for the treatment of several types of cancer, including colorectal cancer, however its use can lead to serious adverse effects, as diarrhea and myelosuppression. Liposomes are widely used as drug delivery systems that can improve chemotherapeutic activity and decrease side effects. Liposomes can also be pH-sensitive to release its content preferentially in acidic environments, like tumors, and be surface-functionalized for targeting purposes. Herein, we developed a folate-coated pH-sensitive liposome as a drug delivery system for IRN to reach improved tumor therapy without potential adverse events. Liposomes were prepared containing IRN and characterized for particle size, polydispersity index, zeta potential, concentration, encapsulation, cellular uptake, and release profile. Antitumor activity was investigated in a murine model of colorectal cancer, and its toxicity was evaluated by hematological/biochemical tests and histological analysis of main organs. The results showed vesicles smaller than 200 nm with little dispersion, a surface charge close to neutral, and high encapsulation rate of over 90%. The system demonstrated prolonged and sustained release in pH-dependent manner with high intracellular drug delivery capacity. Importantly, the folate-coated pH-sensitive formulation had significantly better antitumor activity than the pH-dependent system only or the free drug. Tumor tissue of IRN-containing groups presented large areas of necrosis. Furthermore, no evidence of systemic toxicity was found for the groups investigated. Thus, our developed nanodrug IRN delivery system can potentially be an alternative to conventional colorectal cancer treatment.

Intake of Lactobacillus delbrueckii (pExu:hsp65) Prevents the Inflammation and the Disorganization of the Intestinal Mucosa in a Mouse Model of Mucositis.

5-Fluorouracil (5-FU) is an antineoplastic drug that causes, as a side effect, intestinal mucositis, acute inflammation in the small bowel. The Heat Shock Protein (Hsp) are highly expressed in inflammatory conditions, developing an important role in immune modulation. Thus, they are potential candidates for the treatment of inflammatory diseases. In the mucositis mouse model, the present study aimed to evaluate the beneficial effect of oral administration of milk fermented by Lactobacillus delbrueckii CIDCA 133 (pExu:hsp65), a recombinant strain. This approach showed increased levels of sIgA in the intestinal fluid, reducing inflammatory infiltrate and intestinal permeability. Additionally, the histological score was improved. Protection was associated with a reduction in the gene expression of pro-inflammatory cytokines such as Tnf, Il6, Il12, and Il1b, and an increase in Il10, Muc2, and claudin 1 (Cldn1) and 2 (Cldn2) gene expression in ileum tissue. These findings are corroborated with the increased number of goblet cells, the electronic microscopy images, and the reduction of intestinal permeability. The administration of milk fermented by this recombinant probiotic strain was also able to reverse the high levels of gene expression of Tlrs caused by the 5-FU. Thus, the rCIDCA 133:Hsp65 strain was revealed to be a promising preventive strategy for small bowel inflammation.

Enhanced antitumor efficacy of lapachol-loaded nanoemulsion in breast cancer tumor model.

Lapachol (LAP) is a natural compound with various biological properties, including anticancer activity. However, its clinical application is limited due to the low aqueous solubility and potential adverse side effects. Nanoemulsions are drug delivery systems that can assist in the administration of hydrophobic drugs, increasing their bioavailability and protecting from degradation. Thus, this study aimed to prepare a LAP-loaded nanoemulsion (NE-LAP), and evaluate its antitumor activity. For this purpose, the nanoemulsion was prepared using a hot homogenization method and characterized morphologically by cryogenic transmission electron microscopy (cryo-TEM). Mean diameter, polydispersity index, and zeta potential was evaluated by DLS, encapsulation efficiency was measured by HPLC. Moreover, the short-term storage stability, the drug release and hemolysis in vitro was determined. Additionally, pharmacokinetic, toxicology and toxicity properties of99mTc-NE-LAP were evaluated in a breast cancer (4T1) tumor model. The cryo-TEM showed spherical globules, and the physicochemical characterization of NE-LAP showed a homogeneous stable nanoemulsion with a mean diameter of ∼170 nm, zeta potential of around -20 mV, and encapsulation greater than 85 %. In vitro studies validated that encapsulation did not impair the cytotoxicity activity of LAP. The nanoemulsion was successfully radiolabeled and 99mTc-NE-LAP showed prolonged blood circulation and tumor affinity was confirmed by tumor-to-muscle ratio. Moreover, NE-LAP showed higher antitumor activity than the free drug and the treatment did not result in any signs of toxicity. Therefore, these findings suggest that NE-LAP can be considered an effective strategy for cancer treatment.

Doxorubicin-loaded pH-sensitive micelles: A promising alternative to enhance antitumor activity and reduce toxicity.

Doxorubicin (DOX) is an anthracycline antibiotic widely used in the treatment of cancer, however, it is associated with the occurrence of adverse reactions that limits its clinical use. In this context, the encapsulation of DOX in micelles responsive to pH variations has shown to be a strategy for tumor delivery of the drug, with the potential to increase therapeutic efficacy and to reduce the toxic effects. In addition, radiolabeling nanoparticles with a radioactive isotope is of great use in preclinical studies, since it allows the in vivo monitoring of the nanostructure through the acquisition of quantitative images. Therefore, this study aimed to develop, characterize, and evaluate the antitumor activity of a pH-sensitive micelle composed of DSPE-PEG2000, oleic acid, and DOX. The micelles had a diameter of 13 nm, zeta potential near to neutrality, and high encapsulation percentage. The critical micellar concentration (CMC) was 1.4 × 10-5 mol L-1. The pH-sensitivity was confirmed in vitro through a drug release assay. Cytotoxicity studies confirmed that the encapsulation of DOX into the micelles did not impair the drug cytotoxic activity. Moreover, the incorporation of DSPE-PEG2000-DTPA into the micelles allowed it radiolabeling with the technetium-99 m in high yield and stability, permitting its use to monitor antitumor therapy. In this sense, the pH-sensitive micelles were able to inhibit tumor growth significantly when compared to non-pH-sensitive micelles and the free drug. in vivo toxicity evaluation in the zebrafish model revealed significantly lower toxicity of pH-sensitive micelles compared to the free drug. These results indicate that the developed formulation presents itself as a promising alternative to potentiate the treatment of tumors.

Encapsulating paclitaxel in polymeric nanomicelles increases antitumor activity and prevents peripheral neuropathy.

Paclitaxel (PTX) has a great clinical significance as an antitumor drug, although several side effects are strongly dose-limiting. In this way, we prepared a PTX-loaded 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)-2000] polymeric micelles (PM/PTX) in an attempt to improve safety and effectiveness of conventional PTX formulation (CrEL/EtOH/PTX). In this study, we evaluated from both formulations: stability after dilution, hemocompatibility, cellular uptake, acute toxicity in healthy mice, antitumor activity, and toxicity after multiple-dose treatment. PM/PTX appeared to be more stable than CrEL/EtOH/PTX after dilution. PM/PTX did not exhibit hemolytic activity (values <1%), even at high concentrations. In vitro cellular uptake study indicated that polymeric micelles were able to deliver more PTX (5.8 %) than CrEL/EtOH (2.7 %) to 4T1 cells. In the acute toxicity evaluation in healthy mice, CrEL/EtOH/PTX (single dose of 20 mg/kg) induced peripheral neuropathy, which was not observed in PM/PTX group. Similar results were observed after tumor-bearing mice received a multiple-dose regimen (seven doses of 10 mg/kg). Worth mentioning, we also evaluated vehicles, and CrEL/EtOH alone was not capable of inducing neuropathic pain. Besides, PM/PTX exhibited a higher antitumor activity with an inhibition ratio approximately 1.5-fold higher than CrEL/EtOH/PTX group. This study suggested that PM/PTX is safer than CrEL/EtOH/PTX, and was able to improve the antitumor effectiveness in a 4T1 breast cancer model.

Co-delivery of doxorubicin, docosahexaenoic acid, and α-tocopherol succinate by nanostructured lipid carriers has a synergistic effect to enhance antitumor activity and reduce toxicity.

Doxorubicin (DOX) is widely used in cancer treatment, however, its use is often limited due to its side effects. To avoid these shortcomings, the encapsulation of DOX into nanocarriers has been suggested. Herein, we proposed a novel nanostructured lipid carrier (NLC) formulation loading DOX, docosahexaenoic acid (DHA), and α-tocopherol succinate (TS) for cancer treatment. DHA is an omega-3 fatty acid and TS is a vitamin E derivative. It has been proposed that these compounds can enhance the antitumor activity of chemotherapeutics. Thus, we hypothesized that the combination of DOX, DHA, and TS in NLC (NLC-DHA-DOX-TS) could increase antitumor efficacy and also reduce toxicity. NLC-DHA-DOX-TS was prepared using emulsification-ultrasound. DOX was incorporated after preparing the NLC, which prevented its degradation during manufacture. High DOX encapsulation efficiency was obtained due to the ion-pairing with TS. This ion-pairing increases lipophilicity of DOX and reduces its crystallinity, contributing to its encapsulation in the lipid matrix. Controlled DOX release from the NLC was observed in vitro, with increased drug release at the acidic environment. In vitro cell studies indicated that DOX, DHA, and TS have synergistic effects against 4T1 tumor cells. The in vivo study showed that NLC-DHA-DOX-TS exhibited the greatest antitumor efficacy by reducing tumor growth in 4T1 tumor-bearing mice. In addition, this formulation reduced mice mortality, prevented lung metastasis, and decreased DOX-induced toxicity to the heart and liver, which was demonstrated by hematologic, biochemical, and histologic analyses. These results indicate that NLC-DHA-DOX-TS may be a promising carrier for breast cancer treatment.

Physical and biological effects of paclitaxel encapsulation on disteraroylphosphatidylethanolamine-polyethyleneglycol polymeric micelles.

Simple size observations of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-mPEG2000) polymeric micelles (PM) with different compositions including or not paclitaxel (PTX) are unable to evidence changes on the nanocarrier structure. In such system a detailed characterization using highly sensitive techniques such as X-ray scattering and asymmetric flow field flow fractionation coupled to multi-angle laser light scattering and dynamic light scattering (AF4-MALS-DLS) is mandatory to observe effects that take place by the addition of PTX and/or more lipid-polymer at PM, leading to complex changes on the structure of micelles, as well as in their supramolecular organization. SAXS and AF4-MALS-DLS suggested that PM can be found in the medium separately and highly organized, forming clusters of PM in the latter case. SAXS fitted parameters showed that adding the drug does not change the average PM size since the increase in core radius is compensated by the decrease in shell radius. SAXS observations indicate that PEG conformation takes place, changing from brush to mushroom depending on the PM composition. These findings directly reflect in in vivo studies of blood clearance that showed a longer circulation time of blank PM when compared to PM containing PTX.

Folate-coated, long-circulating and pH-sensitive liposomes enhance doxorubicin antitumor effect in a breast cancer animal model.

Long circulating pH-sensitive liposomes have been shown to effectively deliver doxorubicin (DOX) to tumors and reduce its toxic effects. Folic acid receptors are upregulated in a wide variety of solid, epithelial tumors, including breast cancer. In order to improve liposomal endocytosis and antitumor activity, folic acid has been added to nanoparticles surfaces to exploit overexpression of folate receptors in tumor cells. The purpose of this study was to evaluate the antitumor activity in vitro and in vivo of long circulating pH-sensitive folate-coated DOX-loaded liposomes (SpHL-DOX-Fol) in a 4T1 breast cancer model system in vitro and in vivo. Biodistribution studies were performed and in vivo electrocardiographic parameters were evaluated. A higher tumor uptake for radiolabeled SpHL-Fol (99mTc-SpHL-Fol) 4 h after intravenous administration was observed in comparision with non-folate-coated liposomes (99mTc-SpHL). Antitumor activity showed that SpHL-DOX-Fol treatment led to a 68% growth arrest and drastically reduce pulmonary metastasis foci. Additionally, eletrocardiographic parameters analysis revealed no dispersion in the QT and QTc interval was observed in liposomal treated mice. In summary, this novel multifunctional nanoplatform deomonstrated higher tumor uptake and antitumor activity. SpHL-DOX-Fol represents a drug delivery platform to improve DOX tumor delivery and reduce dose-limiting toxicity.

Sclareol is a potent enhancer of doxorubicin: Evaluation of the free combination and co-loaded nanostructured lipid carriers against breast cancer.

AIMS: In this work, it was sought to determine if there was synergism between doxorubicin (DOX), a well-known antineoplastic, and sclareol (SC), a diterpene from natural origin, in breast cancer treatment. Moreover, it was investigated if their co-loading in the same nanocarrier would result in a gain of activity and/or a toxicity diminishment. MAIN METHODS: The synergism of the DOX:SC combination was evaluated in MDA-MB-231 and 4T1 cells. A nanostructured lipid carrier (NLC) co-encapsulating DOX and SC in their synergistic molar ratio was prepared and characterised, in terms of mean diameter, zeta potential, DOX encapsulation efficiency, small angle X-ray scattering, differential scanning calorimetry, and polarised light microscopy for further intravenous administration. The anticancer activity of the combination, free and encapsulated, was evaluated in 4T1-tumour bearing mice. KEY FINDINGS: It was determined that DOX:SC combination at the molar ratio 1:1.9 presents better synergistic anticancer activity than the molar ratio 1:7.5 in vitro. DOX:SC-loaded NLC (NLC-DOX-SC) improved in vitro cytotoxic and in vivo antitumour activity compared to free DOX. Although NLC-DOX-SC and free DOX:SC, at the synergistic molar ratio, showed similar activity in the in vivo study, the free combination provoked body weight loss, behaviour alterations and haematological toxicity in the animals, while this was not observed for NLC-DOX-SC. SIGNIFICANCE: This work shows that SC and DOX present synergistic anticancer activity for breast cancer treatment whereas NLC-DOX-SC was a feasible alternative to attain the benefits posed by DOX:SC combination but with none to fewer side effects.

Influence of PEG coating on the biodistribution and tumor accumulation of pH-sensitive liposomes.

Liposomes are lipid vesicles widely used as nanocarriers in targeted drug delivery systems for therapeutic and/or diagnostic purposes. A strategy to prolong the blood circulation time of the liposomes includes the addition of a hydrophilic polymer polyethylene glycol (PEG) moiety onto the surface of the vesicle. Several studies claim that liposome PEGylation by a single chain length or a combination of PEG with different chain lengths may alter the liposomes' pharmacokinetic properties. Therefore, the purpose of this study was to evaluate the influence of PEG on the biodistribution of pH-sensitive liposomes in a tumor-bearing animal model. Three liposomal formulations (PEGylated or not) were prepared and validated to have a similar mean diameter, monodisperse distribution, and neutral zeta potential. The pharmacokinetic properties of each liposome were evaluated in healthy animals, while the biodistribution and scintigraphic images were evaluated in tumor-bearing mice. High tumor-to-muscle ratios were not statistically different between the PEGylated and non-PEGylated liposomes. While PEGylation is a well-established strategy for increasing the blood circulation of nanostructures, in our study, the use of polymer coating did not result in a better in vivo profile. Further studies must be carried out to confirm the feasibility of the non-PEGylated pH-sensitive liposomes for tumor treatment.

The role of radionuclide probes for monitoring anti-tumor drugs efficacy: A brief review.

Despite recent advances in the development of new therapeutic agents and diagnostic imaging modalities, cancer is still one of the main causes of death worldwide. A better understanding of the molecular signature of cancer has promoted the development of a new generation of anti-cancer drugs and diagnostic agents that specifically target molecular components such as genes, ligands, receptors and signaling pathways. However, intrinsic heterogeneity of tumors has hampered the overall success of target therapies even among patients with similar tumor types but unpredictable different responses to therapy. In this sense, post-treatment response monitoring becomes indispensable and nuclear medicine imaging modalities could provide the tools for an early indication of therapeutic efficacy. Herein, we briefly discuss the current role of PET and SPECT imaging in monitoring cancer therapy together with an update on the current radiolabeled probes that are currently investigated for tumor therapy response assessment.

Synthesis, characterization and radiolabeling of polymeric nano-micelles as a platform for tumor delivering.

The use of nanoparticles for diagnostic approaches leads to higher accumulation in the targeting tissue promoting a better signal-to-noise ratio and consequently, early tumor detection through scintigraphic techniques. Such approaches have inherent advantages, including the possibility of association with a variety of gamma-emitting radionuclides available, among them, Tecnethium-99m (99mTc). 99mTc is readily conjugated with nanoparticles using chelating agents, such as diethylenetriaminepentaacetic acid (DTPA). Leveraging this approach, we synthesized polymeric micelles (PM) consisting of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-mPEG2000) functionalized with DTPA for radiolabeling with 99mTc. Micelles made up of DSPE-mPEG2000 and DSPE-PEG2000-DTPA had a mean diameter of ∼10nm, as measured by DLS and SAXS techniques, and a zeta potential of -2.7±1.1mV. Radiolabeled micelles exhibited high radiochemical yields and stability. In vivo assays indicated long blood circulation time (456.3min). High uptake in liver, spleen and kidneys was observed in the biodistribution and imaging studies on healthy and tumor-bearing mice. In addition, a high tumor-to-muscle ratio was detected, which increased over time, showing accumulation of the PM in the tumor region. These findings indicate that this system is a promising platform for simultaneous delivery of therapeutic agents and diagnostic probes.

Development of imaging probes for bone cancer in animal models. A systematic review.

Bone is a dynamic tissue that is constantly remodeled throughout the lifetime to ensure the integrity of the skeleton. Primary cancer cells disseminate into circulation, often extravasating to bone, where they interact with the bone marrow to grow and proliferate, disrupting the bone homeostasis. Although primary bone tumors account for less than 0.2% of all cancers, bone is a common site for the development of metastases, as its microenvironment provides the necessary conditions for the growth and proliferation of cancer cells. Metastases to the skeletal system are observed in up to 70% of all cancer patients and the growth of disseminated tumor metastases is a major cause of mortality. As widely known, a non-invasive diagnosis of bone tumors at early stages is of great importance to provide insights that will help on the decision of therapy regimen, improving treatment outcomes. Early diagnosis of bone metastases is also an important step for establishing palliative care as they may cause serious endocrine, hematologic, neurologic and orthopedic complications as well as intolerable pain. Therefore, development of new imaging techniques, imaging moieties, and animal models to mimic these bone conditions, play an important role in improving the clinical outcome of this disease. In this review, we will briefly describe the advantages and disadvantages of the currently available imaging techniques that aim at identifying bone tumors. In addition, we will provide an update on the animal models applicable at mimicking bone tumor characteristics, as well as describe recent advances on the development of new imaging probes, in the preclinical settings including targeted nanoparticles and radiopharmaceuticals.