Narottam Lamichhane

Highly stable intrinsically radiolabeled indium-111 quantum dots with multidentate zwitterionic surface coating: dual modality tool for biological imaging

Here we describe a novel strategy to incorporate indium-111 into near infrared (NIR) emitting Cu-In-Se quantum dots (CIS-QDs) to synthesize intrinsically radiolabeled QDs (rQDs), as a quantitative tool for in vivo SPECT/fluorescence imaging. Multidentate zwitterionic polymer ligands were used to functionalize and improve the stability of CIS-rQDs and reduce nonspecific binding with plasma proteins/cell membrane. CIS-rQDs were taken up by colorectal adenocarcinoma (COLO-205) and human epidermoid carcinoma (KB-3-1) cells at low uptake rate (∼0.4%, 2 × 105 QDs per cell at 24 h) and reduced nonspecific interaction of zwitterionic CIS-rQDs with cells was observed by fluorescence microscopy. The cytotoxicity of CIS-rQDs was reduced due to the low toxic inorganic composition of QDs and multidentate zwitterionic surface coating. In 5 out of 6 nude mice bearing either COLO-205 or KB-3-1 tumor, both SPECT and fluorescence imaging demonstrated passive localization of CIS-rQDs in the tumor as early as 6 h post-injection. In these mice the passive accumulation of CIS-rQDs in the tumor, due to leaky vasculature, ranged from ∼0.3% ID per g to ∼4.6% ID per g at 48 h post-injection (from region of interest analysis of SPECT imaging). This intrinsic radio-labeling strategy provides a nanoparticle platform which incorporates imaging and potentially therapeutic radionuclides with retention of fluorescence intensity. It also provides complimentary quantitative data capabilities for both in vivo SPECT imaging and radiotracer ex vivo analysis.

Microfluidic radiosynthesis and biodistribution of [18F] 2‐(5‐fluoro‐pentyl)‐2‐methyl malonic acid

Microfluidics technology has emerged as a powerful tool for the radiosynthesis of positron emission tomography (PET) and single-photon emission computed tomography radiolabeled compounds. In this work, we have exploited a continuous flow microfluidic system (Advion, Inc., USA) for the [(18) F]-fluorine radiolabeling of the malonic acid derivative, [(18) F] 2-(5-fluoro-pentyl)-2-methyl malonic acid ([(18) F]-FPMA), also known as [(18) F]-ML-10, a radiotracer proposed as a potential apoptosis PET imaging agent. The radiosynthesis was developed using a new tosylated precursor. Radiofluorination was initially optimized by manual synthesis and served as a basis to optimize reaction parameters for the microfluidic radiosynthesis. Under optimized conditions, radio-thin-layer chromatography analysis showed 79% [(18) F]-fluorine incorporation prior to hydrolysis and purification. Following hydrolysis, the [(18) F]-FPMA was purified by C18 Sep-Pak, and the final product was analyzed by radio-HPLC (high-performance liquid chromatography). This resulted in a decay-corrected 60% radiochemical yield and ≥98% radiochemical purity. Biodistribution data demonstrated rapid blood clearance with less than 2% of intact [(18) F]-FPMA radioactivity remaining in the circulation 60 min post-injection. Most organs showed low accumulation of the radiotracer, and radioactivity was predominately cleared through kidneys (95% in 1 h). Radio-HPLC analysis of plasma and urine samples showed a stable radiotracer at least up to 60 min post-injection.

[18F]-Fluorinated Carboplatin and [111In]-Liposome for Image-Guided Drug Delivery

Radiolabeled liposomes have been employed as diagnostic tools to monitor in vivo distribution of liposomes in real-time, which helps in optimizing the therapeutic efficacy of the liposomal drug delivery. This work utilizes the platform of [111In]-Liposome as a drug delivery vehicle, encapsulating a novel 18F-labeled carboplatin drug derivative ([18F]-FCP) as a dual-molecular imaging tool as both a radiolabeled drug and radiolabeled carrier. The approach has the potential for clinical translation in individual patients using a dual modal approach of clinically-relevant radionuclides of 18F positron emission tomography (PET) and 111In single photon emission computed tomography (SPECT). [111In]-Liposome was synthesized and evaluated in vivo by biodistribution and SPECT imaging. The [18F]-FCP encapsulated [111In]-Liposome nano-construct was investigated, in vivo, using an optimized dual-tracer PET and SPECT imaging in a nude mouse. The biodistribution data and SPECT imaging showed spleen and liver uptake of [111In]-Liposome and the subsequent clearance of activity with time. Dual-modality imaging of [18F]-FCP encapsulated [111In]-Liposome showed significant uptake in liver and spleen in both PET and SPECT images. Qualitative analysis of SPECT images and quantitative analysis of PET images showed the same pattern of activity during the imaging period and demonstrated the feasibility of dual-tracer imaging of a single dual-labeled nano-construct.

Fluorine-18 Labeled Carboplatin Derivative for PET Imaging of Platinum Drug Distribution

Increasing evidence indicates that reduced intracellular drug accumulation is the parameter most consistently associated with platinum drug resistance, emphasizing the need to directly measure the intratumor drug concentration. In the era of precision medicine and with the advent of powerful imaging and proteomics technologies, there is an opportunity to better understand drug resistance by exploiting these techniques to provide new knowledge on drug–target interactions. Here, we contribute to this endeavor by reporting on the development of an 18F-labeled carboplatin derivative (18F-FCP) that has the potential to image drug uptake and retention, including intratumoral distribution, by PET. Methods: Fluorinated carboplatin (19F-FCP) was synthesized using 19F-labeled 2-(5-fluoro-pentyl)-2-methyl malonic acid (19F-FPMA) as the labeling agent to coordinate with the cisplatin–aqua complex. It was then used to treat cell lines and compared with cisplatin and carboplatin at different concentrations. Manual radiosynthesis and characterization of 18F-FCP were performed using 18F-FPMA for coordination with the cisplatin–aqua complex. Automated radiosynthesis of 18F-FCP was optimized on the basis of manual synthesis procedures. The stability of 18F-FCP was verified using high-performance liquid chromatography. 18F-FCP was evaluated using ex vivo biodistribution and in vivo PET imaging in non–tumor-bearing animals as well as in KB-3-1 and COLO-205 tumor xenograft–bearing nude mice. Results: In vitro cytotoxicity studies demonstrated that 19F-FCP has an antitumor activity profile similar to that of the parent drug carboplatin. In vivo plasma and urine stability analysis showed intact 18F-FCP at 24 h after injection. PET imaging and biodistribution studies showed fast clearance from blood and major accumulation in the kidneys, indicating substantial renal clearance of 18F-FCP. Using 18F-FCP PET, we could image and identify the intratumor drug profile. Conclusion: Our results demonstrated that 19F-FCP, like carboplatin, retains antitumor activity in various cell lines. 18F-FCP could be a useful imaging tool for measuring the intratumor drug distribution. This strategy of using a new therapeutic carboplatin derivative to quantify and track platinum drugs in tumors using PET has the potential to translate into a clinically useful imaging tool for individual patients.

Abstract 4532: Fluorine-18- carboplatin derivative for imaging and therapeutic applications.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC DNA-damaging agents, such as cisplatin and other platinum drugs are the largest class of anti-cancer drugs. They are most important in the clinical use for the treatment of various cancers, although ovarian cancer cells often become resistant. Besides resistance, non-specific uptake in normal tissues and related toxicity is a dose limiting factor and affects their overall effectiveness. Knowledge of the drug concentration in the tumor as well as its overall concentration in the body of a patient will be helpful in accurately predicting the overall responsiveness of a patient to the drug. This type of knowledge can be accomplished by the development of a drug analog with positron emission tomography (PET) imaging capability, so that the accumulation of the drug in the tumor and normal organs can be tracked and quantified during the course of therapy to predict its effectiveness in a patient. Therefore, we developed a novel fluorinated carboplatin derivative, towards a hybrid agent for imaging and therapy. We synthesized 19F fluorinated carboplatin derivative using 2-(5-fluoro-pentyl)-2-methyl malonic acid by co-ordination with cis-platinum aqua complex. It was then used to treat various cell lines and compared with Cis-platin and Carboplatin at different concentrations ranging from 0.001 μM to 100 μM for 72 hrs and 96 hrs. LC50 values calculated from cell viability indicate that fluorinated carboplatin is a more potent drug than Carboplatin but less effective than Cisplatin. | Cell line | Cisplatin (μM) | Carboplatin(μM) | Fluorinated Carboplatin (μM) | |:--------- | -------------- | --------------- | ---------------------------- | ------ | | | 72 hrs | 96 hrs | 72 hrs | 96 hrs | 72 hrs | 96 hrs | | COLO 205 | 28.78 | 1.35 | >100 | 48.98 | 92.52 | 31.56 | | SK-OV-3 | 4.34 | 1.28 | 33.7 | 18.94 | 20.3 | 12.56 | | FaDu | 2.77 | <2 | 34.72 | 11.26 | 21.54 | 8.55 | | A549 | 11.01 | 3.07 | 56.56 | 31.78 | 41.18 | 24.8 | | A498 | 13.35 | 3.42 | 152.83 | 39.34 | 57.25 | 18.5 | | LNCaP | 19.2 | 7.18 | 113.51 | 63.4 | 80.09 | 46.06 | | RWPE-1 | 6.27 | <1 | 65.19 | 36.8 | 34.69 | 10.2 | | KB 3-1 | 4.13 | 2.04 | 59.82 | 26.08 | 22.76 | 13.46 | Table 1: LC50 values of fluorinated carboplatin and known platinum drugs We have also developed a microfluidic method to synthesize [18F]-2-(5-fluoro-pentyl)-2-methyl malonic acid, which will co-ordinate with cis-platinum aqua complex to yield 18F labeled carboplatin derivative. Our approach to synthesis various derivatives of 18F labeled fluorinated carboplatin will allow us to develop anticancer drugs with PET imaging capabilities. Citation Format: Gajanan K. Dewkar, Purnima Jose, Narottam Lamichhane, Celina Thadigiri, Gobalakrishnan Sundaresan, Nicholas Farrell, Jamal Zweit. Fluorine-18- carboplatin derivative for imaging and therapeutic applications. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4532. doi:10.1158/1538-7445.AM2013-4532