Enhancing oral bioavailability of Ca-DTPA by self double emulsifying drug delivery system (SDEDDS).

OBJECTIVE: BCS class III drug (highly soluble, poorly permeable) possesses low oral bioavailability. The research work highlights the utility of self-double emulsifying drug delivery system (SDEDDS) which are stable isotropic mixture of w/o primary emulsion and hydrophilic surfactants for improving oral bioavailability of Ca-DTPA (Calcium diethylenetriamine pentaacetate). Upon oral administration, SDEDDS rapidly emulsifies into w/o/w double emulsions in the aqueous gastrointestinal environment, with hydrophilic drugs entrapped inside oil reservoirs. METHODS: SDEDDS formulation was successfully developed using excipients, that is, medium chain triglycerides, oleic acid, phospholipids, Span 80, Tween 80 using double emulsification technique. RESULTS: The optimized formulation F4 (Aq. phase: 11.6%w,w; MCT & oleic acid: 70.9%w/w; Span 80:17.5%w/w; Lecithin:16%w/w and Tween 80 (10%w/w)) appeared bright yellow liquid which upon dilution appeared milky white within 2 min, droplet size (501.7 nm), pdi value (0.044), zeta potential (-52 mV), entrapment efficiency (79.6 ± 1.63), viscosity (72.2 ± 1.8 mpA.s), significant high cumulative in vitro drug permeation (CDP) and 2.17-fold increase in apparent permeability coefficient. Pharmacokinetic studies in rats showed 1.17-fold increases in AUC of F4 and comparatively higher plasma levels (Cmax) compared with pure drug administered orally. The Absolute (OF4, OD) and Relative bioavailability was found to be 14.52%, 12.35%, and 117.47%, respectively. CONCLUSION: The present studies have clearly demonstrated that SDEDDS could readily form w/o/w double emulsions in vivo with enhanced in vitro and in vivo oral bioavailability. Therefore, considerable augmentation in the rate and extent of oral drug absorption ratified the better performance of the SDEDDS in enhancing the bioavailability of Ca-DTPA.

Investigation of Chelating Agents for the Removal of Thorium from Human Teeth upon Nuclear Contamination.

Thorium-232 (232Th) is a radioactive heavy metal that is of increasing interest as a source of nuclear energy. However, upon nuclear incidents, the ingestion or inhalation of Th in major quantities can contribute to chemical and radiological health problems, including accumulation in the bone tissue and an increased risk of developing pancreatic, lung, and hematopoietic cancers. The major mineral component of the bone is hydroxyapatite (HAP)─also the major mineral component of the teeth. As such, the teeth are the first site of exposure upon oral ingestion of Th-contaminated materials, and Th can pose a potential risk to teeth development. In essence, in the case of human contamination, it is critical to identify effective chelating agents capable of removing Th. Using a batch study methodology, this present work investigates the uptake and the removal of Th from synthetic HAP and from teeth samples by diethylenetriamine pentaacetate (DTPA), ethylenediaminetetraacetic acid (EDTA), and other promising chelating agents. Th uptake over synthetic HAP exceeds 98% at physiological pH with <1 min of contact time and uptake exceeds 90% across the entire pH range. Regarding teeth, over 1 mg Th uptaken per gram of tooth is observed after 24 h. The overall effectiveness of chelating agents for the removal of Th from is as follows: DTPA > EDTA > NaF/mouthwash/3,4,3-LI(1,2-HOPO); this trend was observed both in synthetic HAP and Th-impregnated teeth samples.

Novel Strategy to Drive the Intracellular Uptake of Lipid Nanoparticles for Photodynamic Therapy.

Nanoparticles' uptake by cancer cells upon reaching the tumor microenvironment is often the rate-limiting step in cancer nanomedicine. Herein, we report that the inclusion of aminopolycarboxylic acid conjugated lipids, such as EDTA- or DTPA-hexadecylamide lipids in liposome-like porphyrin nanoparticles (PS) enhanced their intracellular uptake by 25-fold, which was attributed to these lipids' ability to fluidize the cell membrane in a detergent-like manner rather than by metal chelation of EDTA or DTPA. EDTA-lipid-incorporated-PS (ePS) take advantage of its unique active uptake mechanism to achieve >95 % photodynamic therapy (PDT) cell killing compared to <5 % cell killing by PS. In multiple tumor models, ePS demonstrated fast fluorescence-enabled tumor delineation within minutes post-injection and increased PDT potency (100 % survival rate) compared to PS (60 %). This study offers a new nanoparticle cellular uptake strategy to overcome challenges associated with conventional drug delivery.

Prolonged Circulating Lipid Nanoparticles Enabled by High-Density Gd-DTPA-Bis(stearylamide) for Long-Lasting Enhanced Tumor Magnetic Resonance Imaging.

Porphysomes (PS) were explored to incorporate different types of diethylenetriaminepentaacetic-acid-gadolinium-(III) (Gd-DTPA)-lipids into their bilayer membrane to assess PS potential as an MRI contrast agent. The Gd-dPS-BSA by integration of over 30% Gd-DTPA-bis(stearylamide) (Gd-DTPA-BSA)-lipids in PS construction resulted in exceptional serum stability and T1 and T2 relaxivity measurements of 13 mM-1 s-1 and 19 mM-1 s-1, respectively. The Gd-dPS-BSA demonstrated significantly enhanced retention in blood circulation with a half-life of 13.6 h and high tumor accumulation up to 19.5%ID/g at 72 h post-injection in select cancer mouse models. Additionally, Gd-dPS-BSA displayed excellent MRI tumor enhancement over 24, 48, and 72 h with contrast enhancements from the baseline of 35.8%, 38.2%, and 38.3%, respectively. Results reported here highlight a high-density incorporation of Gd-DTPA-BSA-lipids within PS, and other liposome formulations can enhance circulatory longevity, independently of particles' concentration, suggesting effective MRI contrast agent potential for Gd-dPS-BSA and potential utility of Gd-DTPA-BSA-lipids to enhance other liposomal-influenced diagnostic and therapeutic functions.

A Radiolabeled Self-assembled Nanoparticle Probe for Diagnosis of Lung-Metastatic Melanoma.

Melanoma is a highly malignant skin cancer that frequently metastasizes to the lung, bone, and brain at an early phase. Therefore, noninvasive detection of metastasized melanoma could be beneficial to determine suitable therapeutic strategies. We previously reported a biocompatible ternary anionic complex composed of plasmid DNA (pDNA), polyethyleneimine (PEI), and γ-polyglutamic acid (γ-PGA) based on an electrostatic interaction, which was highly taken up by melanoma cells (B16-F10), even if it was negatively charged. Here, we developed a radiolabeled γ-PGA complex by using indium-111 (111In)-labeled polyamidoamine dendrimer (4th generation; G4) instead of pDNA and iodine-125 (125I)-labeled PEI instead of native PEI, and evaluated its effectiveness as a melanoma-targeted imaging probe. This ternary complex was synthesized at a theoretical charge ratio; carboxyl groups of 111In-diethylenetriaminepentaacetic acid (DTPA)-G4 : amino groups of 125I-PEI : carboxyl groups of γ-PGA was 1 : 8 : 16, and the size and zeta potential were approximately 29 nm and -33 mV, respectively. This complex was taken up by B16-F10 cells with time. Furthermore, a biodistribution study, using normal mice, demonstrated its accumulation in the liver, spleen, and lung, where macrophage cells are abundant. Almost the same level of radioactivity derived from both 111In and 125I was observed in these organs at an early phase after probe injection. Compared with the normal mice, significantly higher lung-to-blood ratios of radioactivity were observed in the B16-F10-lung metastatic cancer model. In conclusion, the radiolabeled γ-PGA complex would hold potentialities for nuclear medical imaging of lung metastatic melanoma.

Polyethylenimine-based theranostic nanoplatform for glioma-targeting single-photon emission computed tomography imaging and anticancer drug delivery.

BACKGROUND: Glioma is the deadliest brain cancer in adults because the blood-brain-barrier (BBB) prevents the vast majority of therapeutic drugs from entering into the central nervous system. The development of BBB-penetrating drug delivery systems for glioma therapy still remains a great challenge. In this study, we aimed to design and develop a theranostic nanocomplex with enhanced BBB penetrability and tumor-targeting efficiency for glioma single-photon emission computed tomography (SPECT) imaging and anticancer drug delivery. RESULTS: This multifunctional nanocomplex was manufactured using branched polyethylenimine (PEI) as a template to sequentially conjugate with methoxypolyethylene glycol (mPEG), glioma-targeting peptide chlorotoxin (CTX), and diethylenetriaminepentaacetic acid (DTPA) for 99mTc radiolabeling on the surface of PEI. After the acetylation of the remaining PEI surface amines using acetic anhydride (Ac2O), the CTX-modified PEI (mPEI-CTX) was utilized as a carrier to load chemotherapeutic drug doxorubicin (DOX) in its interior cavity. The formed mPEI-CTX/DOX complex had excellent water dispersibility and released DOX in a sustainable and pH-dependent manner; furthermore, it showed targeting specificity and therapeutic effect of DOX toward glioma cells in vitro and in vivo (a subcutaneous tumor mouse model). Owing to the unique biological properties of CTX, the mPEI-CTX/DOX complex was able to cross the BBB and accumulate at the tumor site in an orthotopic rat glioma model. In addition, after efficient radiolabeling of PEI with 99mTc via DTPA, the 99mTc-labeled complex could help to visualize the drug accumulation in tumors of glioma-bearing mice and the drug delivery into the brains of rats through SPECT imaging. CONCLUSIONS: These results indicate the potential of the developed PEI-based nanocomplex in facilitating glioma-targeting SPECT imaging and chemotherapy.

COMPARATIVE RENAL DISPOSITION OF CREATINE, AND TECHNETIUM DIAGNOSTIC CONTRAST AGENTS IN THE PIGEON (COLUMBA LIVIA).

Clinical assessment of renal function in avian species often involves the measurement of plasma uric acid and blood urea nitrogen, relatively insensitive markers of renal dysfunction and dehydration. In mammals, endogenous creatinine is widely used as an indicator of renal glomerular dysfunction. However, avian species produce primarily creatine. Here, renal creatine, 99mTc99-DTPA (diethylenepentaacetic acid, DTPA) and 99mTc-MAG3 (mercaptoacetyl triglycine, MAG3) renal clearances are characterized in the pigeon avian model by infusing DTPA with inulin and creatine with each tracer and examining the slope of their blood disappearance curves. Clearance curves for inulin and DTPA were parallel, suggesting DTPA is cleared by renal filtration. MAG3 clearance (slope: -2.74 × 105, r2 = 0.97) had a slope almost 10-fold steeper than for DTPA (slope: -6.29 × 104, r2 = 0.90), and orders of magnitude steeper than for creatine (slope: -1.4, r2 = 1.0). These results suggest that DTPA is cleared by glomerular filtration like inulin, while MAG3 is filtered and actively excreted in a manner similar to mammals. In contrast, creatine is filtered and resorbed, has a larger volume of distribution (Vd), or exhibits a greater blood protein binding, making it more complex as a renal marker, when compared with creatinine handling in mammals. The two radiotracers can be readily adapted for use in birds, inviting both qualitative and semiquantitative functional evaluation of avian renal function for research and clinical purposes. The elimination of creatine appears to be more complex requiring further study.

Imaging doxorubicin and polymer-drug conjugates of doxorubicin-induced cardiotoxicity with bispecific anti-myosin-anti-DTPA antibody and Tc-99m-labeled polymers.

BACKGROUND: Radiolabeled anti-myosin imaging is well-established for imaging doxorubicin-induced cardiotoxicity. However, to enable imaging of drug-induced cardiotoxicity in small experimental animals, pretargeting with bispecific anti-myosin-anti-DTPA-Fab-Fab' and targeting with high-specific radioactivity Tc-99m-DTPA-succinylated-polylysine (DSPL) was developed. METHODS: Mice were injected biweekly with 10 mg/kg Dox or its equivalent as D-Dox-PGA. Tc-99m-DSPL myocardial activity after pretargeting with bsAb-Fab-Fab' was determined after gamma imaging performed at day 7 for Dox-treated mice and day 39 for all others. RESULTS: Mice treated with 10 mg/kg Dox lost 10% total body weight in 1 week and 20% after a second dose. Pretargeted mice treated with 30 mg/kg cumulative D-Dox-PGA dose showed no loss of body weight for the duration of the study. Cardiotoxicity was confirmed by gamma imaging and scintillation counting (1.9 ± 0.25 [mean% ID/g ± SD]) after 1 dose of Dox. Mice injected with 3 × 10 mg/kg Dox equivalent as D-Dox-PGA (0.4 ± 0.04, P < .01) and untreated 2 control groups (0.20 ± 0.05 and 0.19 ± 0.04, P < .01) showed significantly lower myocardial anti-myosin radioactivity relative to the 10 mg/kg Dox group. CONCLUSION: Pretargeting with bsAb-Fab-Fab' and targeting with Tc-99m labeled high-specific activity polymers enabled early visualization of doxorubicin induce cardiotoxicity in mice. Tolerated dose of D-Dox-PGA was greater than to 30 mg/kg Dox-equivalent dose with minimal cardiotoxicity.

Synthesis and Photochemical Studies on Gallium and Indium Complexes of DTPA-PEG3-ArN3 for Radiolabeling Antibodies.

Photochemistry is a rich source of inspiration for developing alternative methods to functionalize proteins with drug molecules, fluorophores, and radioactive probes. Here, we report the synthesis and photochemical reactivity of a modified diethylenediamine pentaacetic acid chelate that was derivatized with a light-responsive aryl azide group (DTPA-PEG3-ArN3, compound 1). The corresponding nonradioactive and radioactive nat/68Ga3+ and nat/111In3+ complexes of DTPA-PEG3-ArN3 were synthesized and their physical and photochemical properties were studied to evaluate the potential of employing this ligand system in the photochemical synthesis of radiolabeled antibodies. Photodegradation kinetics revealed that irradiation with ultraviolet light (365 nm) induced rapid photoactivation of compound 1 and the metal complexes nat/68Ga-1- and nat/111In-1-. Light-induced reactions were complete in <100 s, with measured first-order rate constants of 0.078 ± 0.045 s-1, 0.093 ± 0.009 s-1, and 0.117 ± 0.054 s-1 (n = 2, per species) for compound 1, natGa-1-, and natIn-1-, respectively. Photochemically induced bioconjugation reactions between DTPA-PEG3-ArN3 and the monoclonal antibody trastuzumab, as well as pre- and postconjugation 68Ga- and 111In-radiolabeling experiments, were performed using either a one-pot or two-step strategy. Both approaches yielded radiolabeled trastuzumab ([68Ga]GaDTPA-azepin-trastuzumab) with average radiochemical conversions of 3.9 ± 1.0% (n = 4, one-pot), and 10.0 ± 1.0% (n = 3, two-step). One-pot radiolabeling reactions with [111In]InCl3 produced the corresponding [111In]InDTPA-azepin-trastuzumab radiotracer in a similar radiochemical conversion of 5.4 ± 0.8% (n = 3). Radiochemical conversions for the desired bimolecular coupling between the chelate and the protein were comparatively low. This observation is likely caused by the high photoinduced reactivity of the compounds and subsequent competition with background reactions. Nevertheless, access to DTPA-PEG3-ArN3 increases the scope of photoradiochemical methods to include metal ions like In3+ that form complexes with higher coordination numbers.

Gadolinium (III) oxide nanoparticles coated with folic acid-functionalized poly(ß-cyclodextrin-co-pentetic acid) as a biocompatible targeted nano-contrast agent for cancer diagnostic: in vitro and in vivo studies.

OBJECTIVES: In this study, a novel targeted MRI contrast agent was developed by coating gadolinium oxide nanoparticles (Gd2O3 NPs) with ß-cyclodextrin (CD)-based polyester and targeted by folic acid (FA). MATERIALS AND METHODS: The developed Gd2O3@PCD-FA MRI contrast agent was characterized and evaluated in relaxivity, in vitro cell targeting, cell toxicity, blood compatibility and in vivo tumor MR contrast enhancement. RESULTS: In vitro cytotoxicity and hemolysis assays revealed that Gd2O3@PCD-FA NPs have no significant cytotoxicity after 24 and 48 h against normal human breast cell line (MCF-10A) at concentration of up to 50 µg Gd+3/mL and have high blood compatibility at concentration of up to 500 µg Gd+3/mL. In vitro MR imaging experiments showed that Gd2O3@PCD-FA NPs enable targeted contrast T1- and T2-weighted MR imaging of M109 as overexpressing folate receptor cells. Besides, the in vivo analysis indicated that the maximum contrast-to-noise ratio (CNR) of tumor in mice increased after injection of Gd2O3@PCD-FA up to 5.89 ± 1.3 within 1 h under T1-weighted imaging mode and reduced to 1.45 ± 0.44 after 12 h. While CNR increased up to maximum value of 1.98 ± 0.28 after injection of Gd2O3@PCD within 6 h and reduced to 1.12 ± 0.13 within 12 h. CONCLUSION: The results indicate the potential of Gd2O3@PCD-FA to serve as a novel targeted nano-contrast agent in MRI.

Vascular Targeting of Radiolabeled Liposomes with Bio-Orthogonally Conjugated Ligands: Single Chain Fragments Provide Higher Specificity than Antibodies.

Liposomes are a proven, versatile, and clinically viable technology platform for vascular delivery of drugs and imaging probes. Although targeted liposomes have the potential to advance these applications, complex formulations and the need for optimal affinity ligands and conjugation strategies challenge their translation. Herein, we employed copper-free click chemistry functionalized liposomes to target platelet-endothelial cell adhesion molecule (PECAM-1) and intracellular adhesion molecule (ICAM-1) by conjugating clickable monoclonal antibodies (Ab) or their single chain variable fragments (scFv). For direct, quantitative tracing, liposomes were surface chelated with 111In to a >90% radiochemical yield and purity. Particle size and distribution, stability, ligand surface density, and specific binding to target cells were characterized in vitro. Biodistribution of liposomes after IV injection was characterized in mice using isotope detection in organs and by noninvasive imaging (single-photon emission computed tomography/computed tomography, SPECT/CT). As much as 20-25% of injected dose of liposomes carrying PECAM and ICAM ligands, but not control IgG accumulated in the pulmonary vasculature. The immunospecificity of pulmonary targeting of scFv/liposomes to PECAM-1 and ICAM-1, respectively, was 10-fold and 2.5-fold higher than of Ab/liposomes. Therefore, the combination of optimal ligands, benign conjugation, and labeling yields liposomal formulations that may be used for highly effective and specific vascular targeting.

Targeted Delivery of Amantadine-loaded Methacrylate Nanosphere-ligands for the Potential Treatment of Amyotrophic Lateral Sclerosis.

PURPOSE: This study aimed to develop and analyse poly(DL-lactic acid)-methacrylic acid nanospheres bound to the chelating ligand diethylenetriaminepentaacetic acid (DTPA)  for the targeted delivery of amantadine in Amyotrophic Lateral Sclerosis (ALS). METHODS: The nanospheres were prepared by a double emulsion solvent evaporation technique statistically optimized employing a 3-Factor Box-Behnken experimental design. Analysis of the particle size, zeta potential, polydispersity (Pdl), morphology, drug entrapment and drug release kinetics were carried out. RESULTS: The prepared nanospheres were determined to have particle sizes ranging from 68.31 to 113.6 nm (Pdl ≤ 0.5). An initial burst release (50% of amantadine released in 24 hr) was also obtained, followed by a prolonged release phase of amantadine over 72 hr. Successful conjugation of the chelating ligand onto the surface of the optimised nanospheres was thereafter achieved and confirmed by TEM. The synthesized modified nanospheres were spherical in shape, 105.6 nm in size, with a PdI of 0.24 and zeta potential of -28.0 mV. Conjugation efficiency was determined to be 74%. In vitro and ex vivo cell study results confirmed the intracellular uptake of the modified nanospheres by the NSC-34 cell line and the non-cytotoxicity of the synthesized nanospheres. CONCLUSIONS: Biocompatible amantadine-loaded nanospheres were successfully designed, characterized and optimized employing the randomized Box-Behnken statistical design. Delivery of amantadine over 72 hrs was achieved, with the nanospheres being of a size capable of internalization by the NSC- 34 cells. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Design and In Vitro Evaluation of Bispecific Complexes and Drug Conjugates of Anticancer Peptide, LyP-1 in Human Breast Cancer.

PURPOSE: LyP-1, a nine-amino-acid tumor homing peptide, selectively binds to its cognate receptor, p32. Overexpression of p32 in certain tumors should allow use of LyP-1 as a targeting agent for the delivery of therapeutic or diagnostic agents. Peptide conjugates are developed for enhanced pre-targeting of MDA-MB-231 breast cancer cells with peptide-antibody bispecific complexes and targeting with multiple-drug/-fluorophore-conjugated nano-polymers. METHODS: LyP-1-anti-DTPA bispecific antibody complexes (LyP-1-bsAbCx) were generated by conjugation of anti-DTPA antibody and LyP-1. LyP-1-doxorubicin (Dox), Dox-DTPA-succinyl-polylysine (Dox-DSPL), Dox-DSPL-LyP-1, DTPA-Dox-poly glutamic acid (D-Dox-PGA) or DTPA-rhodamine conjugated polylysine (DSPL-RITC) were prepared. In vitro therapeutic efficacy and targeting by immunofluorescence in MDA-MB-231 breast cancer cells were assessed with Dox-LyP-1. Immunofluorescence visualization of cancer cells was evaluated after pretargeting with LyP-1-bsAbCx and targeting with DSPL-RITC. RESULTS: Cytotoxicity of Dox-LyP-1 conjugates was significantly greater than free doxorubicin (p < 0.0001). For fluorescent-labeled LyP-1, internalization occurred in 30 min in tumor cells. Fluorescence intensity of two-step targeted cells showed that pretargeting with LyP-1-bsAbC, followed by targeting with DSPL-RITC was greater than non-pretargeted DSPL-RITC (p < 0.05). CONCLUSIONS: Peptide-conjugates are effective targeting agents for MDA-MB-231 breast cancer cells in culture. LyP-1-bsAbCx and Dox-LyP-1 conjugates may allow development of novel targeted cancer therapy and diagnosis.

An Activatable Fluorescent γ-Polyglutamic Acid Complex for Sentinel Lymph Node Imaging.

Sentinel lymph nodes (SLN) are the first lymph nodes (LN) where cancer cells metastasize from the primary tumor. We designed fluorophore-quencher-based activatable nanoparticles for SLN imaging. We selected TAMRA as a fluorophore and BHQ2 or QSY7 as a quencher. Ternary anionic complexes were constructed with generation 4th polyamidoamine dendrimer (G4) modified with TAMRA and p-SCN-Bn-DTPA (DTPA), polyethyleneimine (PEI) modified with BHQ2 or QSY7, and γ-polyglutamic acid (γ-PGA) by the electrostatic self-assembly system. TAMRA-G4-DTPA/PEI-BHQ2/γ-PGA and TAMRA-G4-DTPA/PEI-QSY7/γ-PGA complexes had a particle size of about 40 nm and a ζ-potential of -50 mV, and showed fluorescence resonance energy transfer (FRET) quenching. Fluorescence microscopy studies demonstrated that TAMRA-G4-DTPA/PEI-QSY7/γ-PGA complex produced intracellular fluorescent signals in the lysosome. During in vivo fluorescent imaging, TAMRA-G4-DTPA/PEI-QSY7/γ-PGA complex enabled the detection of mouse popliteal LN. The fluorophore-quencher conjugated γ-PGA complex based on FRET quenching would be useful for fluorescence-based optical imaging of SLN.

Metal-Chelating Polymers (MCPs) with Zwitterionic Pendant Groups Complexed to Trastuzumab Exhibit Decreased Liver Accumulation Compared to Polyanionic MCP Immunoconjugates.

Metal-chelating polymers (MCPs) can amplify the radioactivity delivered to cancer cells by monoclonal antibodies or their Fab fragments. We focus on trastuzumab (tmAb), which is used to target cancer cells that overexpress human epidermal growth factor receptor 2 (HER2). We report the synthesis and characterization of a biotin (Bi) end-capped MCP, Bi-PAm(DET-DTPA)36, a polyacrylamide with diethylenetriaminepentaacetic acid (DTPA) groups attached as monoamides to the polymer backbone by diethylenetriamine (DET) pendant groups. We compared its behavior in vivo and in vitro to a similar MCP with ethylenediamine (EDA) pendant groups (Bi-PAm(EDA-DTPA)40). These polymers were complexed to a streptavidin-modified Fab fragment of tmAb, then labeled with (111)In to specifically deliver multiple copies of (111)In to HER2+ cancer cells. Upon decay, (111)In emits γ-rays that can be used in single-photon emission computed tomography radioimaging, as well as Auger electrons that cause lethal double strand breakage of DNA. Our previous studies in Balb/c mice showed that radioimmunoconjugates (RICs) containing the Bi-PAm(EDA-DTPA)40 polymer had extremely short blood circulation time and high liver uptake and were, thus, unsuitable for in vivo studies. The polymer Bi-PAm(EDA-DTPA)40 carries negative charges on each pendant group at neutral pH and a net charge of (-1) on each pendant group when saturated with stable In(3+). To test our hypothesis that charge associated with the polymer repeat unit is a key factor affecting its biodistribution profile, we examined the biodistribution of RICs containing Bi-PAm(DET-DTPA)36. While this polymer is also negatively charged at neutral pH, it becomes a zwitterionic MCP upon saturation of the DTPA groups with stable In(3+) ions. In both nontumor bearing Balb/c mice and athymic mice implanted with HER2+ SKOV-3 human ovarian cancer tumors, we show that the zwitterionic MCP has improved biodistribution, higher blood levels of radioactivity, lower levels of normal tissue uptake, and higher tumor uptake. Surface plasmon resonance experiments employing the extracellular domain of HER2 show that the MCP immunoconjugates retain high affinity antigen recognition, with dissociation constants in the low nM range. In vitro studies with SKOV-3 cells for both MCP immunoconjugates show a combination of specific binding that can be completed in the presence of excess tmAb IgG and nonspecific binding (NSB) that persists in the presence of tmAb IgG. We conclude that zwitterionic MCPs represent a much better choice than polymers with charges along the backbone for in vivo delivery of RICs to HER2+ cancer cells.

Bioreducible polyethylenimine nanoparticles for the efficient delivery of nucleic acids.

Recently, non-viral vectors for nucleic acid delivery have received considerable attention. Among the various non-viral vectors, branched polyethylenimine (bPEI, 25 kDa) has been one of the most widely used carrier systems due to its high transfection efficiency, however, it imparts high cytotoxicity. In this study, we have crosslinked bPEI with a bioreducible linker, 3,3'-dithiodipropionic acid (DTPA), via electrostatic interactions to obtain DTPA crosslinked bPEI (DP) nanoparticles. The crosslinking significantly reduced the cytotoxicity of the nanoparticles. To arrive at the best formulation in terms of nucleic acid transfection, a series of DP nanoparticles were prepared by varying the percentage of crosslinking. The dual action of DTPA, i.e. partial blocking of the charge density as well as crosslinking to convert bPEI into its nanoparticles, did not alter the pDNA condensation ability of the so-formed nanoparticles, rather the strategy favoured the unpackaging of the complexes inside the cells improving the release of pDNA, which resulted in a higher transfection efficiency. All the formulations carried nucleic acids inside the cells and exhibited significantly higher transfection efficiencies than native bPEI and the commercial transfection reagent, Lipofectamine™. Sequential siRNA delivery displayed significant suppression in the target gene expression. All together, the evaluation of the delivery systems demonstrates that the newly synthesized DP NPs are quite promising as non-viral gene carriers.

Cross-linkable liposomes stabilize a magnetic resonance contrast-enhancing polymeric fastener.

Liposomes are commonly used to deliver drugs and contrast agents to their target site in a controlled manner. One of the greatest obstacles in the performance of such delivery vehicles is their stability in the presence of serum. Here, we demonstrate a method to stabilize a class of liposomes that load gadolinium, a magnetic resonance (MR) contrast agent, as a model cargo on their surfaces. We hypothesized that the sequential adsorption of a gadolinium-binding chitosan fastener on the liposome surface followed by covalent cross-linking of the lipid bilayer would provide enhanced stability and improved MR signal in the presence of human serum. To investigate this hypothesis, liposomes composed of diyne-containing lipids were assembled and functionalized via chitosan conjugated with a hydrophobic anchor and diethylenetriaminepentaacetic acid (DTPA). This postadsorption cross-linking strategy served to stabilize the thermodynamically favorable association between liposome and polymeric fastener. Furthermore, the chitosan-coated, cross-linked liposomes proved more effective as delivery vehicles of gadolinium than uncross-linked liposomes due to the reduced liposome degradation and chitosan desorption. Overall, this study demonstrates a useful method to stabilize a broad class of particles used for systemic delivery of various molecular payloads.

Solid dispersions of the penta-ethyl ester prodrug of diethylenetriaminepentaacetic acid (DTPA): formulation design and optimization studies.

The penta-ethyl ester prodrug of diethylenetriaminepentaacetic acid (DTPA), which exists as an oily liquid, was incorporated into a solid dispersion for oral administration by the solvent evaporation method using blends of polyvinylpyrrolidone (PVP), Eudragit® RL PO and α-tocopherol. D-optimal mixture design was used to optimize the formulation. Formulations that had a high concentration of both Eudragit® RL PO and α-tocopherol exhibited low water absorption and enhanced stability of the DTPA prodrug. Physicochemical properties of the optimal formulation were evaluated using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). In vitro release of the prodrug was evaluated using the USP Type II apparatus dissolution method. DSC studies indicated that the matrix had an amorphous structure, while FTIR spectrometry showed that DTPA penta-ethyl ester and excipients did not react with each other during formation of the solid dispersion. Dissolution testing showed that the optimized solid dispersion exhibited a prolonged release profile, which could potentially result in a sustained delivery of DTPA penta-ethyl to enhance bioavailability. In conclusion, DTPA penta-ethyl ester was successfully incorporated into a solid matrix with high drug loading and improved stability compared to prodrug alone.

Modular columnar supramolecular polymers as scaffolds for biomedical applications.

Self-assembly of discotic molecules into supramolecular polymers offers a flexible approach for the generation of multicomponent one-dimensional columnar architectures with tuneable biomedical properties. Decoration with ligands induces specific binding of the self-assembled scaffold to biological targets. The modular design allows the easy co-assembly of different discotics for the generation of probes for targeted imaging and cellular targeting with adjustable ligand density and composition.

Dual-purpose polymer labels for fluorescent and mass cytometric affinity bioassays.

We describe the synthesis and characterization of a family of poly(N-alkylacrylamide) polymers carrying 2-6 fluorescent dye molecules, ∼70 pendant DTPA (diethylenetriaminepentaacetic acid) groups, and an orthogonal maleimide end-group for covalent attachment to an antibody (Ab). These dual-purpose labels were designed for use in multiplexed immunoassays based on both mass cytometry and fluorescent flow cytometry. A challenge in the polymer synthesis was finding conditions for attaching a sufficient number of dye molecules to each polymer chain. Although attachment of a terminal maleimide to the polymers was not as efficient as anticipated, the end-functional polymers were still effective in labeling Abs. Secondary goat antimouse IgG was labeled with the four dual-label polymers as well as a control polymer, and while the resultant antibody-polymer conjugates showed positive performance in mass cytometric and fluorescent assays, some trials showed problems such as low signal and nonspecific adsorption. Four primary antibody conjugates were prepared and used to stain cells in 4-plex assays. The results of both primary assays are bittersweet in that the CD3-FITC and CD45-DyLight 649 conjugates performed well, while the CD13-DyLight 405 and the CD38-DyLight 549 conjugates did not.