A Novel Single-Step-Labeled 212Pb-CaCO3 Microparticle for Internal Alpha Therapy: Preparation, Stability, and Preclinical Data from Mice

Lead-212 is recognized as a promising radionuclide for targeted alpha therapy for tumors. Many studies of 212Pb-labeling of various biomolecules through bifunctional chelators have been conducted. Another approach to exploiting the cytotoxic effect is coupling the radionuclide to a microparticle acting as a carrier vehicle, which could be used for treating disseminated cancers in body cavities. Calcium carbonate may represent a suitable material, as it is biocompatible, biodegradable, and easy to synthesize. In this work, we explored 212Pb-labeling of various CaCO3 microparticles and developed a protocol that can be straightforwardly implemented by clinicians. Vaterite microparticles stabilized by pamidronate were effective as 212Pb carriers; labeling yields of ≥98% were achieved, and 212Pb was strongly retained by the particles in an in vitro stability assessment. Moreover, the amounts of 212Pb reaching the kidneys, liver, spleen, and skeleton of mice following intraperitoneal (i.p.) administration were very low compared to i.p. injection of unbound 212Pb2+, indicating that CaCO3-bound 212Pb exhibited stability when administered intraperitoneally. Therapeutic efficacy was observed in a model of i.p. ovarian cancer for all the tested doses, ranging from 63 to 430 kBq per mouse. Lead-212-labeled CaCO3 microparticles represent a promising candidate for treating intracavitary cancers.

Synthesis and Biodistribution of 99mTc-Labeled PLGA Nanoparticles by Microfluidic Technique

The aim of present study was to develop radiolabeled NPs to overcome the limitations of fluorescence with theranostic potential. Synthesis of PLGA-NPs loaded with technetium-99m was based on a Dean-Vortex-Bifurcation Mixer (DVBM) using an innovative microfluidic technique with high batch-to-batch reproducibility and tailored-made size of NPs. Eighteen different formulations were tested and characterized for particle size, zeta potential, polydispersity index, labeling efficiency, and in vitro stability. Overall, physical characterization by dynamic light scattering (DLS) showed an increase in particle size after radiolabeling probably due to the incorporation of the isotope into the PLGA-NPs shell. NPs of 60 nm (obtained by 5:1 PVA:PLGA ratio and 15 mL/min TFR with 99mTc included in PVA) had high labeling efficiency (94.20 ± 5.83%) and > 80% stability after 24 h and showed optimal biodistribution in BALB/c mice. In conclusion, we confirmed the possibility of radiolabeling NPs with 99mTc using the microfluidics and provide best formulation for tumor targeting studies.

PSI-6 Characterization of in vitro stability for two multi-functional processive endoglucanases as exogenous biocatalysts in pig nutrition

Poor efficiency of dietary fibre utilization limits global pork production profit margins and mitigation of footprint on environment. The objective of this study was to characterize in vitro stability for two unique processive endoglucanases of tCel5A1 and p4818Cel5_2A that are reported to hydrolyze natural cellulose and have multi-functionality towards hemicelluloses (Basit and Akhtar, Biotechnology and Bioengineering, 2018, 115:1675; Wang et al., Scientific Reports 2019, 9:13630). Both tCel5A1 and p4818Cel5_2A were modelled with the SWISS-MODEL online server and analyzed and visualized by PyMOL2.4.1. These two cellulases were overexpressed in ClearColi®BL21(DE3). Their endoglucanase activities were determined using 0.70 % sodium carboxymethyl cellulose and 5 mM dithiothreitol (DTT) with or without N2 gas purging; and incubated at pH 6.5–7.0 and 37 °C for 15 min. The three-dimensional models showed 1 and 4 Cys residues on the surfaces of tCel5A1 and p4818Cel5_2A, respectively, suggesting their susceptibility to auto-oxidation by air-borne O2. This prediction was tested by comparing the activities of N2-purged and non-purged enzyme preparations as well as their processing and incubation handling. Both tCel5A1 and p4818Cel5_2A activities were enhanced (P < 0.01) by 50% when 5-mM DTT and N2-purging were adopted. Furthermore, after incubating both tCel5A1 and p4818Cel5_2A enzyme preparations under the porcine gastric pH (3.5) and pepsin (274 U/mL) as well as intestinal trypsin (78 U/mL) and chymotrypsin (20 U/mL) activities at pH 6.5 during 0–5 h, Eadie-Hofstee inhibition kinetic analyses showed that tCel5A1 and p4818Cel5_2A respectively lost 18 and 68% (P < 0.01) of their initial activities after 2 h under the gastric conditions and more than 90% (P < 0.01) of their initial activities after 2–3 h under the intestinal conditions. Therefore, further enzyme protein engineering and/or post-fermentation treatments, such as coating for by-passing the gastric-intestinal environment, will be required to enable these two processive endoglucanases as efficacious exogenous fibre enzymes.

Synthesis and Characterization of Porous, Electro-Conductive Chitosan–Gelatin–Agar-Based PEDOT: PSS Scaffolds for Potential Use in Tissue Engineering

Herein we report the synthesis and characterization of electro-conductive chitosan–gelatin–agar (Cs-Gel-Agar) based PEDOT: PSS hydrogels for tissue engineering. Cs-Gel-Agar porous hydrogels with 0–2.0% (v/v) PEDOT: PSS were fabricated using a thermal reverse casting method where low melting agarose served as the pore template. Sample characterizations were performed by means of scanning electron microscopy (SEM), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR), X-ray diffraction analysis (XRD) and electrochemical impedance spectroscopy (EIS). Our results showed enhanced electrical conductivity of the cs-gel-agar hydrogels when mixed with DMSO-doped PEDOT: PSS wherein the optimum mixing ratio was observed at 1% (v/v) with a conductivity value of 3.35 × 10−4 S cm−1. However, increasing the PEDOT: PSS content up to 1.5 % (v/v) resulted in reduced conductivity to 3.28 × 10−4 S cm−1. We conducted in vitro stability tests on the porous hydrogels using phosphate-buffered saline (PBS) solution and investigated the hydrogels’ performances through physical observations and ATR–FTIR characterization. The present study provides promising preliminary data on the potential use of Cs-Gel-Agar-based PEDOT: PSS hydrogel for tissue engineering, and these, hence, warrant further investigation to assess their capability as biocompatible scaffolds.

Chitosan/PVA Based Membranes Processed by Gamma Radiation as Scaffolding Materials for Skin Regeneration

Some of the current strategies for the development of scaffolding materials capable of inducing tissue regeneration have been based on the use of polymeric biomaterials. Chitosan, in particular, due to its recognized biological activity has been used in a number of biomedical applications. Aiming the development of chitosan-based membranes with improved cell adhesion and growth properties to be used as skin scaffolds allowing functional tissue replacement, different formulations with chitosan of different molecular weight, poly (vinyl alcohol) and gelatin, were evaluated. To meet the goal of getting ready-to-use scaffolds assuring membranes’ required properties and sterilization, preparation methodology included a lyophilization procedure followed by a final gamma irradiation step. Two radiation dose values were tested. Samples were characterized by TGA, FTIR, and SEM techniques. Their hydrophilic properties, in vitro stability, and biocompatibility were also evaluated. Results show that all membranes present a sponge-type inner structure. Chitosan of low molecular weight and the introduction of gelatin are more favorable to cellular growth leading to an improvement on cells’ morphology and cytoskeletal organization, giving a good perspective to the use of these membranes as potential skin scaffolds.