Antibody-Hapten Recognition at the Surface of Functionalized Liposomes Studied by SPR: Steric Hindrance of Pegylated Phospholipids in Stealth Liposomes Prepared for Targeted Radionuclide Delivery

Endothelial-Specific Targeting of RhoA Signaling via CD31 Antibody-Conjugated Nanoparticles

Existing vascular endothelial growth factor-oriented antiangiogenic approaches are known for their high potency. However, significant side effects associated with their use drive the need for novel antiangiogenic strategies. The small GTPase RhoA is an established regulator of actin cytoskeletal dynamics. Previous studies have highlighted the impact of endothelial RhoA pathway on angiogenesis. Rho-associate kinase (ROCK), a direct RhoA effector, is potently inhibited by Fasudil, a clinically relevant ROCK inhibitor. Here, we aimed to target the RhoA signaling in endothelial cells by generating Fasudil-encapsulated CD31-targeting liposomes as a potential antiangiogenic therapy. The liposomes presented desirable characteristics, preferential binding to CD31-expressing HEK293T cells and to endothelial cells, inhibited stress fiber formation and cytoskeletal-related morphometric parameters, and inhibited in vitro angiogenic functions. Overall, this work shows that the nanodelivery-mediated endothelial targeting of RhoA signaling can offer a promising strategy for angiogenesis inhibition in vascular-related diseases. SIGNIFICANCE STATEMENT: Systemic administration of antiangiogenic therapeutics induces side effects to non-targeted tissues. This study, among others, has shown the impact of the RhoA signaling in the endothelial cells and their angiogenic functions. Here, to minimize potential toxicity, this study generated CD31-targeting liposomes with encapsulated Fasudil, a clinically relevant Rho kinase inhibitor, and successfully targeted endothelial cells. In this proof-of-principle study, the efficient Fasudil delivery, its impact on the endothelial signaling, morphometric alterations, and angiogenic functions verify the benefits of site-targeted antiangiogenic therapy.

Systemically Applicable Glutamine-Functionalized Polymer Exerting Multivalent Interaction with Tumors Overexpressing ASCT2

Transporter ASCT2, which predominantly imports glutamine (Gln), is overexpressed in a variety of cancer cells, and targeting ASCT2 is expected to be a promising approach for tumor diagnosis and therapy. In this work, we designed a series of glutamine-modified poly(l-lysine) (PLys(Gln)) homopolymers and PEG-PLys(Gln) block copolymers and investigated their tumor-targeting abilities. With increasing degree of polymerization in the PLys(Gln) homopolymers, their cellular uptake was gradually enhanced through multivalent interactions with ASCT2. The performance of PEG-PLys(Gln) in blood circulation and tumor accumulation could be controlled by tuning of the molecular weight of PEG. Our results highlight the utility of molecular recognition in ASCT2/PLys(Gln) for tumor targeting through systemic administration.

Equilibrium, affinity, dissociation constants, IC5O: Facts and fantasies

The interaction between ligands and receptors is often described in terms of 50% inhibitory concentrations (IC50). However, IC50 values do not accurately reflect the dissociation constants (Kd), and the domain of application and precision of proposed approximations for Kd estimation are unclear. The effect of affinity and of experimental conditions on the differences between IC50 and Kd has been assessed from exact mass action law calculations and from computer simulations. Competitions between [¹¹¹ In]DTPA-indium and a few metal-DTPA complexes for binding to a specific antibody are discussed as a practical example. Exact calculations of competition assays have been implemented in Microsoft Excel and performed for a variety of concentrations of receptor, tracer, and competitor. The results are identical to those of software packages. IC50 is found larger than Kd by less than 20% only when tracer concentration is small compared with Kd and to the receptor concentration and when this receptor concentration is small compared with Kd. Otherwise, Kd and IC50 may be very different and approximations proposed in the literature to obtain Kd values from graphically derived IC50 are not acceptable as soon as the concentrations of tracer or of receptor approach Kd. Under most experimental conditions, IC50 values do not reflect Kd values. Using available software packages to determine and report Kd values would allow for more meaningful comparisons of results obtained under different experimental conditions.

Selective Delivery of PEGylated Compounds to Tumor Cells by Anti-PEG Hybrid Antibodies

Polyethylene glycol (PEG) is attached to many peptides, proteins, liposomes, and nanoparticles to reduce their immunogenicity and improve their pharmacokinetic and therapeutic properties. Here, we describe hybrid antibodies that can selectively deliver PEGylated medicines, imaging agents, or nanomedicines to target cells. Human IgG1 hybrid antibodies αPEG:αHER2 and αPEG:αCD19 were shown by ELISA, FACS, and plasmon resonance to bind to both PEG and HER2 receptors on SK-BR-3 breast adenocarcinoma and BT-474 breast ductal carcinoma cells or CD19 receptors on Ramos and Raji Burkitt's lymphoma cells. In addition, αPEG:αHER2 specifically targeted PEGylated proteins, liposomes, and nanoparticles to SK-BR-3 cells that overexpressed HER2, but not to HER2-negative MCF-7 breast adenocarcinoma cells. Endocytosis of PEGylated nanoparticles into SK-BR-3 cells was induced specifically by the αPEG:αHER2 hybrid antibody, as observed by confocal imaging of the accumulation of Qdots inside SK-BR-3 cells. Treatment of HER2(+) SK-BR-3 and BT-474 cancer cells with αPEG:αHER2 and the clinically used chemotherapeutic agent PEGylated liposomal doxorubicin for 3 hours enhanced the in vitro effectiveness of PEGylated liposomal doxorubicin by over two orders of magnitude. Hybrid anti-PEG antibodies offer a versatile and simple method to deliver PEGylated compounds to cellular locations and can potentially enhance the therapeutic efficacy of PEGylated medicines.

Bacterial cytoplasm as an effective cell compartment for producing functional VHH-based affinity reagents and Camelidae IgG-like recombinant antibodies

BACKGROUND

The isolation of recombinant antibody fragments from displayed libraries represents a powerful alternative to the generation of IgGs using hybridoma technology. The selected antibody fragments can then be easily engineered into (multi)-tagged constructs of variable mass and complexity as well as reconstituted into Camelidae IgG-like molecules when expressed fused to Fc domains. Nevertheless, all antibody constructs depend on an oxidizing environment for correct folding and consequently still belong to the proteins difficult to express in bacteria. In such organisms they are mostly produced at low yields in the periplasmic space.

RESULTS

We demonstrate that fusion constructs of recombinant antibodies in combination with multiple tags can be produced at high yields and totally functional in the cytoplasm of bacteria expressing sulfhydryl oxidase. The method was applied to structurally demanding molecules such as VHHs fused to SNAP and Fc domains and was validated using the antibody-derived reagents in a variety of immune techniques (FACS, ELISA, WB, IP, SPR, and IF).

CONCLUSIONS

The collected data demonstrate the feasibility of a method that establishes a totally new approach for producing rapidly and inexpensively functional Camelidae IgG-like monoclonal antibodies and antibody-based reagents containing multiple disulfide bonds and suitable for both basic research and clinical applications.

Synthesis and in vitro studies of gold nanoparticles loaded with docetaxel

The aim of these studies was to synthesize, characterize and evaluate the efficacy of pegylated gold nanoparticles (AuNPs) that differed in their PEG molecular weight, using PEG 550 and PEG 2000. The synthesis of the gold nanoparticles was carried out by modified Brust method with a diameter of 4-15 nm. The targeting agent folic acid was introduced by the covalent linkage. Finally, the anti-cancer drug docetaxel was encapsulated by the AuNPs by non covalent adsorption. The nanoparticles were characterized by transmission electron microscopy and used for in vitro studies against a hormone-responsive prostate cancer cell line, LnCaP. The loaded nanoparticles reduced the cell viability in more than 50% at concentrations of 6 nM and above after 144 h of treatment. Moreover, observation of prostate cancer cells by optical microscopy showed damage to the cells after exposure to drug-loaded AuNPs while unloaded AuNPs had much less effect.

Recent trends in multifunctional liposomal nanocarriers for enhanced tumor targeting

Liposomes are delivery systems that have been used to formulate a vast variety of therapeutic and imaging agents for the past several decades. They have significant advantages over their free forms in terms of pharmacokinetics, sensitivity for cancer diagnosis and therapeutic efficacy. The multifactorial nature of cancer and the complex physiology of the tumor microenvironment require the development of multifunctional nanocarriers. Multifunctional liposomal nanocarriers should combine long blood circulation to improve pharmacokinetics of the loaded agent and selective distribution to the tumor lesion relative to healthy tissues, remote-controlled or tumor stimuli-sensitive extravasation from blood at the tumor's vicinity, internalization motifs to move from tumor bounds and/or tumor intercellular space to the cytoplasm of cancer cells for effective tumor cell killing. This review will focus on current strategies used for cancer detection and therapy using liposomes with special attention to combination therapies.