Particle shape enhances specificity of antibody-displaying nanoparticles.

Monoclonal antibodies are used in numerous therapeutic and diagnostic applications; however, their efficacy is contingent on specificity and avidity. Here, we show that presentation of antibodies on the surface of nonspherical particles enhances antibody specificity as well as avidity toward their targets. Using spherical, rod-, and disk-shaped polystyrene nano- and microparticles and trastuzumab as the targeting antibody, we studied specific and nonspecific uptake in three breast cancer cell lines: BT-474, SK-BR-3, and MDA-MB-231. Rods exhibited higher specific uptake and lower nonspecific uptake in all cells compared with spheres. This surprising interplay between particle shape and antibodies originates from the unique role of shape in determining binding and unbinding of particles to cell surface. In addition to exhibiting higher binding and internalization, trastuzumab-coated rods also exhibited greater inhibition of BT-474 breast cancer cell growth in vitro to a level that could not be attained by soluble forms of the antibody. The effect of trastuzumab-coated rods on cells was enhanced further by replacing polystyrene particles with pure chemotherapeutic drug nanoparticles of comparable dimensions made from camptothecin. Trastuzumab-coated camptothecin nanoparticles inhibited cell growth at a dose 1,000-fold lower than that required for comparable inhibition of growth using soluble trastuzumab and 10-fold lower than that using BSA-coated camptothecin. These results open unique opportunities for particulate forms of antibodies in therapeutics and diagnostics.

Using shape effects to target antibody-coated nanoparticles to lung and brain endothelium.

Vascular endothelium offers a variety of therapeutic targets for the treatment of cancer, cardiovascular diseases, inflammation, and oxidative stress. Significant research has been focused on developing agents to target the endothelium in diseased tissues. This includes identification of antibodies against adhesion molecules and neovascular expression markers or peptides discovered using phage display. Such targeting molecules also have been used to deliver nanoparticles to the endothelium of the diseased tissue. Here we report, based on in vitro and in vivo studies, that the specificity of endothelial targeting can be enhanced further by engineering the shape of ligand-displaying nanoparticles. In vitro studies performed using microfluidic systems that mimic the vasculature (synthetic microvascular networks) showed that rod-shaped nanoparticles exhibit higher specific and lower nonspecific accumulation under flow at the target compared with their spherical counterparts. Mathematical modeling of particle-surface interactions suggests that the higher avidity and specificity of nanorods originate from the balance of polyvalent interactions that favor adhesion and entropic losses as well as shear-induced detachment that reduce binding. In vivo experiments in mice confirmed that shape-induced enhancement of vascular targeting is also observed under physiological conditions in lungs and brain for nanoparticles displaying anti-intracellular adhesion molecule 1 and anti-transferrin receptor antibodies.

Polymer nanoneedle-mediated intracellular drug delivery.

Delivery of drugs into the cellular cytoplasm of target cells represents a major hurdle in treating various diseases. This challenge can be addressed by encapsulation of drugs onto or within nanoparticles, which can then be targeted to diseased cells. Here, needle-shaped particles are shown to exhibit substantially higher cytoplasmic delivery of drugs such as siRNA compared to their spherical counterparts. Furthermore, these needles are designed to lose their sharp tips over time and can render themselves ineffective over time, thereby offering control over their duration of activity and toxicity. Such polymer nanoneedles open new avenues for delivering drug molecules directly into the cytoplasm with low toxicity.

Increasing Tumor Accessibility with Conjugatable Disulfide-Bridged Tumor-Penetrating Peptides for Cancer Diagnosis and Treatment.

Tumor-homing peptides with tissue-penetrating properties increase the efficacy of targeted cancer therapy by delivering an anticancer agent to the tumor interior. LyP-1 (CGNKRTRGC) and iRGD (CRGDKGPDC) are founding members of this class of peptides. The presence of the cysteines forming the cyclizing disulfide bond complicates conjugation of these peptides with other molecules, such as drugs. Here, we report the synthesis of conjugatable disulfide-bridged peptides and their conjugation to biologically important molecules. We have synthesized the LyP-1, iRGD, and CRGDC (GACRGDCLGA) peptides with a cysteine or maleimidohexanoic acid added externally at N-terminus of the sequences. Subsequent conjugation to payloads yielded stable compounds in which the tumor-homing properties of the peptide and the biological activity of the payload were retained.

Synthetic surfaces for human embryonic stem cell culture.

Human embryonic stem cells (hESCs) have numerous potential biomedical applications owing to their unique abilities for self-renewal and pluripotency. Successful clinical application of hESCs and derivatives necessitates the culture of these cells in a fully defined environment. We have developed a novel peptide-based surface that uses a high-affinity cyclic RGD peptide for culture of hESCs under chemically defined conditions.