Polyglycerol and Poly(ethylene glycol) exhibit different effects on pharmacokinetics and antibody generation when grafted to nanoparticle surfaces.

Poly(ethylene glycol) (PEG) is widely employed for passivating nanoparticle (NP) surfaces to prolong blood circulation and enhance localization of NPs to target tissue. However, the immune response of PEGylated NPs-including anti-PEG antibody generation, accelerated blood clearance (ABC), and loss of delivery efficacy-is of some concern, especially for treatments that require repeat administrations. Although polyglycerol (PG), which has the same ethylene oxide backbone as PEG, has received attention as an alternative to PEG for NP coatings, the pharmacokinetic and immunogenic impact of PG has not been studied systematically. Here, linear PG, hyperbranched PG (hPG), and PEG-coated polylactide (PLA) NPs with varying surface densities were studied in parallel to determine the pharmacokinetics and immunogenicity of PG and hPG grafting, in comparison with PEG. We found that linear PG imparted the NPs a stealth property comparable to PEG, while hPG-grafted NPs needed a higher surface density to achieve the same pharmacokinetic impact. While linear PG-grafted NPs induced anti-PEG antibody production in mice, they exhibited minimal accelerated blood clearance (ABC) effects due to the poor interaction with anti-PEG immunoglobulin M (IgM). Further, we observed no anti-polymer IgM responses or ABC effects for hPG-grafted NPs.

PEGylation of poly(amine-co-ester) polyplexes for tunable gene delivery.

There is growing interest in PEGylation of cationic polymeric vehicles for gene delivery in order to improve vehicle stability and reduce toxicity, but little is known about the effects of PEG coatings on transfection. We used a polymer from the poly(amine-co-ester) (PACE) family blended with PEG-conjugated PACE at different ratios in order to explore the effects of polyplex PEGylation on the transfection efficiency of plasmid DNA, mRNA, and siRNA in vitro and mRNA in vivo. We discovered that concentrations of PACE-PEG as low as 0.25% by weight improved polyplex stability but also inhibited transfection in vitro. In vivo, the effect of PACE-PEG incorporation on mRNA transfection varied by delivery route; the addition of PACE-PEG improved local delivery to the lung, but PEGylation had little effect on intravenous systemic delivery. By both delivery routes, transfection was inhibited at concentrations higher than 5 wt% PACE-PEG. These results demonstrate that excess PEGylation can be detrimental to vehicle function, and suggest that PEGylation of cationic vehicles must be optimized by PEG content, cargo type, and delivery route.

Nonsurgical treatment of skin cancer with local delivery of bioadhesive nanoparticles.

Keratinocyte-derived carcinomas, including squamous cell carcinoma (SCC), comprise the most common malignancies. Surgical excision is the therapeutic standard but is not always clinically feasible, and currently available alternatives are limited to superficial tumors. To address the need for a nonsurgical treatment for nodular skin cancers like SCC, we developed a bioadhesive nanoparticle (BNP) drug delivery system composed of biodegradable polymer, poly(lactic acid)-hyperbranched polyglycerol (PLA-HPG), encapsulating camptothecin (CPT). Nanoparticles (NPs) of PLA-HPG are nonadhesive NPs (NNPs), which are stealthy in their native state, but we have previously shown that conversion of the vicinal diols of HPG to aldehydes conferred NPs the ability to form strong covalent bonds with amine-rich surfaces. Herein, we show that these BNPs have significantly enhanced binding to SCC tumor cell surfaces and matrix proteins, thereby significantly enhancing the therapeutic efficacy of intratumoral drug delivery. Tumor injection of BNP-CPT resulted in tumor retention of CPT at ∼50% at 10 d postinjection, while CPT was undetectable in NNP-CPT or free (intralipid) CPT-injected tumors at that time. BNP-CPT also significantly reduced tumor burden, with a portion (∼20%) of BNP-CPT-treated established tumors showing histologic cure. Larger, more fully established PDV SCC tumors treated with a combination of BNP-CPT and immunostimulating CpG oligodeoxynucleotides exhibited enhanced survival relative to controls, revealing the potential for BNP delivery to be used along with local tumor immunotherapy. Taken together, these results indicate that percutaneous delivery of a chemotherapeutic agent via BNPs, with or without adjuvant immunostimulation, represents a viable, nonsurgical alternative for treating cutaneous malignancy.

High-throughput quantitative microscopy-based half-life measurements of intravenously injected agents.

Accurate analysis of blood concentration and circulation half-life is an important consideration for any intravenously administered agent in preclinical development or for therapeutic application. However, the currently available tools to measure these parameters are laborious, expensive, and inefficient for handling multiple samples from complex multivariable experiments. Here we describe a robust high-throughput quantitative microscopy-based method to measure the blood concentration and circulation half-life of any fluorescently labeled agent using only a small (2 µL) amount of blood volume, enabling additional end-point measurements to be assessed in the same subject. To validate this method, we demonstrate its use to measure the circulation half-life in mice of two types of fluorescently labeled polymeric nanoparticles of different sizes and surface chemistries and of a much smaller fluorescently labeled monoclonal antibody. Furthermore, we demonstrate the improved accuracy of this method compared to previously described methods.