Skip to main content

Sustainable Polypeptide Nanoparticle Platform for Drug Delivery

Periodic Reporting for period 1 - NanoCap (Sustainable Polypeptide Nanoparticle Platform for Drug Delivery)

Reporting period: 2016-04-01 to 2018-03-31

Nanoparticles gained attention for their ability to serve as viable carriers of active compounds in a broad range of applications. Examples are the delivery of fertilizers to plants, food additives, cosmetic ingredients as well as pharmaceutically active compounds such as vaccines, genes, drugs and other biomolecules (drug delivery) for example through skin or injection. However, health authorities are very attentive to the potential negative effects that may be induced by non-biodegradable nanoparticles. For example, EU member states have adopted a single regulation on the use of nanomaterials in any cosmetic products, including those carrying biologically active ingredients (so-called cosmeceuticals), requiring the disclosure of strict safety information. Exempt are nanoparticles that will be degraded in the skin over a reasonable period of time and not elicit any adverse effect especially if the degradation products are safe. For pharmaceutical products even stricter regulations apply in terms of product safety and efficacy, and stringent product approval from government authorities (e.g. FDA) is required. It is thus clear that the Life Science Sector has a strong demand for biodegradable nanoparticles.
Numerous examples in the academic and patent literature discuss enhanced biocompatibility, superior cargo encapsulation, and convenient release profiles for a number of cargoes from biodegradable nanoparticles to be used in a variety of applications in the field of medicine and cosmetics. Most widely used are polymeric nanoparticles based on natural polymers have advantages and drawbacks, making them more or less suited for certain application areas, e.g. natural polymers usually have a good biocompatibility. However, obtaining reproducible sample quality from natural sources is challenging. PLGA can be produced reproducibly but is hydrophobic in nature, which makes loading of hydrophilic drugs challenging. Next generation carrier systems should offer enhanced functionality to readily enable loading with multiple classes of active agents, allow chemical modification, bioconjugation or diagnostic labelling, if needed. Moreover, they should be easy to produce from natural building blocks, omitting the use of harsh synthetic agents. While the pharmaceutical/medical sector is more conservative, for the cosmetic sector it was stated, that “Terms such as ‘natural’, ‘organic’, ‘no artificial preservatives’ and ‘no animal ingredients’ are drawing formidable attention. This trend is creating heightened demand for products formulated as cosmeceuticals with natural and nutraceutical ingredients. Functional ingredients and innovative delivery systems are driving the new product development arena.”

The overall objective of this project is to develop a new biodegradable polypeptide nanomaterials platform and demonstrate its technical feasibility as nano-carrier platform for active ingredients for Life Science applications exclusively from amino acid building blocks. A series of copolypeptides was synthesized and their structure verified. These were successfully formulated into nanoparticles of 200-300 nm diameter and it was demonstrated that dyes as well as drug molecules can be loaded into the polypeptide nanoparticles. The simple preparation method of synthetic polypeptide nanoparticles will be useful as an advanced technology to develop fully biodegradable nanoparticles used as nanocarriers for active ingredients in biomedical science application.
The first part of the project aimed at the development of a scalable process that allowed the synthesis of nanoparticles fully based on α-amino acids. A process was developed whereby no organic solvents were used to avoid potential toxicity and through careful optimization of reaction conditions polypeptide nanoparticles of ca. 200 nm diameter were obtained. The process for synthesis of nanoparticles was then extended by investigating the introduction of two additional amino acids, i.e. glutamic acid (Glu) and lysine (Lys), to the nanoparticles as they provide convenient handles for further functionalization. The synthetic feasibility of the protocol was investigated by optimizing the reaction conditions as well as the composition of the formulations. In all experiments monomodal (single) distribution of nanoparticles was observed indicating the controlled nature of the polymerization. By further processing steps nanoparticles of approximately 200-300 nm diameter were obtained. This line of research was then extended to the synthesis of statistical copolymers. The reaction kinetics was conveniently monitored by dynamic light scattering and nanoparticle size was approximately 230 nm diameter with a relatively narrow polydispersity (PDI= 0.098 – 0.121) and monomodal size distribution that remained constant throughout the reaction.

In the second part of the project the range of cargo types that can be successfully encapsulated within the polypeptide nanoparticles was investigated in order to determine the scope of their utility. In the first instance a simple model dye rhodamine B was incorporated into the hydrophobic nanoparticles. Rhodamine B-loaded nanoparticles showed mostly spherical morphology with a average diameter of ca. 260 nm. In the following stage indomethacine, a model anti-inflammatory drug was used. Indomethacin is a poorly water-soluble drug used to reduce pain, fever, and inflammation. Indomethacine could be efficiently loaded into the nanoparticles owing to the hydrophobic interaction. In order to meet primary requirements for biomedical use, the degradation profiles of the statistical copolypeptide nanoparticles were tested in a preliminary in vitro hydrolysis study. Degradation of the nanoparticles was thus studied by DLS over the period of 4 weeks. The nanoparticles were prepared in distilled deionized water and PBS buffer and then degraded at 37°C. The average nanoparticle size in water decreased initially, and then levelled off after 7 days. The nanoparticle size then increased dramatically after 14 days, indicating significant aggregation. On the other hand, the average nanoparticle size in PBS buffer remains constant for 24 days followed by significant aggregation as determined by DLS analysis.

It is expected that research activities on this project will result in 1 or 2 papers. During my Marie Skłodowska-Curie Individual Research Fellowship at RCSI I have also worked on a side project, which has resulted in the synthesis of novel poly(tert-butyl acrylate)-xanthate macroinitiator as a precursor for RAFT polymerization with N-vinylpyrrolidone. The result of this work has been presented as a poster at the European Polymer Conference in Lyon (EPF2017, MO 017-147049). In addition, I have attended the Marie Skłodowska-Curie alumni association conference (Leuven, February 2nd-3rd 2018) which enabled me to participate in career development events such as workshops on funding and employment opportunities.
A new class of biodegradable nanoparticles was developed in this project and it feasibility for the loading with active ingredients demonstrated. The technology is currently under discussion for patent protection as it offers significant potential as a new bio-derived drug delivery platform. While additional work is needed to gain in vivo and in vitro data, this nanomaterial platform has the potential to be integrated into drug delivery devices to address unmet clinical needs.
TEM images of nanoparticles before (a, b) and after processing (c,d)