Nanoparticle Engineering in Drug Delivery Under the Microscope

In biotherapeutic production, delivery of the therapeutic agent is a significant factor for achieving successful therapeutic effect. With this consideration in mind, the delivery mechanism requires forethought. Among the more innovative drug delivery systems being developed today are those employing nanoparticle technologies.

The development of nanoparticles in recent years has expanded into a range of clinical applications. Nanoparticles were developed to address the limitations posed by free therapeutics as well as to overcome biologics barriers, including systemic, environmental, and cellular barriers. Work in nanoparticle development has focused on ways to optimize drug delivery systems so that these systems can be applied across patient populations and across different diseases (1).

“Safe and effective delivery of therapeutic cargo to its target tissue at a clinically relevant dose is crucial for developing successful drugs regardless of the route of administration,” says John Lewis, PhD, CEO of Entos Pharmaceuticals. “Nanoparticle engineering must be purpose-driven and designed around the physical and biochemical properties of the therapeutic cargo and the disease it is designed to treat. The cargo size, charge, and ability to tolerate chemical modification greatly impact the type of nanoparticle used in a drug development program.”

“Additionally,” Lewis states, “the complexity and cost of manufacturing must also be considered when developing novel therapies. All of these factors need to be considered at the start of the drug development process to maximize both clinical and commercial success.”

The biggest benefits and challenges of using nanoparticles come with designing a nanoparticle delivery system that can deliver a molecule to the right target tissue safely and efficiently, Lewis explains. What’s more, it is challenging to design nanoparticles that do not require complex or costly manufacturing.

“For example, viral vectors transduce target cells with high efficiency but can only be used to deliver DNA, have cargo capacity limits, can be costly to manufacture, and cannot be used for repeat dosing due to their immunogenicity,” Lewis points out.

Currently marketed lipid nanoparticles (LNPs) also have limitations, Lewis adds, such as poor biodistribution that preferentially targets the liver, poor tolerability, especially at high doses, and lack of utility for delivering DNA. To address such limitations, Entos developed a technology platform (Fusogenix PLV) that combines tiny fusion proteins with well-tolerated lipids. The company’s approach combines the best features of viral vectors and LNPs to deliver RNA, DNA, or novel gene-editing technologies safely, effectively, and repeatedly by direct fusion with target cells, Lewis states.

“The nature of your engineered nanoparticle will determine if its benefits outweigh its challenges,” says Lewis.

Engineering in the works

With much discussion in the biopharma industry surrounding nanoparticle technology, specifically for its use in bio-drug delivery, LNPs are at the forefront. “Among the myriad of nanoparticles, LNPs are the leading candidates for delivery of many different biological drugs, which includes nucleic acids such as mRNA [messenger RNA], siRNA [small interfering RNA], pDNA [plasmid DNA], gene editing tools such as CRISPR [clustered regularly interspaced palindromic repeats]/cas9 and oligonucleotides,” says Rajiv Kumar, PhD, principal scientist, Applied Research and Clinical Team, West Pharmaceutical Services (2,3).

Kumar notes that some current key focus areas in the LNP space revolves around designing new novel lipids, such as ionizable lipids to improve the efficiency of delivery and the release of encapsulated payloads from nanoparticles; targetability of LNPs; and improving the toxicity profile of LNPs (4,5). Despite LNPs accounting for the majority of nanoparticles for biologics drug delivery in clinical trials today, preliminary reports have begun to shine light on a new generation of hybrid nanoparticles, such as the combination of lipids and polymers, says Kumar. These reports have been showing high potential in these hybrid nanoparticles of successful biologic drug delivery (6), he adds.

“Polymer nanoparticles and microparticles have shown some early promise in delivery of proteins (peptides and antibodies), however, more work is required to fully utilize the potential of polymer nanoparticles for biologics delivery,” (7) Kumar states.

What’s so special about LNPs?

As LNPs are currently the most well-known and used nanoparticle technology today for biologic-based drug delivery, a closer look at their technical advantages can suggest further applications in the future.

According to Kumar, the types of advantages (3) that LNP systems convey over conventional drug delivery systems include:

• Encapsulation: in the case of nucleic acid-based therapies, the encapsulation of nucleic acids in the core of nanoparticles protect them from degradation by nucleases, thus providing higher stability and protection.
• Immunogenicity: LNPs minimize adverse immunogenic responses.
• Size advantage: the size and compositions of LNPs enable the therapeutic payload, such as nucleic acids, to efficiently cross negatively charged cell membranes and be released into the cell’s cytoplasm.
• Target-specific: targeting of specific disease sites or organs can be achieved by conjugating targeting molecules on the surface of LNPs.
• Safety: the biodegradable nature of lipids used in LNPs provides a safe and non-toxic platform for delivering biological drugs.

Considering the risks

However, despite the advantages that a nanoparticle technology-based drug delivery system may have, what are the risks inherent in their manufacture?

Kumar elaborates that LNPs are the most complex of manufactured nanoparticles in terms of composition and activity. For instance, each individual lipid component (ionizable lipid, helper lipid, cholesterol, and polyethylene glycol [PEG]-lipid) has a specific role—from encapsulation to formation of nanoparticles and from stabilization to successful delivery and therapeutic efficacy. “Although standard lipid components are in place, a precise tuning and optimization is required for designing a LNPs system for a specific biologic drug payload delivery,” (2) he explains.

In addition, LNP production requires an extremely precise process of mixing different components into specific ratios, says Kumar. The reason for this strict precision is to obtain monodisperse nanoparticles that have high encapsulation efficiency. Following initial production, the nanoparticles must then be purified by ultrafiltration/diafiltration processes to conduct buffer exchange and remove any impurities or solvents from nanoparticle suspension. Finally, the purified nanoparticles are sterile filtered before fill/finish (8).

Some of the key challenges in the manufacturing of LNPs are the quality of nanoparticles, which must be monodisperse and with a high payload content; they require highly precise and uniform mixing; and complex downstream processing, especially purification using ultrafiltration, Kumar highlights. Moreover, containment is a challenge. “One of the main risks is the selection of the right type of containment system (e.g., types of vials and stoppers), which still needs to be evaluated as some of the coatings can have an adverse impact on the quality/stability of nanoparticles during storage and transportation,” he explains.

Should the challenges and risks in nanoparticle production be mitigated, then the biopharm industry would have a powerful drug delivery system that, in the end, may alleviate patient concern over safety. Some of the key benefits for the biopharma industry include the availability of a flexible platform for encapsulating a variety of drugs, including hydrophobic drugs (i.e., most small-molecule drugs), hydrophilic drugs (i.e., biologics, protein therapeutics, antisense oligonucleotides), and highly negatively charged drugs (i.e., nucleic acids), emphasizes Kumar.

Furthermore, new disease targets would be accessible through the expedient of designing targeted nanoparticles systems, and combination therapies could be more feasible by means of designing nanoparticles systems that can encapsulate two drugs together for synergistic/combination effects, Kumar adds.

Meanwhile, the benefits to patients include better therapeutic outcomes since nanoparticle-based delivery of drugs results in higher therapeutic benefits compared to conventional drugs. In addition, because nanoparticles-based systems are designed to accumulate in a specific organ or disease site, the undesired side off-target effects typically seen with conventional drug delivery are minimized in patients. This benefit is especially attractive for some of the highly toxic oncology drugs, Kumar says.

Enter the exosome

A new area being explored in the field of drug delivery is the use of exosomes as delivery vehicles. Exosomes are naturally occurring nanovesicles derived from cells that play an integral role in intercellular transport of materials. It has been shown that exosomes can incorporatetherapeutics, such as small molecules or nucleic acid drugs, and deliver them to specific types of cells or tissues; that is to say, exosomes can achieve targeted drug delivery (9).

As above, the benefit of targeted drug delivery is that it increases local concentration of a therapeutic and can thus minimizes side effects. Exosome engineering, however, is still in its infancy. However, early research has shown that exosome-mediated drug delivery demonstrates low toxicity, low immunogenicity, and high engineerability (9).

Kumar notes that exosomes have been studied in biomarker applications and therapeutic agents in several degenerative diseases and oncology applications (10), but that they have already been deployed in several clinical trials and have shown satisfactory results in not only biomarker applications, but also as drug delivery systems, in vaccine applications, and as therapeutic agents themselves (11). However, although exosomes hold potential, their heterogenous nature pose manufacturing challenges, especially related to their isolation and purification. Manufacturing of exosomes requires further exploration and improved standardization, Kumar states.

The use of nanoparticle engineering may be agood solution for current challenges in the delivery of therapeutics, but overcoming manufacturing issues will be required to standardize production and ensure safety, efficacy, and efficiency.

References

1. Mitchell, M. J.; Billingsley, M. M., Haley, R. M.; et al. Engineering Precision Nanoparticles for Drug Delivery. Nat Rev Drug Discov 2021, 20, 101–124. DOI: 10.1038/s41573-020-0090-8
2. Kulkarni, J. A.; Witzigmann, D.; Thomson, S. B.; et al. The Current Landscape of Nucleic Acid Therapeutics. Nat. Nanotechnol. 2021, 16, 630–643. DOI: 10.1038/s41565-021-00898-0
3. Cullis, P. R.; Hope, M. J. Lipid Nanoparticle Systems for Enabling Gene Therapies. Mol Ther. 2017, 25 (7), 1467–1475. DOI: 10.1016/j.ymthe.2017.03.013
4. Sabnis, S.; Kumarasinghe, E. S.; Salerno, T.; et al. A Novel Amino Lipid Series for mRNA Delivery: Improved Endosomal Escape and Sustained Pharmacology and Safety in Non-human Primates. Mol Ther. 2018, 26 (6), 1509–1519. DOI: 10.1016/j.ymthe.2018.03.010
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6. Mukherjee, A.; Waters, A. K.; Kalyan, P.; et al. Lipid-Polymer Hybrid Nanoparticles as a Next-Generation Drug Delivery Platform: State of the Art, Emerging Technologies, and Perspectives. Int J Nanomedicine 2019, 14, 1937–1952. DOI: 10.2147/IJN.S198353
7. Pagels, R. F.; Prud’homme, R. K. Polymeric Nanoparticles and Microparticles for the Delivery of Peptides, Biologics, and Soluble Therapeutics. J Control Release 2015, 219, 519–535. DOI: 10.1016/j.jconrel.2015.09.001
8. Shepherd, S. J.; Warzecha, C. C.; Yadavali, S. et al. Scalable mRNA and siRNA Lipid Nanoparticle Production Using a Parallelized Microfluidic Device. Nano Lett. 2021, 21 (13), 5671–5680. DOI: 10.1021/acs.nanolett.1c01353
9. Liang, Y.; Duan, L.; Lu, J.; Xia, J. Engineering Exosomes for Targeted Drug Delivery. Theranostics 2021, 11 (7), 3183–3195. DOI: 10.7150/thno.52570
10. Muthu, S.; Bapat, A.; Jain, R.; Jeyaraman, N.; Jeyaraman, M. Exosomal Therapy—A New Frontier in Regenerative Medicine. Stem Cell Investig. 2021, 8, 7. DOI: 10.21037/sci-2020-037
11. Rezaie, J.; Feghhi, M.; Etemadi, T. A Review on Exosomes Application in Clinical Trials: Perspective, Questions, and Challenges. Cell Commun Signal. 2022, 20 (1), 145. DOI: 10.1186/s12964-022-00959-4.

About the author

Feliza Mirasol is the science editor for BioPharm International.

Article Details

BioPharm International
Volume 36, No. 9
September 2023
Pages: 8–10

Citation

When referring to this article, please cite it as Mirasol, F. Nanoparticle Engineering in Drug Delivery Under the Microscope. BioPharm International 2023, 36 (9), 8–10.