Abstract

Nanotechnology has made progress in the creation of new materials with potential applications in the biomedical field. The potential uses of viral particles in nanomedicine include applications, in areas such as drug delivery, medical imaging, biosensors, and enzyme replacement therapies. Virus capsids are used as protein cages, scaffolds, and templates for the production of bionanostructured materials, where organic and inorganic molecules could be incorporated in a precise and a controlled fashion. Potential applications of virus particles include the following: (i) gene therapy, in which the virus particle is used as a carrier to deliver the therapeutic gene to target cells; (ii) drug delivery to ensure that pharmaceuticals get into the body and reach the tissue where they are really needed; (iii) imaging, where virus-like particles are coupled with an imaging agent, and then using ultrasound, magnetic resonance, or even traditional X-ray, to visualize the inside of the targeted organ; (iv) biosensors for the detection of diverse analytes or to measure some physicochemical conditions of the target tissue; and (v) VLPs, which have been recently proposed as carriers to deliver enzymatic activity for enzyme replacement therapies. In this work, these potential biomedical applications of virus-like particles are reviewed and discussed.

Keywords: bionanotechnology, nanotechnology, nanomedicine, virus-like particles, virus, capsids

#### 1. Introduction

Nanotechnology involves the study, design, and production of materials at a nanometric scale, from 1 to 100 nm at least in one of their dimensions. At this scale the materials show singular physicochemical properties at electric, optical, and mechanical levels, among others, which originated from the dramatic increase of the ratio of surface area to volume, as also from the electron confinement in a reduced space [1].

Bionanotechnology or nanobiotechnology is a section of nanotechnology that is focused on the research and development of new materials at nanometric scale based on biomolecules, such as proteins, nucleic acids, and carbohydrates for specific uses. Among these natural materials there are the pseudoviral particles or virus-like nanoparticles (VLPs) that have gained attention due to their potential applications in the biomedical field or nanomedicine [2]. In spite of the fact that the viral nanoparticles have been largely used as vaccines [3], new biomedical applications have been proposed, and they are reviewed and discussed here.

The VLPs, opposite to viruses, do not contain their natural genetic material, and thus they are noninfectious and unable to replicate themselves. These viral

nanoparticles could be used as basic templates for the design and production of nanostructured materials (Figure 1). The following are the most important properties of VLPs [4, 5]:


The VLPs show three available interphases to be chemically or genetically manipulated: the external surface exposed to solvent, the internal surface, and the interphase between the protein subunits (Figure 2). The different surfaces can be used to precisely tune new functions for the different applications [7].

2. Medical applications of VLPs

good biological characterization [10].

The VLPs have been largely studied for their use in gene therapy because of their natural capacity to transport nucleic acids and to integrate these genes into the host genome. Mainly, the nanoparticles come from virus of mammals since they have

Scheme of tree interphases in which virus-like nanoparticles can be modified for the addition of new functions

The family of adenovirus is the most used virus to produce VLPs for gene therapy. They are icosahedral capsids containing double chain DNA. So far, 24% of the clinical tests for gene therapy are using this kind of virus. These viral vectors reach a load capacity up to 35 kilobases of nonviral DNA that allow the incorpora-

The VLPs show several advantages; they are easily produced with high viral titers, they have the transduction capacity with high efficiency in both growing and quiescent cells, great genome stability, low levels of viral genome integration, and

The surface of VLPs can be chemically modified with polymers such as polyethylene glycol (PEG) and poly-N-(2-hydroxypropyl) methacrylamide (poly-HPMA) with the aim to decrease their immunogenicity, avoiding a fast elimination. On the other hand, the chemical modification of the VLP's surface could be used to bind ligands for specific cell receptors to be internalized in targeted tissues [11].

In addition to gene transport to targeted cells for gene therapy, the VLPs are able to deliver to specific tissues small molecules as therapeutic agents. The goal is to deliver the therapeutic drug to the tissues, which is needed to increase the treatment efficiency and importantly to reduce the doses and thus the side effects. The

the intrinsic capacity to internalize into human or animal cells [8].

tion of big transgenes as well as regulation elements [9].

2.1 Gene therapy

(figure modified from [7]).

Viral Structures in Nanomedicine

DOI: http://dx.doi.org/10.5772/intechopen.90099

Figure 2.

2.2 Drug delivery

3

Figure 1. Structure of diverse viruses studied in bionanotechnology for medical applications. The icosahedral capsid images were obtained from VIPERdb and the bacteriophage M13 from [6].

#### Figure 2.

nanoparticles could be used as basic templates for the design and production of nanostructured materials (Figure 1). The following are the most important

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1.They are highly ordered structures at nanometric scale and able to auto-

3.There is a diversity of sizes and shapes (icosahedral, tubes, helix, etc.) with

4.They have a high specific surface with a large amount and diversity of reactive

5.They are hollow structures that could be used to encapsulate molecules for

6. Some of them show cell internalization capacity and are biocompatible and

The VLPs show three available interphases to be chemically or genetically manipulated: the external surface exposed to solvent, the internal surface, and the interphase between the protein subunits (Figure 2). The different surfaces can be

Structure of diverse viruses studied in bionanotechnology for medical applications. The icosahedral capsid

images were obtained from VIPERdb and the bacteriophage M13 from [6].

used to precisely tune new functions for the different applications [7].

2.They are monodispersed in size with homogenous composition.

different stabilities to pH, temperature, and ionic strength.

sites that allow the conjugation of a wide range of ligands.

properties of VLPs [4, 5]:

diverse applications.

biodegradable.

Figure 1.

2

assemble.

Scheme of tree interphases in which virus-like nanoparticles can be modified for the addition of new functions (figure modified from [7]).
