Page 800 to 804
Volume 3 • Issue 2 • 2019
Editorial
Chronicles of Pharmaceutical Science
ISSN: 2572-7761
Nanoparticles as Targeted Drug Co-Delivery
in Cancer Therapeutics
Loutfy H Madkour*
Chemistry Department, Faculty of Science, Al Baha University, Baljarashi 65635, Saudi Arabia
*Corresponding Author Loutfy H. Madkour, Chemistry Department, Faculty of Science and Arts, Al Baha University, Baljarashi 65635,
Saudi Arabia.
Received: February 04, 2019; Published: February 08, 2019
Volume 3 Issue 2 February 2019
© All Copy Rights are Reserved by Loutfy H. Madkour.
Nanoparticles can cross the blood–brain barrier (BBB) following the opening of endothelium tight junctions by hyper-osmotic mannitol, which may provide sustained delivery of therapeutic agents for difficult-to-treat diseases like brain tumors [1]. Tween 80-coated
nanoparticles have been shown to cross the BBB as well [2]. Submicron nanoparticles, but not larger microparticles, are taken up by the
majority of cell types [3]. Indeed, 100 nm nanoparticles had a 2.5-fold greater uptake rate than 1 μm microparticles, and a 6-fold greater
uptake than 10 μm microparticles by Caco-2 cells [4]. In a similar study, nanoparticles are shown to penetrate throughout the sub mucosal layers of a rat intestinal loop model, while microparticles were predominantly localized in the epithelial lining [5]. This indicates that
particle distribution can, in part at least, be tuned by controlling particle size.
Various methods can be used to study the release of drug from the nanoparticle: (1) side-by-side diffusion cells with artificial or
biological membranes; (2) dialysis bag diffusion; (3) reverse dialysis bag diffusion; (4) agitation followed by ultracentrifugation/centrifugation; or (5) ultra-filtration. Usually the release study is carried out by controlled agitation followed by centrifugation. Due to the time-
consuming nature and technical difficulties encountered in the separation of nanoparticles from release media, the dialysis technique is
generally preferred. However, these methods prove difficult to replicate and scale-up for industrial use.
Cancer is a difficult disease to treat due to its heterogeneous disease manifestation as well as pathogenic path ways. This necessitates
tailored and sophisticated therapeutic modalities for effective treatment. Polymer-based chemotherapeutic drug or anti- cancer gene
delivery systems have been extensively studied and have the potential to offer many advantages. In particular, polymeric nano- particles
are able to effectively load drugs and/or package genes in order to increase cargo solubility, enhance cargo efficacy compared with free
cargo, and prolong the circulation half-life.
Drug delivery in cancer is important for optimizing the effect of drugs and reducing toxic side effects. Several nanotechnologies, mostly based on nanoparticles, can facilitate drug delivery to tumors. Drug delivery systems based on polymeric nanoparticles have emerged
as one of the most promising carriers for targeted and controlled delivery of cancer therapeutics in recent years. .Ideal characteristics of
nanoparticles include a high drug loading capacity, safe delivery of drug to specific pathological tissues without premature drug leakage
and efficient drug unloading at the site of action. Stimuli-sensitive drug delivery systems, also known as “smart” drug delivery systems,
Citation: Loutfy H. Madkour. “Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics”. Chronicles of Pharmaceutical Science
3.2 (2019): 800-804
Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics
801
particularly suits this need as they can release drugs at the tumor sites at the desired time on an “on-demand” basis in response to numerous chemical (pH, redox), physical (temperature)and biological (enzymes) stim- uli. The association of a drug to conventional carriers leads to modification of the drug bio distribution profile, as it is mainly delivered to the mononuclear phagocyte system (MPS) such
as liver, spleen, lungs and bone marrow. Nanoparticles can be recognized by the host immune system when intravenously administered
and cleared by phagocytes from the circulation. Novel nanosystems can be pre-programmed to alter their structure and properties dur-
ing the drug delivery process, allowing for more effective extra- and intra-cellular delivery of encapsulated drug [6]. Nanoparticles also
can be formulated to deliver drugs across several biological barriers [7, 8]. Anti-neoplastic, anti-viral drugs, and several other types of
drugs are markedly hindered because of inability of these molecules to cross the BBB. The application of nanoparticles to deliver across
this barrier is extremely promising. It has been reported that nanoparticles can cross the BBB following the opening of tight junctions
by hyper-osmotic mannitol, which also may provide sustained delivery of therapeutic agents for difficult-to-treat diseases like brain
tumors [9]. Tween 80-coated nanoparticles also have been shown to cross the BBB [10].
Nanocapsules are vesicular systems in which a drug is confined to a cavity surrounded by a polymer membrane, whereas nano-
spheres are matrix systems in which the drug is physically and uniformly dispersed. Nanoparticles are solid, colloidal particles consist-
ing of macromolecular substances that vary in size from 10 nm to 1000 nm [11]. However, particles >200 nm are not heavily pursued
and nanomedicine often refers to devices < 200 nm (i.e., the width of microcapillaries). Typically, the drug of interest is dissolved, en-
trapped, adsorbed, attached and/or encapsulated into or onto a nano-matrix. Depending on the method of preparation nanoparticles,
nanospheres, or nanocapsules can be constructed to possess different properties and release characteristics for the best delivery or
encapsulation of the therapeutic agent [12-14].
The development of a wide spectrum of nanoscale technologies is beginning to change the scientific landscape in terms of dis-
ease diagnosis, treatment, and prevention. These technological innovations, referred to as nanomedicines by the National Institutes of
Health, have the potential to turn molecular discoveries arising from genomics and proteomics into widespread benefit for patients.
Nanoparticles can mimic or alter biological processes (e.g., infection, tissue engineering, de novo synthesis, etc.). These devices include,
but are not limited to, functionalized carbon nanotubes, nanomachines (e.g., constructed from interchangeable DNA parts and DNA scaffolds), nanofibers, self-assembling polymeric nanoconstructs, nanomembranes, and nano-sized silicon chips for drug, protein, nucleic
acid, or peptide delivery and release, and biosensors and laboratory diagnostics.
It is important to consider both drug release and polymer biodegradation when developing a nanoparticulate delivery system. In
general, the drug release rate depends on: (1) drug solubility; (2) desorption of the surface-bound or adsorbed drug; (3) drug diffusion
through the nanoparticle matrix; (4) nanoparticle matrix erosion or degradation; and (5) the combination of erosion and diffusion processes. Hence, solubility, diffusion, and biodegradation of the particle matrix govern the release process.
Biodegradable polymers have been studied extensively over the past few decades for the fabrication of drug delivery systems. Considerable research is being directed towards developing biodegradable polymeric nanoparticles for drug delivery and tissue engineering, in view of their applications in controlling the release of drugs, stabilizing labile molecules (e.g., proteins, peptides, or DNA) from
degradation, and site-specific drug targeting.
Polymeric nanoparticles made from natural and synthetic polymers have received the majority of attention due to their stability and
ease of surface modification [15, 16]. They can be tailor-made to achieve both controlled drug release and disease-specific localization
by tuning the polymer characteristics and surface chemistry [17-20]. It has been established that nanocarriers can become concentrated preferentially to tumors, inflammatory sites, and at antigen sampling sites by virtue of the enhanced permeability and retention
(EPR) effect of the vasculature. Once accumulated at the target site, hydrophobic biodegradable polymeric nanoparticles can act as
a local drug depot depending on the make-up of the carrier, providing a source for a continuous supply of encapsulated therapeutic
compound(s) at the disease site, e.g., solid tumors. Polymeric nanoparticles have interesting advantages with respect to other non-viral
Citation: Loutfy H. Madkour. “Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics”. Chronicles of Pharmaceutical Science
3.2 (2019): 800-804
Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics
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carriers for siRNA delivery: they are easy to scale-up, have improved stability and better safety regarding both to the materials used and
to the manufacturing processes [21]. Smaller particles also have a greater risk of aggregation during storage, transport, and dispersion.
Polymer degradation also can be affected by particle size.
In early studies, dendrimer-based drug delivery systems focused on encapsulating drugs. However, it was difficult to control the
release of drugs associated with dendrimers. Recent developments in polymer and dendrimer chemistry have provided a new class
of molecules called dendronized polymers, which are linear polymers that bear dendrons at each repeat unit. Their behavior differs
from that of linear polymers and provides drug delivery advantages because of their enhanced circulation time. Another approach is to
synthesize or conjugate the drug to the dendrimers so that incorporating a degradable link can be further used to control the release
of the drug.
Targeted treatments are aimed to block specific biologic transduction pathways or cancer proteins that are involved in tumor
growth and progression, i.e. molecular targets (receptors, growth factors, kinase cascades or molecules related with apoptosis and
angiogenesis) that are present in normal tissues, but are found overexpressed or mutated in cancer. The idea of these revolutionary
therapies is either to block the signals that help malignant cells to grow and divide uncontrollably, produce the death of cancer cells.
By means of induction of apoptosis, stimulate the immune system, or target the delivery of chemotherapy agents specifically to cancer
cells, minimizing the death of normal cells and avoiding the undesirable side effects [22, 23]. The importance of these new anticancer
drugs can be deduced looking at the FDA-approved drugs in the oncology area in the last fourteen years. Among the 19 anticancer drugs
approved in the 2000–2006 period, 14 were targeted therapies. These data increased between 2007 and 2012 when 40 drugs were approved for the treatment of different types of cancer, and 30 of them targeted specific cancer molecules. It should be noted that among
19 cancer drugs approved by the FDA between 2012 and 2014, 18 were targeted cancer drugs based on inhibiting or blocking biologic
transduction pathways and/or specific cancer proteins [24–26].
Active targeting is achieved by attaching specific ligands to the nanoparticle structure, allowing a selective recognition of different
receptors or antigens overexpressed in the tumor cell surfaces, increasing the cytotoxicity of the anticancer agents in tumors and avoiding most of their side effects, since the exposure of healthy cells to the drug is minimized [27]. The functionalization of the surface of
the polymer nanoparticles, not only provides active targeting characteristics to the particles, but also improves therapeutic efficacy of
cytotoxic drugs and overcomes the multidrug resistance (MDR) [28, 29].
Another challenge of loading drugs and genes together in the same carrier is to ensure that the presence of one therapeutic agent
does not affect the other, in terms of loading capacity and functionality. Furthermore, depending on the drug and gene combination
selected, co- encapsulation might not be feasible when their combined presence jeopardizes the loading capacity of the co-delivery carrier. Indeed, this has been the limitation for many co-delivery carriers which have been reported [30-33]. These systems in general can
be used to provide targeted (cellular or tissue) delivery of drugs, improve bioavailability, sustain release of drugs or solubilize drugs
for systemic delivery. This process can be adapted to protect therapeutic agents against enzymatic degradation (i.e., nucleases and
proteases) [34]. Thus, the advantages of using nanoparticles for drug delivery are a result of two main basic properties: small size and
use of biodegradable materials. Nanoparticles, because of their small size, can extravasation through the endothelium in inflammatory
sites, epithelium (e.g., intestinal tract and liver), tumors, or penetrate microcapillaries. In general, the nanosize of these particles allows
for efficient uptake by a variety of cell types and selective drug accumulation at target sites [19, 20, and 35]. Many studies have demonstrated that nanoparticles have a number of advantages over microparticles (>1 μm) as a drug delivery system [36]. Nanoparticles
have another advantage over larger microparticles because they are better suited for intravenous delivery. The smallest capillaries in
the body are 5–6 μm in diameter. The size of particles being distributed into the bloodstream must be significantly smaller than 5 μm,
without forming aggregates, to ensure that the particles do not cause an embolism.
Citation: Loutfy H. Madkour. “Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics”. Chronicles of Pharmaceutical Science
3.2 (2019): 800-804
Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics
803
Finally, it is important to highlight the use of active targeting nanoparticles for the treatment of multi-drug resistant (MDR) cancers
that commonly overexpress the epidermal growth factor receptor (EGFR). For example, to overcome the MDR Milane and co-workers
[37] modified nanoparticles with an EGFR-specific peptide (GE11) and loaded them with a drug combination of paclitaxel, that pre-
vents cell division, and lodinamine, that induces apoptosis and decreases MDR.
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Citation: Loutfy H. Madkour. “Nanoparticles as Targeted Drug Co-Delivery in Cancer Therapeutics”. Chronicles of Pharmaceutical Sci-
ence 3.2 (2019): 800-804