Why I believe nanoparticles are crucial as a carrier for targeted drug delivery

Polymeric nanocarriers: A promising tool for early diagnosis and efficient treatment of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the third most prevalent type of cancer for incidence and second for mortality worldwide. Late diagnosis and inconvenient and expensive current diagnostic tools largely contribute to the progress of the disease. The use of chemotherapy in the management of CRC significantly reduces tumor growth, metastasis, and morbidity rates. However, poor solubility, low cellular uptake, nonspecific distribution, multiple drug resistance and unwanted adverse effects are still among the major drawbacks of chemotherapy that limit its clinical significance in the treatment of CRC. Owing to their remarkable advantages over conventional therapies, the use of nanotechnology-based delivery systems especially polymeric nanocarriers (PNCs) has revolutionized many fields including disease diagnosis and drug delivery.

AIM OF REVIEW

In this review, we shed the light on the current status of using PNCs in the diagnosis and treatment of CRC with a special focus on targeting strategies, surface modifications and safety concerns for different types of PNCs in colonic cancer delivery.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review explores the current progress on the use of PNCs in the diagnosis and treatment of CRC with a special focus on the role of PNCs in improvement of cellular uptake, drug targeting and co-delivery of chemotherapeutic agents. Possible toxicity and biocompatibility issues related to the use of PNCs and imitations and future recommendation for the use of those smart carriers in the diagnosis and treatment of CRC are also discussed.

Arabinogalactan and glycyrrhizin based nanopesticides as novel delivery systems for plant protection

During the past decade, nanotechnologies opened a new era in delivery of plant protection products through the development of nanosized controlled release systems, such as polymer nanoparticles, micelles, and so on using a wide variety of materials. To increase the pesticides penetration into the grain under the presowing seed treatment, a new approach based on non-covalent associate preparation with natural polysaccharides and oligosaccharides as delivery systems (DSs) was applied. Earlier, this approach was tested on antidote 1,8-naphthalic anhydride (NA). Enhancement of the NA solubility and penetration into the barley and wheat seeds had been demonstrated. In the present study, these DSs were used to prepare nanocomposites of pesticides (tebuconazole, imidacloprid, imazalil, prochloraz). The composite formation of the pesticides with poly- and oligosaccharides was proved by NMR relaxation method. Enhancement of the pesticides solubility and improvement of its penetration into the seeds of corn and rapeseeds has been detected. The strongest enhancement of penetration ability was observed for arabinogalactan nanocomposites: 5-folds for tebuconazole and imidacloprid, and more than 10-folds for imazalil and prochloraz. Our data show that the effect of polysaccharides and oligosaccharides on the nanopesticide penetration might be associated with the solubility enhancement, affinity of DSs to the surface of grains, and the modification of cell membranes by poly- and oligosaccharides.

Distributions: The Importance of the Chemist's Molecular View for Biological Materials

Characterization of materials with biological applications and assessment of physiological effects of therapeutic interventions are critical for translating research to the clinic and preventing adverse reactions. Analytical techniques typically used to characterize targeted nanomaterials and tissues rely on bulk measurement. Therefore, the resulting data represent an average structure of the sample, masking stochastic (randomly generated) distributions that are commonly present. In this Perspective, we examine almost 20 years of work our group has done in different fields to characterize and control distributions. We discuss the analytical techniques and statistical methods we use and illustrate how we leverage them in tandem with other bulk techniques. We also discuss the challenges and time investment associated with taking such a detailed view of distributions as well as the risks of not fully appreciating the extent of heterogeneity present in many systems. Through three case studies showcasing our research on conjugated polymers for drug delivery, collagen in bone, and endogenous protein nanoparticles, we discuss how identification and characterization of distributions, i.e., a molecular view of the system, was critical for understanding the observed biological effects. In all three cases, data would have been misinterpreted and insights missed if we had only relied upon spatially averaged data. Finally, we discuss how new techniques are starting to bridge the gap between bulk and molecular level analysis, bringing more opportunity and capacity to the research community to address the challenges of distributions and their roles in biology, chemistry, and the translation of science and engineering to societal challenges.

Natural Poly- and Oligosaccharides as Novel Delivery Systems for Plant Protection Compounds

To increase the bioavailability of plant protection products, we have applied a new approach based on noncovalent association with natural water-soluble polysaccharides and oligosaccharides as delivery systems (DSs). The mechanochemical technique has been applied to prepare the solid-state nanodispersed compositions of antidote 1,8-naphthalic anhydride (NA) with arabinogalactan, sodium salt of carboxymethylcellulose, and glycyrrhizin as DSs. The effect of DSs on the solubility and the penetration of NA into the seeds of barley and wheat has been investigated by various physicochemical techniques. All DSs considerably enhance the solubility of NA and improve its penetration into the grain. The influence of polysaccharides and oligosaccharides on artificial lipid membranes was studied by the NMR relaxation method. It was concluded that the effect of polysaccharides and oligosaccharides on the penetration efficacy of plant protection products might be associated with the detected solubility enhancement and the affinity of DSs to the surface of cell membranes.

Strategies for targeted drug delivery in treatment of colon cancer: current trends and future perspectives

Despite advances in treatment modalities, colon cancer (CC) is the third most common cause of cancer-related death worldwide. Subsequent unfavorable effects owing to toxicity of conventional drugs are a challenging problem associated with chemotherapy. There is noticeable concern toward site-specific/targeted delivery of chemotherapeutic drugs specifically to the affected site of the colon in a predictable and reproducible manner. However, the biggest challenge in successful drug targeting for the colon is avoidance of drug absorption and/or degradation in the upper gastrointestinal tract before the drug reaches the colon. Nanoparticles endowed with targeting abilities offer a novel approach for site-specific delivery of chemotherapeutic agents. The present review focuses on recent approaches for colon-specific drug delivery (CDDS) and aims to unveil the emerging possibilities and advances in the treatment of CC with CDDS.

Dendrimer-protein interactions versus dendrimer-based nanomedicine

Dendrimers are hyperbranched polymers belonging to the huge class of nanomedical devices. Their wide application in biology and medicine requires understanding of the fundamental mechanisms of their interactions with biological systems. Summarizing, electrostatic force plays the predominant role in dendrimer-protein interactions, especially with charged dendrimers. Other kinds of interactions have been proven, such as H-bonding, van der Waals forces, and even hydrophobic interactions. These interactions depend on the characteristics of both participants: flexibility and surface charge of a dendrimer, rigidity of protein structure and the localization of charged amino acids at its surface. pH and ionic strength of solutions can significantly modulate interactions. Ligands and cofactors attached to a protein can also change dendrimer-protein interactions. Binding of dendrimers to a protein can change its secondary structure, conformation, intramolecular mobility and functional activity. However, this strongly depends on rigidity versus flexibility of a protein's structure. In addition, the potential applications of dendrimers to nanomedicine are reviwed related to dendrimer-protein interactions.

Spectroscopic and molecular dynamics characterization of glycyrrhizin membrane-modifying activity

Glycyrrhizic acid (GA) is a triterpene glycoside extracted from licorice root. Due to its amphiphilicity GA is capable of forming complexes with a variety of hydrophobic molecules, substantially increasing their solubility. GA can enhance the therapeutic effects of various drugs. It was hypothesized that the increased bioavailability of the drug by GA is not only due to increased solubility, but also to enhancement of drug permeability through cell membranes. In this study the interaction of GA with POPC liposomes and model DOPC, POPC and DPPC bilayers was investigated by NMR with addition of shift reagents and MD simulations. This work helps to better understand the mechanism of enhanced drug bioavailability in the presence of GA. NMR and MD reveal that GA does penetrate into the lipid bilayer. NMR shows that GA changes the mobility of lipids. GA is predominantly located in the outer "half-layer" of the liposome and that the middle of the hydrophobic tails is the preferred location. GA freely passes through the bilayer surface to the inner part bringing a few water molecules. Also both approaches indicate pore formation in the presence of GA. The GA interaction with membranes is an additional aspect of the biological activity of GA-based drug delivery systems.

Characterization of Folic Acid and Poly(amidoamine) Dendrimer Interactions with Folate Binding Protein: A Force-Pulling Study

Atomic force microscopy force-pulling experiments have been used to measure the binding forces between folic acid (FA) conjugated poly(amidoamine) (PAMAM) dendrimers and folate binding protein (FBP). The generation 5 (G5) PAMAM conjugates contained an average of 2.7, 4.7, and 7.2 FA per dendrimer. The most probable rupture force was measured to be 83, 201, and 189 pN for G5-FA2.7, G5-FA4.7, and G5-FA7.2, respectively. Folic acid blocking experiments for G5-FA7.2 reduced the frequency of successful binding events and increased the magnitude of the average rupture force to 274 pN. The force data are interpreted as arising from a network of van der Waals and electrostatic interactions that form between FBP and G5 PAMAM dendrimer, resulting in a binding strength far greater than that expected for an interaction between FA and FBP alone.

Multifunctional drug nanocarriers formed by cRGD-conjugated βCD-PAMAM-PEG for targeted cancer therapy

Polyamidoamine (PAMAM) dendrimer was conjugated with both carboxymethyl-β-cyclodextrin (βCD) and poly(ethylene glycol) (PEG). Cyclic RGD peptide, used as a tumor targeting ligand, was then selectively conjugated onto the distal ends of the PEG arms. The resulting βCD-PAMAM-PEG-cRGD polymer was able to form stable and uniform nanoparticles (NPs) in aqueous solution. Doxorubicin (Dox), a model hydrophobic anticancer drug, was effectively encapsulated in the NPs via an inclusion complex formed between the drug and βCD. The Dox loading level was 16.8 wt%. The cellular uptake of cRGD-conjugated Dox-loaded NPs in the U87MG cell line was much higher than that of non-targeted NPs. Furthermore, the anti-proliferative effect of the cRGD-conjugated NPs was superior to that of free drug and non-targeted NPs. These results suggest that NPs formed by βCD-PAMAM-PEG-cRGD with a high drug payload may significantly improve the anticancer efficacy by tumor-targeted delivery and enhanced cellular uptake.

Advances in combination therapies based on nanoparticles for efficacious cancer treatment: an analytical report

The main objective of nanomedicine research is the development of nanoparticles as drug delivery systems or drugs per se to tackle diseases as cancer, which are a leading cause of death with developed nations. Targeted treatments against solid tumors generally lead to dramatic regressions, but, unfortunately, the responses are often short-lived due to resistant cancer cells. In addition, one of the major challenges of combination drug therapy (called "cocktail") is the crucial optimization of different drug parameters. This issue can be solved using combination nanotherapy. Nanoparticles developed in oncology based on combination nanotherapy are either (a) those designed to combat multidrug resistance or (b) those used to circumvent resistance to clinical cancer drugs. This review provides an overview of the different nanoparticles currently used in clinical treatments in oncology. We analyze in detail the development of combinatorial nanoparticles including dendrimers for dual drug delivery via two strategic approaches: (a) use of chemotherapeutics and chemosensitizers to combat multidrug resistance and (b) use of multiple cytotoxic drugs. Finally, in this review, we discuss the challenges, clinical outlook, and perspectives of the nanoparticle-based combination therapy in cancer.

Poly(amidoamine) dendrimer-methotrexate conjugates: the mechanism of interaction with folate binding protein

Generation 5 poly(amidoamine) (G5 PAMAM) methotrexate (MTX) conjugates employing two small molecular linkers, G5-(COG-MTX)_n, G5-(MFCO-MTX)_n were prepared along with the conjugates of the G5-G5 (D) dimer, D-(COG-MTX)_n, D-(MFCO-MTX)_n. The monomer G5-(COG-MTX)_n conjugates exhibited only a weak, rapidly reversible binding to folate binding protein (FBP) consistent with monovalent MTX binding. The D-(COG-MTX)_n conjugates exhibited a slow onset, tight-binding mechanism in which the MTX first binds to the FBP, inducing protein structural rearrangement, followed by polymer–protein van der Waals interactions leading to tight-binding. The extent of irreversible binding is dependent on total MTX concentration and no evidence of multivalent MTX binding was observed.

Multivalent polymers for drug delivery and imaging: the challenges of conjugation

Multivalent polymers offer a powerful opportunity to develop theranostic materials on the size scale of proteins that can provide targeting, imaging, and therapeutic functionality. Achieving this goal requires the presence of multiple targeting molecules, dyes, and/or drugs on the polymer scaffold. This critical review examines the synthetic, analytical, and functional challenges associated with the heterogeneity introduced by conjugation reactions as well as polymer scaffold design. First, approaches to making multivalent polymer conjugations are discussed followed by an analysis of materials that have shown particular promise biologically. Challenges in characterizing the mixed ligand distributions and the impact of these distributions on biological applications are then discussed. Where possible, molecular-level interpretations are provided for the structures that give rise to the functional ligand and molecular weight distributions present in the polymer scaffolds. Lastly, recent strategies employed for overcoming or minimizing the presence of ligand distributions are discussed. This review focuses on multivalent polymer scaffolds where average stoichiometry and/or the distribution of products have been characterized by at least one experimental technique. Key illustrative examples are provided for scaffolds that have been carried forward to in vitro and in vivo testing with significant biological results.

Isolation and characterization of precise dye/dendrimer ratios

Fluorescent dyes are commonly conjugated to nanomaterials for imaging applications using stochastic synthesis conditions that result in a Poisson distribution of dye/particle ratios and therefore a broad range of photophysical and biodistribution properties. We report the isolation and characterization of generation 5 poly(amidoamine) (G5 PAMAM) dendrimer samples containing 1, 2, 3, and 4 fluorescein (FC) or 6-carboxytetramethylrhodamine succinimidyl ester (TAMRA) dyes per polymer particle. For the fluorescein case, this was achieved by stochastically functionalizing dendrimer with a cyclooctyne "click" ligand, separation into sample containing precisely defined "click" ligand/particle ratios using reverse-phase high performance liquid chromatography (RP-HPLC), followed by reaction with excess azide-functionalized fluorescein dye. For the TAMRA samples, stochastically functionalized dendrimer was directly separated into precise dye/particle ratios using RP-HPLC. These materials were characterized using (1)H and (19)F NMR spectroscopy, RP-HPLC, UV/Vis and fluorescence spectroscopy, lifetime measurements, and MALDI.