HOW THE MULTIFUNCTIONAL NANOCARRIER MAKES THE MEDICINE «SMART»?

Two principal problems that exist in pharmaceutics are the non-addressed action of medicines causing negative side effects in the organism and rapid development of drug resistance in treated patients. Here we present examples how drug encapsulation in the polymeric or mineral nanoscale platform can enhance its treatment effect, improve its targeting in the organism, as well as provide the drug with ability to circumvent drug-resistance mechanisms. Thus, such encapsulation makes the drug “smarter” during its action. ЯК МУЛЬТИФУНКЦІОНАЛЬНИЙ НАНОНОСІЙ РОБИТЬ МЕДИЦИНУ «РОЗУМНОЮ»?


ОГЛЯД REVIEW
Classical medicines consist of the drug substance together with inert (non-toxic, mostly useless) fi lling substance that is utilized because the drug is often applied in mini (micro) amount. While medicines of new generation consist of drug immobilized on the delivery nanoscale platform (polymeric micelle, hydrogel, or nanoparticle, used as carrier). This platform should be "smart" in order to overcome two major problems in pharmaceutics: 1) low effi ciency of drugs due to their non-addressed action (only 0.01% of drugs applied intravenously can reach their biological targets in the organism) [1]; 2) development of drug resistance (during one year, approximately 50% of cancer patients gain resistance to applied chemotherapeutic drugs) [2]. How one can decrease negative side effects, namely cardio-, hepato-, nephro-, neuro-, and immunotoxicities observed at drug action in the organism? The elimination of such effects can be achieved via a decrease of acting drug concentration, or "masking" of toxic drug substance in order to avoid its non-addressed action in the treated organism.
The last two decades demonstrated a real burst of investigations dedicated to creation of novel nanomaterials for biology and medicine, as well as in development of the overlapping branches such as agriculture, ecology, cosmetic industry and others. If the early nanomaterials for the biomedical application possessed a limit-

Coating of nanoparticles:
• Biocompatible synthetic shell based on vinyl pyrrolidone, vinyl alcohol, oxyethylated and fl uorinated copolymers and their complexes with biopolymers; • Bio-surfactants of microbial origin; • Others.
Chemical structure of the biodegradable drug carrier: • Poly (aspartic acid), poly (glutamic acid), poly (malic acid), poly (lactic acid), polysaccharides, others; • Polymers can be considered degradable when they have following groups in their backbone chain: -O-, -NH-, -S-, and -S-S-• In order to avoid immunogenicity, the number and kinds of amino acids should be kept low; maximum biological effi cacy is possible at minimum immune response.
Biocompatibility of the developed nanoparticles can be achieved by: • Size unimodality; • Controlled amount and distribution of active groups; • Opsonization of the particle surface by the biocompatible macromolecules.

Activation of nanoparticle surface:
• Incorporation of chemically active groups and branches such as hydroxyl, carboxyl, amino, aldehyde, epoxy, others.

Bio-functionalization of nanoparticles is done by:
• Lectins -recognition of carbohydrate moieties on cell surface and within different molecules • Immunoglobulins -antibodies recognizing specifi c antigen structures on cell surface and macromolecules Besides these proteins, other molecules can be used for "vectorization" of drug-functionalized nanoparticles. Immobilization of Doxorubicin and KP-1019 on a new polymeric-phospholipidic hybrid delivery system distinctly enhanced the accumulation and activity of these drugs in all tested tumor cell lines including several drug-resistant lines [4,5]. The resistance levels against Doxorubicin were reduced 6-to 22-fold (Figure 1). The new nanocarriers were shown to rapidly (within 10 min) and effectively transport Doxorubicin into drug-resistant as well as drug-sensitive tumor cells. The treatment with new Doxorubicin-containing nanocarriers resulted in effective cell cycle arrest in G2/M phase and ROS-induced cell death. In both in vivo tumor models -murine NK/Ly lymphoma and murine L1210 leukemia -Doxorubicin delivery by the new nanoformulation resulted in 100% cured animals already at low concentrations (0.1 mg/kg), while the native Dox solely extended a survival time. Thus, polymeric nanocarriers functionalized with phospholipids and PEG enhance the efficacy and reduce the toxicity of Doxorubicin. In another set of experiments, Doxorubicin or Cisplatin (CDDP) were immobilized on Fullerene C60 that enhanced an ability of these anticancer drugs to circumvent resistance of tumor cells to chemotherapy in vitro [6,7]. Cytotoxic activity of CDDP-C60 nano-complex towards different lines of drug-resistant tumor cells was 1.5-2.0 times higher than that of native CDDP. In parallel, an enhanced uptake of this drug and double induction of apoptosis in target tumor cells were observed. The anticancer effect of CDDP-C60 nano-complex was confi rmed in tumor-bearing mice.
We also functionalized the developed polymeric nanocarriers with specifi c antibody or lectin in order to improve their cell targeting properties. We created functional nanoparticles targeting glycocalyx and used them for detection and isolation of specifi c mammalian cells [8]. Heterogeneity of murine lymphoma NK/Ly cells on peanut agglutinin (PNA) binding was revealed. Lymphoma cells were treated with native PNA, and bound PNA was detected by the anti-PNA antibodies labeled with colloidal gold and intensifi ed by silver staining [8]. Such approach can be used for a search and isolation of drug resistant tumor cells.
Treatment effects of native and nanocapsulated anticancer drugs was also studied in vitro using several human and animal tumor cells and in vivo using murine NK/Ly lymphoma and L1210 leukemia as experimental models. In both in vitro and in vivo [4,5] experiments, a decrease of acting concentrations of highly toxic anticancer drugs (ex. Doxorubicin) from 50% to 10 times (depending on specifi c target tumor cells and drugs) was found. Doxorubicin was encapsulated in the nanoscale polymeric carrier A-24-PEG-Ph (0.1 mg/kg of mouse weight, 5-10 injections). Principal negative side effects of the action of toxic anticancer agents were shown to be signifi cantly diminished by drug encapsulation and treatment of laboratory mice and rats. These effects are: hepatotoxicity, cardiotoxicity, nephrotoxicity. Stop of the neurotoxicity and immunosuppression is also suggested at using drug nanoformulation. In order to prove such effects, numerous biochemical indicators were measured in blood serum of animals treated with native and encapsulated anticancer drug [9,10,11].
Thus, anticancer drug delivery by the developed polymeric nanocarrier increased significantly a therapeutic index that is an important indicator of the effectiveness and biosafety of drug action (Figure 2).
The main ideas presented in this paper were recently analyzed in the monograph that was edited by the author [12]. Some results noted in the paper were obtained in collaboration with investigators who are mentioned in the Acknowledgement below.