Approaches to improve the association of amikacin sulphate to poly(alkylcyanoacrylate) nanoparticles

Formulation of protein-loaded nanoparticles via freeze-drying

Several nanotechnology-based formulation strategies have been reported for the oral administration of biological drugs. However, a prerequisite often overlooked in developing these formulations is their adaptation to a solid dosage form. This study aimed to incorporate a freeze-drying step, using either mannitol or sucrose laurate (SLAE), into the formulation of new insulin-zinc nanocomplexes to render them resistant to intestinal fluids while maintaining a high protein loading. The resulting freeze-dried insulin-zinc nanocomplexes exhibited physicochemical properties consistent with the target product profile, including a particle size of ∼ 100 nm, a zeta potential close to neutrality (∼ -15 mV) and a high association efficiency (> 90%). Importantly, integrating the freeze-drying step in the formulation significantly improved the colloidal stability of the system and preserved the stability of the insulin molecules. Results from in vitro and in vivo studies indicated that the insulin activity remained fully retained throughout the entire formulation and freeze-drying processes. In brief, we present a novel protein formulation strategy that incorporates a critical freeze-drying step, resulting in a dry powder enabling efficient protein complexation with zinc and optimized for oral administration.

Fabrication of poly(D, L-lactic acid) nanoparticles as delivery system for sustained release of L-theanine

L-theanine is present in tea as a unique, free, non-protein amino acid. Due to various beneficial effects on brain activity, it is widely used as a nutraceutical. After consumption, it is rapidly absorbed and metabolised followed by excretion through urine. Therefore, the authors developed an L-theanine delivery system by encapsulating into polymeric nanoparticles to release it slowly and make it available for a longer period of time. Poly(D, L-lactic acid) nanoparticle (PLANP) was fabricated by the double emulsion method and L-theanine was encapsulated into it (PLANP-T). Spherical nanoparticles with a hydrodynamic diameter of 247 and 278 nm and surface charge of -14.5 and -25.7 mV for PLANP and PLANP-T, respectively, were fabricated. The Fourier transform infrared spectroscopic data indicated encapsulation of L-theanine into PLANP. The PLANP showed high L-theanine encapsulation capacity (71.65%) with a sustained release character. The maximum release (66.3%) of L-theanine was recorded in pH 7.3 at 48 h. The release kinetics followed the Higuchi model and the release mechanism was determined as super case-II transport (erosion). This slow release will make it available to the target tissue for a longer period of time (sustain release effect) and will also avoid immediate metabolism and clearance from the circulation.

From poly(alkyl cyanoacrylate) to squalene as core material for the design of nanomedicines

This review article covers the most important steps of the pioneering work of Patrick Couvreur and tries to shed light on his outstanding career that has been a source of inspiration for many decades. His discovery of biodegradable poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs) has opened large perspectives in nanomedicine. Indeed, NPs made from various types of alkyl cyanoacrylate monomers have been used in different applications, such as the treatment of intracellular infections or the treatment of multidrug resistant hepatocarcinoma. This latest application led to the Phase III clinical trial of Livatag^®, a PACA nanoparticulate formulation of doxorubicin. Despite the success of PACA NPs, the development of a novel type of NP with higher drug loadings and lower burst release was tackled by the discovery of squalene-based nanomedicines where the drug is covalently linked to the lipid derivative and the resulting conjugate is self-assembled into NPs. This pioneering work was accompanied by a wide range of novel applications which mainly dealt with the management of unmet medical needs (e.g. pancreatic cancer, brain ischaemia and spinal cord injury).

Unified Scaling of the Structure and Loading of Nanoparticles Formed by Diffusion-Limited Coalescence

The present study establishes the scaling laws describing the structure of spherical nanoparticles formed by diffusion-limited coalescence. We produced drug-loaded nanoparticles from a poly(ethylene glycol)-poly(d,l-lactic acid) diblock polymer (PEG- b-PLA) by the nanoprecipitation method using different types of micromixing chambers to explore multiple mixing regimes and characteristic times. We first show that the drug loading of the nanoparticles is not controlled by the mixing time but solely by the drug-to-polymer ratio (D:P) in the feed and the hydrophobicity of the drug scaled via the partition coefficient P. We then procure compelling evidence that particles formed via diffusion/coalescence exhibit a relative distribution of PEG blocks between the particle core and its shell that depends only on mixing conditions (not on D:P). Scaling laws of PEG relative distribution and chain surface density were derived in different mixing regimes and showed excellent agreement with experimental data. In particular, results made evident that PEG blocks entrapment in the core of the particles occurs in the slow-mixing regime and favors the overloading (above the thermodynamic limit) of the particles with hydrophilic drugs. The present analysis compiles effective guidelines for the scale up of nanoparticles structure and properties with mixing conditions, which should facilitate their future translation to medical and industrial settings.

Studies on drug-polymer interaction, in vitro release and cytotoxicity from chitosan particles excipient

Nonobvious controlled polymeric pharmaceutical excipient, chitosan nanoparticles (CS-NPs) for lenalidomide encapsulation were geared up by the simple ionic cross linking method to get better bioavailability and to reduce under as well as overloading of hydrophobic and sparingly soluble drug lenalidomide towards cancer cells. Lenalidomide loaded chitosan nanoparticles (LND-CS-NPs) were in the size range of 220-295 nm and characterized by DLS, TEM, FT-IR, TGA and XRD. Encapsulation of lenalidomide over chitosan nanoparticles was observed about 99.35% using UV spectrophotometry method. In vitro release and the cytotoxic studies were performed using LND-CS-NPs. This study implies the new drug delivery route for lenalidomide and illustrates that the CS-NPs serves as the effective pharmaceutical carrier for sustained delivery of lenalidomide.

Liposomal-lupane system as alternative chemotherapy against cutaneous leishmaniasis: macrophage as target cell

Leishmania amazonensis causes human diseases that range from self-healing to diffusion cutaneous lesions. The chemotherapy of leishmaniasis requires long-term treatment and has been based on the use of pentavalent antimonials. Liposomes have been used as antileishmanial drug carries and have adjuvant activity in vaccines against several microorganisms, representing an important option to the development of new therapeutics for the disease. In this study, we developed a liposomal formulation containing lupane [3β,6β,16β-trihydroxylup-20(29)-ene], isolated from fruits of Combretum leprosum with pharmacological properties as antinociceptive, anti-inflammatory, antiulcerogenic and antileishmanial activities. The aim of the present study was to evaluate the efficacy of liposomal-lupane in L. amazonensis-infection model. Liposomes were prepared by the extrusion method with DPPC, DPPS and cholesterol at 5:1:4 weight ratio. The lupane (2 mg/mL) was added to the lipid mixture, solubilized in chloroform and dried under nitrogen flow. The activity of liposomal-lupane was conducted in vitro with mouse peritoneal infected macrophages. Furthermore, mice were infected in the right hind footpad with 10(5) stationary growth phase of L. amazonensis promastigotes. After 6 weeks, animals were treated with liposomal-lupane for 15 days by intraperitoneal injection. The evolution of disease was monitored weekly by measuring footpad thickness with a caliper. Three days after the treatment, peritoneal macrophages were collected, plated and production of the cytokines IL-10 and IL-12 was evaluated in supernatants of the cultures after 24 h. The results indicate that the liposomal system containing lupane achieved here is a promising tool to confer antileishmanial activity to infected macrophages.

Colloidal nanocarriers: a review on formulation technology, types and applications toward targeted drug delivery

Colloidal nanocarriers, in their various forms, have the possibility of providing endless opportunities in the area of drug delivery. The current communication embodies an in-depth discussion of colloidal nanocarriers with respect to formulation aspects, types, and site-specific drug targeting using various forms of colloidal nanocarriers with special insights to the field of oncology. Specialized nanotechnological approaches like quantum dots, dendrimers, integrins, monoclonal antibodies, and so forth, which have been extensively researched for targeted delivery of therapeutic and diagnostic agents, are also discussed. Nanotechnological patents, issued by the U.S. Patent and Trademark Office in the area of drug delivery, are also included in this review to emphasize the importance of nanotechnology in the current research scenario.

FROM THE CLINICAL EDITOR

Colloidal nanocarriers provide almost endless opportunities in the area of drug delivery. While the review mainly addresses potential oncological applications, similar approaches may be applicable in other conditions with a requirement for targeted drug delivery. Technologies including quantum dots, dendrimers, integrins, monoclonal antibodies are discussed, along with US-based patents related to these methods.

Controlled release of avermectin from porous hollow silica nanoparticles

Porous hollow silica nanoparticles (PHSNs) with a diameter of ca 100 nm and a pore size of ca 4.5 nm were synthesized via a sol-gel route using inorganic calcium carbonate nanoparticles as templates. The synthesized PHSNs were subsequently employed as pesticide carriers to study the controlled release behaviour of avermectin. The avermectin-loaded PHSN (Av-PHSN) samples were characterized by BET, thermogravimetric analysis and IR, showing that the amount of avermectin encapsulated in the PHSN carrier could reach 58.3% w/w by a simple immersion loading method, and that most of the adsorption of avermectin on the Av-PHSN carrier might be physical. Avermectin may be loaded on the external surface, the pore channels in the wall and the inner core of the PHSN carriers, thus leading to a multi-stage sustained-release pattern from the Av-PHSN samples. Increasing pH or temperature intensified the avermectin release.

Synthesis and characterization of polyurethane and poly(ether urethane) nanocapsules using a new technique of interfacial polycondensation combined to spontaneous emulsification

Polyurethane polymers and poly(ether urethane) copolymers were chosen as drug carriers for alpha-tocopherol. This active ingredient is widely used as a strong antioxidant in many medical and cosmetic applications, but is rapidly degraded, because of its light, heat and oxygen sensitivity. Polyurethane and poly(ether urethane)-based nanocapsules were synthesized by interfacial reaction between two monomers. Interfacial polycondensation combined with spontaneous emulsification is a new technique for nanoparticles formation. Nanocapsules were characterized by studying particle size (150-500 nm), pH, yield of encapsulation and morphologies. Polyurethanes (PUR) were obtained from the condensation of diisocyanate (isophorone diisocyanate: IPDI) and polyol: 1,2-ethanediol (EG), 1,4-butanediol (BD), 1,6-hexanediol (HD). Poly(ether urethane) copolymers were obtained by replacing diols by polyethylene glycol oligomers (PEG) M(w) 200, 300, 400 and 600. Molecular weights of di- and polyols have a considerable influence on nanocapsules characteristics cited above. The increase of molecular weight of polyols tends to increase the mean size of nanocapsules from (232+/-3)nm using EG to (615+/-39)nm using PEG 600, and led to the apparition of a population of agglomerate particles. We also noted that the yield of encapsulation increases with the increase of polyol length (from 85.6 to 92.2% w/w). Microscopic observations confirmed particle size analysis, but cannot predict the membrane structure owing the small size of the particles.

Factors influencing the entrapment of hydrophilic compounds in nanocapsules prepared by interfacial polymerisation of water-in-oil microemulsions

This study demonstrates the effect of drug properties and method of loading (sorption and encapsulation) on entrapment within poly(alkyl cyanoacrylate) nanocapsules prepared by interfacial polymerisation of biocompatible water-in-oil microemulsions. For small molecular weight compounds (<1000 Da), entrapment efficiency is more dependent on charge of the compound than on the method used for entrapment. Entrapment efficiency within the negatively charged nanocapsules (zeta potential approximately -30 mV) was in the order cationic compound > neutral compound > anionic compound. Only minimal differences for entrapment efficiency were noted between sorption (addition of the compound 4 h after initiation of the polymerisation) and encapsulation (addition of the compound to microemulsion prior to polymerisation). For high molecular weight compounds, the method used for entrapment however, is very important. For hydrophilic macromolecules such as proteins, high entrapment efficiencies can only be achieved by encapsulation. Entrapment of such compounds seems to be independent of the net charge of the compound being encapsulated but depended on the molecular weight. For nanocapsules prepared by interfacial polymerisation of water-in-oil microemulsions, these findings are useful as a foundation in the development of nanocapsules with desired properties.

Biodegradable polymeric nanoparticles as drug delivery devices

This review presents the most outstanding contributions in the field of biodegradable polymeric nanoparticles used as drug delivery systems. Methods of preparation, drug loading and drug release are covered. The most important findings on surface modification methods as well as surface characterization are covered from 1990 through mid-2000.

Poly epsilon-caprolactone nanoparticles containing a poorly soluble pesticide: formulation and stability study

In 1997, a research program was initiated in the laboratories to assess the ability of nanosperes (NS) to improve the biodelivery of new active ingredients (AI) to plants. The goal was to obtain stable poly (epsilon-caprolactone) NS (PeC-NS) with the smallest size and the largest amount of encapsulated AI, using a nanoprecipitation method. The smallest particles obtained were in the range of 200-250 nm. The highest encapsulation is obtained with Montanox 80 as surfactant and is between 5-10% (expressed in per cent weight relative to the total weight of polymer), which corresponds to an encapsulation yield of 95%. There is no desorption of the AI with time. In contrast, the dilution of the NS suspension in water is followed by a large removal of the AI in the aqueous phase. This suggests that NS are complex dynamic systems in equilibrium with the external medium and disturbances of this system lead to a loss of AI.

Polymeric nanoparticles as delivery system for influenza virus glycoproteins

The objective of this work was to develop a new delivery system which could enhance the mucosal immune response to influenza virus antigens. Poly(D,L-lactide-co-glycolide) nanoparticles of about 200 nm containing hemagglutinin were chosen as the delivery system. Due to the amphiphilic nature of hemagglutinin (hydrophilic HA1 and hydrophobic HA2), nanoparticles were prepared by both classical oil in water solvent evaporation technique as well as by a [(water-in-oil) in water] solvent evaporation technique. Hemagglutinin was well encapsulated in nanoparticles prepared by both techniques. Molecular weight and antigenicity of entrapped hemagglutinin were not affected by the entrapment procedure.

Labelled polycyanoacrylate nanoparticles for human in vivo use

Isobutyl and isohexyl cyanoacrylate nanoparticles are used as drug carriers, particularly for some anti-cancer drugs. Body distribution as well as pharmacokinetics have been well studied in animal and partially in man. Labelling of the monomer itself or of the carried drug with beta-emitters allowed such studies. In man, however, organ distribution and uptake could easily be done and followed by means of scintigraphy (imaging) techniques if one could achieve nanoparticle labelling with gamma-emitting isotopes. We have developed labelling methods able to supply such carriers using gamma-emitters like radioactive iodine (125I or 131I), indium or technetium. We used DTPA as a spacer in order to fix the last two isotopes. This would mean that any other gamma-emitting cation can theoretically be tried pending on its ability to be chelated by DTPA. The preparations were obtained with high labelling yields, usually > 80% and were relatively stable in human plasma over the whole period of investigation. 111In and 99mTc labelled forms have been administered to rabbit and then to man with 60-75% accumulation in the reticulo-endothelial system.

Improvement of ocular penetration of amikacin sulphate by association to poly(butylcyanoacrylate) nanoparticles

The main objective of this paper was to investigate the ability of polycyanoacrylate nanoparticles to improve the corneal penetration of hydrophilic drugs. Three different nanoparticle formulations were prepared by changing the nature of the stabilizer agent (Dextran 70000, Synperonic F 68 and sodium lauryl sulphate). The significant influence of the stabilizer type on the particle size, electrophoretic mobility and on the drug loading efficiency was proved. Moreover, the ocular disposition of amikacin was affected by its association to nanoparticles, displaying the most interesting results when Dextran 70000 was employed for preparation of nanoparticles. The increase of the amikacin concentration in cornea and aqueous humour was statistically significant for this nanoparticle formulation with respect to the other formulations and the control solution. The in-vitro release profiles obtained using a dialysis system were similar for all the nanoparticle formulations and for the control solution, indicating that drug molecules are desorbed from the nanoparticles quickly enough to maintain the equilibrium concentration in the dialysis system.