The effect of cosolvents on the formulation of nanoparticles from low-molecular-weight poly(l)lactide

Microfluidic-assisted synthesis of multifunctional iodinated contrast agent polymeric nanoplatforms

Contrast Induced Nephropathy is the most severe side-effect arising after non-ionic iodinated contrast agents (CAs) intravenous administration. The use of antioxidants (i.e., N-Acetylcysteine; NAC) is one of the attempted prevention approaches. Herein, we describe the microfluidic-assisted synthesis of iodinated polymeric nanoparticles (NPs) as new multifunctional blood pool CA. The aim of this research is to co-encapsulate Iohexol (IOX; iodinated CA) and NAC (preventive agent) into poly-D,L-lactide-co-glycolide (PLGA) and PEGylated-PLGA (PLGA-PEG) NPs to exploit CA diagnostic proprieties and NAC preventing antioxidant activity. A microfluidic-assisted nanoprecipitation protocol has been set-up for PLGA and PLGA-PEG NPs, evaluating the effect of formulation and microfluidic parameters by analysing the size, PDI and IOX and NAC encapsulation efficiency. The optimized NPs (PLGA-PEG, L:G 50:50, 5% PEG, Mw 90 kDa) formulated with a size of 67 ± 2.8 nm with PDI < 0.2, spherical shape, and an IOX and NAC encapsulation efficiency of 38% and 20%, respectively. The IOX and NAC encapsulation was confirmed by FTIR and DSC. In vitro release study showed an IOX retention into the polymeric matrix and NAC sustained release up to 24-48 h stating microfluidics as powerful tool for the formulation of multifunctional nanoplatforms. Finally, the protective effect of NPs and NAC were preliminary assessed on human kidney cells.

Engineering Lignin Nanomicroparticles for the Antiphotolysis and Controlled Release of the Plant Growth Regulator Abscisic Acid

Lignin is the most abundant aromatic biopolymer in nature and is a major byproduct from the paper industry. The unlocking of lignin's potential for high-value applications has gained increasing attention in recent years. In this study, alkali lignin (AL), with a rigid conjugated structure and amphiphilic property, was used as a sustainable and eco-friendly encapsulation material for the protection and controlled release of photosensitive abscisic acid (ABA), an important and widely used plant growth regulator. Cetyltrimethylammonium bromide (CTAB) was used to induce the formation of AL-CTAB nanomicroparticles by self-assembly. The size and morphology of AL-CTAB particles were modified by changing the AL concentration and the dispersion agent. AL (0.3 M) dissolved in tetrahydrofuran could form a uniform size (300 nm) of particles with a regular spherical structure. Subsequently, ABA was loaded on the prepared nanomicroparticles to synthesize the capsule formulation of ABA@AL-CTAB. The controlled-release behavior and the antiphotolysis performance as well as the thermal stability of ABA@AL-CTAB were proved to be superior. Lasting inhibition of Arabidopsis and rice seed germination by ABA@AL-CTAB under light irradiations implied protection of ABA from photolysis. In addition, ABA@AL-CTAB could effectively regulate plant stomata, thereby increasing plant drought resistance. Overall, lignin is suitable for the preparation of agrochemical formulations with excellent controlled release and antiphotolysis performances.

Modelling protein therapeutic co-formulation and co-delivery with PLGA nanoparticles continuously manufactured by microfluidics

Formulating protein therapeutics into nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA) provides key features such as protection against clearance, sustained release and less side effects by possible attachment of targeting ligands.

Evaluation of sodium valproate loaded nanoparticles in acute and chronic pentylenetetrazole induced seizure models

BACKGROUND AND PURPOSE

Efficacy of sodium valproate in epilepsy is limited by its poor blood brain barrier penetration and side effects. Nanoparticles may offer a better drug delivery system to overcome these limitations. This study evaluated the efficacy of sodium valproate encapsulated in nanoparticles in pentylenetetrazole (PTZ) induced acute and kindling models of seizures in male Wistar rats.

METHODS

Poly lactic-co-glycolic acid (PLGA) based, polysorbate 80 stabilized sodium valproate loaded nanoparticles (nano sodium valproate) and rhodamine loaded nanoparticles (RLN) were formulated by double emulsion- solvent evaporation method and characterized for their size, shape, zeta potential and drug loading percentage. RLN was used to demonstrate blood brain barrier (BBB) permeability of nanoparticles. Serum drug levels were estimated using high performance liquid chromatography. The efficacy of standard sodium valproate (300 mg/kg) and nano sodium valproate (∼300, ∼150 and ∼75 mg/kg of sodium valproate) were evaluated in experimental animal models of seizures along with their effects on behavioral and oxidative stress parameters. Drugs were administered 60 min before PTZ in acute model. In the kindling model, drugs were administered every day while PTZ was administered on alternate days 60 min after drug administration. All the study drugs/compounds were administered intraperitoneally.

RESULTS

RLN were observed to be clustered in cortex which implied that the nanoparticles crossed BBB. Both standard sodium valproate and nano sodium valproate reached therapeutic serum level at 15 min and 1 h, but were undetectable in serum at 24 h. In acute PTZ (60 mg/kg) model, nano sodium valproate (∼300 mg/kg of sodium valproate) and standard sodium valproate showed protection against seizures till 6 h and 4 h, respectively. There were significant behavioral impairment and oxidative stress with standard sodium valproate in acute model as compared to nano sodium valproate at 6 h. In kindling model, induced with PTZ (30 mg/kg, every alternate day for 42 days), complete protection from seizures was observed with nano sodium valproate (∼150 mg/kg and ∼75 mg/kg of sodium valproate) and standard sodium valproate (300 mg/kg). Similarly, significant protection from behavioral impairment and oxidative stress was observed with standard sodium valproate and nano sodium valproate as compared to PTZ.

CONCLUSION

When compared to conventional therapy, nano sodium valproate showed protection from seizures at reduced doses and for a longer duration in animal models of epilepsy. This study suggests the potential of nano sodium valproate in the treatment of epilepsy.

A novel elastic liposome for skin delivery of papain and its application on hypertrophic scar

This study aims to investigate the therapeutic effects of papain elastic liposomes (PEL) on hypertrophic scar through topical application. PEL were prepared using the reverse-phase evaporation method and optimized by response surface methodology. The transdermal absorption of optimized PEL was tested by vertical Franz diffusion cells in vitro. The effects of PEL were investigated in rabbit model of hypertrophic scar in vivo, histological analysis and scar-related proteins were detected to reveal potential scar repair mechanism. The best formulation of PEL had EE (43.8±1.4%), particle size (100.9±2.2nm), PDI (0.037±0.003), zeta potential (-26.3±1.3mV), and DI (21.9±3.1). PEL gave the cumulative amounts and steady state fluxes in the receiver solution of 381.9±32.4μg/cm², 11.4±1.5μg/cm²/h, and showed drug deposition in skin of 19.1±3.2% after 24h. After topical application, the scar elevation index, microvascular density, and collagen fiber were significantly decreased with regular arrangement. The expressions of TGF-β₁, P-Smad-3, P-NF-κB p65, and P-IKBa in hypertrophic scar were significantly down regulated in contrast with those in model group. PEL were proven as an excellent topical preparation for hypertrophic scar treatment.

Long-term release of a thiobenzamide from a backbone functionalized poly(lactic acid)

Hydrogen sulfide is emerging as a critically important molecule in medicine, yet there are few methods for the long-term delivery of molecules that degrade to release H2S. In this paper the first long-term release of a thiobenzamide that degrades to release H2S is described. A series of polymers were synthesized by the copolymerization of L-lactide and a lactide functionalized with 4-hydroxythiobenzamide. A new method to attach functional groups to a derivative of L-lactide is described based on the addition of a thiol to an α,β-unsaturated lactide using catalytic I2. This reaction proceeded under mild conditions and did not ring-open the lactone. The copolymers had molecular weights from 8 to 88 kg mol-1 with PDIs below 1.50. Two sets of microparticles were fabricated from a copolymer; the average diameters of the microparticles were 0.53 and 12 μm. The degradation of the smaller microparticles was investigated in buffered water to demonstrate the slow release of thiobenzamide over 4 weeks. Based on the ability to synthesize polymers with different loadings of thiobenzamide and that thiobenzamide is a known precursor to H2S, these particles provide a polymer-based method to deliver H2S over days to weeks.

Bioactive Hybrid Particles from Poly(D,L-lactide-co-glycolide) Nanoparticle Stabilized Lipid Droplets

Biodegradable and bioactive hybrid particles composed of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles and medium-chain triglycerides were prepared by spray drying lipid-in-water emulsions stabilized by PLGA nanoparticles, to form PLGA-lipid hybrid (PLH) microparticles approximately 5 μm in mean diameter. The nanoparticle stabilizer was varied and mannitol was also incorporated during the preparation to investigate the effect of stabilizer charge and cryoprotectant content on the particle microstructure. An in vitro lipolysis model was used to demonstrate the particles' bioactivity by manipulating the digestion kinetics of encapsulated lipid by pancreatic lipase in simulated gastrointestinal fluid. Lipid digestion kinetics were enhanced in PLH and PLGA-lipid-mannitol hybrid (PLMH) microparticles for both stabilizers, compared to a coarse emulsion, in biorelevant media. An optimal digestion rate was observed for the negatively charged PLMH system, evidenced by a 2-fold increase in the pseudo-first-order rate constant compared to a coarse emulsion. Improved microparticle redispersion, probed by dual dye confocal fluorescence microscopy, increased the available surface area of lipid for lipase adsorption, enhancing digestion kinetics. Thereby, lipase action was controlled in hybrid microparticles by altering the surface charge and carbohydrate content. Our results demonstrate that bioactive microparticles composed of versatile and biodegradable polymeric particles and oil droplets have great potential for use in smart food and nutrient delivery, as well as safer and more efficacious oral delivery of drugs and drug combinations.

Evaluation of In Vivo Transfection Efficiency of Eudragit Coated Nanoparticles of Chitosan-DNA: A pH-sensitive System Prepared for Oral DNA Delivery

Background:

Success of any gene therapy protocol relies mostly on using an efficient carrier to direct nucleic acid to the place of action. The system should also have transfection ability at release site. Different routes are available for delivering genetic materials to the target organs, amongst them; oral delivery is particularly attractive for certain reasons. However, serious obstacles, like acidic environment of stomach and presence of protease and nuclease enzymes in gastrointestinal (GI) tract, make oral route a highly challenging option.

Objectives:

The present study suggests preparation of gene nanoparticles (NPs) of chitosan within a layer of Eudragit L100 for oral delivery of nucleic acid. The nanoparticles have some features both in size and polymer properties that can be penetrating enough to transfect epithelial layer cells of intestine and protect the entrapped materials against stomach harsh condition.

Materials and Methods:

In this experimental study, conducted in Iran, particles were prepared by coacervation technique followed by encapsulation of nanoparticle within a coat of Eudragit L100 using solvent evaporation technique. Formulation behavior was monitored both in vitro and in vivo. Stability of particle construction and release profile of DNA were examined at pH of ± 0.8 environ pKa of Eudragit. Size and zeta potential of particles were measured. To demonstrate transfection efficiency of the constructed carrier, reverse transcription polymerase chain reaction (RT-PCR) was carried out using human insulin specific primers on total RNA extracted from upper part of small intestine of 48-hour post-transfected rats (sampled by simple random selection, n = 3).

Results:

The mean size and zeta potential of particles were 300 ± 4 nm and 14 ± 0.5 mV, respectively. Encapsulation of this system was 89.6 ± 1.2%. DNA release from batches was less than 12% at pH = 5.2 and more than 60% at pH = 6.8 with significant difference of P < 0.05. RT-PCR product confirmed the presence of insulin transcript of 437 bp in upper intestinal extracts of the transfected rats. No band of DNA was seen after RT-PCR of placebo form of nanoparticles received group.

Conclusions:

Eudragit coated nanoparticle of chitosan is an efficient choice for oral delivery of DNA to upper part of GI tract.

Preparation and evaluation of 17-allyamino-17-demethoxygeldanamycin (17-AAG)-loaded poly(lactic acid-co-glycolic acid) nanoparticles

In the present study, we developed the novel 17-allyamino-17-demethoxygeldanamycin (17-AAG)-loaded poly(lactic acid-co-glycolic acid) (PLGA) nanoparticles (NPs) using the combination of sodium lauryl sulfate and poloxamer 407 as the anionic and non-ionic surfactant for stabilization. The PLGA NPs were prepared by emulsification/solvent evaporation method. Both the drug/polymer ratio and phase ratio were 1:10 (w/w). The optimized formulation of 17-AAG-loaded PLGA NPs had a particle size and polydispersity index of 151.6 ± 2.0 and 0.152 ± 0.010 nm, respectively, which was further supported by TEM image. The encapsulation efficiency and drug loading capacity were 69.9 and 7.0%, respectively. In vitro release study showed sustained release. When in vitro release data were fitted to Korsmeyer-Peppas model, the n value was 0.468, which suggested that the drug was released by anomalous or non-Fickian diffusion. In addition, 17-AAG-loaded PLGA NPs in 72 h, displayed approximately 60% cell viability reduction at 10 µg/ml 17-AAG concentration, in MCF-7 cell lines, indicating sustained release from NPs. Therefore, our results demonstrated that incorporation of 17-AAG into PLGA NPs could provide a novel effective nanocarrier for the treatment of cancer.

Rivastigmine-loaded L-lactide-depsipeptide polymeric nanoparticles: decisive formulation variable optimization

The main aim of the investigation was to explore a novel L-lactide-depsipeptide copolymer for the development of rivastigmine-loaded polymeric nanoparticles. L-lactide-depsipeptide synthesis was based on the ring opening polymerization reaction of L-lactide with the cyclodepsipeptide, cyclo(Glc-Leu), using tin 2-ethyl hexanoate as an initiator. Rivastigmine-loaded nanoparticles were prepared by the single emulsion-solvent evaporation technique. The influence of various critical formulation variables like sonication time, amount of polymer, amount of drug, stabilizer concentration, drug-to-polymer ratio, and organic-to-aqueous phase ratio on particle size and entrapment efficiency was studied. The optimized formulation having a particle size of 142.2 ± 21.3 nm with an entrapment efficiency of 60.72 ± 3.72% was obtained. Increased rivastigmine entrapment within the polymer matrix was obtained with a relatively low organic-to-aqueous phase ratio and high drug-to-polymer ratio. A decrease in the average size of the nanoparticles was observed with a decrease in the amount of polymer added and an increase in the sonication time. Prolonged sonication time, however, decreased rivastigmine entrapment. From the different lyoprotectant tested, only trehalose was found to prevent nanoparticle aggregation upon application of the freeze-thaw cycle. Drug incorporation into the polymeric matrix was confirmed by the DSC and XRD study. The spherical nature of the nanoparticles was confirmed by the SEM study. The in vitro drug release study showed the sustained release of more than 90% of the drug up to 72 h. Thus, L-lactide-depsipeptide can be used as an efficient carrier for the nanoparticle preparation of rivastigmine.

Preparation, characterization, in vivo biodistribution and pharmacokinetic studies of donepezil-loaded PLGA nanoparticles for brain targeting

OBJECTIVE

Alzheimer's disease (AD) is a progressive neurodegenerative disorder manifested by cognitive, memory deterioration and variety of neuropsychiatric symptoms. Donepezil is a reversible cholinesterase inhibitor used for the treatment of AD. The purpose of this work is to prepare a nanoparticulate drug delivery system of donepezil using poly(lactic-co-glycolic acid) (PLGA) for sustained release and efficient brain targeting.

MATERIALS AND METHODS

PLGA nanoparticles (NPs) were prepared by the solvent emulsification diffusion-evaporation technique and characterized for particle size, particle-size distribution, zeta potential, entrapment efficiency, drug loading and interaction studies and in vivo studies using gamma scintigraphy techniques.

RESULTS AND DISCUSSION

The size of drug-loaded NPs (drug polymer ratio 1:1) was found to be 89.67 ± 6.43 nm. The TEM and SEM images of the formulation suggested that particle size was within 20-100 nm and spherical in shape, smooth morphology and coating of Tween-80 on the NPs was clearly observed. The release behavior of donepezil exhibited a biphasic pattern characterized by an initial burst release followed by a slower and continuous sustained release. The biodistribution studies of donepezil-loaded PLGA NPs and drug solution via intravenous route revealed higher percentage of radioactivity per gram in the brain for the nanoparticulate formulation as compared with the drug solution (p < 0.05).

CONCLUSION

The high concentrations of donepezil uptake in brain due to coated NPs may help in a significant improvement for treating AD. But further, more extensive clinical studies are needed to check and confirm the efficacy of the prepared drug delivery system.

Intracellular drug delivery in Leishmania-infected macrophages: Evaluation of saponin-loaded PLGA nanoparticles

Drug delivery systems present an opportunity to potentiate the therapeutic effect of antileishmanial drugs. Colloidal carriers are rapidly cleared by the phagocytic cells of the reticuloendothelial system (RES), rendering them ideal vehicles for passive targeting of antileishmanials. This paper describes the development of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) for the antileishmanial saponin β-aescin. NPs were prepared using the combined emulsification solvent evaporation/salting-out technique. Confocal microscopy was used to visualise the internalisation and intracellular trafficking of fluorescein- and nile red-labelled PLGA NPs in J774A.1 macrophages infected with GFP-transfected Leishmania donovani. The in vitro activity of aescin and aescin-loaded NPs on L. infantum was determined in the axenic model as well as in the ex vivo model. The developed PLGA NPs were monodispersed with Z(ave)<300 nm, exhibited negative zeta potentials and had relatively high drug loadings ranging from 5.80 to 8.68% w/w PLGA. The fluorescent NPs were internalised by the macrophages and trafficked towards the lysosomes after 2 h in vitro incubation. Co-localisation of the NPs and the parasite was not shown. A two-fold increase in activity was observed in the ex vivo macrophage model by encapsulating β-aescin in PLGA NPs (IC(50), 0.48-0.76 µg/mL vs. 1.55 ± 0.32 µg/mL for the free drug).

Formulation optimization of sustained-release ammonio methacrylate copolymer microspheres. Effects of log p and concentration of polar cosolvents, and role of the drug/copolymer ratio

The objectives of this work were the formulation optimization of the preparation process parameters and to evaluate spray-dried sustained-release microspheres using ammonio methacrylate copolymer (AMC) as a polymer matrix. The effects of log P and the concentrations of the cosolvents (acetone, methyl ethyl ketone and n-butyl acetate) and different drug/copolymer ratios as independent variables on the physicochemical parameters (the W1/O emulsion viscosity, the microsphere production yield, the average particle size, the encapsulation efficiency) and the cumulative in vitro drug release as dependent variables were studied. The optimization was carried out on the basis of the 33 factorial design study. The optimization process results showed that addition of polar cosolvents proved effective, linear relationships were observed between the independent and the dependent variables. The best conditions were achieved by microspheres prepared by using a low/medium cosolvent log P, cosolvent concentration of 25-50% v/v and a drug/copolymer ratio of 1:16. The microspheres ensured sustained release with Nernst and Baker-Lonsdale release profiles.

Peroral amphotericin B polymer nanoparticles lead to comparable or superior in vivo antifungal activity to that of intravenous Ambisome® or Fungizone™

Background

Despite advances in the treatment, the morbidity and mortality rate associated with invasive aspergillosis remains unacceptably high (70–90%) in immunocompromised patients. Amphotericin B (AMB), a polyene antibiotic with broad spectrum antifungal activity appears to be a choice of treatment but is available only as an intravenous formulation; development of an oral formulation would be beneficial as well as economical.

Methodology

Poly(lactide-co-glycolode) (PLGA) nanoparticles encapsulating AMB (AMB-NPs) were developed for oral administration. The AMB-NPs were 113±20 nm in size with ∼70% entrapment efficiency at 30% AMB w/w of polymer. The in vivo therapeutic efficacy of oral AMB-NPs was evaluated in neutropenic murine models of disseminated and invasive pulmonary aspergillosis. AMB-NPs exhibited comparable or superior efficacy to that of Ambisome® or Fungizone™ administered parenterally indicating potential of NPs as carrier for oral delivery.

Conclusions

The present investigation describes an efficient way of producing AMB-NPs with higher AMB pay-load and entrapment efficiency employing DMSO as solvent and ethanol as non-solvent. The developed oral formulation was highly efficacious in murine models of disseminated aspergillosis as well as an invasive pulmonary aspergillosis, which is refractory to treatment with IP Fungizone™and responds only modestly to AmBisome®.

Influence of process and formulation parameters on the formation of submicron particles by solvent displacement and emulsification-diffusion methods critical comparison

Solvent displacement and emulsification-diffusion are the methods used most often for preparing biodegradable submicron particles. The major difference between them is the procedure, which results from the total or partial water miscibility of the organic solvents used. This review is devoted to a critical and a comparative analysis based on the mechanistic aspects of particle formation and reported data on the influence of operating conditions, polymers, stabilizing agents and solvents on the size and zeta-potential of particles. In addition, a systematic study was carried out experimentally in order to obtain experimental data not previously reported and compare the data pertaining to the different methods. Thus the discussion of the behaviors reported in the light of the results obtained from the literature takes into account a wide range of theoretical and practical information. This leads to discussion on the formation mechanism of the particles and provides criteria for selecting the adequate method and raw materials for satisfying specific objectives in submicron particle design.

Electrospray encapsulation of hydrophilic and hydrophobic drugs in poly(L-lactic acid) nanoparticles

An electrospray method is developed for preparation of beclomethasone-dipropionate- and salbutamol-sulfate-loaded biodegradable poly(L-lactic acid) nanoparticles. Different set-up parameters for electrospraying are examined on particle size, and preparation conditions are optimized for producing spherical-drug-loaded nanoscale particles by controllable processing parameters. Polylactide (PLA)-drug nanoparticles with average diameters of around 200 nm are achieved in a stable cone-jet mode with a flow rate of 4 microL min(-1), polymer concentration of 1%, and ammonium hydroxide content of 0.05%. Morphology and size of the drug-polymer nanoparticles are analyzed by scanning electron microscopy and transmission electron microscopy. Changes in the crystallinity of the PLA polymer and the model drugs are detected by X-ray powder diffraction, and the absence of molecular interactions are confirmed by thermal analyses. The results indicate clearly that electrospraying is a potential method for producing polymeric nanoparticles and for encapsulating both hydrophilic and hydrophobic drugs efficiently into the nanoparticles.

Poly(lactic-co-glycolic acid) nanospheres and microspheres for short- and long-term delivery of bioactive ciliary neurotrophic factor

Ciliary neurotrophic factor (CNTF) has been shown to be neuroprotective in the central nervous system (CNS). However, systemic administration and bolus injections have shown significant side effects and limited efficacy. Sustained, local delivery may lead to effective neuroprotection and avoid or limit adverse side effects, but sustained CNTF delivery has proven difficult to achieve and control. For controlled, sustained delivery, we investigated several processing variables in making poly(DL-lactic-co-glycolic acid) (PLGA) nano- and microspheres to optimize CNTF encapsulation and release. Nano- and microspheres were 314.9 +/- 24.9 nm and 11.69 +/- 8.16 microm in diameter, respectively. CNTF delivery from nanospheres was sustained over 14 days, and delivery from microspheres continued over more than 70 days. To assess protein bioactivity after encapsulation, neural stem cells (NSCs) were treated with CNTF released from nanospheres and compared to those treated with unencapsulated CNTF as a control. NSCs treated with CNTF expressed markers specific to mature cells, notably astrocytes; some increase in oligodendrocytic and neuronal marker expression was also observed. Significantly, cells treated with CNTF released by nanospheres exhibited a similar degree of differentiation when compared to those treated with control CNTF of equivalent concentration, showing that the process of protein encapsulation did not reduce its potency.

PLGA nanoparticles for oral delivery of hydrophobic drugs: influence of organic solvent on nanoparticle formation and release behavior in vitro and in vivo using estradiol as a model drug

The aim of present investigation was to screen different solvents for optimizing nanoparticle preparation in terms of particle size, entrapment efficiency, and finally, release behavior using a model drug estradiol. Nanoparticles were prepared following emulsion-diffusion-evaporation method using didodecyldimethyl ammonium bromide (DMAB) or polyvinyl alcohol (PVA) as stabilizers. Ethyl acetate (EA), acetone (ACE), chloroform (CHL), and dichloromethane (DCM) were used as organic solvents either individually or in combinations. DMAB when used as surfactant led to smaller particle size as compared to PVA irrespective of the solvents and combinations used, but on the other hand, PVA produced particles with higher entrapment when combinations of solvents used. DCM in combination with EA resulted in highest entrapment with both the stabilizers. All the formulations exhibited similar in vitro release profile (Zero order) irrespective of stabilizer (DMAB or PVA) used, however, the average release per day was higher in case of DCM formulations due to greater entrapment. In situ uptake studies suggest that smaller the particle size better is the uptake. The bioavailability from nanoparticles was assessed in male Sprague Dawley (SD) rats at a dose of 1 mg drug/rat. EA/DMAB (size 116.0 +/- 2.6 nm) and DCM:EA 70:30/DMAB (size 253.0 +/- 5.5 nm) showed the release for 9 and 5 days, respectively, whereas EA/PVA (size 279.3 +/- 2.5 nm) released the drug over the periods of 3 days suggesting that particle size has significant role in determining the fate of nanoparticles in vivo. Histopathological examination revealed absence of any inflammatory response with the formulations under the studied period.

PLA Nano- and Microparticles for Drug Delivery: An Overview of the Methods of Preparation

The controlled release of medicaments remains the most convenient way of drug delivery. Therefore, a wide variety of reports can be found in the open literature dealing with drug delivery systems. In particular, the use of nano- and microparticles devices has received special attention during the past two decades. PLA and its copolymers with GA and/or PEG appear as the preferred substrates to fabricate these devices. The methods of fabrication of these particles will be reviewed in this article, describing in detail the experimental variables associated with each one with regard to the influence of them on the performance of the particles as drug carriers. An analysis of the relationship between the method of preparation and the kind of drug to encapsulate is also included. Furthermore, certain issues involved in the addition of other monomeric substrates than lactic acid to the particles formulation as well as novel devices, other than nano- and microparticles, will be discussed in the present work considering the published literature available.

A Practical Approach to the use of Nanoparticles for Vaccine Delivery

The objective of this work was to obtain a nanoparticle formulation that could be sterile filtered, lyophilized, and resuspended to the initial size with excipients appropriate for use as a vaccine formulation. Poly(lactide-co-glycolide) (PLG) polymers were used to create nanoparticles ranging in size from 110 to 230 nm. Protein antigens were adsorbed to the particles; the protein-nanoparticles were then lyophilized with the excipients. Vaccine compatible excipient combinations of sugars alone, surfactants alone, and sugars and surfactants were tested to find conditions where initial particle size was recovered. Sterile filtration of smaller nanoparticles led to minimal PLG losses and allowed the particle preparation to be a nonaseptic process. We found that the smaller nanoparticles of size approximately 120 nm required higher surfactant concentration to resuspend postlyophilization than slightly larger ( approximately 220 nm) particles. To resuspend 120 nm nanoparticles formulations of poly(vinyl alcohol) (PVA) with sucrose/mannitol or dioctyl sodium sulfosuccinate (DSS) with trehalose/mannitol were sufficient. The protein-nanoparticles resuspension with the same excipients was dependent on the protein and protein loading level. The nanoparticle formulations in vivo were either similar or had enhanced immunogenicity compared to aluminum hydroxide formulations. A lyophilized nanoparticle formulation with adsorbed protein antigen and minimal excipients is an effective vaccine delivery system.

Layer-by-layer polyelectrolyte coating of low molecular weight poly(lactic acid) nanoparticles

Low molecular weight (M(w)) poly(L-lactic acid) (PLA) nanoparticles were coated with polyelectrolytes (PEs) by layer-by-layer (LbL) technique using a filtration approach. Poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) were applied as PEs in coating. LbL coating is aimed to use in producing (nano)particulate drug delivery systems with improved biocompatibility and sustained or targeted release of drug substances. Nanoparticles of rapidly biodegradable polymers, like the low M(w) PLA, open up a possibility to control the release of the encapsulated substance by the coating, but set challenges to the coating process due to increased aggregation tendency and degradation rate of the polymer. When the core PLA nanoparticles were prepared by nanoprecipitation, surface properties of the nanoparticles were affected by solvent selection. Successful LbL coating of the PLA nanoparticles was obtained only with chloroform, but not with dichloromethane as the solvent during nanoprecipitation. Reason for this was found to be the more charged surface of the nanoparticles prepared with chloroform compared to the nanoparticles prepared with dichloromethane.

Effect of nanoprecipitation on the physicochemical properties of low molecular weight poly(l-lactic acid) nanoparticles loaded with salbutamol sulphate and beclomethasone dipropionate

A modified nanoprecipitation (interfacial polymer deposition following solvent displacement) method was used to produce nanoparticles from low molecular weight poly(L-lactic acid). Model drugs, either salbutamol sulphate or beclomethasone dipropionate, were encapsulated in the particles. The influence of the preparation method on the physicochemical state of the polymer and the drugs as well as on the drug-polymer interactions were studied by electron microscopy, X-ray diffractometry, thermal analysis and infrared spectroscopy. Nanoprecipitation lowered the crystallinity of the PLA polymer. The crystallinity of the polymer was higher in the particles containing salbutamol sulphate then those containing beclomethasone dipropionate. The crystal form of beclomethasone dipropionate was changed from an anhydrate to a monohydrate as a result of nanoprecipitation. Although changes in the crystallinity of the polymer and the model drugs were seen, no clear interactions between the polymer and the drug were detected.

Nanoparticles containing ketoprofen and acrylic polymers prepared by an aerosol flow reactor method

The purpose of this study was to outline the effects of interactions between a model drug and various acrylic polymers on the physical properties of nanoparticles prepared by an aerosol flow reactor method. The amount of model drug, ketoprofen, in the nanoparticles was varied, and the nanoparticles were analyzed for particle size distribution, particle morphology, thermal properties, IR spectroscopy, and drug release. The nanoparticles produced were spherical, amorphous, and had a matrix-type structure. Ketoprofen crystallization was observed when the amount of drug in Eudragit L nanoparticles was more than 33% (wt/wt). For Eudragit E and Eudragit RS nanoparticles, the drug acted as an effective plasticizer resulting in lowering of the glass transition of the polymer. Two factors affected the preparation of nanoparticles by the aerosol flow reactor method, namely, the solubility of the drug in the polymer matrix and the thermal properties of the resulting drug-polymer matrix.

Improved entrapment efficiency of hydrophilic drug substance during nanoprecipitation of poly(l)lactide nanoparticles

The purpose of this research was to improve the entrapment efficiency of a model hydrophilic drug substance, sodium cromoglycate, loaded inside polylactic acid nanoparticles by a modified nanoprecipitation method. The effect of formulation parameters was studied to improve the entrapment efficiency of the drug substance inside the nanoparticles. Several parameters (changes in the amount of model drug, solvent selection, electrolyte addition, pH alteration) were tested in order to increase the loading of the hydrophilic drug in the hydrophobic nanoparticles. Lowering of the pH was the most efficient way to increase the drug loading; up to approximately 70% of the sodium cromoglycate used in the particle formation process could be loaded inside the particles. The loading efficiency without the pH change was around 10% to 15% at maximum. The crystallinity values and crystal habits of the sodium cromoglycate nanoparticles were studied (x-ray diffraction) before and after the lowering of the pH. The change in pH conditions during the nanoprecipitation process did not affect markedly the crystallinity properties of the drug substance. According to this study, it is possible to improve the entrapment efficiency of hydrophilic sodium cromoglycate inside of the nanoparticles by small changes in the process parameters without alterations in the physical properties of the original drug substance.