Hemocompatibility of Degrading Polymeric Biomaterials: Degradable Polar Hydrophobic Ionic Polyurethane versus Poly(lactic-co-glycolic) Acid.

The use of degradable polymers in vascular tissue regeneration has sparked the need to characterize polymer biocompatibility during degradation. While tissue compatibility has been frequently addressed, studies on polymer hemocompatibility during degradation are limited. The current study evaluated the differences in hemocompatibility (platelet response, complement activation, and coagulation cascade initiation) between as-made and hydrolyzed poly(lactic-co-glycolic) acid (PLGA) and degradable polar hydrophobic ionic polyurethane (D-PHI). Platelet activation decreased (in whole blood) and platelet adhesion decreased (in blood without leukocytes) for degraded versus as-made PLGA. D-PHI showed minimal hemocompatibility changes over degradation. Leukocytes played a major role in mediating platelet activation for samples and controls, as well as influencing platelet-polymer adhesion on the degraded materials. This study demonstrates the importance of assessing the blood compatibility of biomaterials over the course of degradation since the associated changes in surface chemistry and physical state could significantly change biomaterial hemocompatibility.

Photoresponsive lipid-polymer hybrid nanoparticles for controlled doxorubicin release.

Currently, photoresponsive nanomaterials are particularly attractive due to their spatial and temporal controlled drug release abilities. In this work, we report a photoresponsive lipid-polymer hybrid nanoparticle for remote controlled delivery of anticancer drugs. This hybrid nanoparticle comprises three distinct functional components: (i) a poly(D,L-lactide-co-glycolide) (PLGA) core to encapsulate doxorubicin; (ii) a soybean lecithin monolayer at the interface of the core and shell to act as a molecular fence to prevent drug leakage; (iii) a photoresponsive polymeric shell with anti-biofouling properties to enhance nanoparticle stability, which could be detached from the nanoparticle to trigger the drug release via a decrease in the nanoparticle's stability under light irradiation. In vitro results revealed that this core-shell nanoparticle had excellent light-controlled drug release behavior (76% release with light irradiation versus 10% release without light irradiation). The confocal microscopy and flow cytometry results also further demonstrated the light-controlled drug release behavior inside the cancer cells. Furthermore, a CCK8 assay demonstrated that light irradiation could significantly improve the efficiency of killing cancer cells. Meanwhile, whole-animal fluorescence imaging of a tumor-bearing mouse also confirmed that light irradiation could trigger drug release in vivo. Taken together, our data suggested that a hybrid nanoparticle could be a novel light controlled drug delivery system for cancer therapy.

Long-term distribution of biodegradable microparticles in rat muscle quantified noninvasively by MRI.

PURPOSE: To demonstrate the feasibility of MRI to monitor longitudinally the fate of PLGA microparticles in muscle tissue after intramuscular injection in rats using standard equipment. METHODS: MRI was performed at different time points and until day 28 after intramuscular administration of microparticles. Image segmentation was used to quantify the MRI signals. Histology was performed at selected time points to validate the in vivo observations. The SOM230-long acting release formulation was used as test compound. RESULTS: Microparticles were detected in vivo until 28 days following their administration. Imaging and histology data indicated that the MRI signals followed three phases: in an early phase (≤ 48 h after injection), vehicle, edema and hydration of microparticles contributed to the signals. In the second (days 3-17) and third phases (day 17 onward), microparticle hydration was the main contributor. SOM230 in blood displayed peaks at days 2 and 17. CONCLUSION: MRI was suitable to follow longitudinally the presence of PLGA microparticles in the rat muscle without labeling them. This is advantageous, because labeling could potentially alter the properties and pharmacokinetics of the microparticles. Data were consistent with an initial compound release followed by diffusion and microparticle erosion as main mechanisms of SOM230 release.

Comparative study of kanamycin sulphate microparticles and nanoparticles for intramuscular administration: preparation in vitro release and preliminary in vivo evaluation.

Kanamycin sulphate (KS) is a Mycobacterium tuberculosis protein synthesis inhibitor. KS is polycationic, a property responsible for KS poor oral absorption half-life (2.5 h) and rapid renal clearance, which results in serious nephrotoxicity/ototoxicity. The current study aimed to develop KS-loaded PLGA vitamin-E-TPGS microparticles (MPs) and nanoparticles (NPs) to reduce the dosing frequency and dose-related adverse effect. In vitro release was sustained up to 10 days for KS PLGA-TPGS MPs and 13 days for KS PLGA-TPGS NPs in phosphate-buffered saline (PBS) pH 7.4. The in vivo pharmacokinetic test in Wistar rats showed that the AUC0-∞ of KS PLGA-TPGS NPs (280.58 µg/mL*min) was about 1.62-fold higher than that of KS PLGA-TPGS MPs (172.30 µg/mL*min). Further, in vivo protein-binding assay ascribed 1.20-fold increase in the uptake of KS PLGA-TPGS NPs through the alveolar macrophage (AM). The studies, therefore, could provide another useful tool for successful development of KS MPs and NPs.

In situ-forming PLGA implants loaded with leuprolide acetate/ß-cyclodextrin complexes: mathematical modelling and degradation.

Drug release mechanism of in situ-forming implants (ISIs) based on poly(lactic acid-co-glycolic acid) (PLGA) loaded with leuprolide acetate/ß-cyclodextrin (LA/ß-CD) complexes via fitting with four diffusion-based semi-empirical models were studied. The release rate constants and release exponent of ISIs were calculated. The main drug release mechanism was Fickian diffusion. The LA diffusion coefficient and release constant were decreased via increasing the portion of ß-CD in complexes. The release curve was parabolic, with a higher initial slope and then consistent with the exponential. All ISIs containing LA/ß-CD complexes better fitted with the Korsmeyer-Peppas, Weibull and Peppas-Sahlin models rather than first-order model. Furthermore, the effect of LA/ß-CD complexation on the degradation of ISIs was studied through scanning electron microscopy (SEM). Results showed that hydrophilic nature of ß-CD facilitated the surface erosion of PLGA chains, however after 18 d, ISI-1/10 had still a proper structural strength, due to no hydrolytic degradation of ß-CD in this implant.

Melatonin releasing PLGA micro/nanoparticles and their effect on osteosarcoma cells.

Melatonin loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles and microparticles in the diameter of ∼200 nm and 3.5 µm, respectively, were prepared by emulsion-diffusion-evaporation method. Melatonin entrapment into the particles was significantly improved with the addition of 0.2% (w/v) melatonin into the aqueous phase and encapsulation efficiencies were found as 14 and 27% for nanoparticles and microparticles, respectively. At the end of 40 days, ∼70% of melatonin was released from both of particles, with high burst release. Both blank and melatonin loaded PLGA nanoparticles caused toxic effect on the MG-63 cells due to their uptake by the cells. However, when 0.05 mg microparticle that is carrying ∼1.7 µg melatonin was added to the cm(2) of culture, inhibitory effect of melatonin on the cells were obviously observed. The results would provide an expectation about the usage of melatonin as an adjunct to the routine chemotherapy of osteosarcoma by encapsulating it into a polymeric carrier system.

Encapsulation of low lipophilic and slightly water-soluble dihydroartemisinin in PLGA nanoparticles with phospholipid to enhance encapsulation efficiency and in vitro bioactivity.

CONTEXT: PLGA nanoparticles have been widely utilised to encapsulate lipophilic drugs for sustained release. OBJECTIVE: This study was to enhance encapsulation efficiency and drug loading for the poorly lipophilic drug dihydroartemisinin (DHA) in PLGA nanoparticles, where amphiphilic phospholipid was employed as the intermediate. MATERIALS AND METHODS: DHA-phospholipid complex formulation was optimised using the response surface method. DHA-phospholipid complex-nanoparticles (DHA-PLC-NPs) were prepared using the solvent evaporation method. RESULTS: The particle size, zeta potential, entrapment efficiency and drug loading of the nanoparticles were 265.3 ± 7.9 nm, -21.4 ± 6.3 mV, 74.2 ± 6.5% and 2.80 ± 0.35%, respectively. Compared with the rapidly released free form, DHA underwent sustained release from the nanoparticles. DHA-PLC-NPs presented stronger cell proliferative inhibition than DHA treatment alone and apoptosis was obviously induced after DHA-PLC-NPs treatment. CONCLUSION: Phospholipid complexes are useful intermediate to improve the lipophilicity of drugs, the interaction with the hydrophobic core of PLGA and the encapsulation efficiency of poorly lipophilic drugs in polymeric nanoparticles.

[An experimental study on a slow-release complex with rifampicin-polylactic-co-glycolic acid-calcium phosphate cement].

OBJECTIVE: To prepare the slow-release complex with rifampicin (RFP)-polylactic-co-glycolic acid (PLGA)-calcium phosphate cement (CPC) (RFP-PLGA-CPC complex), and to study its physical and chemical properties and drug release properties in vitro.
 METHODS: The emulsification-solvent evaporation method was adopted to prepare rifampicin polylactic acid-glycolic acid (RFP-PLGA) slow-release microspheres, which were divided into 3 groups: a calcium phosphate bone cement group (CPC group), a CPC embedded with RFP group (RFP-CPC group), and a PLGA slow-release microspheres carrying RFP and the self-curing CPC group (RFP- PLGA-CPC complex group). The solidification time and porosity of materials were determined. The drug release experiments in vitro were carried out to observe the compressive strength, the change of section morphology before and after drug release. 
 RESULTS: The CPC group showed the shortest solidification time, while the RFP-PLGA-CPC complex group had the longest one. There was statistical difference in the porosity between the CPC group and the RFP-CPC group (P<0.05); Compared to the RFP-PLGA-CPC complex group, the porosity in the CPC group and the RFP-CPC group were significantly changed (both P<0.01). There was significant difference in the compressive strength between the RFP- PLGA-CPC complex group and the CPC group (P<0.01), while there was significant difference in the compressive strength between the RFP-CPC group and the CPC group (3 days: P<0.05; 30 and 60 days: P<0.01). The change of the compressive strength in the CPC was not significant in the whole process of degradation. The sizes of PLGA microspheres were uniform, with the particle size between 100-150 µm. The microspheres were spheres or spheroids, and their surface was smooth without the attached impurities. There was no significant change in the section gap in the CPC group after soaking for 3 to 60 days. The microstructure change in the RFP-CPC group was small, and the cross section was formed by small particles. The pores of section in the RFP-PLGA-CPC complex group increased obviously, and PLGA microspheres gradually disappeared until the 60th day when there were only empty cavities left. The RFP-PLGA-CPC complex group had no obvious drugs sudden release, and the cumulative drug release rate was nearly 95% in the 60 days. The linear fitting was conducted for the drug release behavior of the complex, which was in accordance with zero order kinetics equation F=0.168×t.
 CONCLUSION: The porosity of RFP-PLGA-CPC complex is significantly higher than that of CPC, and it can keep slow release of the effective anti-tuberculosis drugs and maintain a certain mechanical strength for a long time.

Use of Polylactide-Co-Glycolide-Nanoparticles for Lysosomal Delivery of a Therapeutic Enzyme in Glycogenosis Type II Fibroblasts.

Glycogenosis type II, or Pompe Disease, is a lysosomal storage disease caused by the deficiency of acid alpha-glucosidase (GAA), leading to glycogen accumulation in muscles. A recombinant human GAA (rhGAA, Myozyme®) is currently used for enzyme replacement therapy. Despite its efficacy in most of patients, some of them show a diminished response to the treatment with rapidly progressive clinical deterioration, due to immuno-mediated enzyme inactivation. To demonstrate that Nanoparticles (NPs) could be profitably exploited to carry macromolecules, PLGA NPs loaded with rhGAA (GAA-NPs) were prepared by double emulsion solvent evaporation. Their surface morphology, particle size, zeta-potential and biochemical activity were assessed. "Pulse and chase" experiments were made by administrating GAA-NPs on patients' fibroblasts. Biochemical activity tests showed a more efficient cellular uptake of rhGAA loaded to NPs and a more significant stability of the enzyme (up to 7 days) in vitro, if compared to the same amount of rhGAA free enzyme. This data allows to envision in vivo experiments, in significant animal models, to further characterize lysosomal enzyme loaded-NPs' efficacy and toxicity.

Polymer assisted entrapment of netilmicin in PLGA nanoparticles for sustained antibacterial activity.

This study was aimed to develop poly(dl-lactide-co-glycolide) (PLGA) nanoparticle of highly water soluble antibiotic drug, netilmicin sulfate (NS) with improved entrapment efficiency (EE) and antibacterial activity. Dextran sulfate was introduced as helper polymer to form electrostatic complex with NS. Nanoparticles were prepared by double emulsification method and optimized using 2(5-1) fractional factorial design. EE was mainly influenced by dextran sulfate: NS charge ratio and PLGA concentration, whereas particle size (PS) was affected by all factors examined. The optimized NS-loaded-NPs had EE and PS of 93.23 ± 2.7% and 140.83 ± 2.4 nm respectively. NS-loaded-NPs effectively inhibited bacterial growth compared to free NS. Sustained release protected its inactivation and reduced the decline in its killing activity over time even in presence of bronchial cells. A MIC value of 18 µg/mL was observed for NPs on P. aeruginosa. Therefore, NPs with sustained bactericidal efficiency against P. aeruginosa may provide therapeutic benefit in chronic pulmonary infection, like cystic fibrosis.

Drug-loaded PLGA-mPEG microparticles as treatment for atopic dermatitis-like skin lesions in BALB/c mice model.

This study evaluated the feasibility of mizolastine-loaded microparticles as therapy for atopic dermatitis. Microparticles have been researched for decades as a controlled-release drug delivery system, but seldom been used as treatment for skin disease. In this research, we induced dermatitis in BALB/c mice model by repeated topical application of dinitrofluorobenzene and compared the mizolastine microparticles injection and daily mizolastine injection treatment. The results showed that the mizolastine microparticles treatments significantly inhibited ear thickness and dermatitis index in dermatitis model compared with the dermatitis mice without treatment, showing a similar curative effect compared with daily mizolastine injection treatment, and the improvement continued for several days. Inflammatory cells infiltration into the ears and the plasma level of immunoglobulin E were also suppressed by mizolastine microparticles according to the histopathology analysis. In conclusion, the results suggested that drug-loaded microparticles could be a proper candidate for the treatment of skin diseases.

SN-38 active loading in poly(lactic-co-glycolic acid) nanoparticles and assessment of their anticancer properties on COLO-205 human colon adenocarcinoma cells.

SN-38 is a highly effective drug against many cancers. The development of an optimal delivery system for SN-38 is extremely challenging due to its low solubility and labile lactone ring. Herein, SN-38 encapsulated in poly(D,L-lactide-co-glycolide) nanoparticles (NPs) is introduced to enhance its solubility, stability and cellular uptake. SN-38-loaded NPs prepared by spontaneous emulsification solvent diffusion (SESD) method had an average diameter of 310 nm, a zeta potential of -9.69 mV and a loading efficiency of 71%. They were able to protect the active lactone ring of SN-38 against inactivation under physiological condition. A colorectal adenocarcinoma cell line (COLO-205) was used to assess the NPs effects on cytotoxicity and cellular uptake. Result showed a significant decreased cell proliferation and cell apoptosis. These results suggest that these SN-38-loaded NPs can be an effective delivery system for the treatment of colon cancer and potentially for other types of cancers.

[Kinetics of methyluracil release from bioresorbable polymeric carriers].

Bioresorbable poly(lactic-co-glycolic) matrix-carriers containing 20 wt. % of 6-methyluracil (MU) have been prepared by supercritical fluid monolithization without organic solvents. Raman spectroscopy was used to analyze both the spatial distribution MU over polymer matrices and the MU release kinetics from the carrier into phosphate buffer solution. It was found that, during the first 24 h, the amount of released MU did not exceed 15-20% of its encapsulated content. After that, the MU release kinetics passed to almost linear regime with simultaneous retarding of the process. On the 40th day of observation, the MU content in solution reached up to 80% of its initial content in the carriers. Thus, using 6-methyluracil as a model, it was shown that the proposed bioresorbable and bioactive composites can be used as matrix-carriers for targeted and long-term drug release.

The effect of nanoparticle properties, detection method, delivery route and animal model on poly(lactic-co-glycolic) acid nanoparticles biodistribution in mice and rats.

A review of poly(lactic-co-glycolic) acid (PLGA) nanoparticle (NP) biodistribution was conducted with the intent of identifying particle behavior for drug delivery applications. Databases such as Science Direct and Web of Science were used to locate papers on biodistribution of intravenous (i.v.) and orally delivered PLGA NPs in mice and rats. The papers included in the review were limited to those that report biodistribution data in terms of % dose particles/g tissue in the liver, kidney, spleen, lung, heart and brain. Noted trends involved particle behavior based on individual organ, particle size, animal model, type of indicator (entrapped versus covalently linked) and method of delivery (oral or i.v.). The liver showed the highest uptake of particles in mice, and the lung showed the highest uptake in rats. Minimal amounts of particles were detected in both the heart and brain of rats and mice. In rats, the concentration of particles approached 0% dose/g or decreased significantly over 24 h after administration of a single dose of particles. Higher concentrations of smaller particles were evident in the liver, kidney and spleen. Orally delivered drugs showed little to no uptake within the 24 h analysis when compared with i.v. delivered NPs. Differences in particle concentrations between rats and mice were also observed as expected when expressed as % dose/g organ. Particles with covalently linked indicators showed lower concentrations in tissues than particles with physically entrapped indicators. Further research on oral delivery of PLGA NPs as well as distribution beyond 24 h is needed to fully understand particle behavior in vivo for successful application of NPs in drug delivery.

In vivo toxicity and biodistribution of intraperitoneal and intravenous poly-L-lysine and poly-L-lysine/poly-L-glutamate in rats.

The combination of two differently charged polypeptides, poly-L-lysine (PL) and poly-L-glutamate (PG), has shown excellent postsurgical antiadhesive properties. However, the high molecular, positively charged PL is toxic in high doses, proposed as lysis of red blood cells. This study aims to elucidate the in vivo toxicity and biodistribution of PL and complex bound PLPG comparing intravenous and intraperitoneal administration. Fifty-six Sprague-Dawley rats were used in a model with repeated blood samples within 30 min examining blood gases and blood smears. Similarly, FITC labelled PL were used to track bio distribution and clearance of PL, given as single dose and complex bound to PG after intravenous and intraperitoneal administration. Tissue for histology and immunohistochemistry was collected. Blood gases and blood smears as well as histology points to a toxic effect of high dose PL given intravenously but not after intraperitoneal administration. The toxic effect is exerted through endothelial disruption and subsequent bleeding in the lungs, provoking sanguineous lung edema. FITC-labelled PL experiments reveal a rapid clearance with differences between routes and complex binding. This study advocates a new theory of the toxic effects in vivo of high molecular PL. PLPG complex is safe to use as antiadhesive prevention based on this toxicity study given that PL is always intraperitoneally administered in combination with PG and that the dose is adequate.

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.

Impact of microparticle formulation approaches on drug burst release: a level A IVIVC.

AIM: To study the effect of poly(d,l-lactic-co-glycolic acid) (PLGA) microparticles (MPs) preparation techniques on particle physical characterization with special emphasis on burst drug release. METHODS: A basic drug clozapine was used in combination with acid-terminated PLGA. Two approaches for MP preparation were compared; the in situ forming microparticle (ISM) and the emulsion-solvent evaporation (ESE) methods using an experimental design. The MPs obtained were compared according to their physical characterization, burst release and T80%. An in vivo pharmacokinetic study with in vitro-in vivo correlation (IVIVC) was also performed for the selected formula. RESULTS: Both methods were able to sustain drug release for three weeks. ISM produced more porous particles and was not effective as ESE for controlling burst release. A good IVIVC (R(2) = 0.9755) was attained when injecting the selected formula into rats. CONCLUSION: MPs prepared with ESE showed a minimum burst release and a level A IVIVC was obtained when administered to rats.

Double-effective chitosan scaffold-PLGA nanoparticle system for brain tumour therapy: in vitro study.

The chitosan scaffold, which has both of anticancer and antivascularization effects, was developed for using in local therapy of brain tumours. This is why, poly-lactic-co-glycolic acid (50:50) nanoparticles (~200 nm) including an anticancer drug, 5-fluorouracil (5-FU), were prepared by emulsion-solvent evaporation method. Then, these nanoparticles and antivascularization agent, bevacizumab, were loaded into the scaffold during manufacturing by freeze-drying and embedding after freeze-drying, respectively. The idea behind this system is to destroy tumour tissue by releasing 5-FU and to prevent the proliferation of tumour cells by releasing bevacizumab. In addition, 3D scaffold can support healthy tissue formation in the tumourigenic region. In vitro effectiveness of this system was investigated on T98G human glioblastoma cell line and human umbilical vein endothelial cells. The results show that the chitosan scaffold containing 100 µg 5-FU and 100 µg bevacizumab has a potential to prevent the tumour formation in vitro conditions.

Randomized controlled trial of osteoconductive fixation screws for anterior cruciate ligament reconstruction: a comparison of the Calaxo and Milagro screws.

PURPOSE: To compare the outcome of 2 bioabsorbable screws for tibial interference fixation in anterior cruciate ligament reconstruction with reference to rate of absorption, osteoconductive properties, and clinical outcome. METHODS: Patients undergoing primary anterior cruciate ligament reconstruction with hamstring autograft in a single unit were invited to participate in this study. Patients were randomized to receive either the Calaxo screw (Smith & Nephew, Andover, MA) or Milagro screw (DePuy Mitek, Raynham, MA) for tibial fixation. Patients were reviewed with subjective and objective evaluation by use of the International Knee Documentation Committee form, Lysholm score, KT-1000 arthrometry (MEDmetric, San Diego, CA), and clinical examination. Magnetic resonance imaging was performed at 1 year and computed tomography scanning at 1 week and at 6, 12, and 24 months. RESULTS: Sixty patients agreed to participate in the study, with 32 patients randomized to the Calaxo screw and 28 to the Milagro screw for tibial fixation. There was no significant difference in subjective or objective clinical outcome between the 2 groups. At 24 months, 88% of Calaxo screws showed complete screw resorption compared with 0% of Milagro screws (P < .001). Tibial cysts were present in 88% of the Calaxo group and 7% of the Milagro group (P = .001). At 24 months, the mean volume of new bone formation for the Calaxo group was 21% of original screw volume. Ossification of the Milagro screw was unable to be accurately assessed as a result of incomplete screw resorption. CONCLUSIONS: Both screws showed similar favorable objective and subjective outcomes at 2 years. The Calaxo screw resorbed completely over a period of 6 months and was associated with a high incidence of intra-tunnel cyst formation. The Milagro screw increased in volume over a period of 6 months, followed by a gradual resorption, which was still ongoing at 2 years. Both screws were associated with tunnel widening, and neither showed evidence of significant tunnel ossification. We conclude that, despite satisfactory clinical outcomes, the addition of "osteoconductive" materials to bioabsorbable screws is not associated with bone formation at the screw site at 2 years. LEVEL OF EVIDENCE: Level I, randomized controlled trial.

Preparation and characterization of metformin hydrochloride loaded-Eudragit®RSPO and Eudragit®RSPO/PLGA nanoparticles.

The aim of the present study was to develop and characterize metformin HCl-loaded nanoparticle formulations. Nanoparticles were prepared by the nanoprecipitation method using both a single polymer (Eudragit(®)RSPO) and a polymer mixture (Eudragit/PLGA). The mean particle size ranged from 268.8 to 288 nm and the nanoparticle surface was positively charged (9.72 to 10.1 mV). The highest encapsulation efficiency was observed when Eudragit®RSPO was used. All formulations showed highly reproducible drug release profiles and the in vitro drug release in phosphate buffer (pH = 6.8) ranged from 92 to 100% in 12 h. These results suggest that Eudragit(®)RSPO or Eudragit/PLGA nanoparticles might represent a promising sustained-release oral formulation for metformin HCl, reducing the necessity of repeated administrations of high doses to maintain effective plasma concentrations, and thus, increasing patient compliance and reducing the incidence of side-effects.