Effect of ethanol as a processing co-solvent on the PLGA microsphere characteristics

Rawat, Archana; Burgess, Diane J.

doi:10.1016/j.ijpharm.2010.05.013

Cited by 44 publications

(19 citation statements)

References 24 publications

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“…[15] The PVA hydrogel was loaded with dexamethasone-containing poly(lactic-coglycolic acid) (PLGA) microspheres with an average size of 7 ± 3 μm. [23] The PVA hydrogel provides a continuous hydrophilic pathway for glucose diffusion as well as the GO xcatalyzed byproducts to diffuse outwards. [16] On the other hand, the hydrophobic PLGA microspheres locally release dexamethasone through their gradual degradation, [15] which is schematically shown in Figure 1 with three vertical sections corresponding to an idealized case of 0, 7, and 30 days incubation.…”

Section: Resultsmentioning

confidence: 99%

Macroscopic porosity generation in outer hydrogel membranes to offset sensitivity loss in implantable glucose sensors

Vaddiraju

Wang

Qiang

et al. 2013

2013 IEEE International Conference on Body Sensor Networks

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The function of implantable glucose sensor is hindered by post-implantation effects such as biofouling and negative tissue responses both of which lead to permeability reducing fibrous encapsulation. Utilization of drug-eluting composite coatings based on dexamethasone-containing poly (lactic-coglycolic) acid (PLGA) microspheres and poly (vinyl alcohol) (PVA) hydrogel matrix has been shown to suppress inflammation over a period of 1-3 months. Herein, it is shown that these coatings provide another auxiliary venue to offset the negative effects of protein adsorption through generation of macroscopic porosity following microsphere degradation. Long-term studies in serum have indicated that, while biofouling clogs the microporosity of the hydrogel, it has been offset by the generated macroscopic porosity following microsphere degradation. This resulted in a two-fold recovery in sensor sensitivity as compared to controls. These findings suggest that the use of macroscopic porosity can reduce biofouling-induced sensitivity losses, an approach synergistic with drug-delivery based methodologies to mitigate negative tissue responses.

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Section: Resultsmentioning

confidence: 99%

Macroscopic porosity generation in outer hydrogel membranes to offset sensitivity loss in implantable glucose sensors

Vaddiraju

Wang

Qiang

et al. 2013

2013 IEEE International Conference on Body Sensor Networks

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“…The PLGA microspheres were prepared using an oil/water emulsion based solvent evaporation/ extraction as described before. [16][17][18] A mold fabrication process was used to coat the dummy sensors with the PLGA microsphere/PVA hydrogel composite as reported before. 7 Briefly, an appropriate amount of PLGA microspheres (the dexamethasone loading was approximately 7.3% w/w) was dispersed in PVA (MW 133 kDa) solution (5% w/v).…”

Section: Methodsmentioning

confidence: 99%

“…Each rat received 3 same-sized dummy sensors (0.5 × 0.5 × 5 mm), which were implanted using 3 different-sized hypodermic needles (18,16, and 14 gauge). Figure 3 shows tissue sections taken from the vicinity of the dummy sensors on the predetermined days covering both the acute and chronic inflammatory phases.…”

Section: The Effect Of Insertion Needle Diameter On the Extent Of Formentioning

confidence: 99%

Foreign Body Reaction to Implantable Biosensors

Wang

Vaddiraju

et al. 2015

J Diabetes Sci Technol

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Background: Implantable biosensors for continuous glucose monitoring can greatly improve diabetes management. However, their applications are still associated with some challenges and one of these is the gradual functionality loss postimplantation as a consequence of the foreign body response (FBR). Sensor miniaturization in combination with drug-eluting biocompatible coatings is a promising strategy to enhance in vivo performance. However, limited study has been performed to understand the effect of initial trauma and implant size on foreign body reaction as well as in vivo performance of implantable glucose sensors. Methods: Different initial trauma was induced by implanting composite coated dummy sensors into rats using various sized needles and 3 different-sized dummy sensors were implanted to examine the size effect. Histological evaluation was performed to relate the inflammatory cell counts and foreign body capsule thickness with the implantation needle size and sensor size respectively. The effect of biocompatible coating on the performance of implantable glucose sensors was determined using both coated amperometric glucose sensors and microdialysis probes. Results: The results revealed that the degree of acute inflammation was mainly controlled by the extent of the initial trauma: the greater the trauma, the greater the acute inflammatory response. Implant size did not affect the acute inflammatory phase. However, the extent of chronic inflammation and fibrous encapsulation were affected by sensor size: the smaller the size the less the extent of chronic inflammation and fibrous encapsulation. Glucose sensors implanted using 14 gauge needles showed significantly lower initial in vivo response compared to those implanted using 16 gauge needles. This was not observed for sensors with dexamethasone-eluting biocompatible coatings since inflammation was suppressed. Conclusions: The results of the current study indicate that the extent of the inflammatory response post–sensor implantation varies as a function of the initial tissue trauma as well as the sensor size. Accordingly, miniaturization of implantable biosensors together with the utilization of a drug-eluting biocompatible composite coating may be a promising strategy to achieve long-term reliable continuous glucose monitoring.

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“…Em alguns casos, em particular, para peptídeos e proteínas, podem ser utilizados sistemas de co-solventes para aumentar a solubilidade do princípio ativo na solução polimérica. Quando se recorre a um sistema de co-solventes, utiliza-se como solvente polar o metanol [47] o etanol [47,48] a dimetilformamida ou a N-metil-2-pirrolidona [49] . A solução orgânica, que constitui a fase interna da emulsão, é então adicionada sob agitação, à uma solução aquosa, contendo um agente tensoativo do tipo O/A, como, por exemplo, o acetato de polivinila (PVA) [10] .…”

Section: Polímeros Biodegradáveisunclassified

Polímeros sintéticos biodegradáveis: matérias-primas e métodos de produção de micropartículas para uso em drug delivery e liberação controlada

et al. 2011

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Resumo: Micropartículas produzidas a partir de polímeros sintéticos têm sido amplamente utilizadas na área farmacêutica para encapsulação de princípios ativos. Essas micropartículas apresentam as vantagens de proteção do princípio ativo, mucoadesão e gastrorresistência, melhor biodisponibilidade e maior adesão do paciente ao tratamento. Além disso, utiliza menores quantidade de princípio ativo para obtenção do efeito terapêutico proporcionando diminuição dos efeitos adversos locais, sistêmicos e menor toxidade. Os polímeros sintéticos empregados na produção das micropartículas são classificados biodegradáveis ou não biodegradáveis, sendo os biodegradáveis mais utilizados por não necessitam ser removidos cirurgicamente após o término de sua ação. A produção das micropartículas poliméricas sintéticas para encapsulação tanto de ativos hidrofílicos quanto hidrofóbicos pode ser emulsificação por extração e/ou evaporação do solvente; coacervação; métodos mecânicos e estão revisados neste artigo evidenciando as vantagens, desvantagens e viabilidade de cada metodologia. A escolha da metodologia e do polímero sintético a serem empregados na produção desse sistema dependem da aplicação terapêutica requerida, bem como a simplicidade, reprodutibilidade e factibilidade do aumento de escala da produção. Palavras-chave: Polímeros, micropartículas, liberação controlada, métodos de produção. Biodegradable Synthetic Polymers: Raw-Materials and Production Methods of Microparticles for Drug Delivery and Controlled ReleaseAbstract: Microparticles produced from synthetic polymers have been widely used in the pharmaceutical field for encapsulation of drugs. These microparticles show several advantages such as drug protection, mucoadhesion, gastro-resistance, improved bioavailability and increased patient's compliance. In addition, it is possible to use lower amount of drug to achieve therapeutic efficiency with reduced local/ systemic adverse side effects and low toxicity. Synthetic polymers used for the production of microparticles are classified as biodegradable or non-biodegradable, being the former more popular since these do not need to be removed after drug release. Production of polymeric microparticles can be used for encapsulation of hydrophilic and hydrophobic drugs, by emulsification following solvent extraction/ evaporation, coacervation, methods that are revised in this paper, including advantages, disadvantages and viability of each methodology. Selection of methodology and synthetic polymer depends of the therapeutic purpose, as well as simplicity, reproducibility and possibility to scale up. Keywords: Polymers, microparticles, controlled release, production processes. IntroduçãoPolímeros sintéticos têm sido amplamente empregados para a produção de micropartículas de estrutura matricial (microesferas) ou vesicular (microcápsula) para veiculação de fármacos, proteínas e peptídeos [1] . As vantagens obtidas com o uso das micropartículas poliméricas sintéticas são proteção do princípio ativo [2] , mucoadesão [3][4][5] ; ga...

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Effect of ethanol as a processing co-solvent on the PLGA microsphere characteristics

Cited by 44 publications

References 24 publications

Macroscopic porosity generation in outer hydrogel membranes to offset sensitivity loss in implantable glucose sensors

Macroscopic porosity generation in outer hydrogel membranes to offset sensitivity loss in implantable glucose sensors

Foreign Body Reaction to Implantable Biosensors

Polímeros sintéticos biodegradáveis: matérias-primas e métodos de produção de micropartículas para uso em drug delivery e liberação controlada

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