2012 IEEE 2nd Portuguese Meeting in Bioengineering (ENBENG), 2012
ABSTRACT The evaluation of corneal nerve morphology by optical methods may form the basis of a si... more ABSTRACT The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non-invasive technique for early diagnosis and accurate assessment of peripheral diabetic neuropathy. Currently, corneal nerves can be imaged in vivo using corneal confocal microscopy, an expensive technique that is only available at large medical units. Our goal is to develop an optical technique for peripheral neuropathy assessment, through corneal nerves imaging, based on simple, easy to operate and widespread instrumentation. This technique will be built upon automatic algorithms for corneal nerves segmentation and morphometric analysis and an optical confocal module for recording corneal nerves images using a standard slit-lamp, the most commonly used instrument in ophthalmic practice to observe the anterior eye. Here we present the current status and results of this ongoing project.
Topical drug treatment aims at providing high concentrations of drugs at the site of application ... more Topical drug treatment aims at providing high concentrations of drugs at the site of application so as to avoid adverse systemic effects associated with oral administration. Smart polymers, or stimuli-responsive polymers, are able to respond to a stimulus by showing physical or chemical changes in their behaviour as, for example, the delivery of the drug carried by them. The thermo-responsive nature of Pluronic® F-127 (Basf, Ludwigshafen, Germany) makes it an excellent candidate for the delivery of drugs at various application sites. In recent years, PF-127, and later, Pluronic lecithin organogels (PLO), have attracted particular interest in the design of dermal and transdermal delivery systems with a view to promoting, improving or retarding drug permeation through the skin, bearing in mind that for topical delivery systems, accumulation in the skin with minimal permeation is desired, while for systemic delivery, the opposite behaviour is preferred. In this review, we discuss the p...
The unique properties and characteristics of ocular tissues and the whole set of defense mechanis... more The unique properties and characteristics of ocular tissues and the whole set of defense mechanisms of the ocular globe make the instillation of ocular drugs into a difficult task with a low rate of therapeutic response. One of the challenges for the new generation of ophthalmic pharmaceutical formulations is to increase the bioavailability of drugs administered by the ocular route and, therefore, their therapeutic efficacy. This can be achieved with the use of some strategies that provide an increase in the formulation pre-corneal residence time, mucoadhesion and penetration across the eye tissues. Colloidal carrier systems have been very successfully used for the selective and targeted delivery of drugs for several routes of administration. In this context, nanoparticles prepared with specific polymers or lipids and coated, dispersed or suspended in polymer solutions with mucoadhesion properties or in situ gelling properties, will be an excellent strategy that desserves attention ...
Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques, 2012
Topical drug treatment aims at providing high concentrations of drugs at the site of application ... more Topical drug treatment aims at providing high concentrations of drugs at the site of application so as to avoid adverse systemic effects associated with oral administration. Smart polymers, or stimuli-responsive polymers, are able to respond to a stimulus by showing physical or chemical changes in their behaviour as, for example, the delivery of the drug carried by them. The thermo-responsive nature of Pluronic® F-127 (Basf, Ludwigshafen, Germany) makes it an excellent candidate for the delivery of drugs at various application sites. In recent years, PF-127, and later, Pluronic lecithin organogels (PLO), have attracted particular interest in the design of dermal and transdermal delivery systems with a view to promoting, improving or retarding drug permeation through the skin, bearing in mind that for topical delivery systems, accumulation in the skin with minimal permeation is desired, while for systemic delivery, the opposite behaviour is preferred. In this review, we discuss the p...
Controlled drug delivery is useful because it allows to obtain better drug product effectiveness,... more Controlled drug delivery is useful because it allows to obtain better drug product effectiveness, reliability and safety. Interest in stimuli-responsive polymers is steadily gaining increasing momentum especially in the fields of controlled and self-regulated drug delivery. Stimuliresponsive or "smart" polymers are macromolecules that display a significant physiochemical change in response to small changes in their environment such as temperature, pH, light, magnetic field, ionic factors, etc. The changes are reversible, and therefore, the smart polymers are capable of returning to its initial state as soon as the trigger is removed. They have become one important class of polymers and their applications have been increasing significantly in the last three decades. Smart polymers have very promising applications in the biomedical field as delivery systems of therapeutic agents, tissue engineering scaffolds, cell culture supports, bioseparation devices, etc. The versatility and untapped potential of smart polymeric materials makes them one of the most promising interfaces of chemistry and biology.
Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques, 2014
The unique properties and characteristics of ocular tissues and the whole set of defence mechanis... more The unique properties and characteristics of ocular tissues and the whole set of defence mechanisms of the ocular globe make the instillation of ocular drugs into a difficult task with a low rate of therapeutic response. One of the challenges for the new generation of ophthalmic pharmaceutical formulations is to increase the bioavailability of drugs administered by the ocular route and, therefore, their therapeutic efficacy. This can be achieved with the use of some strategies that provide an increase in the formulation pre-corneal residence time, mucoadhesion and penetration across the eye tissues. Colloidal carrier systems have been very successfully used for the selective and targeted delivery of drugs for several routes of administration. In this context, nanoparticles prepared with specific polymers or lipids and coated, dispersed or suspended in polymer solutions with mucoadhesion properties or in situ gelling properties will be an excellent strategy that deserves attention an...
2012 IEEE 2nd Portuguese Meeting in Bioengineering (ENBENG), 2012
The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non... more The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non-invasive technique for early diagnosis and accurate assessment of peripheral diabetic neuropathy. Currently, corneal nerves can be imaged in vivo using corneal confocal microscopy, an expensive technique that is only available at large medical units. Our goal is to develop an optical technique for peripheral neuropathy assessment, through corneal nerves imaging, based on simple, easy to operate and widespread instrumentation. This technique will be built upon automatic algorithms for corneal nerves segmentation and morphometric analysis and an optical confocal module for recording corneal nerves images using a standard slitlamp, the most commonly used instrument in ophthalmic practice to observe the anterior eye. Here we present the current status and results of this ongoing project.
An ideal ophthalmic formulation is one that not only prolongs the contact time of the vehicle on ... more An ideal ophthalmic formulation is one that not only prolongs the contact time of the vehicle on the ocular surface but also slows down the drug elimination. The poor bioavailability and therapeutic response exhibited by the conventional ophthalmic solutions due to pre-corneal elimination of the drug may be overcome by the use of in situ gel forming systems. In situ gelling systems increase the viscosity by changing the pH or temperature in the pre-corneal region and lead to an increase of drug bioavailability by slowing drainage. Poloxamers are polyols with thermal gelling properties which are frequently included in ophthalmic formulations to improve the ocular bioavailability of drugs by increasing vehicle viscosity. An overview on the unique physiological characteristics of ocular globe and the limitations and disadvantages of the conventional ophthalmic pharmaceutical formulations. Readers will appreciate the different strategies to improve the absorption of drugs in the ocular globe, especially the incorporation of poloxamers in ophthalmic formulations, understanding the main advantages of the poloxamers and also learning about the different examples of applications of these polymers in ophthalmic pharmaceutical formulations. Poloxamers offers a new strategy to improve bioavailability and decrease the side effects induced by the systemic absorption of topically applied ophthalmic drugs.
The low therapeutic efficacy exhibited by conventional ophthalmic solutions owing to precorneal e... more The low therapeutic efficacy exhibited by conventional ophthalmic solutions owing to precorneal elimination of the drug, drainage by gravity, nasolacrimal drainage, conjunctival absorption, and the absence of controlled release and of bioadhesive properties, can be overcome by the use of in situ gelling systems. The combination in the same formulation of different in situ gelling polymers with different stimuli-responsiveness mechanisms exploiting the unique physicochemical characteristics of the ocular tissues is one such strategy that has produced improved results compared with conventional systems. As we discuss here, the recent use of biodegradable and biocompatible polymers in colloidal carrier systems has proved to be the most effective strategy, resulting in the exponential increase of the bioavailability of the ophthalmic drugs.
In recent years, Poloxamers had attracted a particular interest in the design of dermal and trans... more In recent years, Poloxamers had attracted a particular interest in the design of dermal and transdermal delivery systems in order to improve or retard drug permeation through the skin. In the present study, the influence of different parameters, such as, temperature, storage time, type of polymer (Lutrol(®) F-127 and Lutrol(®) F-108) and the addition of two types of drugs (ibuprofen and hydrocortisone) in the pH, texture and rheological behavior of topical pharmaceutical formulations containing poloxamers was assessed. In fact, the type of polymer used in the preparation of the hydrogels, the type of drug incorporated, the temperature and the storage time caused changes in the pH, texture and rheological behavior of topical formulations containing Lutrol(®) F-127 and Lutrol(®) F-108. Lutrol(®) F-127 hydrogels showed higher values of pH, firmness, adhesiveness and viscosity than Lutrol(®) F-108 hydrogels. The chemical nature of the drugs incorporated in these poloxamer hydrogels influence the pH of the preparations. Low percentages of drug incorporated into both types of hydrogels didn't affect significantly their textural and rheological characteristics. The hydrogels prepared with Lutrol(®) F- 127 proved to be more resistant to temperature variations, maintaining their rheological behavior over time.
2012 IEEE 2nd Portuguese Meeting in Bioengineering (ENBENG), 2012
ABSTRACT The evaluation of corneal nerve morphology by optical methods may form the basis of a si... more ABSTRACT The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non-invasive technique for early diagnosis and accurate assessment of peripheral diabetic neuropathy. Currently, corneal nerves can be imaged in vivo using corneal confocal microscopy, an expensive technique that is only available at large medical units. Our goal is to develop an optical technique for peripheral neuropathy assessment, through corneal nerves imaging, based on simple, easy to operate and widespread instrumentation. This technique will be built upon automatic algorithms for corneal nerves segmentation and morphometric analysis and an optical confocal module for recording corneal nerves images using a standard slit-lamp, the most commonly used instrument in ophthalmic practice to observe the anterior eye. Here we present the current status and results of this ongoing project.
Topical drug treatment aims at providing high concentrations of drugs at the site of application ... more Topical drug treatment aims at providing high concentrations of drugs at the site of application so as to avoid adverse systemic effects associated with oral administration. Smart polymers, or stimuli-responsive polymers, are able to respond to a stimulus by showing physical or chemical changes in their behaviour as, for example, the delivery of the drug carried by them. The thermo-responsive nature of Pluronic® F-127 (Basf, Ludwigshafen, Germany) makes it an excellent candidate for the delivery of drugs at various application sites. In recent years, PF-127, and later, Pluronic lecithin organogels (PLO), have attracted particular interest in the design of dermal and transdermal delivery systems with a view to promoting, improving or retarding drug permeation through the skin, bearing in mind that for topical delivery systems, accumulation in the skin with minimal permeation is desired, while for systemic delivery, the opposite behaviour is preferred. In this review, we discuss the p...
The unique properties and characteristics of ocular tissues and the whole set of defense mechanis... more The unique properties and characteristics of ocular tissues and the whole set of defense mechanisms of the ocular globe make the instillation of ocular drugs into a difficult task with a low rate of therapeutic response. One of the challenges for the new generation of ophthalmic pharmaceutical formulations is to increase the bioavailability of drugs administered by the ocular route and, therefore, their therapeutic efficacy. This can be achieved with the use of some strategies that provide an increase in the formulation pre-corneal residence time, mucoadhesion and penetration across the eye tissues. Colloidal carrier systems have been very successfully used for the selective and targeted delivery of drugs for several routes of administration. In this context, nanoparticles prepared with specific polymers or lipids and coated, dispersed or suspended in polymer solutions with mucoadhesion properties or in situ gelling properties, will be an excellent strategy that desserves attention ...
Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques, 2012
Topical drug treatment aims at providing high concentrations of drugs at the site of application ... more Topical drug treatment aims at providing high concentrations of drugs at the site of application so as to avoid adverse systemic effects associated with oral administration. Smart polymers, or stimuli-responsive polymers, are able to respond to a stimulus by showing physical or chemical changes in their behaviour as, for example, the delivery of the drug carried by them. The thermo-responsive nature of Pluronic® F-127 (Basf, Ludwigshafen, Germany) makes it an excellent candidate for the delivery of drugs at various application sites. In recent years, PF-127, and later, Pluronic lecithin organogels (PLO), have attracted particular interest in the design of dermal and transdermal delivery systems with a view to promoting, improving or retarding drug permeation through the skin, bearing in mind that for topical delivery systems, accumulation in the skin with minimal permeation is desired, while for systemic delivery, the opposite behaviour is preferred. In this review, we discuss the p...
Controlled drug delivery is useful because it allows to obtain better drug product effectiveness,... more Controlled drug delivery is useful because it allows to obtain better drug product effectiveness, reliability and safety. Interest in stimuli-responsive polymers is steadily gaining increasing momentum especially in the fields of controlled and self-regulated drug delivery. Stimuliresponsive or "smart" polymers are macromolecules that display a significant physiochemical change in response to small changes in their environment such as temperature, pH, light, magnetic field, ionic factors, etc. The changes are reversible, and therefore, the smart polymers are capable of returning to its initial state as soon as the trigger is removed. They have become one important class of polymers and their applications have been increasing significantly in the last three decades. Smart polymers have very promising applications in the biomedical field as delivery systems of therapeutic agents, tissue engineering scaffolds, cell culture supports, bioseparation devices, etc. The versatility and untapped potential of smart polymeric materials makes them one of the most promising interfaces of chemistry and biology.
Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques, 2014
The unique properties and characteristics of ocular tissues and the whole set of defence mechanis... more The unique properties and characteristics of ocular tissues and the whole set of defence mechanisms of the ocular globe make the instillation of ocular drugs into a difficult task with a low rate of therapeutic response. One of the challenges for the new generation of ophthalmic pharmaceutical formulations is to increase the bioavailability of drugs administered by the ocular route and, therefore, their therapeutic efficacy. This can be achieved with the use of some strategies that provide an increase in the formulation pre-corneal residence time, mucoadhesion and penetration across the eye tissues. Colloidal carrier systems have been very successfully used for the selective and targeted delivery of drugs for several routes of administration. In this context, nanoparticles prepared with specific polymers or lipids and coated, dispersed or suspended in polymer solutions with mucoadhesion properties or in situ gelling properties will be an excellent strategy that deserves attention an...
2012 IEEE 2nd Portuguese Meeting in Bioengineering (ENBENG), 2012
The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non... more The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non-invasive technique for early diagnosis and accurate assessment of peripheral diabetic neuropathy. Currently, corneal nerves can be imaged in vivo using corneal confocal microscopy, an expensive technique that is only available at large medical units. Our goal is to develop an optical technique for peripheral neuropathy assessment, through corneal nerves imaging, based on simple, easy to operate and widespread instrumentation. This technique will be built upon automatic algorithms for corneal nerves segmentation and morphometric analysis and an optical confocal module for recording corneal nerves images using a standard slitlamp, the most commonly used instrument in ophthalmic practice to observe the anterior eye. Here we present the current status and results of this ongoing project.
An ideal ophthalmic formulation is one that not only prolongs the contact time of the vehicle on ... more An ideal ophthalmic formulation is one that not only prolongs the contact time of the vehicle on the ocular surface but also slows down the drug elimination. The poor bioavailability and therapeutic response exhibited by the conventional ophthalmic solutions due to pre-corneal elimination of the drug may be overcome by the use of in situ gel forming systems. In situ gelling systems increase the viscosity by changing the pH or temperature in the pre-corneal region and lead to an increase of drug bioavailability by slowing drainage. Poloxamers are polyols with thermal gelling properties which are frequently included in ophthalmic formulations to improve the ocular bioavailability of drugs by increasing vehicle viscosity. An overview on the unique physiological characteristics of ocular globe and the limitations and disadvantages of the conventional ophthalmic pharmaceutical formulations. Readers will appreciate the different strategies to improve the absorption of drugs in the ocular globe, especially the incorporation of poloxamers in ophthalmic formulations, understanding the main advantages of the poloxamers and also learning about the different examples of applications of these polymers in ophthalmic pharmaceutical formulations. Poloxamers offers a new strategy to improve bioavailability and decrease the side effects induced by the systemic absorption of topically applied ophthalmic drugs.
The low therapeutic efficacy exhibited by conventional ophthalmic solutions owing to precorneal e... more The low therapeutic efficacy exhibited by conventional ophthalmic solutions owing to precorneal elimination of the drug, drainage by gravity, nasolacrimal drainage, conjunctival absorption, and the absence of controlled release and of bioadhesive properties, can be overcome by the use of in situ gelling systems. The combination in the same formulation of different in situ gelling polymers with different stimuli-responsiveness mechanisms exploiting the unique physicochemical characteristics of the ocular tissues is one such strategy that has produced improved results compared with conventional systems. As we discuss here, the recent use of biodegradable and biocompatible polymers in colloidal carrier systems has proved to be the most effective strategy, resulting in the exponential increase of the bioavailability of the ophthalmic drugs.
In recent years, Poloxamers had attracted a particular interest in the design of dermal and trans... more In recent years, Poloxamers had attracted a particular interest in the design of dermal and transdermal delivery systems in order to improve or retard drug permeation through the skin. In the present study, the influence of different parameters, such as, temperature, storage time, type of polymer (Lutrol(®) F-127 and Lutrol(®) F-108) and the addition of two types of drugs (ibuprofen and hydrocortisone) in the pH, texture and rheological behavior of topical pharmaceutical formulations containing poloxamers was assessed. In fact, the type of polymer used in the preparation of the hydrogels, the type of drug incorporated, the temperature and the storage time caused changes in the pH, texture and rheological behavior of topical formulations containing Lutrol(®) F-127 and Lutrol(®) F-108. Lutrol(®) F-127 hydrogels showed higher values of pH, firmness, adhesiveness and viscosity than Lutrol(®) F-108 hydrogels. The chemical nature of the drugs incorporated in these poloxamer hydrogels influence the pH of the preparations. Low percentages of drug incorporated into both types of hydrogels didn't affect significantly their textural and rheological characteristics. The hydrogels prepared with Lutrol(®) F- 127 proved to be more resistant to temperature variations, maintaining their rheological behavior over time.
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