In vitro dissolution methods for hydrophilic and hydrophobic porous silicon microparticles

Colonic Delivery of α-Linolenic Acid by an Advanced Nutrient Delivery System Prolongs Glucagon-Like Peptide-1 Secretion and Inhibits Food Intake in Mice

Scope

Nutrients stimulate the secretion of glucagon‐like peptide‐1 (GLP‐1), an incretin hormone, secreted from enteroendocrine L‐cells which decreases food intake. Thus, GLP‐1 analogs are approved for the treatment of obesity, yet cost and side effects limit their use. L‐cells are mainly localized in the distal ileum and colon, which hinders the utilization of nutrients targeting GLP‐1 secretion. This study proposes a controlled delivery system for nutrients, inducing a prolonged endogenous GLP‐1 release which results in a decrease food intake.

Methods and Results

α‐Linolenic acid (αLA) was loaded into thermally hydrocarbonized porous silicon (THCPSi) particles. In vitro characterization and in vivo effects of αLA loaded particles on GLP‐1 secretion and food intake were studied in mice. A total of 40.4 ± 3.2% of loaded αLA is released from particles into biorelevant buffer over 24 h, and αLA loaded THCPSi significantly increased in vitro GLP‐1 secretion. Single‐dose orally given αLA loaded mesoporous particles increased plasma active GLP‐1 levels at 3 and 4 h and significantly reduced the area under the curve of 24 h food intake in mice.

Conclusions

αLA loaded THCPSi particles could be used to endogenously stimulate sustain gastrointestinal hormone release and reduce food intake.

Development and in vitro evaluation of microparticles of fluoxetine in galactomannan against biofilms of S. aureus methicilin resistant

The emergence of multidrug-resistant (MDR) bacteria is a global problem, by reducing the effectiveness of traditional antibiotics and decreasing the therapeutic arsenal to treat bacterial infections. This has led to an increase in researches about how to overcome this resistance to antibiotics. One strategy is the repositioning (or repurposing) of existing drugs not previously used to combat microorganisms, rather than the development of new drugs. Fluoxetine (FLX) is a selective serotonin reuptake inhibitor (SSRIs) and is considered one of the first highly selective antidepressants of the monoamine neurotransmitter serotonin (5-HT). The objective of this study is to prepare and physically characterize fluoxetine microparticles with galactomannan and evaluate their efficacy against strains of Staphylococcus aureus sensitive and resistant to methicillin. The microparticles were analyzed by differential scanning calorimetry (DSC), infrared analysis (IR) and X-ray diffraction (XRD). In addition, the percentage of encapsulation efficiency (EE%) and drug release kinetics were determined in vitro, along with the determination of the minimum inhibitory concentration (MIC) and evaluation of the action against biofilms. Physical tests were conducted to characterize galactomannan (GAL), FLX, oxacillin (OXA) and the galactomannan/fluoxetine microparticles (GFM). The EE% value was 98 % and, in regard the release, tests with the microparticles released about 60 % of the drug in 200 min. The isolated MIC results for FLX (255 μg/mL) and OXA MIC (1.97-15.62 μg/mL) showed that the strains were resistant. Furthermore, in the biofilms, microparticles showed statically significant improvement for all concentrations used. The study revealed that fluoxetine encapsulated in microparticles has the potential to act as an effective antimicrobial agent.

Nanocarriers and the delivered drug: effect interference due to intravenous administration

Intravenously administered nanocarriers are widely studied to improve the delivery of various therapeutic agents. However, recent in vivo studies have demonstrated that intravenously administered nanocarriers that do not contain any drug may affect cardiovascular function. Here we provide an example where the drug and the nanocarrier both affect the same cardiovascular parameters following intravenous administration. The peptide ghrelin antagonist (GhA) increases arterial pressure, while thermally hydrocarbonized porous silicon nanoparticles (THCPSi) transiently decrease it, as assessed with radiotelemetry in conscious rats. As a result, intravenous administration of GhA-loaded THCPSi nanoparticles partially antagonized GhA activity: arterial pressure was not increased. When the cardiovascular effects of GhA were blocked with atenolol pretreatment, GhA-loaded nanoparticles reduced arterial pressure to similar extent as drug-free nanoparticles. These data indicate that the biological activity of a drug delivered within a nanocarrier may be obscured by the biological responses induced by the nanocarrier itself.

Recent advances in porous silicon technology for drug delivery

Porous silicon (pSi) is a nanostructured carrier system that has received considerable attention over the past 10 years, for use in a wide variety of biomedical applications, including biosensing, biomedical imaging, tissue scaffolds and drug delivery. This interest is due to several key features of pSi, including excellent in vivo biocompatibility, the ease of surface chemistry modification and the control over its 3D porous network structure. With control of these physical parameters pSi has successfully been used for the delivery of a variety of therapeutics, ranging from small-molecule drugs to larger peptide/protein-type therapeutics. In this review, the authors provide a brief overview of pSi fabrication methods, particularly with regard to the need to passivate the highly reactive Si-Hx surface species of native pSi, typically via thermal oxidation, hydrocarbonization or hydrosilylation. This surface modification, in turn, controls both the loading and release of therapeutics. The authors will then report on specific case studies of leading examples on the use of pSi as a therapeutic-delivery system. Specifically, the first reported in vivo study that demonstrated the use of pSi to improve the delivery of a Biopharmaceutical Classification System Class 2 poorly soluble drug (indomethacin), by using thermally oxidized pSi, is discussed, as well as highlighting a study that determined the biodistribution of 18F-radiolabeled thermally hydrocarbonized pSi after oral dosing. The authors also report on the development of composite pSi–poly(D,L-lactide-co-glycolide) microparticles for the controlled delivery of protein therapeutics. Finally, the use of pSi in the delivery of bioactives, such as the successful use of thermally carbonized pSi to deliver Melanotan II, an unspecific agonist for the melanocortin receptors that are involved in controlling fluid uptake is discussed. With a growing body of literature reporting the successful use of pSi to deliver a range of therapeutics, we are entering what may be a golden age for this drug-delivery system, which may finally see the long-held promises finally achieved.