Current Drug Delivery - Volume 7, Issue 3, 2010

Fluorescent coupling of bovine serum albumin (BSA) and extracellular antigen of melanoma (ECA) using modified carbodiimide method was evaluated enabling BSA to serve as model protein to evaluate the release profiles of different microsphere formulations and uptake in B16 melanoma cells. Properties of the fluorescent labeled BSA (FBSA) including stability, transition temperature and fluorescent intensity were evaluated. It was found that FBSA produced using this method showed comparable transition temperature and fluorescent intensity compared to the commercially available FITC-labeled BSA and demonstrated stability of the fluorescent-protein linkage after overnight treatment with both trypsin and human plasma using fluorescent microscope. This study showed that the modified carbodiimide labeling method can serve as an alternative method for fluorescent labeling of target protein at reasonable cost particularly when sufficient amount of target protein is required for microsphere formulation screening.

Targeting essential nutrients (eg., those required for DNA synthesis) to inhibit cancer cell growth is a well established therapeutic strategy. A good example is the highly successful folate antagonist, methotrexate. However, up until recently, strategies to target iron which is also crucial for DNA synthesis have not been systematically explored to develop agents for the treatment of cancer. Over the last 15 years, our laboratory has embarked upon structure-activity studies designed to develop novel Fe chelators with anti-cancer efficacy. These studies have led to the development of the dipyridyl thiosemicarbazone chelators that show potent and selective anti-cancer activity and which overcome resistance to other cytotoxic agents. This class of compounds include the chelator, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), which at optimal doses markedly inhibits tumour growth and is well tolerated. Moreover, this ligand does not induce overt Fe-depletion in vivo, probably because very low doses (0.4 mg/kg) are effective at inhibiting tumour growth. Importantly, our compounds are far more active and less toxic than the chelator, Triapine®, that is being assessed in a wide variety of international clinical trials. A vital part of the mechanism of action of these compounds is their ability to form a redox-active Fe complex that generates radicals to inhibit tumour growth. Due to their relatively high lipophilicity and low molecular weight of this class of compounds, oral activity may be expected in addition to their well known efficacy via the intravenous route.

Drug/polymer interactions occur during in situ polymerization of poly(alkylcyanoacrylate) (PACA) formulations. We have used MALDI ionization coupled tandem time-of-flight (TOF) mass spectrometry as an accurate method to characterize covalent peptide/polymer interactions of PACA nanoparticles with the bioactives D-Lys6-GnRH, insulin, [Asn1-Val5]-angiotensin II, and fragments of insulin-like growth factor 1 (IGF-1 (1-3)) and human adrenocorticotropic hormone (h-ACTH, (18-39)) at the molecular level. Covalent interactions of peptide with alkylcyanoacrylate were identified for D-Lys6-GnRH, [Asn1-Val5]-angiotensin II and IGF-1 (1-3). D-Lys6-GnRH and [Asn1-Val5]-angiotensin II were modified at their histidine side chain within the peptide, whilst IGF-1 (1-3) was modified at the C-terminal glutamic acid residue. The more complex protein insulin was not modified despite the presence of 2 histidine residues. This might be explained by the engagement of histidine residues in the folding and sterical arrangement of insulin under polymerization conditions. As expected, h-ACTH (18-39) that does not contain histidine residues did not interfere in the polymerization process. Lowering the pH did not prevent the covalent association of PACA with D-Lys6-GnRH or IGF-1 (1-3). Conclusively, protein and peptide bioactives are potentially reactive towards alkylcyanoacrylate monomers via various mechanisms with limited interference of pH. Histidines and C-terminal glutamic acid residues have been identified as potential sites of interaction. The likelihood of their engagement in the polymerization process (initiators), however, seems dependent on their sterical availability. The reactivity of nucleophilic functional groups should always be considered and bioactives examined for their potential to covalently interfere with alkylcyanoacrylate monomers, especially when designing PACA delivery systems for protein and peptide biopharmaceuticals.

Percutaneous transvascular coronary angioplasty and stenting is one of the most commonly employed interventional procedures for the treatment of occlusive coronary artery disease. The common long-term complication of this treatment is re-stenosis occuring at the site of the atherosclerotic lesion following stenting. The rate of re-stenosis within 6 months could be as high as 20-30% of patients resulting in increased morbidity and tremendous costs to the health care system. The incidence has been somewhat reduced with the development of drug eluting stents, releasing drugs like paclitaxel, sirolimus, zotarolimus and everolimus with varied sustained release profiles. However the long-term benefits from large studies are still controversial and delayed onset of thrombosis is a major ongoing concern and lifelong anti-platelets therapy has been suggested clinically in patients bearing such pharmacological stents. Drug-eluting polymeric bioresorbable stent is being considered to hold immense promise to effectively address such pertinent complications mainly because of its improved biocompatibility, transient nature of supporting the intervened artery, eliminating local effect and damage of permanent metals, allowing smoother restoration of vasoreactivity and physiologic healing, and higher local drug delivery capacity in comparison to permanent metallic stents. In this article we review the current standpoint of drug eluting metallic stent, which has so long been considered as a major medical innovation in the field of pharmaceutical sciences, and its rapid evolution to pharmacological bioresorbable stent in order to promote proper vascular remodeling and achieve better risk-benefit ratio under diverse clinical challenges.

Objectives: Currently, for actinomycetoma, combined antimicrobial therapy is preferred to the use of a single compound. This is in order to provide a broader-spectrum coverage due to a combinatory or synergistic effect between the drugs, and to decrease the possibility of emergence of natural resistant strains. A new oxazolidinone pro-drug, DA-7218 [(R)-3-(4-(2-(2-methyltetrazol-5-yl)-pyridin-5-yl)-3-fluorophenyl)-2-oxo-5-oxazolidinyl) methyl-disodium-phosphate] (recently re-named TR-701), has shown very good in vitro and in vivo activities against several gram-positive bacteria including Nocardia spp. Methods: In the present work we evaluated the effect of DA-7218 at two different doses, alone and combined with trimethoprim/ sulfamethoxazole (SXT), in an experimental Nocardia brasiliensis actinomycetoma murine model. We also included a negative and a positive control group (linezolid and saline solution respectively). Results: At the end of the treatment period, we observed a clinically and statistically significant difference among the drug receiving groups (combined, alone and linezolid) and the control group (P=0.004). The difference was higher (P= 0.004) between the groups receiving DA-7218 (25mg/kg) alone or combined with SXT, and the control group (saline solution). Conclusions: In this work we proved that DA-7218 alone and combined with SXT is effective in the treatment of experimental actinomycetoma by Nocardia brasiliensis and that it could be potentially useful in the treatment of human actinomycetoma.

In the present study, a phase transited nondisintegrating polymeric capsular system in achieving delayed as well as improved osmotic flow for the model drug cefadroxil was developed. Asymmetric membrane capsule (AMC) was prepared by precipitation of asymmetric membrane (AM) on the fabricated glass mold pins via wet phase inversion process. Effect of different formulation variables were studied based on 23 factorial design, namely, level of osmogen, ethylcellulose, pore former, apart from studying the effect of varying osmotic pressure on drug release. Scanning electron microscopy showed an outer dense non-porous region and an inner lighter porous region for the prepared AMC. Statistical test (Dunnett multiple comparison test) was applied for in vitro drug release (n=6) at P < 0.05. The best formulation in the design closely corresponded to the extra design checkpoint formulation by a similarity factor (f2) of 98.91, and a difference factor (f1) of 2.17. The drug release was independent of agitation intensity but dependent on the osmotic pressure of the dissolution medium. The release kinetics followed Higuchi model, and mechanism of release was Fickian diffusion.

Conventional eye drops show relatively low bioavailability due to poor precorneal contact time. In situ hydrogels are of great importance in providing sustained ocular drug delivery. By exhibiting elastic properties they resist ocular drainage of the drug leading to longer contact times. In the present study an in situ gelling thermoreversible mucoadhesive gel was formulated of an antibacterial agent, Moxifloxacin HCl using a combination of poloxamer 407 and poloxamer 188 with different mucoadhesive polymers such as Xanthan gum and Sodium alginate with a view to increase gel strength and bioadhesion force and thereby increased precorneal contact time and bioavailability of the drug. Formulations were evaluated for physical parameters like clarity, pH, spreadability, drug content, gelation temperature, gel strength, bioadhesion force and in vitro drug release study. Formulations were found transparent, uniform in consistency and had good spreadability within a pH range of 6.8 to 7.4. A satisfactory bioadhesion (3298 to 4130 Dyne/cm2) on the sheep's corneal surface and good gel strength (95 to 128 sec) was also observed. As the concentration of mucoadhesive polymers in the gel formulation increased, the rate of drug release decreased. The order of drug release was in order: Xanthan gum > Sodium alginate. It was concluded that a thermoreversible in situ gel of Moxifloxacin HCl can be formulated by combining with mucoadhesive polymers and used effectively as safe and sustained ocular drug delivery. This combination provided greater bioadhesion force and gel strength as compared to the thermoreversible polymers i.e., poloxamer 407 (PF 127) or 188 (PF 68) when used alone.

Micro and nanoparticulate carriers have been in focus in ophthalmic drug delivery with the objective of improving bioavailability, drug targeting and reducing pulse entry of the drug in ocular cul de sac. Polymeric nanoparticles for ocular purpose have potential in reducing the pulse entry and frequency of dosing, thus improving patient compliance. In the present study, mucoadhesive sodium alginate nanoparticles were developed for Brimonidine Tartrate (BT) as a model antiglaucoma drug by controlled ionic gelation technique. These nanoparticles would not only prolong drug's residence time but also reduce pulse entry in cul de sac. Nanoparticles were evaluated for morphology, surface characteristics, drug polymer interactions, particle size, polydispersibility index, zeta potential, entrapment efficiency, in vitro release profile and in vivo efficacy. The effect of various stabilizers on stabilization of blank and drug loaded nanoparticles was investigated. Irregular shape and loss of crystallinity for BT loaded sodium alginate nanoparticles was observed by TEM and SEM images respectively. IR spectra and DSC thermograms revealed the physicochemical interaction was involved during sodium alginate nanoparticle formation and entrapment of BT. The developed nanoparticles have average particle size of 450nm with PI 0.65, the entrapment efficiency ranged from 4-18 % and zeta potential values ranged from -27.5 mV to -24.1 mV. In vitro release profile showed a gradual drug release over the period of 3 hrs. In-vivo experiments showed that it was possible to prolong the drug release over a period of 8 hr, on topical instillation of BT loaded nanoparticles to albino rabbits, hence reducing the dosage frequency.

Ion-exchange resins are light, porous, three-dimensional high molecular weight cross -linked matrix of hydrocarbon chains carrying positively or negatively charged sites that can attract an ion of opposite charge from the surrounding medium. There is stoichiometric exchange of mobile ions between the solid and the solution called as Ion-exchange which does not lead to any radical change in the properties and structure of the solid. Depending upon the type of Ionexchanged it can be either Cation-exchange or Anion-exchange. They are prepared in the form of granules, beads or sheets. As drug delivery systems they have received considerable attention after the 1950s due to their inertness, freedom from side effects, high drug loading capacity, ease of sterilization and the fact that their structure can be easily altered to achieve the desired drug release characteristics. Their use is revolutionizing all traditional delivery systems namely- oral, nasal, ophthalmic and parenteral. Ion- exchange resins have been used for the development of novel drug delivery systems (NDDSs), to modify the characteristics of the dosage form and various other biomedical applications. The present article deals with the varied applications of ion-exchange resins for taste making, as resinates (simple and microencapsulated or coated), Pennkinetic systems, in selective recovery of pharmaceuticals, in pH and ionic strength responsive systems, in gastro-retentive systems, in hollow fiber systems, as sigmoidal release systems, as site specific delivery systems and as inotophoretically assisted transdermal drug delivery systems. They also have an immense importance when used as disintegrants / superdisintegrants in formulation of orodispersible tablets, powder processing aids and in the dissolution and stabilization of drugs.