Current Drug Delivery - Volume 16, Issue 7, 2019

Gene therapy has the potential to treat both acquired and inherited genetic diseases. Generally, two types of gene delivery vectors are used - viral vectors and non-viral vectors. Non-viral gene delivery systems have attracted significant interest (e.g. 115 gene therapies approved for clinical trials in 2018; clinicaltrials.gov) due to their lower toxicity, lack of immunogenicity and ease of production compared to viral vectors. To achieve the goal of maximal therapeutic efficacy with minimal adverse effects, the cell-specific targeting of non-viral gene delivery systems has attracted research interest. Targeting through cell surface receptors; the enhanced permeability and retention effect, or pH differences are potential means to target genes to specific organs, tissues, or cells. As for targeting moieties, receptorspecific ligand peptides, antibodies, aptamers and affibodies have been incorporated into synthetic nonviral gene delivery vectors to fulfill the requirement of active targeting. This review provides an overview of different potential targets and targeting moieties to target specific gene delivery systems.

Despite advances in the development of new vaccines, there are still some diseases with no vaccine solutions. Therefore, further efforts are required to more comprehensively discern the different antigenic components of these microorganisms on a molecular level. This review summarizes advancement in the development of new carbohydrate-based vaccines. Following traditional vaccine counterparts, the carbohydrate-based vaccines introduced a new approach in fighting infectious diseases. Carbohydrates have played various roles in the development of carbohydrate-based vaccines, which are described in this review, including carbohydrates acting as antigens, carriers or targeting moieties. Carbohydrate-based vaccines against infectious diseases, such as group A streptococcus, meningococcal meningitis and human immunodeficiency virus, are also discussed. A number of carbohydrate- based vaccines, such as Pneumovax 23, Menveo and Pentacel, have been successfully marketed in the past few years and there is a promising standpoint for many more to come in the near future.

Background: Glycyrrhizic acid (GA) is a glycoside that has shown considerable promise as a penetration enhancer and drug carrier to improve the absorption of poorly water-soluble drugs. The aggregation behavior of GA and its ability to form large micelles at higher solution concentrations are thought to contribute to these bioavailability enhancing properties. The oral absorption of Paclitaxel (PTX) for example, an anti-cancer agent which exhibits poor oral bioavailability, has been found to significantly increase in the presence of GA. Methods: In an attempt to visualize the aggregation behavior of GA and its subsequent association with PTX, 100 ns molecular dynamics simulation of a 5 mM aqueous solution of GA with 10 molecules of PTX was conducted using GROMACS and an all-atom forcefield. Results: Aggregation of GA molecules was found to occur quickly at this level of saturation leading to two stable aggregates of 13 and 17 GA molecules with an effective radius of 10.17 nm to 10.92 nm. These aggregates form not in isolation, but together with PTX molecule embedded within the structures, which reduces the number of interactions and hydrogen-bonding with water. Conclusion: GA aggregation occurs around PTX molecules in solution, forming co-joined GA-PTX cluster units at a ratio of 3:1. These clusters remain stable for the remainder of the 100ns simulation and serve to isolate and protect PTX from the aqueous environment.

Background: The tocopherol-based excipient, TPM, when incorporated into a medium-chain triglyceride (MCT)-based lipid formulation, has been previously shown to improve the solubilization of Coenzyme Q10 (CoQ10) during in vitro digestion which is strongly correlated with enhanced exposure in vivo. Methods: The current study aimed to gain further understanding of the MCT + TPM co-formulation, by assessing the formulation performance under fasted and fed in vitro digestion conditions, with different drug and excipient loading levels. Natural and synthetic-derived TPM were equivalent, and with d-α- tocopherol polyethylene glycol 1000 succinate (TPGS) outperformed other derivatives in enhancing the solubilisation of CoQ10 during digestion. Result: Fed conditions significantly improved the solubility of CoQ10 during in vitro digestion of the formulation in comparison with fasted conditions. The addition of TPM at 10% (w/w) of the total MCT + TPM provided optimal performance in terms of CoQ10 solubilization during digestion. Conclusion: The results further highlights the potential of TPM as an additive in lipid formulations to improve the solubilization and oral bioavailability of poorly water-soluble compounds.

Background: Inflammation is a hallmark of epileptogenic brain tissue. Previously, we have shown that inflammation in epilepsy can be delineated using systemically-injected fluorescent and magnetite- laden nanoparticles. Suggested mechanisms included distribution of free nanoparticles across a compromised blood-brain barrier or their transfer by monocytes that infiltrate the epileptic brain. Objective: In the current study, we evaluated monocytes as vehicles that deliver nanoparticles into the epileptic brain. We also assessed the effect of epilepsy on the systemic distribution of nanoparticleloaded monocytes. Methods: The in vitro uptake of 300-nm nanoparticles labeled with magnetite and BODIPY (for optical imaging) was evaluated using rat monocytes and fluorescence detection. For in vivo studies we used the rat lithium-pilocarpine model of temporal lobe epilepsy. In vivo nanoparticle distribution was evaluated using immunohistochemistry. Results: 89% of nanoparticle loading into rat monocytes was accomplished within 8 hours, enabling overnight nanoparticle loading ex vivo. The dose-normalized distribution of nanoparticle-loaded monocytes into the hippocampal CA1 and dentate gyrus of rats with spontaneous seizures was 176-fold and 380-fold higher compared to the free nanoparticles (p<0.05). Seizures were associated with greater nanoparticle accumulation within the liver and the spleen (p<0.05). Conclusion: Nanoparticle-loaded monocytes are attracted to epileptogenic brain tissue and may be used for labeling or targeting it, while significantly reducing the systemic dose of potentially toxic compounds. The effect of seizures on monocyte biodistribution should be further explored to better understand the systemic effects of epilepsy.

Background: Amphotericin B (AmB) is important for the treatment of systemic fungal infections. Nowadays, only intravenous administration (IV) of AmB has been available due to its low aqueous solubility. Two forms of AmB are available. The first is Fungizone®, a mixture of AmB and sodium deoxcycholate that produces severe nephrotoxicity. The second are lipid-based formulations that reduce nephrotoxicity, but they are costly and require higher dose than Fungizone®. Thus, a cheaper delivery system with reduced AmB toxicity is required. Objective: To develop and characterize AmB loaded-nanostructured lipid carriers (AmB-loaded NLCs) for IV administration to reduce AmB toxicity. Methods: AmB-loaded NLCs with different solid lipids were prepared by the high-pressure homogenization technique. Their physicochemical properties and the drug release profile were examined. The molecular structure of AmB, antifungal and hemolysis activities of developed AmB-loaded NLCs were also evaluated. Results: AmB-loaded NLCs ~110 to ~140 nm in diameter were successfully produced with a zeta potential of ~-19 mV and entrapment efficiency of ~75%. In vitro release showed fast release characteristics. AmB-loaded NLCs could reduce the AmB molecular aggregation as evident from the absorbance ratio of the first to the fourth peak showing a partial aggregation of AmB. This result suggested that AmB-loaded NLCs could offer less nephrotoxicity compared to Fungizone®. In vitro antifungal activity of AmB-loaded NLCs showed a minimum inhibitory concentration of 0.25 μgmL-1. Conclusion: AmB-loaded NLCs present high potential carriers for effective IV treatment with prolonged circulation time and reduced toxicity.

Background: Prolonged chemodrug delivery to the tumor site is a prerequisite to maintaining its localised therapeutic concentrations for effective treatment of malignant solid tumors. Objective: The current study aims to develop implantable polymeric depots through conventional electrospinning for sustained drug delivery, specifically to the peritoneum. Methods: Non-woven electrospun mats were fabricated by simple electrospinning of Polydioxanone solution loaded with the chemodrug, Paclitaxel. The implants were subjected to the analysis of morphology, mechanical properties, degradation and drug release in phosphate buffer and patient-derived peritoneal drain fluid samples. In vivo studies were conducted by surgical knotting of these implants to the peritoneal wall of healthy mice. Results: Non-woven electrospun mats with a thickness of 0.65±0.07 mm, weighing ~ 20 mg were fabricated by electrospinning 15 w/v% polymer loaded with 10 w/w% drug. These implants possessing good mechanical integrity showed a drug entrapment efficiency of 87.82±2.54 %. In vitro drug release studies in phosphate buffer showed a sustained profile for ~4 weeks with a burst of 10 % of total drug content, whereas this amounted to >60% in patient samples. Mice implanted with these depots remained healthy during the study period. The biphasic drug release profile obtained in vivo showed a slow trend, with peritoneal lavage and tissues retaining good drug concentrations for a sustained period. Conclusion: The results indicate that non-woven electrospun mats developed from biodegradable Polydioxanone polymer can serve as ideal candidates for easily implantable drug depots to address the challenges of peritoneal metastasis in ovarian cancer.

Background: Sirolimus (SIR) is a macrocyclic lactone antibiotic and used therapeutically as a potent immunosuppressant for prophylaxis of kidney transplant rejection. The development of an oral dosage form is challenging because of very poor aqueous solubility (2.6μg/ml). The oral bioavailability of SIR is only 15-20 % and is affected by food and other drugs. The main reasons for low bioavailability are intestinal degradation by enzymes especially by cytochrome P4503A4, efflux by P-glycoprotein and hepatic first-pass metabolism. Objective: The main objective was to prepare a mouth dissolving film dosage form of amorphous SIR to improve dissolution. Methods: Crystalline SIR was transformed to its form amorphous by milling for 2 h at room temperature. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder x-ray diffraction (PXRD) were used for characterisation. The stability of amorphous SIR was studied at 4°C and 40°C/75% RH. Amorphous SIR was formulated as oral films by melt extrusion with polyvinylpyrrolidone- vinyl acetate (PVP-VA), Soluplus® and hydroxypropyl cellulose (HPC) as carriers. The films were characterized for drug content, physical state, dissolution profile and stability at 4°C and 40°C/75% RH. Results: The PRXD and DSC confirmed the conversion of crystalline SIR to amorphous form by milling. The solubility of amorphous SIR was several folds higher than its crystalline form, but amorphous SIR was highly unstable at all tested temperatures (4° and 40°C). The extruded films exhibited higher dissolution and stability compared to milled SIR powder alone, but the process of extrusion had some detrimental effect on the chemical stability of amorphous SIR. Conclusion: The film formulations showed a significant improvement in the storage stability of the amorphous form of SIR and the solubility advantage of the amorphous form was evident in the dissolution testing. The oral films can potentially improve the bioavailability of SIR by absorption through the buccal mucosa.

Background: In this study, four nanoparticle formulations (F1 to F4) comprising varying ratios of alginate, Pluronic F-68 and calcium chloride with a constant amount of insulin and chitosan as a coating material were prepared using polyelectrolyte complexation and ionotropic gelation methods to protect insulin against enzymatic degradation. Methods: This study describes the formulation design, optimisation, characterisation and evaluation of insulin concentration via oral delivery in rats. A reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated to quantify insulin concentration in rat plasma. The proposed method produced a linear response over the concentration range of 0.39 to 50 μg/ml. Results: In vitro release study showed that dissolution of insulin in simulated gastric juice of pH 1.2 was prevented by alginate core and chitosan coating but rapidly released in simulated intestinal fluid (pH 6.8). Additionally, Formulation 3 (F3) has a particle size of 340.40 ± 2.39 nm with narrow uniformity exhibiting encapsulation efficiency (EE) of 72.78 ± 1.25 % produced highest absorption profile of insulin with a bioavailability of 40.23 ±1.29% and reduced blood glucose after its oral administration in rats. Conclusion: In conclusion, insulin oral delivery system containing alginate and chitosan as a coating material has the ability to protect the insulin from enzymatic degradation thus enhance its absorption in the intestine. However, more work should be done for instance to involve human study to materialise this delivery system for human use.