Ka-Wai Wan

Emergence of 3D Printed Dosage Forms: Opportunities and Challenges

The recent introduction of the first FDA approved 3D-printed drug has fuelled interest in 3D printing technology, which is set to revolutionize healthcare. Since its initial use, this rapid prototyping (RP) technology has evolved to such an extent that it is currently being used in a wide range of applications including in tissue engineering, dentistry, construction, automotive and aerospace. However, in the pharmaceutical industry this technology is still in its infancy and its potential yet to be fully explored. This paper presents various 3D printing technologies such as stereolithographic, powder based, selective laser sintering, fused deposition modelling and semi-solid extrusion 3D printing. It also provides a comprehensive review of previous attempts at using 3D printing technologies on the manufacturing dosage forms with a particular focus on oral tablets. Their advantages particularly with adaptability in the pharmaceutical field have been highlighted, which enables the preparation of dosage forms with complex designs and geometries, multiple actives and tailored release profiles. An insight into the technical challenges facing the different 3D printing technologies such as the formulation and processing parameters is provided. Light is also shed on the different regulatory challenges that need to be overcome for 3D printing to fulfil its real potential in the pharmaceutical industry.

PEGylated graphene oxide for tumor-targeted delivery of paclitaxel.

AIM The graphene oxide (GO) sheet has been considered one of the most promising carbon derivatives in the field of material science for the past few years and has shown excellent tumor-targeting ability, biocompatibility and low toxicity. We have endeavored to conjugate paclitaxel (PTX) to GO molecule and investigate its anticancer efficacy. MATERIALS & METHODS We conjugated the anticancer drug PTX to aminated PEG chains on GO sheets through covalent bonds to get GO-PEG-PTX complexes. The tissue distribution and anticancer efficacy of GO-PEG-PTX were then investigated using a B16 melanoma cancer-bearing C57 mice model. RESULTS The GO-PEG-PTX complexes exhibited excellent water solubility and biocompatibility. Compared with the traditional formulation of PTX (Taxol®), GO-PEG-PTX has shown prolonged blood circulation time as well as high tumor-targeting and -suppressing efficacy. CONCLUSION PEGylated graphene oxide is an excellent nanocarrier for paclitaxel for cancer targeting.

Distribution and Visualisation of Chlorhexidine Within the Skin Using ToF-SIMS: A Potential Platform for the Design of More Efficacious Skin Antiseptic Formulations

ABSTRACTPurposeIn order to increase the efficacy of a topically applied antimicrobial compound the permeation profile, localisation and mechanism of action within the skin must first be investigated.MethodsTime-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to visualise the distribution of a conventional antimicrobial compound, chlorhexidine digluconate, within porcine skin without the need for laborious preparation, radio-labels or fluorescent tags.ResultsHigh mass resolution and high spatial resolution mass spectra and chemical images were achieved when analysing chlorhexidine digluconate treated cryo-sectioned porcine skin sections by ToF-SIMS. The distribution of chlorhexidine digluconate was mapped throughout the skin sections and our studies indicate that the compound appears to be localised within the stratum corneum. In parallel, tape strips taken from chlorhexidine digluconate treated porcine skin were analysed by ToF-SIMS to support the distribution profile obtained from the skin sections.ConclusionsToF-SIMS can act as a powerful complementary technique to map the distribution of topically applied compounds within the skin.

Anti-glioma activity and the mechanism of cellular uptake of asiatic acid-loaded solid lipid nanoparticles

Asiatic acid (AA), a pentacyclic triterpene found in Centella Asiatica, has shown neuroprotective and anti-cancer activity against glioma. However, owing to its poor aqueous solubility, effective delivery and absorption across biological barriers, in particular the blood brain barrier (BBB), are challenging. Solid lipid nanoparticles (SLNs) have shown a promising potential as a drug delivery system to carry lipophilic drugs across the BBB, a major obstacle in brain cancer therapy. Nevertheless, limited information is available about the cytotoxic mechanisms of nano-lipidic carriers with AA on normal and glioma cells. This study assessed the anti-cancer efficacy of AA-loaded SLNs against glioblastoma and their cellular uptake mechanism in comparison with SVG P12 (human foetal glial) cells. SLNs were systematically investigated for three different solid lipids; glyceryl monostearate (MS), glyceryl distearate (DS) and glyceryl tristearate (TS). The non-drug containing MS-SLNs (E-MS-SLNs) did not show any apparent toxicity towards normal SVG P12 cells, whilst the AA-loaded MS-SLNs (AA-MS-SLNs) displayed a more favourable drug release profile and higher cytotoxicity towards U87 MG cells. Therefore, MS-SLNs were chosen for further in vitro studies. Cytotoxicity studies of SLNs (± AA) were performed using MTT assay where AA-SLNs showed significantly higher cytotoxicity towards U87 MG cells than SVG P12 normal cells, as confirmed by flow cell cytometry. Cellular uptake of SLNs also appeared to be preferentially facilitated by energy-dependent endocytosis as evidenced by fluorescence imaging and flow cell cytometry. Using the Annexin V-PI double staining technique, it was found that these AA-MS-SLNs displayed concentration-dependent apoptotic activity on glioma cells, which further confirms the potential of exploiting these AA-loaded MS-SLNs for brain cancer therapy.

Thymopentin Nanoparticles Engineered with High Loading Efficiency, Improved Pharmacokinetic Properties, and Enhanced Immunostimulating Effect Using Soybean Phospholipid and PHBHHx Polymer

Formulation of protein and peptide drugs with sustained release properties is crucial to enhance their therapeutic effect and minimize administration frequency. In this study, immunomodulating polymeric systems were designed by manufacturing PHBHHx nanoparticles (NPs) containing thymopentin (TP5). The release profile of the drug was studied over a period of 7 days. The PHBHHx NPs containing TP5-phospholipid (PLC) complex (TP5-PLC) displayed a spherical shape with a mean size, zeta potential, and encapsulation efficiency of 238.9 nm, -32.0 mV, and 72.81%, respectively. The cytotoxicity results showed the PHBHHx NPs had a relatively low toxicity in vitro. TP5 entrapped in the NPs could hardly release in vitro, while the NPs had longer than 7 days release duration after a single subcutaneous injection in Wistar rats. The immunodepression rat model was built to evaluate the immunomodulating effects of TP5-PLC-NPs in vivo. The results of T-lymphocyte subsets (CD3(+), CD4(+), CD8(+), and CD4(+)/CD8(+) ratio) analysis and superoxide dismutase (SOD) values suggested that TP5-PLC-NPs had stronger immunoregulation effects than TP5 solution. In conclusion, an applicable approach to markedly enhancing the loading of a water-soluble peptide into a hydrophobic polymer matrix has been introduced. Thus, TP5-PLC-NPs are promising nanomedicine systems for sustained release effects of TP5.

Novel paclitaxel formulations solubilized by parenteral nutrition nanoemulsions for application against glioma cell lines.

The aim of this study is to investigate using nanoemulsion formulations as drug-delivery vehicles of paclitaxel (PX), a poor water-soluble anticancer drug. Two commercially available nanoemulsion fat formulations (Clinoleic 20% and Intralipid 20%) were loaded with PX and characterised based on their size, zeta potential, pH and loading efficiency. The effect of formulation on the cytotoxicity of PX was also evaluated using MTT assay. The droplet size of the Clinoleic emulsion increased from 254.1nm to 264.7nm when paclitaxel (6mg/ml) was loaded into the formulation, compared to the drug-free formulation. Similarly, the droplet size of Intralipid increased from 283.3 to 294.6nm on inclusion of 6mg/ml paclitaxel. The Polydispersity Indexes (PDIs) of all the nanoemulsion formulations (Clinoleic and Intralipid) were less than 0.2 irrespective of paclitaxel concentration indicating that all nanoemulsion formulations used were homogeneously sized. The pH range for the Clinoleic formulations (7.1-7.5) was slightly higher than that of the Intralipid formulations (6.5-6.9). The zeta potential of linoleic had a greater negative value than that of Intralipid. Loading efficiencies for paclitaxel were 70.4-80.2% and 44.2-57.4% for Clinoleic and Intralipid formulations, respectively. Clinoleic loaded with paclitaxel decreased the viability of U87-MG cell to 6.4±2.3%, compared to Intralipid loaded with paclitaxel (21.29±3.82%). Both nanoemulsions were less toxic to the normal glial cells (SVG-P12), decreasing the cell viability to 25-35%. This study suggests that nanoemulsions are useful and potentially applicable vehicles of paclitaxel for treatment of glioma.

Stability of parenteral nanoemulsions loaded with paclitaxel: the influence of lipid phase composition, drug concentration and storage temperature

Abstract Paclitaxel was loaded into licensed parenteral nutrition nanoemulsions (Clinoleic® and Intralipid®) using bath sonication, and the stability of the formulations was investigated following storage for two weeks at room temperature or at 4 °C. In general, Clinoleic droplets were smaller than Intralipid droplets, being around 255 and 285 nm, respectively, for blank and freshly loaded emulsions. Regardless of storage temperature, the Clinoleic exhibited a very slight or no increase in droplet size upon storage, whilst the droplet size of the Intralipid emulsion increased significantly. The droplet size of both emulsions was minimally affected by paclitaxel concentration within the range of 0, 1, 3 and 6 mg/ml. The pH of both emulsions markedly decreased upon storage at room temperature, which was possibly attributed to the production of fatty acids resulting from phospholipid hydrolysis. However, at 4 °C, the pH of Clinoleic emulsion was unaffected by storage or paclitaxel concentration while the Intralipid emulsion demonstrated a trend for pH reduction. Both nanoemulsions had a negative zeta potential, with the Clinoleic formulations having the highest charge, possibly explaining the better size stability of this emulsion. Overall, this study has shown that paclitaxel was successfully loaded into clinically licensed parenteral emulsions and that Clinoleic showed greater stability than the Intralipid.

Ethanol-Based Proliposome Delivery Systems of Paclitaxel for In Vitro Application Against Brain Cancer Cells

Abstract In this study the anticancer activity of paclitaxel-loaded nano-liposomes on glioma cell lines was investigated. Soya phosphatidylcholine:cholesterol (SPC:Chol), hydrogenated soya phosphatidylcholine:cholesterol (HSPC:Chol) or dipalmitoylphosphatidylcholine:cholesterol (DPPC:Chol) in 1:1 mole ratio were used to prepare ethanol-based proliposomes. Following hydration of proliposomes, the size of resulting vesicles was subsequently reduced to nanometer scale via probe-sonication. The resulting formulations were characterized in terms of size, zeta potential and morphology of the vesicles, and entrapment efficiency of paclitaxel (PX) as well as the final pH of the preparations. DPPC-liposomes entrapped 35–92% of PX compared to 27–74% and 25–60% entrapped by liposomes made from SPC and HSPC formulations respectively, depending on drug concentration. The entrapment efficiency of liposomes was dependent on the lipid bilayer properties and ability of PX to modify surface charge of the vesicles. In vitro cytotoxicity studies revealed that PX-liposome formulations were more selective at inhibiting the malignant cells. The cytotoxicity of PX-liposomes was dependent on their drug-entrapment efficiency. This study has shown PX-liposomes generated from proliposomes have selective activity against glioma cell lines, and the synthetic DPPC phospholipid was most suitable for maximized drug entrapment and highest activity against the malignant cells in vitro.

Improved transdermal delivery of morin efficiently inhibits allergic contact dermatitis

The skin is an important site for local or systemic application of drugs. However, most of the drugs have poor permeability through the skins outermost layer, stratum corneum. The aim of this study was to develop a method to enable transdermal delivery of morin (3, 5, 7, 2, 4-pentahydroxyflavone), which is a poorly water-soluble drug with anti-inflammatory properties obtained from natural products. Morin phospholipid complex (MPC) was prepared and then loaded in Carbopol 940 hydrogel (MPC-gel), which can significantly increase the transdermal flux of morin based on the in vitro skin penetration data presented in this paper. To further enhance permeation, different compositions of penetration enhancers were dispersed in the gel and screened. After applied onto the mouse skin, MPC-gel showed apparent reduction of ear swelling in 2, 4-dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis (ACD). Further determination of cytokines levels, histopathological analysis and T lymphocytes proliferation indicates that the MPC-gel is potent enough to reduce the inflammatory response mediated by the DNFB in ACD mice model. Collectively, we anticipate that such an approach may provide a new treatment for topical ACD.

Dendrimer pre-treatment enhances the skin permeation of chlorhexidine digluconate: Characterisation by in vitro percutaneous absorption studies and Time-of-Flight Secondary Ion Mass Spectrometry

Abstract Skin penetration and localisation of chlorhexidine digluconate (CHG) within the skin have been investigated in order to better understand and optimise the delivery using a nano polymeric delivery system of this topically‐applied antimicrobial drug. Franz‐type diffusion cell studies using in vitro porcine skin and tape stripping procedures were coupled with Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) to visualise the skin during various treatments with CHG and polyamidoamine dendrimers (PAMAM). Pre‐treatment of the skin with PAMAM dendrimers significantly increased the amount and depth of permeation of CHG into the skin in vitro. The effect observed was not concentration dependant in the range 0.5–10 mM PAMAM. This could be important in terms of the efficiency of treatment of bacterial infection in the skin. It appears that the mechanism of enhancement is due to the PAMAM dendrimer disrupting skin barrier lipid conformation or by occluding the skin surface. Franz‐type diffusion cell experiments are complimented by the detailed visualisation offered by the semi‐quantitative ToF‐SIMS method which provides excellent benefits in terms of sensitivity and fragment ion specificity. This allows a more accurate depth profile of chlorhexidine permeation within the skin to be obtained and potentially affords the opportunity to map the co‐localisation of permeants with skin structures, thus providing a greater ability to characterise skin absorption and to understand the mechanism of permeation, providing opportunities for new and more effective therapies. Graphical Abstract Figure. No Caption available.