Ka-Yun Ng

Preparation and evaluation of zinc–pectin–chitosan composite particles for drug delivery to the colon: Role of chitosan in modifying in vitro and in vivo drug release

Zinc-pectin-chitosan composite microparticles were designed and developed as colon-specific carrier. Resveratrol was used as model drug due to its potential activity on colon diseases. Formulations were produced by varying different formulation parameters (cross-linking pH, chitosan concentration, cross-linking time, molecular weight of chitosan, and drug concentration). Single-step formulation technique was compared with multi-step technique. Effect of these parameters was investigated on shape, size, weight, weight loss (WL), moisture content (MC), encapsulation efficiency (EE), drug loading (L), and drug release pattern of the microparticles. The formulation conditions were optimized from the drug release study. In vivo pharmacokinetics of the zinc-pectinate particles was compared with the zinc-pectin-chitosan composite particles in rats. Formulations were spherical with 920.48-1107.56 μm size, 21.19-24.27 mg weight of 50 particles, 89.83-94.34% WL, 8.31-13.25% MC, 96.95-98.85% EE, and 17.82-48.31% L. Formulation parameters showed significant influence on drug release pattern from the formulations. Formulation prepared at pH 1.5, 1% chitosan, 120 min cross-linking time, and pectin:drug at 3:1 ratio demonstrated colon-specific drug release. Microparticles were stable at 4 °C and room temperature. Pharmacokinetic study indicated in vivo colon-specific drug release from the zinc-pectin-chitosan composite particles only.

Resveratrol-loaded calcium-pectinate beads: Effects of formulation parameters on drug release and bead characteristics

Resveratrol has potential therapeutic efficacy on several lower gastro-intestinal (GI) diseases such as colitis and colorectal cancer. But resveratrol is quickly absorbed and metabolized at the upper GI tract, which renders it unsuitable for this purpose. This study aimed at devising a delayed release formulation of resveratrol as calcium-pectinate (Ca-pectinate) beads and investigated the impact of various formulation parameters on bead characteristics. Ca-pectinate beads were prepared by varying six formulation parameters (cross-linking pH, cross-linker concentration, cross-linking time, drying condition, pectin concentration, and resveratrol concentration). Their effects were investigated on calcium entrapment, moisture content and weight loss during drying, particle shape and size, resveratrol entrapment and loading efficiency, swelling-erosion, and resveratrol retention pattern of formulated beads. Preparative conditions were optimized from these studies and optimized beads were further subjected to morphological examination, drug-polymer interaction, and enzymatic degradation study. Almost all prepared beads were spherical with approximately 1 mm diameter. Swelling-erosion and drug retention pattern were changed with formulation variables. Release data of almost all beads showed linearity of the plots for the cumulative percent resveratrol released versus square root of time often after an initial lag period. Observations from the present study revealed that optimized Ca-pectinate beads can encapsulate a very high amount of resveratrol (>97.5%) and can be used for delayed release and site-specific delivery to the lower GI tract. Depending on the formulation parameters, release of resveratrol after 10 h incubation in the intestinal media was 80-100%.

Design of a pectin-based microparticle formulation using zinc ions as the cross-linking agent and glutaraldehyde as the hardening agent for colonic-specific delivery of resveratrol: In vitro and in vivo evaluations

The aim of this study was to develop a colon-specific microparticle formulation based on pectin. Resveratrol was used as a model drug due to its potential therapeutic efficacy on colitis and colon cancer. Microparticles were produced by cross-linking pectin molecules with zinc ions and with glutaraldehyde as hardening agent for pectins. Different microparticles were prepared by varying the formulation variables. Effect of these formulation variables were investigated on particle shape and size, moisture content and weight-loss during drying, encapsulation efficiency, swelling–erosion ratio, and drug release pattern of the formulated microparticles. Formulation conditions were optimized based on the in vitro drug release study. Morphology, Fourier transform infrared spectroscopy, stability, and in vivo pharmacokinetic study of the microparticles prepared at the optimized formulation conditions were performed. Microparticles were spherical with <1 mm diameter and encapsulation efficiencies of >94%. The glutaraldehyde-modified microparticles prepared at optimized formulation conditions revealed colon specific in vitro and in vivo drug release. Plasma appearance of drug was delayed for 4–5 h after their administration directly into stomach, but displayed comparable area under the curve to other controls in the experiment, indicating the potential of the developed formulation as a colon-specific drug delivery system.

Impact of glutaraldehyde on in vivo colon-specific release of resveratrol from biodegradable pectin-based formulation.

Despite potential therapeutic efficacy of resveratrol on colitis and colorectal cancer, rapid absorption and metabolism at the upper gastro-intestinal (GI) tract prevent its clinical application. To overcome this, we attempted to develop colon-specific multi-particulate calcium-pectinate (Ca-pectinate) formulations of resveratrol. However, they were unable to prevent premature drug release at the upper GI tract. Thus, glutaraldehyde (Glu) was used for further cross-linking of the pectin chains. The formulation conditions and procedure were optimized from the in vitro drug release study. The optimized formulation was subjected to in vivo pharmacokinetic study in rats and compared with the unmodified Ca-pectinate and suspension formulation of resveratrol. Spherical particles (∼1 mm diameter) with high drug encapsulation were produced. Low cross-linking solution pH (1.5), minimum Glu concentration (2.5%) and cross-linking time (2 h) were crucial to exhibit colon-specific drug release. As Glu was added in the cross-linking solution, cross-linking between pectin chains and Glu occurred simultaneously during Ca-pectinate network formation, which appeared as a cost-effective formulation technique. Most importantly, the pharmacokinetic study demonstrated in vivo colon-specific drug release from the optimized formulation, while faster drug release was observed from the unmodified and suspension formulations. Hence, the developed formulation has potential to be used as colon-specific delivery system of resveratrol.

Cone milling of compacted flakes: process parameter selection by adopting the minimal fines approach.

Cone mill was well studied for milling of wet agglomerates. This study evaluated the effects of various process parameters of cone milling roller compacted flakes on the granules produced. Impeller sidearm shapes, screen surface profiles and impeller speeds were studied. Impeller speed was found to play a major role in determining the granule attributes. Besides this, median size, size distribution and percent fines of a milled granule population were mainly determined by the size reduction mechanisms of different impellers and screens. Pre-breaking followed by shearing and slicing of flakes inside the milling chamber was primarily responsible for determining the size, size distribution and percent fines of milled granules. The pre-breaking action could be achieved using teethed round sidearm impeller and lowered the need for screen-based size reduction, thus generating less fines. The shearing and slicing of flakes due to the raised impaction edges of the grater screen also helped to minimize the production of fines. Therefore, the lowest percentage of fines was observed when the teethed round sidearm impeller was used with a grater screen. The results indicated that fines can be reduced considerably with the judicious selection of a suitable impeller and screen combination in the cone mill.

Polyethyleneimine-modified pectin beads for colon-specific drug delivery: In vitro and in vivo implications

Calcium-pectinate (Ca-pectinate) beads have shown immense potential as colon-specific drug carrier. However, Ca-pectinate itself is unable to prevent its swelling/degradation in the upper gastro-intestinal (GI) conditions. Hence, polyethyleneimine (PEI) was added in the cross-linking solution to strengthen the Ca-pectinate network. Resveratrol was used as a model drug due to its promising therapeutic activity towards several colonic diseases. Beads were prepared by varying cross-linking solution pH and other formulation variables. The effects of these formulation variables were investigated on the beads characteristics. Furthermore, surface morphology, drug–polymer interaction, stability, and in vivo pharmacokinetic study of the optimized formulation were performed. The optimized PEI-modified beads prevented drug release in the upper GI conditions, while released the drug in simulated colonic fluid. Furthermore, in vivo pharmacokinetics studies in rats demonstrated delayed appearance of drug in blood after oral administration. The optimized Ca-pectinate beads demonstrated both in vitro and in vivo colon-specific drug release.

QUANTIFICATION OF TRANS-RESVERATROL IN RAT PLASMA BY A SIMPLE AND SENSITIVE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD AND ITS APPLICATION IN PRE-CLINICAL STUDY

The intention of this study was to develop and validate a simple, sensitive, and accurate high performance liquid chromatography (HPLC) method for quantification of trans-resveratrol in rat plasma. Trans-resveratrol was recovered from plasma samples by liquid-liquid extraction. A reverse phase HPLC column was used and the assay was performed at 35°C through isocratic delivery (1 mL · min−1) of acetonitrile and phosphate buffer solution, pH 7.0 (30:70 v/v). UV absorbance was monitored at 320 nm. Plasma samples were stable (>99%) at −80°C for 3 months. The recovery of trans-resveratrol from plasma was >95%. The HPLC method was validated. The retention times of trans-resveratrol and carbamazepine were 5.5 and 10.4 min, respectively. The calibration curve was linear (R2 = 0.9999) within the range of 5–1,000 ng · mL−1. The lower limits of detection and quantification of trans-resveratrol were 2.5 and 5 ng · mL−1, respectively. The intra-day and inter-day variations were <5% and accuracy was >95%. This simple HPLC method was subsequently applied to measure trans-resveratrol concentration in plasma following oral administration of trans-resveratrol suspension in rats. The plasma concentration of trans-resveratrol at 30 min after oral administration was quantified as 151.66 ± 120.53 ng · mL−1.