Yin Yin Teo

Distribution and health risk assessment of trace metals in freshwater tilapia from three different aquaculture sites in Jelebu Region (Malaysia).

The trace metal concentrations in edible muscle of red tilapia (Oreochromis spp.) sampled from a former tin mining pool, concrete tank and earthen pond in Jelebu were analysed with microwave assisted digestion-inductively coupled plasma-mass spectrometry. Results were compared with established legal limits and the daily ingestion exposures simulated using the Monte Carlo algorithm for potential health risks. Among the metals investigated, arsenic was found to be the key contaminant, which may have arisen from the use of formulated feeding pellets. Although the risks of toxicity associated with consumption of red tilapia from the sites investigated were found to be within the tolerable range, the preliminary probabilistic estimation of As cancer risk shows that the 95th percentile risk level surpassed the benchmark level of 10(-5). In general, the probabilistic health risks associated with ingestion of red tilapia can be ranked as follows: former tin mining pool > concrete tank > earthen pond.

N-succinyl chitosan preparation, characterization, properties and biomedical applications: A state of the art review

Abstract N-succinyl chitosan (NSC) remains a promising chitosan derivative to develop targeted drug delivery, wound dressings, and tissue engineering systems. All these systems are important in life sciences. NSC is an amphiprotic derivative obtained from the N-acylation of chitosan. NSC exhibits extraordinary biocompatibility, significantly increased aqueous solubility in acidic and basic media without affecting the biological properties, appreciable transfection efficiency, and the ability to stimulate osteogenesis. NSC shows enhanced bioavailability, which highlights its potential applications in the biomedical field. This review briefly introduces chitosan, including its limitations as a biomaterial, and modifications of chitosan with a particular focus on acylation, along with a comprehensive overview of the synthesis, characterization, properties, biodistribution, and toxicological/biopharmaceutical profile of NSC. Furthermore, it extensively surveys current state-of-the-art NSC-based formulations for drug delivery with special emphasis on protein delivery, anti-cancer activity in the colon, as well as nasal and ophthalmic targeted gene/drug delivery. Moreover, it discusses NSC-based biomaterial applications in articular, adipose, and bone tissue engineering. In addition, it describes recent contributions of NSC-based hydrogels in wound dressings along with a brief account of drug delivery in combination with tissue engineering. Finally, it presents potential current challenges and future perspectives of NSC-based formulations in the biomedical field.

pH responsive N-succinyl chitosan/Poly (acrylamide-co-acrylic acid) hydrogels and in vitro release of 5-fluorouracil

[This corrects the article DOI: 10.1371/journal.pone.0179250.].

Effect of pH on physicochemical properties and encapsulation efficiency of PEGylated linolenic acid vesicles

The preparation of vesicle from a mixture of linolenic acid and 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy-(polyethylene glycol) -2000] (DPPE-PEG2000) has been successfully carried out by using dry lipid hydration method. The effect of pH on particle size, zeta potential, encapsulation efficiency and critical vesiculation concentration (CVC) of the prepared vesicle suspensions in aqueous were studied. Macroscopic stability of the vesicles was also evaluated through their particle size and zeta potential for a period of 30 days. We found that CVC vary according to the pH, with higher pH of the bulk solution, CVC is higher. Vesicles formed at pH 8.5 were the most stable suspension throughout a period of 30 days compared to those at pH 7.5 and pH 9.0. Addition of DPPE-PEG2000 into the preparation of vesicle at pH 8.5 caused a reduction of the vesicle size to the scale of nanometer which is an advantage to their application. On the other hand, encapsulation of calcein and vitamin E were carried out. Certain amount of these compounds could be successfully loaded into the resulting liposomes under this experimental condition.

Rheological behavior of biodegradable N-succinyl chitosan-g-poly (acrylic acid) hydrogels and their applications as drug carrier and in vitro theophylline release

Novel pH sensitive N-succinyl chitosan-g-poly (acrylic acid) hydrogels were synthesized through free radical mechanism. Rheometer was used to observe the mechanical strength of the hydrogels. In vitro degradation was conducted in SIF (pH 7.4). The effect of concentration of monomers, initiator, and crosslinking agent and pH and ionic strength of NaCl, CaCl2, and AlCl3 on swelling of the hydrogels was observed. The results showed that equilibrium swelling ratio was highly influenced by concentration of monomers, initiator, and crosslinking agent concentration, and pH and salt solutions of NaCl, CaCl2, and AlCl3. The swelling kinetics revealed that swelling followed non-Fickian anomalous transport. Furthermore, theophylline loading (DL %) and encapsulation efficiency (EE %) of the hydrogels was in the range of 15.5 ± 0.15-22.8 ± 0.06% and 62 ± 0.15-91 ± 0.26%, respectively. The release of theophylline in physiological mediums was strongly influenced by the pH. The theophylline release was in the range of 51 ± 0.20-92 ± 0.12% in SIF and 7.4 ± 0.02-14.9 ± 0.03% in SGF (pH 1.2), respectively. The release data fitted well to Korsmeyer-Peppas model. The chemical activity of the theophylline suggested that drug maintained its chemical activity after release in vitro. The results suggest that synthesized hydrogels are excellent drug carriers.

Physicochemical evaluation of DEAE-Dx coated liposomes for long alkyl chain lipids

The purpose of this work was to study the potential of diethylaminoethyl dextran (DEAE-Dx) coated liposomes as drug carriers. Thin film hydration method was employed to prepare 1,2-dipalmitoyl-sn-glycero-3-phospocholine (DPPC) and 1,2-distearoyl-sn-glycero-3-phospocholine (DSPC). The critical vesicular concentration (CVC) of DPPC and DSPC was found to be 0.08% (w/v) and 0.06% (w/v), respectively. As stability is a general problem with liposomes, DEAE-Dx as a polymer was used to promote steric stabilization by coating the surface of the DPPC and DSPC liposomes. Liposomes stabilized by DEAE-Dx were superior to the corresponding non-coated liposomes. The surface behaviour of DPPC and DSPC was investigated through surface tension analysis before and after the addition of DEAE-Dx. All the liposomes were evaluated based on their particle size, zeta potential and morphology. A thirty-five day stability study shows that the particle size and zeta potential of DEAE-Dx coated liposomes were stable at room temperature. The DEAE-Dx coated liposomes were loaded with an antihistamine drug, diphenhydramine hydrochloride (DPH). The encapsulation efficiency profile shows that DEAE-Dx coated DPPC (DPPC-DEAE-Dx) liposomes have higher entrapment of DPH compared to DEAE-Dx coated DSPC liposome (DSPC-DEAE-Dx). An in vitro release experiment demonstrated DEAE-Dx coated liposomes had the best controlled release system.

Effect of PEGylated lipid and Lecinol S-10 on physico-chemical properties and encapsulation efficiency of palmitoleate–palmitoleic acid vesicles

Abstract A vesicle is a microscopic particle composed of a lipid bilayer membrane that separates the inner aqueous compartment from the outer aqueous environment. Palmitoleate–palmitoleic acid vesicles were prepared and their physico-chemical properties were investigated. Moreover, mixed vesicles composed of palmitoleic acid and PEGylated lipid and/or a mixture of phospholipids were also prepared. The stabilizing effects of these double-chain lipids on the formation of palmitoleate–palmitoleic acid vesicles were studied. Stability of the vesicle suspension was examined using particle size and zeta potential at 30 °C. The magnitude of the zeta potential was relatively lower in the vesicle suspension with the presence of phospholipid. Although some of the mixed vesicles that were formed were not very stable, they displayed potential for encapsulating the active ingredient calcein and the encapsulation efficiencies of calcein were encouraging. The palmitoleate–palmitoleic acid–DPPE-PEG2000 vesicle showed the most promising stability and encapsulation efficiency.