Poly (lactic-co-glycolic acid) as a controlled release delivery device

Poly (lactic-co-glycolic acid) (PLGA) is a biodegradable polymer used to make resorbable sutures, and is also used in other applications in tissue engineering. Being an artificial polymer, its degradation rate can be tailored to suit its application. It can be easily moulded into structures with suitable mechanical strength and degrades into relatively harmless products in the body. Its adjustable degradation rate also makes it a potentially excellent controlled release delivery device. However, the functionalization of PLGA with bioactive molecules usually requires extensive chemical modification. Chemical modification may compromise the mechanical strength of PLGA and inactivate the bioactive molecules. In this paper, a study is done to investigate the coating of an angiogenic factor on unmodified PLGA suture substrates for the differentiation of human mesenchymal stem cells (hMSC) into endothelial cells (EC). The results show that the method used to anchor vascular endothelial growth factor (VEGF) onto the PLGA surface can enable the gradual release of VEGF from the substrate into solution to induce the differentiation of hMSCs into ECs. Thus, this method can potentially be used to coat PLGA materials like sutures, meshes and scaffolds, rendering them functional as effective controlled release delivery devices for a wide range of bioactive molecules.     

PalmHashing: a novel approach for dual-factor authentication

Many systems require a reliable personal authentication infrastructure to recognise the identity of a claimant before granting access to him/her. Conventional secure measures include the possession of an identity card or special knowledge like password and personal identification numbers (PINs). These methods are insecure as they can be lost, forgotten and potentially be shared among a group of co-workers for a long time without change. The fact that biometric authentication is convenient and non-refutable makes it a popular approach for a personal identification system. Nevertheless, biometric methods suffer from some inherent limitations and security threats. A more practical approach is to combine two-factor or more authenticators to achieve a higher level of security. This paper proposes a novel dual-factor authenticator based on the iterated inner product between tokenised pseudo-random numbers and user-specific palmprint features. This process generates a set of user-specific compact code called PalmHash, which is highly tolerant of data offset. There is no deterministic way to get the user-specific code without having both PalmHash and the user palmprint feature. This offers strong protection against biometric fabrication. Furthermore, the proposed PalmHashing technique is able to produce zero equal error rate (EER) and yields clean separation of the genuine and imposter populations. Hence, the false acceptance rate (FAR) can be eliminated without suffering from the increased occurrence of the false rejection rate (FRR).This revised version was published online in August 2004 with corrections to the section numbers.     

Detecting flaws and intruders with visual data analysis

The task of sifting through large amounts of data to find useful information spawned the field of data mining. Most data mining approaches are based on machine-learning techniques, numerical analysis, or statistical modeling. They use human interaction and visualization only minimally. Such automatic methods can miss some important features of the data. Incorporating human perception into the data mining process through interactive visualization can help us better understand the complex behaviors of computer network systems. This article describes visual-analytics-based solutions and outlines a visual exploration process for log analysis. Three log-file analysis applications demonstrate our approach's effectiveness in discovering flaws and intruders in network systems.     

Determination of boric acid in foods: Comparative study of three methods

Three methods for the determination of boric acid in foods were studied in detail, namely the titrimetric method using mannitol, and two colorimetric procedures using carminic acid or curcumin. Agar-agar strips, pickled mango, noodles and prawns were analysed and the repeatability, sensitivity and recovery of the methods compared. The titrimetric and curcumin methods gave mean values for boric acid which were significantly (P < 0·05) higher than those of the carminic acid method. Results with the titrimetric method did not differ from those with the curcumin method; the latter method gave good recoveries (～ 100%) for all four foods at all levels of addition. Analyses carried out on NBS Standard Material showed that the curcumin method gave the most accurate results. This method was also found to show the least internal variation both in terms of mean boric acid content and recovery. Furthermore, the method possessed practical advantages over the other two techniques. Based on the results obtained from the comparative studies, the curcumin method was found to be the most reliable and hence would be the method of choice for boric acid determination in foods.     

Klebsiella pneumoniae yggG Gene Product: A Zinc-Dependent Metalloprotease

Klebsiella pneumoniae causes neonatal sepsis and nosocomial infections. One of the strains, K. pneumoniae MGH 78578, shows high level of resistance to multiple microbial agents. In this study, domain family, amino acid sequence and topology analyses were performed on one of its hypothetical protein, YggG (KPN_03358). Structural bioinformatics approaches were used to predict the structure and functionality of YggG protein. The open reading frame (ORF) of yggG, which was a putative metalloprotease gene, was also cloned, expressed and characterized. The ORF was PCR amplified from K. pneumoniae MGH 78578 genomic DNA and cloned into a pET14-b vector for heterologous expression in Escherichia coli. The purified YggG protein was subsequently assayed for casein hydrolysis under different conditions. This protein was classified as peptidase M48 family and subclan gluzincin. It was predicted to contain one transmembrane domain by TMpred. Optimal protein expression was achieved by induction with 0.6 mM isopropyl thiogalactoside (IPTG) at 25 °C for six hours. YggG was purified as soluble protein and confirmed to be proteolytically active under the presence of 1.25 mM zinc acetate and showed optimum activity at 37 °C and pH 7.4. We confirmed for the first time that the yggG gene product is a zinc-dependent metalloprotease.     

Synthesis,characterization and biophysical evaluation of the 2D Ti2CTx MXene using 3D spheroid-type cultures

MXenes are novel 2-D materials which have been extensively investigated for use in advanced biocomposites, water purification, biosensors, bioimaging and antibacterial systems. However, the knowledge associated with the mechanism of cytotoxic response is still limited to lack of verification against 3D spheroid-type cultures. Herein, we present a report on the in vitro cytotoxicity of Ti₂CT_x MXene against cervical cancer cell lines (HeLa) in a form of 3D spheroid with comparison to 2D cell culture system. Ti₂CT_x MXenes can be characterized by their multi-layered structure that is produced by the efficient elimination of Al and appearance of the surface functional groups. The biological results with 2D and 3D HeLa indicated that the Ti₂CT_x MXene was moderately cytotoxic to cells and the cytotoxicity was dose dependent. Our results showed that the toxicity of MXenes is potentially due to direct contact of the Ti₂CT_x MXene with the cell membrane wall. The Raman spectra suggested that the Ti₂CT_x MXenes interfered with the cytoplasmic proteins’ conformation and the surrounding microenvironment. This inherently modified the biochemistry of the cell membrane and caused cell apoptosis. This paper contributes to the pool of knowledge regarding the biocompatibility and biophysical properties of Ti₂CT_x MXene.     

Directed Evolution of an Antitumor Drug (Arginine Deiminase PpADI) for Increased Activity at Physiological pH

Arginine deiminase (ADI; EC 3.5.3.6) has been studied as a potential antitumor drug for the treatment of arginine‐auxotrophic tumors, such as hepatocellular carcinomas (HCCs) and melanomas. Studies with human lymphatic leukemia cell lines confirmed that ADI is an antiangiogenic agent for treating leukemia. The main limitation of ADI from Pseudomonas plecoglossicida (PpADI) lies in its pH‐dependent activity profile, its pH optimum is at 6.5. A pH shift from 6.5 to 7.5 results in an approximately 80 % drop in activity. (The pH of human plasma is 7.35 to 7.45.) In order to shift the PpADI pH optimum, a directed‐evolution protocol based on an adapted citrulline‐screening protocol in microtiter‐plate format was developed and validated. A proof of concept for ADI engineering resulted in a pH optimum of pH 7.0 and increased resistance under physiological and slightly alkaline conditions. At pH 7.4, variant M2 (K5T/D44E/H404R) is four times faster than the wild‐type PpADI and retains ～50 % of its activity relative to its pH optimum, compared to ～10 % in the case of the wild‐type PpADI.