The comparison of 0.05% sodium fluoride and 0.2% chlorhexidine usage and aquadest to the plaque index on fixed orthodontic patients

The fixed orthodontic appliance will cause changes in microbial flora the oral cavity and food debris accumulation and will be formed especially around the gingival sulcus. Plaque control using chemical means can be done by using mouth rinse. This research compared the influence of 0.05% sodium fluoride mouth rinse with aquadest and 0.2% chlorhexidine to the plaque index in fixed orthodontic patients. A double-blind and cross over clinical assessment were applied using a sample size of 16 male fixed orthodontic patients with the age above 21 years. 0.05% sodium fluoride, 0.2% chlorhexidine mouth rinse was given to all patients as a positive control and aquadest as a negative control. Plaque index was then measured after 24 hours without tooth brushing, after using the mouth rinse and a week after using the mouth rinse with tooth brushing. The results showed that the use of 0.05% sodium fluoride mouth rinse reduced plaque index more significantly compared to 0.2% chlorhexidine. The mechanical plaque control by tooth brushing is still the most influential mean to reduce plaque index in fixed orthodontic patients. Mouth rinse is just an additional mean to reduce plaque

Non-invasive nanosensor monitoring of mRNA expression for regenerative medicine application

The field of regenerative medicine focuses on utilizing therapeutic cells either on itself or in conjunction with scaffolds to replace, repair or allow regeneration of injured tissues. Thus far, various approaches involving wide ranges of cell and biomaterial types have been proposed and validated at the bench-side (laboratory). However, their translation towards the clinical side have been minimal, with most approaches failing in pre- or early clinical trial phase. One limiting factor that is very crucial in ensuring successful treatment efficacy and thus translation process is quality control of cells to be injected/implanted. Prior to its re-introduction, cells of various sources need to be validated for their functionality (i.e. phenotype). Conventionally, such verification is achieved through end-point, population-based methods like polymerase chain reaction (PCR; for mRNA expression) or western blotting (for protein expression). These assays however, necessitate sample disruption for isolation of analytes. As such, it only provides a snapshot of the dynamic processes occurring (i.e. provides no temporal resolution). To this end, incorporation of reporter gene constructs enable continuous, longitudinal tracking of gene-of-interest’s expression profile. Nevertheless, it also has limitations including the tedious and lengthy development, and risks of introducing random mutations which make modified cells less clinically-friendly. In this thesis, application of nanosensor platform as a safe, non-integrative alternative for prolonged monitoring of cellular biomarkers is proposed and demonstrated. Specifically, nanosensors were fabricated by incorporating molecular beacons (MBs), oligonucleotide-based hairpin probes with specific target gene recognition ability, into biocompatible, biodegradable polymeric nanoparticles. Encapsulated within the nanocarriers, MBs can be effectively internalized by cells without requiring transfection procedures. Crucially, sustained release of MBs into the cytoplasmic region prolongs intracellular monitoring window of MBs, which are rapidly digested and cleared from cells otherwise. This was initially proven using MB targeted towards housekeeping gene of β-actin, against pore-inducing bolus MBs delivery method. Subsequently, nanosensor was applied to validate and track osteogenic (2D) and chondrogenic (3D hydrogel) differentiation of MSCs. In both cases, loading of nanosensors with both functional MBs (against specific differentiation markers) and reference MBs (against housekeeping gene), enable accurate depiction of cellular gene expression with good correlation against results from gold-standard of PCR (R2 value between 0.8 to 0.9). Finally, nanosensors were adapted to evaluate successful reprogramming induction of somatic fibroblast cells, relative to both PCR and gene-reporter validation. Aside from its monitoring performance, safety aspect of nanosensor labeling was studied in detail. Labeling concentration was assessed and optimized to ensure minimal influence over cell metabolism and proliferation rate. Meanwhile, multi-potency of labeled mesenchymal stem cells was minorly affected towards three differentiation lineages: adipogenesis, osteogenesis and chondrogenesis. At the same time, Oct4 protein expression and reprogramming efficacy were not impaired by nanosensor labeling. In conclusion, a facile, versatile yet safe nanosensor monitoring platform is introduced in this thesis. Especially for the field of regenerative medicine, such nanosensor can facilitate swifter translation of various therapeutic approaches by providing scientists information regarding dynamic cellular changes with both spatial and temporal resolution. In the future, such tool can be applied for optimization of culture conditions as well as purifying heterogenous cell populations to optimize treatment efficacy.Doctor of Philosophy (SCBE

Toward miniaturizing microelectronics using covalent organic framework dielectric

As miniaturization of microelectronics reaches sub-10 nm scale, signal crosstalk and parasitic resistive-capacitive delay significantly limit device performance. While low dielectric constant (low-κ) dielectrics are widely recognized to address such issue, their poor thermal conductivity impedes heat management. Recently, scientists from Northwestern University and University of Virginia demonstrated the fabrication of pristine covalent organic framework (COF) thin films as a thermally conducting low-κ dielectric. Specifically, reported COF-5 film complements low-κ dielectric value (κ = 1.6) with high thermal conductivity (1 W m-1 K-1), offering promising adaptations in microelectronics with high power density.Ministry of Education (MOE)Submitted/Accepted versionThe authors acknowledge the Ministry of Education Singapore under the Academic Research Funds (MOE-MOET2EP10120-0003)

A Concise Review of Gold Nanoparticles-Based Photo-Responsive Liposomes for Controlled Drug Delivery

Abstract The focus of drug delivery is shifting toward smart drug carriers that release the cargo in response to a change in the microenvironment due to an internal or external trigger. As the most clinically successful nanosystem, liposomes naturally come under the spotlight of this trend. This review summarizes the latest development about the design and construction of photo-responsive liposomes with gold nanoparticles for the controlled drug release. Alongside, we overview the mechanism involved in this process and the representative applications

Real-time and non-invasive monitoring of embryonic stem cell survival during the development of embryoid bodies with smart nanosensor

Embryonic stem cells (ESCs)-derived embryoid body (EB) is a powerful model for the study of early embryonic development and the discovery of therapeutics for tissue regeneration. This article reports a smart nanosensor platform for labeling and tracking the survival and distribution of ESCs during the EB development in a real-time and non-invasive way. Compared with the cell tracker (i.e. DiO) and the green fluorescent protein (GFP), nanosensors provide the homogenous and highly-efficient ESC labeling. Following the internalization, intracellular nanosensors gradually release the non-fluorescent molecules that become fluorescent only in viable cells. This allows a continuous monitoring of ESC survival and distribution during the process of EB formation. Finally, we confirm that nanosensor labeling does not cause the significant influences to biological properties of the ESCs and EBs.MOE (Min. of Education, S’pore)Accepted versio

Nanosensors for regenerative medicine

Assessing biodistribution, fate, and function of implanted therapeutic cells in preclinical animal experiments is critical to realize safe, effective and efficient treatments for subsequent implementation within the clinic. Currently, tissue histology, the most prevalent analytical technique to meet this need, is limited by end-point analysis, high cost and long preparation time. Moreover, it is disadvantaged by an inability to monitor in real-time, qualitative interpretation and ethical issues arising from animal sacrifice. While genetic engineering techniques allow cells to express molecules with detectable signals (e.g., fluorescence, luminescence, T1 (spin–lattice)/T2 (spin–spin) contrast in magnetic resonance imaging, radionuclide), concerns arise regarding technical complexity, high-cost of genetic manipulation, as well as mutagenic cell dysfunction. Alternatively, cells can be labeled using nanoparticle-sensors—nanosensors that emit signals to identify cell location, status and function in a simple, cost-effective, and non-genetic manner. This review article provides the definition, classification, evolution, and applications of nanosensor technology and focuses on how they can be utilized in regenerative medicine. Several examples of direct applications include: (1) monitoring post-transplantation cell behavior, (2) revealing host response following foreign biomaterial implantation, and (3) optimization of cell bioprocess operating conditions. Incorporating nanosensors is expected to expedite the development of cell-based regenerative medicine therapeutics

A Nanoparticle-based Sensor Platform for Cell Tracking and Status/Function Assessment

Nanoparticles are increasingly popular choices for labeling and tracking cells in biomedical applications such as cell therapy. However, all current types of nanoparticles fail to provide real-time, noninvasive monitoring of cell status and functions while often generating false positive signals. Herein, a nanosensor platform to track the real-time expression of specific biomarkers that correlate with cell status and functions is reported. Nanosensors are synthesized by encapsulating various sensor molecules within biodegradable polymeric nanoparticles. Upon intracellular entry, nanosensors reside within the cell cytoplasm, serving as a depot to continuously release sensor molecules for up to 30 days. In the absence of the target biomarkers, the released sensor molecules remain ‘Off’. When the biomarker(s) is expressed, a detectable signal is generated (On). As a proof-of-concept, three nanosensor formulations were synthesized to monitor cell viability, secretion of nitric oxide, and β-actin mRNA expression.Published versio

Transdermal delivery of Chinese herbal medicine extract using dissolvable microneedles for hypertrophic scar treatment

Hypertrophic scars are unfavorable skin diseases characterized by excessive collagen deposition. Although systemic treatments exist in clinic to manage hypertrophic scars, they pose significant side effects and tend to lose efficacy over prolonged applications. Traditional Chinese medicine (TCM) offers as a promising candidate to treat pathological scars. A large number of TCMs have been studied to show anti-scarring effect, however, the natural barrier of the skin impedes their penetration, lowering its therapeutic efficacy. Herein, we reported the use of dissolvable hyaluronic acid (HA) microneedles (MNs) as a vehicle to aid the transdermal delivery of therapeutic agent, a model TCM called shikonin for the treatment of hypertrophic scars. Here, shikonin was mixed with HA to make MNs with adequate mechanical strength for skin penetration, making its dosage controllable during the fabrication process. The therapeutic effect of the shikonin HA MNs was studied in vitro using HSFs and then further verified with quantitative reverse transcriptase polymerase chain reaction. Our data suggest that the shikonin HA MNs significantly reduce the viability and proliferation of the HSFs and downregulate the fibrotic-related genes (i.e., TGFβ1, FAP-α and COL1A1). Furthermore, we observed a localized therapeutic effect of the shikonin HA MNs that is beneficial for site-specific treatment.Agency for Science, Technology and Research (A*STAR)Published versionChenjie Xu acknowledges the funding support from SingaporeAgency for Science, Technology and Research (A)STAR) Sci-ence and Engineering Research Council Additive Manufacturingfor Biological Materials (AMBM) program (A18A8b0059,Singapore), City University of Hong Kong (#9610472, China),General Research Fund (GRF) from University Grant Committeeof Hong Kong (UGC) Research Grant Council (RGC) (#9042951,China), and NSFC/RGC Joint Research Scheme (N_CityU118/20,China)

Near Infrared light-responsive liposomal contrast agent for photoacoustic imaging and drug release applications

Photoacoustic imaging has become an emerging tool for theranostic applications. Not only does it help in in vivo, noninvasive imaging of biological structures at depths but it can also be used for drug release and therapeutic applications. We explore near-infrared light-sensitive liposomes coated with gold nanostars (AuNSs) for both imaging and drug release applications using a photoacoustic imaging system. Being amphiphilic, the liposomes lipid bilayer and the aqueous core enable encapsulation of both hydrophobic and hydrophilic drugs. The AuNSs on the surface of the liposomes act as photon absorbers due to their intrinsic surface plasmon resonance. Upon excitation by laser light at specific wavelength, AuNSs facilitate rapid release of the contents encapsulated in the liposomes due to local heating and pressure wave formation (photoacoustic wave). Herein, we describe the design and optimization of the AuNSs-coated liposomes and demonstrate the release of both hydrophobic and hydrophilic model drugs (paclitaxel and calcein, respectively) through laser excitation at near-infrared wavelength. The use of AuNSs-coated liposomes as contrast agents for photoacoustic imaging is also explored with tissue phantom experiments. In comparison to blood, the AuNSs-coated liposomes have better contrast (approximately two times) at 2-cm imaging depth.MOE (Min. of Education, S’pore)Accepted versio