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CRISPR/Cas9 in plant biotechnology: applications and challenges

Gan WC, Ling APK

BioTechnologia (Pozn), 2022;103(1):81-93.
PMID: 36605382 DOI: 10.5114/bta.2022.113919

The application of plant biotechnology to enhance beneficial traits in crops is now indispensable because of food insecurity due to increasing global population and climate change. The recent biotechnological development of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated system 9 (Cas9) allows for a more simple and precise method of gene editing, which is now preferred compared to Zinc Finger Nucleases (ZFNs) and Transcription Activator-like Effector Nucleases (TALENs). In this review, recent progress in utilizing CRISPR/Cas9-mediated gene editing in plants to enhance certain traits in beneficial crops, including rice, soybean, and oilseed rape, is discussed. In addition, novel methods of applying the CRISPR/Cas9 system in live cell imaging are also extensively reviewed. Despite all the applications, the existing delivery methods of CRISPR/Cas9 fail to provide consistent results and are inefficient for in planta transformation. Hence, research should be focused on improving current delivery methods or developing novel ones to facilitate CRISPR/Cas9-based gene editing studies. Strict regulations on the sale and commercial growth of gene-edited crops have restricted more efforts in applying CRISPR/Cas9 technology in plant species. Therefore, a shift in public viewpoint toward gene editing would help to propel scientific progress rapidly.
Fulltext Current updates and research on plant-based vaccines for coronavirus disease 2019

Uthaya Kumar A, Kadiresen K, Gan WC, Ling APK

Clin Exp Vaccine Res, 2021 Jan;10(1):13-23.
PMID: 33628750 DOI: 10.7774/cevr.2021.10.1.13

The primary outbreak of severe acute respiratory syndrome coronavirus 2, causing pneumonia-like symptoms in patients named coronavirus disease 2019 (COVID-19) had evolved into a global pandemic. COVID-19 has surpassed Middle East respiratory syndrome and severe acute respiratory syndrome in terms of rate and scale causing more than one million deaths. Development of an effective vaccine to fight against the spread of COVID-19 is the main goal of many countries around the world and plant-based vaccines are one of the available methods in vaccine developments. Plant-based vaccine has gained its reputation among researchers for its known effective manufacturing process and cost effectiveness. Many companies around the world are participating in the race to develop an effective vaccine by using the plant system. This review discusses different approaches used as well as highlights the challenges faced by various companies and research groups in developing the plant-based COVID-19 vaccine.
Fulltext Fundamental Understanding of Multicellular Triboelectric Nanogenerator with Different Electrical Configurations

Li Z, Gan WC, Tang L, Aw KC

Micromachines (Basel), 2023 Jun 29;14(7).
PMID: 37512644 DOI: 10.3390/mi14071333

The single-cell triboelectric nanogenerator (TENG) often produces insufficient energy, leading to the use of a multicellular TENG structure. This work experimented with and simulated a dual-cell TENG with various configurations in parallel and series arrangements. The working principle of charge generation during each phase of a contact-separation cycle was explained through the analysis and comparison of five electrical configurations of a dual-cell TENG. Our observations indicate that measuring the output charge of a TENG provides a more reliable performance comparison. Finally, multicellular TENG with four cells arranged in an X-shape (X-TENG), self-supporting structure is fabricated and further experimented with, validating our conjectures derived from a dual-cell TENG.
Fulltext Hot plate annealing at a low temperature of a thin ferroelectric P(VDF-TrFE) film with an improved crystalline structure for sensors and actuators

Mahdi RI, Gan WC, Abd Majid WH

Sensors (Basel), 2014;14(10):19115-27.
PMID: 25317763 DOI: 10.3390/s141019115

Ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer 70/30 thin films are prepared by spin coating. The crystalline structure of these films is investigated by varying the annealing temperature from the ferroelectric phase to the paraelectric phase. A hot plate was used to produce a direct and an efficient annealing effect on the thin film. The dielectric, ferroelectric and pyroelectric properties of the P(VDF-TrFE) thin films are measured as a function of different annealing temperatures (80 to 140 °C). It was found that an annealing temperature of 100 °C (slightly above the Curie temperature, Tc) has induced a highly crystalline β phase with a rod-like crystal structure, as examined by X-ray. Such a crystal structure yields a high remanent polarization, Pr = 94 mC/m2, and pyroelectric constant, p = 24 μC/m2K. A higher annealing temperature exhibits an elongated needle-like crystal domain, resulting in a decrease in the crystalline structure and the functional electrical properties. This study revealed that highly crystalline P(VDF-TrFE) thin films could be induced at 100 °C by annealing the thin film with a simple and cheap method.
Structural control of the dielectric, pyroelectric and ferroelectric properties of poly(vinylidene fluoride-co-trifluoroethylene) thin films

Ng CYB, Gan WC, Velayutham TS, Goh BT, Hashim R

Phys Chem Chem Phys, 2020 Jan 29;22(4):2414-2423.
PMID: 31939468 DOI: 10.1039/c9cp01556f

The effects of solvents and temperature on the crystal formation were investigated for vinylidene fluoride/trifluoroethylene copolymer P(VDF-TrFE). Highly crystalline P(VDF-TrFE) thin films were fabricated by spin-casting using various polar solvents such as diethyl carbonate (DEC), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Ferroelectric polarisation reversal of the P(VDF-TrFE) was evidenced by a displacement (D)-electric field (E) hysteresis loop measurement and supported by the presence of pyroelectric activity. The samples which were annealed above 100 °C gave elongated rod-like crystalline structures and the highest crystallinity, Xc of 83% was formed at 120 °C. Consequently, remnant polarisation (85 mC m-2) and the pyroelectric coefficient (30 μC m-2 K-1) were enhanced. Thus, annealing plays a substantial role in controlling the crystalline structure of P(VDF-TrFE) films regardless of the choice of solvent. Although, the crystalline structure control is almost independent of the solvent's polarity, the choice of solvent is essential in preparing a smoother film surface. Molecular dynamics of P(VDF-TrFE) are discussed from the observation of two dielectric relaxation processes, β and γ related to the segmental micro-Brownian and local modes, respectively. The complete ferroelectric polarization reversal caused a reduction in the dielectric polarization and reduced the lattice spacing of the 110/200 planes.
Phase sensitive molecular dynamics of self-assembly glycolipid thin films: a dielectric spectroscopy investigation

Velayutham TS, Ng BK, Gan WC, Abd Majid WH, Hashim R, Zahid NI, et al.

J Chem Phys, 2014 Aug 28;141(8):085101.
PMID: 25173043 DOI: 10.1063/1.4893873

Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assemble without the presence of a solvent. Here, the dielectric and conductivity properties of three synthetic glycolipid thin films in different thermotropic liquid crystal phases were investigated over a frequency and temperature range of (10(-2)-10(6) Hz) and (303-463 K), respectively. The observed relaxation processes distinguish between the different phases (smectic A, columnar/hexagonal, and bicontinuous cubic Q) and the glycolipid molecular structures. Large dielectric responses were observed in the columnar and bicontinuous cubic phases of the longer branched alkyl chain glycolipids. Glycolipids with the shortest branched alkyl chain experience the most restricted self-assembly dynamic process over the broad temperature range studied compared to the longer ones. A high frequency dielectric absorption (Process I) was observed in all samples. This is related to the dynamics of the hydrogen bond network from the sugar group. An additional low-frequency mechanism (Process II) with a large dielectric strength was observed due to the internal dynamics of the self-assembly organization. Phase sensitive domain heterogeneity in the bicontinuous cubic phase was related to the diffusion of charge carriers. The microscopic features of charge hopping were modelled using the random walk scheme, and two charge carrier hopping lengths were estimated for two glycolipid systems. For Process I, the hopping length is comparable to the hydrogen bond and is related to the dynamics of the hydrogen bond network. Additionally, that for Process II is comparable to the bilayer spacing, hence confirming that this low-frequency mechanism is associated with the internal dynamics within the phase.
Fulltext A hybrid piezoelectric and triboelectric nanogenerator with lead-free BZT-BCT/PDMS composite and PVA film for scavenging mechanical energy

Gopal SR, Velayutham TS, Gan WC, Cheong JY, Soh AE

RSC Adv, 2023 Mar 08;13(12):7921-7928.
PMID: 36909754 DOI: 10.1039/d3ra00077j

A hybrid piezo/triboelectric nanogenerator (H/P-TENG) is designed for mechanical energy harvesting using polymer ceramic composite films; polydimethylsiloxane/Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (PDMS/BZT-BCT) and polyvinyl alcohol (PVA). A lead-free BZT-BCT piezoelectric ceramic was prepared via solid-state method and blended into PDMS to form a series of polymer-ceramic composite films, ranging from 5% to 30% by weight. The films were forward/reverse poled with corona poling and their electrical properties were compared to non-poled samples. The H/P-TENG constructed with forward-poled 15 wt% BZT-BCT in PDMS achieved the highest open-circuit voltage, V oc of 127 V, short-circuit current density, J sc of 67 mA m-2, short-circuit charge density, Q sc of 118 μC m-2, and peak power density of 7.5 W m-2, an increase of 190% over pristine PDMS-based TENG. It was discovered that incorporating BZT-BCT into the PDMS matrix improved the triboelectric properties of PDMS. The overlapping electron cloud (OEC) model was used to explain the enhancement and the effect of poling direction of the PDMS/BZT-BCT composite used in H/P-TENG, providing fundamental knowledge of the influence of piezoelectric polarisation on contact electrification.
Fulltext Enhancing the tribopositive characteristics of polyvinyl alcohol (PVA)-carbon composites by optimizing the PVA-carbon interaction with various carbon fillers

Cheong JY, Koay JSC, Gopal SR, Velayutham TS, Gan WC

Nanoscale Adv, 2025 Jan 28;7(3):819-829.
PMID: 39691558 DOI: 10.1039/d4na00820k

Incorporating carbon-based fillers into triboelectric nanogenerators, TENGs, is a compelling strategy to enhance the power output. However, the lack of systematic studies comparing various carbon fillers and their impact on tribopositive contact layers necessitates further research. To address these concerns, various carbon fillers (including buckminsterfullerene (C60), graphene oxide (GO), reduced graphene oxide (rGO), multi-wall carbon nanotube (MWCNT), and super activated carbon (SAC)) with distinct structural and electrical properties are mixed with polyvinyl alcohol, PVA, to form PVA-carbon composites and used as tribopositive layers in the contact-separation of TENGs. The results show that PVA-SAC provides the largest enhancements to the electrical outputs of the TENG. At the optimal loading of 1 wt%, PVA-SAC composites yielded a peak power density of 12.8 W m-2, a substantial 220% enhancement compared to pristine PVA. The mechanism governing the enhancement is determined by analysing the changes in electrical and structural characteristics caused by the addition of various carbon fillers. Dielectric measurements indicated that enhanced dielectric properties did not significantly contribute to the observed increase in the triboelectric performance. Instead, Raman and FTIR analyses revealed a correlation between the PVA-carbon interactions and an increase in the D/G ratio of carbon fillers, accompanied by a reduction in hydrogen-bonded -OH groups within PVA. This suggests that the interaction between the π electrons of sp2 hybridized carbon atoms and the oxygen lone pairs in PVA inhibits hydrogen bond formation, leading to an increase in free -OH groups. Consequently, these free -OH groups enhanced the electron-donating capability and improved the tribopositive behaviour of the PVA-carbon composites. Our results proved that filler-matrix interactions are paramount in engineering high-performance TENGs by controlling the electron affinity of the triboelectric layers.
Fulltext Triboelectric Nanogenerator-Based Stretch Sensor

Wang Y, Shi L, Zhong M, Tang L, Gan WC, Zhu Y, et al.

Sensors (Basel), 2026 Oct 14;26(20).
PMID: 42944356 DOI: 10.3390/s26206493

Triboelectric nanogenerators (TENGs) have been extensively investigated as both energy harvesters and self-powered sensors. While their application as force sensors has been widely reported, the use of TENGs as stretch sensors remains relatively unexplored. Stretch sensors are important for monitoring human joint and limb movements, with significant potential in rehabilitation applications such as post-stroke therapy and recovery following knee surgery. In this work, we present a preliminary TENG-based stretch sensor comprising a multi-triangular elastomer structure and an arched copper electrode. The primary objective is to establish the viability of the sensing concept and validate its fundamental operating principle. The device generates an output voltage that is proportional to the bending angle. This behavior arises from the increased contact and friction between the elastomer (Dragon Skin silicone) and copper layers as deformation increases, resulting in enhanced triboelectric charge generation and a higher output voltage. Owing to the inherent capacitive characteristics of the TENG under high-impedance loading conditions, the generated voltage can be retained for several seconds after the bending motion ceases. This retention time is sufficient for signal acquisition and joint-motion detection electronics. Experimental results demonstrate that the proposed TENG-based stretch sensor can reliably measure bending angles under both quasi-static and dynamic operating conditions, highlighting its potential for wearable motion-monitoring and rehabilitation systems.
Molecular dynamics of anhydrous glycolipid self-assembly in lamellar and hexagonal phases

Velayutham TS, Nguan HS, Ng BK, Gan WC, Manickam Achari V, Zahid NI, et al.

Phys Chem Chem Phys, 2016 06 01;18(22):15182-90.
PMID: 27199168 DOI: 10.1039/c6cp00583g

The molecular dynamics of a synthetic branched chain glycolipid, 2-decyl-tetradecyl-β-d-maltoside (C14-10G2), in the dry assemblage of smectic and columnar liquid crystal phases has been studied by dielectric spectroscopy as a function of frequency and temperature during the cooling process. Strong relaxation modes were observed corresponding to the tilted smectic and columnar phases, respectively. At low frequency (∼900 Hz to 1 kHz) in the smectic phase, Process I* was observed due to the tilted sugar bilayer structure. The process continued in the columnar phase (Process I) with an abrupt dynamic change due to phase transition in the frequency range of ∼1.3 kHz to 22 kHz. An additional process (Process II) was observed in the columnar phase with a broader relaxation in the frequency range of ∼10 Hz to 1 kHz. A bias field dependence study was performed in the columnar phase and we found that the relaxation strength rapidly decreased with increased applied dc bias field. This relaxation originates from a collective motion of polar groups within the columns. The results of dielectric spectroscopy were supported by a molecular dynamics simulation study to identify the origin of the relaxation processes, which could be related to the chirality and hydrogen bonds of the sugar lipid.
Health-related quality of life amongst children with chronic kidney disease in Malaysia: performance of the Bahasa Melayu version of the PedsQL 3.0 ESRD Module : (PedsQL 3.0 VerBATIM: version in Bahasa Melayu. Translated for use in Malaysia)

Bakar KA, Muhamad NA, Sarpin MA, Shaharudin S, Sidhu S, Yap SL, et al.

Pediatr Nephrol, 2023 Jun;38(6):1897-1905.
PMID: 36272027 DOI: 10.1007/s00467-022-05774-0

BACKGROUND: The PedsQL 3.0 End Stage Renal Disease (ESRD) Module is a well-accepted instrument internationally but it is not available in the local language. We aimed to validate the Bahasa Melayu (Malay language) version and determine the health-related quality of life (HRQoL) scores amongst children with CKD in Malaysia.
METHODS: The source questionnaire in English was translated into Bahasa Melayu. Linguistic validation guidelines by the MAPI Research Institute were followed. The already validated Bahasa Melayu PedsQL 4.0 Generic Core Scales was used for comparison. Sociodemographic data were collected during the interview. Statistical analyses were performed using SPSS version 25.0.
RESULTS: Sixty-nine children aged 8 to 18 with CKD stages 4 and 5, with or without dialysis, and their caregivers were recruited. Mean age was 12.62 ± 2.77 (SD). Evaluation of the PedsQL 3.0 ESRD Module Bahasa Melayu version demonstrated good internal consistency (Cronbach alpha 0.82). There was good agreement between child self-report and parent proxy report in all domains; average intraclass correlation coefficients (ICC) were 0.78, 95% CI (0.71, 0.84). Scores obtained from Generic 4.0 scales correlated with the disease-specific ESRD 3.0 scale, Spearman's rho = 0.32, p = 0.007. The Kruskal-Wallis H test indicated that there were no significant differences between stages of CKD and their respective mean HRQoL score, χ2(2) = 2.88, p = 0.236.
CONCLUSIONS: The PedsQL 3.0 ESRD Module Bahasa Melayu version is a reliable and feasible tool for cross-cultural adaptation. A longer prospective study may help better illustrate the quality of life in this group of children.

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