Advances in two-dimensional transition metal dichalcogenides-based sensors for environmental, food, and biomedical analysis: A review

Transition metal dichalcogenides (TMDCs) are versatile two-dimensional (2D) nanomaterials used in biosensing applications due to their excellent physical and chemical properties. Due to biomaterial target properties, biosensors' most significant challenge is improving their sensitivity and stability. In environmental analysis, TMDCs have demonstrated exceptional pollutant detection and removal capabilities. Their high surface area, tunable electronic properties, and chemical reactivity make them ideal for sensors and adsorbents targeting various contaminants, including heavy metals, organic pollutants, and emerging contaminants. Furthermore, their unique electronic and optical properties enable sensitive detection techniques, enhancing our ability to monitor and mitigate environmental pollution. In the food analysis, TMDCs-based nanomaterials have shown remarkable potential in ensuring food safety and quality. These nanomaterials exhibit high specificity and sensitivity for detecting contaminants, pathogens, and adulterants in various food matrices. Their integration into sensor platforms enables rapid and on-site analysis, reducing the reliance on centralized laboratories and facilitating timely interventions in the food supply chain. In biomedical studies, TMDCs-based nanomaterials have demonstrated significant strides in diagnostic and therapeutic applications. Their biocompatibility, surface functionalization versatility, and photothermal properties have paved the way for novel disease detection, drug delivery, and targeted therapy approaches. Moreover, TMDCs-based nanomaterials have shown promise in imaging modalities, providing enhanced contrast and resolution for various medical imaging techniques. This article provides a comprehensive overview of 2D TMDCs-based biosensors, emphasizing the growing demand for advanced sensing technologies in environmental, food, and biomedical analysis.

Spinal analgesia and auditory functions: a comparison of two sizes of Quincke needle

AIM

Spinal anaesthesia may produce complications ranging from minor problems such as pain on injection, backache and urinary retention to more serious consequences such as post-dural puncture headache (PDPH), neurological complications like meningitis, cranial and peripheral nerve palsies and even cardiac arrest. Impaired auditory function is a relatively lesser-recognized complication of spinal analgesia. The objective of this study was to investigate the effects of spinal analgesia on vestibular dysfunction, using different sizes of the same type of spinal needle.

METHODS

The study included 30 ASA I patients who had received spinal analgesia for lower abdominal surgery. Pure tone audiometry was performed before surgery and on postoperative day 2. In addition, any patient with hearing impairment of >15 dB was scheduled to undergo electrocochleography. Hearing levels were measured from 250 Hz to 8 kHz. In group 1 (n=15), a 26gauge Quincke needle was used. In group 2 (n=15), a 23-gauge Quincke needle was used.

RESULTS

Comparison of hearing thresholds showed a significant reduction in the hearing level (P<0.05) in 2 patients in group 2 but none in group 1.

CONCLUSION

The use of a 23-gauge Quincke needle is associated with a greater reduction in the mean hearing level compared to a 26-gauge needle of the same type.

Effects of variation in timing of palatal repair on articulation skills in complete cleft lip and palate cases--a retrospective study

The effects of variation in the timing of palatal repair on articulation skills in complete cleft lip and palate was evaluated from fifty subjects. The present study confirmed that development of articulation was similar in the groups operated upon before 24 months and between 24 to 36 months. The insignificant difference suggests that articulation was good irrespective of the early or medium timing of palatal repair.

Detrimental effects of noise on anaesthetists

To study the detrimental effects of operating room noise, noise levels in operating rooms were first measured and the average noise level was calculated in Decibels, which was 77.32 dB(A). An audiocassette of 90 min duration was prepared recording the operating room noise. The same audiocassette was used later to expose the 20 anaesthesia residents to the operating room noise in the acoustically treated rooms of audiology department. The noise level during exposure was maintained at 77.32 dB(A). Two cognitive functions, mental efficiency and short-term memory were studied. The tests used were the Trail Making Test and Digit Symbol Test for mental efficiency and the Benton Visual Retention Test for short-term memory. The mean pre-exposure scores for the Trail Making Test, Digit Symbol Test and Benton Visual Retention Test were 22.9 +/- 1.94, 83 +/- 2.62 and 9.55 +/- 0.51 respectively. The mean during-exposure scores were 16.35 +/- 1.39, 74.05 +/- 3.46 and 5.8 +/- 0.41 respectively (P < 0.05). In conclusion, we observed that operating room noise reduced the mental efficiency and short-term memory of anaesthesia residents.

Auditory functions in anaesthesia residents during exposure to operating room noise

Twenty anaesthesia residents were exposed to a pre-recorded audio cassette of operating room noise. The noise level during exposure was maintained at 77.32 +/- 1 dB (A), which was the calculated average operating room noise in our institute. Two auditory functions i.e., speech reception threshold and speech discrimination were studied before and during exposure to noise in a pre-fixed order. The right and left ears were tested separately. Speech reception threshold showed a mean increase of 23.75 +/- 6.86 dB (A) for the right ear and 26.25 +/- 6.90 dB(A) for the left ear during exposure to noise, suggesting that speech communication may be possible only by raising the voice. Speech discrimination showed a mean percentage decrease of 23.3 +/- 4.82 per cent for the right ear and 23.5 +/- 3.89 per cent for the left ear implying that there can be a steep decrease in the ability to discriminate spoken words.

A study of P300 in melancholic depression--correlation with psychotic features

The relationship between delusions and hallucinations (psychotic features) in melancholic depression and auditory P300 was studied. Forty patients with melancholic depression as per DSM-III-R were studied, 20 of whom had hallucinations and/or delusions. The 20 patients of the two groups were individually matched on age, gender, sociodemographic variables, and psychopathology (except for psychotic features). Auditory P300 obtained by the "oddball paradigm" showed that those with hallucinations and/or delusions had a significantly smaller P3 amplitude. Significant correlations between "psychotic features" and P3 amplitude was found. Implications of these findings on research, classification, and management of depression have been outlined.

Brain stem electric response audiometry in neonates with hyperbilirubinemia

Auditory evoked responses using BERA were studied in 30 newborn babies with plasma bilirubin > or = 15 mgm/dl and repeated after treatment of neonatal jaundice with bilirubin levels of < or = 10 mgm/dl. A few jaundiced babies (16.5%) showed absent BERA response at the initial/subsequent examination. After treatment, 3/30 babies showed absent wave form responses and 2 of these were clinically kernicteric. Jaundiced babies had prolonged wave peak latencies and inter peak latencies. Treated babies showed a tendency towards recovery in their BERA responses which were however not complete. Total plasma bilirubin value at the time of BERA examination and mean maximal bilirubin values had no correlation with the incidence and degree of BERA abnormalities.

Electrical response audiometry (ERA) in infants

The electric response audiometry is a useful diagnostic technique for identifying hearing loss in infants. Among the various electrical responses, the BSER enables us to arrive at an accurate early clinical diagnosis of hearing loss in infants so that effective auditory input, which is the prime requisite for the conceptual foundation for the growth of communication, can be provided through appropriate intervention programmes. The electric response audiometry provides information regarding the physiologic state of the peripheral organs and auditory pathways but however, cannot ascertain whether the infant can hear, in terms of perceiving auditory information. Inspite of this major limitation, the growing acceptance of brainstem electrical potentials in clinics and laboratories throughout the world attests to their increasing importance especially in the assessment of hearing sensitivity of infants.

Brain stem evoked response audiometry in neonates

Brain stem evoked response audiometry (BERA) was performed in 50 normal full term newborn infants (25 male, 25 female) to generate normative data base for this age group. The stimuli of 30 dB, 40 dB and 80 dB nHL (normal hearing level) intensities were delivered to each subjects. 30 dB stimulus failed to produce clear wave patterns, whereas upto six vertex positive waves were recognised among which waves I, III and V were commonly present. The absolute latencies of waves I and V at 40 dB nJL were 2.54 +/- 0.21 msec and 7.56 +/- 0.26 msec and at 80 dB nHL these were 2.06 +/- 0.15 msec and 7.09 +/- 0.17 msec respectively. I-V interpeak latencies (IPL) were 5.02 +/- 0.13 msec at 40 dB and 5.03 +/- 0.13 at 80 dB nHL. The latencies of waves I and V were decreased with the increase of intensity of stimuli with the rate of 0.012 msec/dB, bit I-V IPL, i.e., central conduction time remained almost constant. There were no statistically significant differences in the brain stem auditory evoked responses between male and female subjects. Brain stem evoked response audiometry is objective and reliable for hearing screening in neonates.