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General Surgery
Published in Tjun Tang, Elizabeth O'Riordan, Stewart Walsh, Cracking the Intercollegiate General Surgery FRCS Viva, 2020
Rebecca Fish, Aisling Hogan, Aoife Lowery, Frank McDermott, Chelliah R Selvasekar, Choon Sheong Seow, Vishal G Shelat, Paul Sutton, Yew-Wei Tan, Thomas Tsang
How is surgical equipment sterilised?The majority of surgical instruments and drapes are sterilised using an autoclave (saturated steam at high pressure), at 134°C, a pressure of 2 atm for a holding time of 3 min. This kills all organisms including viruses and heat-resistant spores. The steam penetration is monitored with the Bowie–Dick test, which should be checked prior to every operation.Dry-heat sterilisation is used for moisture-sensitive instruments and those with fine cutting edges. The tools are heated to 160°C for 1 hour.Ethylene oxide is a highly penetrative gas used to sterilise heat-sensitive equipment (rubber, electrical equipment), and it will kill vegetative bacteria, spores and viruses.Gamma irradiation is used in industry to sterilise large batches of single-use items such as catheters and syringes.
Applied surgical science
Published in Jonathan M. Fishman, Vivian A. Elwell, Rajat Chowdhury, OSCEs for the MRCS Part B, 2017
Jonathan M. Fishman, Vivian A. Elwell, Rajat Chowdhury
Physical sterilisation: Heat sterilisationMoist heat (pressurised steam autoclaves) 134°CDry heat: 160°CRadiation sterilisation
Liposome: composition, characterisation, preparation, and recent innovation in clinical applications
Published in Journal of Drug Targeting, 2019
Kamel S. Ahmed, Saied A. Hussein, Abdelmoneim H. Ali, Sameh A. Korma, Qiu Lipeng, Chen Jinghua
In the pharmaceutical application, usage of liposomes as a drug delivery system for specific targeting, sustained, and/or controlled release, as well as for immunisation, was and still is the driving force for innovative technologies development. Surface modification of liposomes provides many targeting approaches and ligand density optimisation on liposomes surface can increase the liposomal uptake in tumour cells. However, increasing the density and the length of the ligand beyond optimum conditions will lead to aggregation and steric hindrance that will influence ligand-receptor affinity and interaction. So, the optimum density and length of the ligands and their impact on the liposomal size, the circulation of liposomes in the blood and the affinity of the ligand to the targeted receptors should be carefully addressed [192–194]. Stability of the liposomal formulation and the leakage of the active components from vesicles after administration are vital problems which need to be monitored to get the optimum therapeutic effect, especially in tumour therapy. Phospholipids used in liposome preparation are very susceptible to oxidation and hydrolysis, so it has a short shelf life. And also, the electrostatic stabilisation of the vesicles cannot offer acceptable stability to liposomes used for encapsulation of substances highly susceptible to disintegration such as enzymes and proteins intended for in vivo applications. The liposome solutions sterility is another great challenge that should be considered, sterilisation is typically carried out using filter membranes to avoid degradation caused by other techniques, for instance, γ-irradiation, ultraviolet (UV) and dry heat sterilisation, unfortunately, filtration techniques characterised by more time consuming and lower efficiency for removal of viruses [195], moreover, because of the higher viscosity of the liposomal preparations that can lead to premature membrane blocking and also, the lower surface tension of these solutions affects the contact angle with filter membrane and decreases bubble point increasing the probability of bacterial penetration through these membranes [196]. Several preparation techniques were developed, however, most of them are suitable for small-scale and laboratory application and less for the large-scale production. Unfortunately, the availability of certain production techniques as well as the quality issues depends on the properties of the lipids themselves. This limits the choice of liposome kinds from which one can select when improving liposome-based drug therapy. Severe control of the product quality is essential to achieve the predictable therapeutic effect, quality control related to unwanted by-products, such as organic solvents residues, degradation products, lysolipids, and other lipid detergents are just as vital as pyrogen-free and sterile conditions.