Citotossicità delle cellule Natural Killer (NK)

The D-value is the time required at a specific temperature to kill 90% (or one log reduction) of a target microorganism population. It is a critical parameter in thermal sterilization, quantifying a microbe's resistance to heat. For example, if a population of [latex]10^6[/latex] spores has a D-value of 2 minutes, it takes 2 minutes to reduce it to [latex]10^5[/latex].

Un metodo di sterilizzazione chimica a bassa temperatura che utilizza gas ossido di etilene. È efficace per sterilizzare materiali sensibili al calore e all'umidità come plastica, dispositivi elettronici e strumenti ottici. Il processo prevede l'alchilazione, in cui l'EtO distrugge il DNA e le proteine ​​dei microrganismi, impedendone la replicazione. Richiede un attento controllo della concentrazione del gas, della temperatura, dell'umidità e del tempo di esposizione.

La citotossicità è la proprietà di una sostanza o di una cellula di essere tossica per altre cellule. Gli agenti citotossici possono indurre la morte cellulare attraverso la necrosi, dove la membrana cellulare perde integrità portando a lisi e infiammazione, o l'apoptosi, un processo di morte cellulare controllato e programmato. Questo si distingue dagli agenti citostatici, che inibiscono solo la divisione cellulare senza causarne direttamente la morte.

Biomimicry is an innovation approach that seeks sustainable solutions to human challenges by emulating nature's time-tested patterns and strategies. The core idea is that nature, through 3.8 billion years of evolution, has already solved many of the problems we are grappling with. It involves observing and learning from the designs and processes of organisms and ecosystems to create more sustainable designs.

Overpotential is the potential difference (voltage) between a half-reaction's thermodynamically determined reduction potential and the potential at which the redox event is experimentally observed. It represents the extra energy required to overcome activation barriers for the electrode reaction to proceed at a significant rate. It is a key factor in the energy efficiency of all electrolytic processes.

Cellular respiration is a series of redox reactions where organic molecules, like glucose, are oxidized to release energy. Glucose ([latex]C_6H_{12}O_6[/latex]) is oxidized to [latex]CO_2[/latex], while oxygen ([latex]O_2[/latex]) is reduced to water ([latex]H_2O[/latex]). This process transfers electrons through an electron transport chain, creating a proton gradient that drives the synthesis of ATP, the cell's primary energy currency.

Electrochemical potential is fundamental to life, driving processes across cell membranes. Ion pumps actively create concentration gradients, while the selective permeability of ion channels establishes an electrical potential (membrane potential). The resulting electrochemical gradient dictates the passive flow of ions, which is crucial for nerve signaling (action potentials), muscle contraction, and cellular energy production (ATP synthesis) in mitochondria.

SAL is a quantitative measure representing the probability of a single viable microorganism surviving on an item after sterilization. A commonly required SAL for medical devices is [latex]10^{-6}[/latex], meaning a one-in-a-million chance of a non-sterile unit. This probabilistic approach acknowledges that absolute sterility cannot be proven, only inferred statistically from process validation.

The MTT assay is a colorimetric method for assessing cell metabolic activity, which serves as a proxy for cell viability, proliferation, and cytotoxicity. Viable cells with active mitochondria contain reductase enzymes that convert the yellow tetrazolium salt MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) into an insoluble purple formazan. The amount of formazan produced is proportional to the number of living cells.