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Bioinorganic > Metal complexes used in medicine > Flashcards

Metal complexes used in medicine Flashcards

1
Q

Medical use of ionising radiation

A

Radiation therapy

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2
Q

Alpha radiation

A

Two protons and two neutrons, identical to He nucleus

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3
Q

Beta radiation

A

High-energy, high-speed electrons or positrons

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4
Q

Gamma radiation

A

A form of high energy electromagnetic radiation

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5
Q

Most common gamma-emitting radionuclide

A

99mTc

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6
Q

Most common positron-emitting radionuclide

A

18F

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7
Q

Design requirements for a radio-imaging probe

A

Stable containment of imaging agent
Lipophilic
Biological targeting using antibody/recognition motifs
Kinetically inert metal-chelate complex

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8
Q

Neutral metal complex

A

Brain imaging

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9
Q

Cationic metal complex

A

Heart imaging

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10
Q

Anionic metal complex

A

Kidney imaging

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11
Q

Neutral, lipophilic metal complex

A

Liver imaging

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12
Q

Phosphato metal complex

A

Bone imaging

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13
Q

Half life of 99mTc

A

6 hours

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14
Q

Brain imaging agents

A

ECD (ethylenecysteine diethylester)
Ceretec
TRODAT - Tc(V) chelate conjugated to a cocaine derivative specific for dopamine receptors in the brain (used to diagnose Parkinson’s at early stage)

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15
Q

Heart imaging agents

A

Tc(I) hexaisocyanide (“Cardiolite”)
Myoview

Taken up by myocardial muscle

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16
Q

Bone imaging agents

A

Diphosphonates form a range of complexes with TcO4^-
All have free O groups that bind to the surface of the bone

MDP (methylenediphosphonate)

17
Q

Kidney imaging agents

A

Tc MAG-3

Tc-DMSA

18
Q

Second generation imaging agents

A

Stable neutral Tc chelate conjugated to a cyclic peptide binds to receptors expressed in certain forms of breast cancer

19
Q

Cu radioisotopes

A 
62Cu = beta+
64Cu = beta+ and beta-
67Cu = beta- and gamma
20
Q

Use of copper-based imaging

A

Imaging hypoxia
Cu(II) reduced to Cu(I) in the cytosol
Radioactive Cu accumulates and is incorporated into the cell’s Cu metabolism

21
Q

Most successful metal drug

A

Cis-platin
[PtCl2(NH3)2]
Trans isomer inactive

22
Q

Side effects of cis-platin

A

Nephrotoxicity
Neurotoxicity
Nausea

23
Q

Pharmacology of cis-platin

A

70-90 % removed from blood serum within 15 mins of injection
More than half of dose excreted, other half distributed to all tissue with highest conc in kidney, uterus, skin and liver

24
Q

Mechanism of action of cis-platin

A

Cis-platin is neutral so can diffuse across the cell membrane
Low [Cl-] inside cell so cis-platin hydrolyses stepwise
[PtCl2(NH3)2] —> PtCl(H2O)(NH3)2]+ —> [Pt(H2O)2(NH3)2]2+
Loss of Cl permits binding of Pt to guanine N7 in DNA
(can also bind to other bases but weaker)

25
Q

Half life of cis-platin in H2O

A

10 hours

Accounts for lag in observed activity after addition to cells

26
Q

Half life of cis-platin in H2O

A

10 hours

Accounts for lag in observed activity after addition to cells

27
Q

Mode of binding of cis-platin to DNA

A

Pt initially binds in a monodentate fashion (not important for cis-platin toxicity)
Then binds to either
Two guanine residues on the same strand (intrastrand binding, accounts for majority of [Pt]-DNA adducts)
Two guanine residues on parallel strands (inter strand binding, accounts for 1 % of [Pt]-DNA adducts)
Binding of Pt(II) causes the bending and unwinding of the DNA helix

28
Q

New Pt-based anti-cancer complexes

A

Carboplatin - 2nd gen, less nephrotoxic
Nedaplatin
JM 216 - trans complex also active! Effective against cis-platin-resistant tumours
BBR 3464 - central Pt binds to DNA via H-bonding, positive charge enhances intrastrand DNA interaction and causes significant unwinding

29
Q

Structure-effect relationship in platinum complexes of relevance for cancer therapy

A

Square planar Pt(II) or octahedral Pt(IV) (less effective)
Cis configuration generally required
Two cis “non-leaving” ligands required, preferably N-based with at least one NH for H-bonding
Two leaving ligands with intermediate stability and exchangeable on therapeutic timescale
Complex must initially be neutral to pass through cell membrane

30
Q

Other important metal complexes for the treatment of cancer

A

Cp2TiCl2
Budotitane
Ru indazole complex

31
Q

PET

A

Positron Emission Tomography
Uses radionuclides that emit positrons e.g. 18F
The emitted positrons combine with electrons to produce gamma rays that travel in exactly opposite directions (“positron annihilation”)

32
Q

SPECT

A

Single Photon Emission Computed Tomography

Uses radionuclides that emit gamma radiation e.g. 99mTc

33
Q

How are the radionuclides for PET scanning produced?

A

In a cyclotron

Bioinorganic (11 decks)

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