Nanoclusters comprising inorganic nanocrystals and a biodegradable polymer are disclosed. The inorganic nanocrystals have a mean particle size of 1 to 500 nm. The inorganic nanocrystals are contained within a core of the nanoclusters, on the surface of the nanoclusters, contained within a core of the nanoclusters, dispersed throughout the nanoclusters, or a combination thereof. The biodegradable polymer allows the inorganic nanocrystals to be excreted renally over a period of time. The nanoclusters can be used for medical imaging or other biomedical applications.

The invention, in some aspects relates to compositions and methods for altering cell activity and function and the introduction and use of light-activated ion channels.

Provided is a method of reducing a number of viable microbes, including contacting microbes with an antibiotic compound and applying pulses of electricity having a duration of between about 50 nanoseconds and about 900 nanoseconds. The pulses of electricity may have an intensity between about 20 kV/cm and about 40 kV/cm. The pulses of electricity may be applied at a frequency of between about 0.1 Hz and about 10 Hz. The microbes may be a gram-negative or a gram-positive strain of bacteria and the antibiotic may be applied at a concentration for a duration, wherein applying the antibiotic to the strain at the concentration for the duration does not reduce a viable number of bacteria of the strain as much, or at all, when the pulses of electricity are not also applied.

Methods for enhancing intracellular uptake of active agents by inducing temporary pore formation in a cell membrane are described. The methods generally comprise introducing nanoparticles to a cell in vivo, ex vivo, or in cell culture to magnetic nanoparticles that are taken up into the cell interior. The methods further comprise introducing active agents to the cell. A magnetic field is applied to the cell for targeted excitation of the internalized magnetic nanoparticles to induce temporary pore formation in the cell membrane, such that the active agent is taken up in an increased amount and/or at an increased rate by the cell.

Provided herein are compositions including biocompatible magnetizeable nanoparticles. The nanoparticles have a diameter (average diameter) from about 10 to about 300 nanometers and are biocompatible and magnetic. The nanoparticles may be a disc formed from iron oxide. The disc may be conjugated to a target-binding moiety capable of binding a target. The target may be cancer cells, pathogens, fat cells, or atherosclerotic plaques.