Polymeric supports in the form of hydrogels, micro- and nano-particles, semi- and inter-penetrated networks sensitive to different stimuli (pH, temperature, light, ionic strength, glucose) are developed by physical or chemical crosslinking or by chemical modifications of natural polymers (polysaccharides). These complex architectures are designed for the controlled release of drugs, as supports for cell encapsulation and cell growth or as materials with antibacterial properties.