Background: Polymer-based systems are attractive in drug delivery and regenerative medicine due to the possibility of tailoring their properties and functions to a specific application. Methods: The present review provides several examples of molecularly engineered polymer systems, including stimuli responsive polymers and supramolecular polymers. Results: The advent of controlled polymerization techniques has enabled the preparation of polymers with controlled molecular weight and well-defined architecture. By using these techniques coupled to orthogonal chemical modification reactions, polymers can be molecularly engineered to incorporate functional groups able to respond to small changes in the local environment or to a specific biological signal. This review highlights the properties and applications of stimuli-responsive systems and polymer therapeutics, such as polymer-drug conjugates, polymer-protein conjugates, polymersomes, and hyperbranched systems. The applications of polymeric membranes in regenerative medicine are also discussed. Conclusion: The examples presented in this review suggest that the combination of membranes with polymers that are molecularly engineered to respond to specific biological functions could be relevant in the field of regenerative medicine.